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Patrick Fitzgerald -
Posted 115 days Ago

WiFi for Train Communications

Communication Systems

  WiFi for Train Communications   WiFi can be used to communicate with moving trains in a metro system. Ordinary WiFi like in my home? Could be.  IEEE802.11g 2.4GHz band, like you use in your home.  But the 5.8-5.9GHz band using 802.11a or 802.11n has certain advantages. There is even an 802.11p available but I think that is reserved for trucking.   http://standards.ieee.org/about/get/802/802.11.html By using WiFi in the 5.8-5.9GHz band you can go to higher power EIRP.  http://en.wikipedia.org/wiki/U-NII  shows this spectrum for 802.11a in the United States.  Most countries, Canada, Europe, Saudi Arabia, etc. will more-or-less follow this spectrum;  perhaps with blocks reserved or different maximum powers. When you want your WiFi access points spread out along the guideway, power determines how close or how far apart your wayside access points can be located.  According to  http://en.wikipedia.org/wiki/U-NII  you can go up to 4Watts=36dBm in the USA. Trains move, fast.  A higher power allows you to space out your Wayside Access points.  100 or 200m being typical.  If the train had to perform a complete logon for every change of access point more time would be spent authenticating than transferring data.  A wireless access controller can reduce time wasted.    http://www.youtube.com/watch?v=0n-uIusTpU8 Finally, everybody has a device that can affect the 2.4GHz range. Laptops, smartphones.  By going to the 5.8-5.9GHz band a cyber-intruder needs to have a wifi device that can work in that "exotic" range. What is in the data? Train position, train speed, commands to stop, commands to go, status and health of train electronics and mechanical equipment, perhaps even who is logged in as driver.  Each manufacturer:  Thales, AnsaldoSTS, Siemens, Bombardier, to name just a few, will have their own proprietary messaging and their own way of doing things for CBTC communications based train control.  But they all have the same goal of moving trains, or stopping trains, without the nuisance of the trains hitting each other. Any WiFi link carrying ATC or CBTC data must be secured.  WPA encryption is only the beginning.  Authentication with passkey and MAC address control are needed, as well.  By writing the CBTC protocol to conform to IEC EN 50159 the actual data messages will be encrypted, again, authenticated and they must make sense to the CBTC servers and clients or they will be rejected.  Any lost messages must be detected and re-transmitted. Just like your home WiFi the SSID beacon can be suppressed.  The train knows what network to connect to and it's not like railway tracks move around a lot.   What else is special about WiFi for Metro Trains Rail alignments are long and skinny. By using a directional antenna you amplify the signal along the track and reduce the waste of power going to the sides. 12-15-18 dBi are common antenna gains. EIRP is the total power put into the antenna, directional gain means the receiver will receive a greater portion of that power. On board the train are many systems using open protocols. To talk to doors, HVAC, break systems you will commonly encounter CANBus, MVB or TWN standards. A voice circuit is needed for a manual operator, a SoftPhone using a VoIP client can connect through the WiFi network along with the ATC, ATS and ATO protocols.   image from researchgate.net

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Suman Pathak -
Posted 96 days Ago

Various Systems of Railway Electrification

Rail Electrification

Various Systems of Railway Electrification Several different types of Railway Traction Electric Power System configurations have been used all over the World. The choice of the system depends on the train service requirements such as  I.    Commuter rail  -Commuter rail typically includes one to two stops per city/town/suburb along a greater rail corridor II.    Freight rail -Rail freight transport is the usage of railroads and trains to transport cargo on land. It can be used for transporting various kinds of goods III.    Light rail -The LRT vehicles usually consist of 2–3 cars operating at an average speed of 55–60 km/h on the lines with more dense stops/stations and 65–70 km/h along the lines with less dense stations IV.    Train load s V.    Electric utility power supply. Railway electrification loads and systems required for light rails, commuter trains, fast high-speed trains, and of course the freight trains are all different. The power demands for these different rail systems are very different. The selection of an appropriate electrification system is therefore very dependent on the Railway system objectives Presently, the following four types of track electrification systems are available: 1. Direct current system—600 V, 750 V, 1500 V, 3000 V  2. Single-phase ac system—15-25 kV, 16 23, 25 and 50 Hz  3. Three-phase ac system—3000-3500 V at 16 2 3 Hz  4. Composite system—involving conversion of single-phase ac into 3-phase ac or dc.   Direct Current Traction System In this traction system, electrical motors are operating on DC supply to produce the necessary movement of the vehicle. Mostly DC series motors are used in this system. For tramways, DC compound motors are used where regenerative braking is required. Regenerative braking   In this type of braking the motor is not disconnected from the supply but remains connected to it and feeds back the braking energy or its kinetic energy to the supply system. The essential condition for this is that the induced emf should be slightly more than the supply voltage.  The various operating voltages of the DC traction system include 600V, 750 V, 1500V, and 3000V. •    DC supply at 600-750V is universally employed for tramways and light metros in urban areas and for many suburban areas. This supply is obtained from a third rail or conductor rail, which involves very large currents. •    DC supply at 1500- 3000 is used for mainline services such as light and heavy metros. This supply is drawn mostly from an overhead line system that involves small currents. Since in the majority of cases, track (or running) rails are used as the return conductor, only one conductor rail is required. Both these supply voltages are fed from substations which are located 3-5 KM for suburban services and 40 to 50KMs for mainline services. These substations receive power (typically, 110/132 KV, 3 phase) from electric power grids. This three-phase high voltage is stepped-down and converted into single-phase low voltage using Scott-connected three phase transformers. This single-phase low voltage is then converted into DC voltage using suitable converters or rectifiers. The DC supply is then applied to the DC motor via a suitable contact system and additional circuitry.   Advantages 1. In the case of heavy trains that require frequent and rapid accelerations, DC traction motors are the better choice as compared to AC motors. 2. DC train consumes less energy compared to AC unit for operating same service conditions. 3. The equipment in the DC traction system is less costly, lighter, and more efficient than the AC traction system. 4. It causes no electrical interference with nearby communication lines. Disadvantages 1. Expensive substations are required at frequent intervals. 2. The overhead wire or third rail must be relatively large and heavy. 3. Voltage goes on decreasing with an increase in length.                 Single-phase ac system In this type of traction system, AC series motors are used to produce the necessary movement of the vehicle. This supply is taken from a single overhead conductor with the running rails. A pantograph collector is used for this purpose. The supply is transferred to the primary of the transformer through an oil circuit breaker. The secondary of the transformer is connected to the motor through switchgear connected to suitable tapping on the secondary winding of the transformer. The switching equipment may be mechanically operated tapping switch or remote-controlled contractor of group switches. The switching connections are arranged in two groups usually connected to the ends of a double choke coil which lies between the collections to adjacent tapping points on the transformer. Thus, the coil acts as a preventive coil to enable tapping change to be made without short-circuiting sections of the transformer winding and without the necessity of opening the main circuit.  Out of various AC systems like 15-25 kV, 16 23, 25, and 50 Hz. Mostly the 25KV voltage is used in railways. The main reason for the 25kV voltage used in the railway is, that 25 kV AC is more economical than a 1.5kV DC voltage system. Since the 25kV voltage system has a higher voltage, the higher voltage reduces the current flow through the conductor; this reflects reducing the conductor size. The cost of the conductor gets less.  However, there are other major advantages for using 25kV voltage system in railway are quick availability and generation of AC that can be easily stepped up or down, easy controlling of AC motors, a smaller number of substations requirement, and the presence of light overhead catenaries that transfer low currents at high voltages, and so on.   Disadvantages 1.  Significant cost of electrification. 2.  Increased maintenance cost of lines. 3.  Upgrading needs additional cost especially in case there are bridges and tunnels. Composite System As the name suggests this system is classified into two types  I single phase to dc system II single phases to 3 phase system Single Phase to DC system The first one single phase to dc system is used where the voltage level is high for transmission and the dc machine is used in the locomotive. This system combines the advantages of high-voltage ac distribution at the industrial frequency with the dc series motors traction. It employs an overhead 25-kV, 50-Hz supply which is stepped down by the transformer installed in the locomotive itself. The low-voltage ac supply is then converted into dc supply by the rectifier which is also carried on the locomotive. This dc supply is finally fed to dc series traction motor fitted between the wheels.                                                                                     Single-phase to 3 phase system Single-phase to 3 phase system is used where 3 phase machine is used in the locomotive and Single-phase track available. In this system, the single-phase 16KV, 50 Hz supply from the sub-station is picked up by the locomotive through the single overhead contact wire. It is then converted into a 3-phase AC supply at the same frequency by means of phase converter equipment carried on the locomotives. This 3-phase supply is then fed to the 3-phase induction motor. References: various EMC Europe IEEE papers, slideshare.net presentations, rail systems, etc.

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Deepu Dharmarajan -
Posted 464 days Ago

SRA (TfNSW) SIGNALLING & ELECTRICAL SYMBOLS

Signalling

CONTENTS   The following pages show the signalling and schematic symbols used by the State Rail Authority of New South Wales on their plans and drawings. They are provided for reference use throughout the course. They are reproduced from SRA (Currently TfNSW) training material.   TRACK PLAN AND WORKING SKETCH SYMBOLS MECHANICAL SIGNALS POWER WORKED SIGNALS SINGLE LIGHT INDICATION WAYSIDE BUILDING AND STRUCTURES TRACK CIRCUIT DEVICES INTERLOCKING SYMBOLS APPARATUS HOUSINGS RELAYS AND CONTACTS CONTACTS OPERATED BY SIGNALS LOWER QUADRANT SEMAPHORE SIGNALS, INCLUDING BANNER SIGNALS CONTACTS OPERATED BY POINTS LEVER CONTACTS CATCH ROD CONTACTS MISCELLANEOUS APPARATUS 

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Josef Winter -
Posted 114 days Ago

Solar-powered video surveillance for tracks

Safety and RAMS

The solar video surveillance system was specially developed for an application without power supply and network connection for railroad use. This system is the ideal and cost-effective solution for video surveillance, at locations without existing infrastructure. The RAILWAY CONTROLLING models can be used in all locations where sunlight and mobile phone reception are available. All models meet strict security requirements.   Ideally suited for: - Track surveillance - Tunnel portal surveillance - Storage yard surveillance - Weather monitoring   Visit: http://railway-controlling.com/index.html  

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Pravin_pasare -
Posted 205 days Ago

Slab track VS Ballasted Track

Rail Tracks

No. DESCRIPTION BALLASTED TRACK BALLASTLESS TRACK 1.       Maintenance Input. Frequent maintenance & non-uniform degradation Less maintenance for geometry. 2.       Cost comparison Relatively low construction costs but higher life cycle cost. Relatively high construction cost but lower life cycle cost. 3.       Elasticity. High elasticity due to ballast. Elasticity is achieved through use of rubber pads and other artificial materials. 4.       Riding Comfort. Good riding comfort at speeds up to 250 – 280 kmph. Excellent riding comfort even at speeds greater than 250 kmph.   5.       Life expectation (20 yrs) (50-yrs) 6.       Stability. Over time, the track tends to “float”, in both longitudinal and lateral directions, as a result of Non-linear, irreversible behaviour of the materials. No such problem. 7.       Lateral resistance Limited  compensated Lateral acceleration in curves, due to the limited lateral resistance offered by the ballast. High lateral resistance to the track which allows future increase in speeds in combination with tilting coach technology. 8.       Noise. Relatively High noise Relatively low noise and vibration nuisance. 9.       Churning up of Ballast. Ballast can be churned up at high speeds, causing serious damage to rails and wheels. No such damage to rails and wheels. 10.  Construction cost of Bridges/Tunnels/ etc. Ballast is relatively heavy, leading to an increase in the costs of building bridges and viaducts if they are to carry a continuous ballasted track. Less cost of construction of bridges and viaducts due to lower dead weight of the ballast-less track. 11.   Construction Depth. Depth of Ballasted track is relatively high, and this has direct consequences for tunnel diameters and for access points. Reduced height.

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TOJO THOMAS -
Posted 35 days Ago

Signalling Installation Design - Part 1

Signalling

In general, least importance are given to Installation Design compared to System Design ! This is mainly due to lack of awareness and knowledge  among  the key personals within an organisation. An error in a system application software or any design engineering document can be rectified by spending few hours and the cost impact is minimal compared to an error in an Installation Design. As a person who worked in both aspect of these two designs, I felt that we should emphasize more on Installation Design. A minor error in a mechanical cable frame, cable junction box, fixing brackets or a signal mast design will have a huge impact on material wastage, impact of schedule and budget in a larger way. There are various things to be considered to produce an error free design, which I describe based on design and site experience I received in the projects I have executed. I have tried to explain in this article the flow of work that happens in Installation design engineering from the Tender to the execution of installation activities at site. I have divided the work done by installation engineer into the following section. It is defined as per the schedule/flow of activities. TENDER: Firstly, before starting any Installation engineering activities we do have a tender phase. In this phase we analyse basically 2 main information which is important for the project management team to decide the cost. Ultimately everything comes down to the cost, each system has forecasted!!! The 2 main information required during the tender phase is the number of hours we will spend and the number of items we will be procuring. This information is collected in the format of BOQ (Bill of quantity and workload file. So, in this section I will explain what should not be missed (inputs and outputs) during the tender phase: Inputs/Reference documents Requirement matrix: This document has the information from the customer required for each system. Installation engineering team has to extract the installation requirements with respect to each other engineering sub system. This drawing also will have the standards(EN, IS, ASTM, IEC, etc) that should be followed in the respective country. Civil Architecture drawings/CSD(Combined Services drawing): These are a set of drawing which will give an outline of the building and the location of the equipment room in the station or control centre. This will also have the general information on the cable routing inside the building. This drawing will help us to calculate the cable length that has to be considered for each run of the cable. Cross Section drawing of the track: This will give a general information on the type of accessories and mounting support we need to consider for each equipment defined in the scheme plan. This will also provide the information on the cable ducts that can be used for SIG and COM. With this drawing, we also get to know what strategy that can be applied to cross the cables between the tracks. Track Alignment drawing: This drawing will give us the gradient of the tracks and the vertical/horizontal alignment of both the up & down track. This drawing along with scheme plan will help us to calculate the cable length along the track along. Also, this drawing will help us to analyse if the track is elevated, on ground and underground which will in turn help the team to analyse the mounting arrangement for trackside equipment. Scheme plan: This is the deliverable from engineering team that defines the kilometric point of each equipment and the number of trackside equipment. It is used to calculate the cable length and quantify the number of mounting arrangements that needs to be considered against each signalling and telecom equipment along the track. System BOQ: This document will have the information on the quantity of the equipment that will be installed along the trackside and in the stations. We can decide on quantity of the support required for each different equipment. Cable layout: This drawing gives a general information on the cabling schematics between the cubicle in the equipment room and trackside equipment. We use this deliverable to define the type of cables and the length required for each type of equipment. Interface management: This is plan created along with the customer on who will give what information. This also states what are the supports other subsystem require from installation team. Planning schedule: This will provide a general information on the schedule of each activity during the execution of project. This will in turn help the team to forecast the installation engineering activities. Output/ Installation Deliverables Installation BOQ: After analysing the inputs from the customer and other engineering team within the project team (inputs are listed above), Installation team will prepare the installation BOQ. This document contains all the items related to installation such as cable trays and it accessories, mounting support and its accessories, cables, material needed for cable crossing the track, cable tags, tags, racks, base frames, conduits, trackside junction box and its accessories, clamps, cable glands, grounding mechanism, etc. Installation workload file: This document consists of the number of deliverables that needs to be considered along with the hours dedicated to each deliverable. This document will also include the information on the scope of work for installation design team with respect to the site activities (Whether shared or full-time resources is dedicated for each activity). We also include the information on the assumptions taken during the workload calculation. According to the planning of the schedule for each activity we forecast the hours.   For Preliminary installation Design to Detailed Installation Design do follow the page for more....

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Somnath Pal -
Posted 108 days Ago

RAMS of a Vital Input Card

Safety and RAMS

CHAPTER -1  Introduction For a Railway Signal Interlocking system, Field Input conditions to be monitored by the Interlocking equipment are Track Cct / Axle Counter, Point Detection, Signal Aspect Proving, Level Crossing Gate, Crank Handle and Panel Buttons. The monitoring is done by reading the Pick-up or Drop contacts of corresponding Relays. This could have been done by operating a Transistor through external Voltage fed via the pick-up Contact of the Relay. The Output of Transistor is processed by the Logic Solver ( Processor). But in that case, there would be no Isolation between external Analog Input and internal Digital Output circuits. An Opto Coupler is used for this purpose, where the Input LED and Output Phototransistor are electrically isolated . The Input through Pick-up contact of Relay operates the LED of the Opto Coupler, light from which turns the output Phototransistor. The  interfacing using a Transistor and an Opto coupler is showed in Fig 1(a)&(b) When the Relay is in Pick-up condition, the Transistor is Forward biased and Collector Output to Processor is ‘0’ . During Drop condition of the Relay, Collector Output is ‘1’ . Input Interface Card converts the Analog information of DC Voltage fed through the Relay contacts to send TTL level to Processor. The basic features of the Card are: All Inputs are fed through Opto Couplers having a minimum Isolation Voltage of 1500V.   All Inputs are protected from Transient Voltages and Surges by using Varistors. To reduce Single-point Failure, both Front and Back potential-free contacts of each external Relay are interfaced. They are read through different Ports and Bits to avoid common-mode failure. Each Card gets Hardware Address of the particular Slot of the Backplane, to which it is inserted. This Address must be matched with the Software Address sent by Logic Solver Card before the external Relay Inputs are read. Input Cards can be inserted or extracted with System Power-ON conditions. A special circuit is used to prevent transient to Stable +5V Supply to ICs, Input data are read employing Input Toggle by the logic Solver or using multiple sets of Opto Couplers ensuring Hardware redundancy. The Input Data Structure of the Interlocking System Inputs is given in Fig 2: Panel Buttons and Keys are called Non-Vital Inputs and a Non-Vital Input / Output Card is used to read 32 Inputs . All other Inputs are Vital Inputs and a Vital Input Card reads 16 Relay Inputs.   A detailed diagram is showed in Fig 3 . Since Railway Interlocking is a Safety-critical System, Inputs from both Pick-up and Drop Contacts of a Relay is analysed. Each Input is monitored by Opto Couplers by supplying Current from an Isolated 12V Supply . The Input to Processor will be ‘ 01’ in Drop Condition and ‘ 10’ in Pick up Condition . These two combinations are Valid Inputs . Other two Inputs ‘ 00’ and ‘ 11’ are Invalid and Processor will show Fault. But during transition of Relay between Drop to Pick-up or Pick- up to Drop , both the Opto Couplers will be OFF . So, Output will be ‘11’ , which is Invalid A De-bouncing circuit (U1) is used for feeding steady Input to the Logic Solver. In this case, during transition of Relay, the Input to Processor will remain unchanged from Last State. When the Relay X is not operated , current flows through the Drop Contact , Inductor, L1, Current Limiter R1, Resistor R2 and input Diode of Opto Coupler OC1. The Opto Coupler conducts and a level ‘ 0 ’ is fed to Pin1 of U1 . This makes output Pin 3 of U1  as ‘ 1 ’. At the same time, since no current passes through Input Diode of OC2, it does not  conduct. Level ‘1’ is fed to  Pin 5 of U1 and output   Pin 6 of U1 to Port becomes ‘0’. Thus we get a pattern 0101 at the Port. When the Relay X is operated , current flows through the Pick-up Contact ,  Inductor L2,  Current Limiter R5, Resistor R6 and input Diode of Opto Coupler OC2. The Opto coupler conducts and a level ‘0 ’ is fed to Pin 5 of U1 . This makes output to Pin 6 of U1   as ‘0’ . At the same time, since no current passes through Input Diode of OC1, it does not  conduct. Level ‘1’ is fed to  Pin 1 of U1 and output to Pin 3 of U1 to Port becomes ‘0’ .This time, the inputs to Port changes to 1010 . We find that Port inputs 0101 and 1010 are the valid levels . All other combinations  are invalid levels. If Hardware De-bounce Cct U1 is replaced by Software De-bounce to reduce Parts Count to enhance Reliability, the inputs to Port will change to 01 when Relay X is not operated and 10 when it is  operated. If a vital decision is taken by   Pick-up condition of Relay X, then a failure to read Pick-up condition as Drop, is a Safe failure . But if Drop condition is read as Pick-up condition, it will be Unsafe failure . Now we shall have to do an Failure Mode Effects & Criticality Analysis (FMECA)  study of the Cct showed in Fig 3 and identify the critical component to cause Unsafe Failure and mitigate the Hazard. Failure Mode Effects & Criticality Analysis (FMECA) We shall first study the failure modes of the components. For every failure mode of components , we shall their effect for Drop and Pick-up conditions. Typical faults of an Electronic component are Open Cct, Short Cct, Drift in Parameter and Functional Faults. Average relative frequencies of Failure Modes of various Components are given in the Table 1 below. Terminating Resistors and Current Limiting Resistors are of mainly Metal Film type for which Short cct Mode is incredible and hence are not considered. When Resistors are used in Nodes with Pull up Totem-pole Driver , even Drift in value is not to  be considered. For open Collector Modes like Opto coupler output, the design ensures much higher Collector current as well as Diode input current , so that even  ± 20% Drift does not affect the Circuit behaviour. So, for Resistors , only Open Cct Mode is considered. For Inductors, any Drift will not affect normal operation and only Open Mode of failure is considered. For Varistor, Open Mode does not affect normal operation and if the Clamp Voltage is chosen much higher than the required Value , Drift also does not have any effect. Only Short cct Mode is analysed . For ICs, both s-a-0 and s-a-1 Faults are considered for every Pin. Now we will consider component-wise FMECA. The effects during Relay Drop  and Pick-up conditions are analysed for each Component Failure. a) If Inductor L1 is Open Relay Drop condition: Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1011’. Fault is detected as Invalid Data and failure is Safe.  Since both the Inputs to Debounce Cct are at ‘1’, its Output will remain at last State, i.e. 01. Relay Pick-up condition : Current  passes through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘0’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  b) If Inductor L2 is Open Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin5  is at ‘1’ and U1 pin 1 is at ‘0’. Output  to Port will be ’0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Current  passes through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  also at ‘1’. Output  to Port will be ’1011’. Fault is  detected  as invalid data. c) if Metal Oxide Varistor RV1 is Short : Relay Drop condition: Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1101’. Fault is detected as invalid data and failure is Safe.  Relay Pick-up condition : Current  passes through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘0’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  d) if Metal Oxide Varistor RV2 is Short : Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin5  is at ‘1’ and U1 pin 1 is at ‘0’. Output  to Port will be ’0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Current does not pass through input of Opto Coupler OC2. U1 pin 5 is at ‘1’ and U1 pin 1 is  aIso ‘1’. Output  to Port will be ’1011’. Fault is detected as invalid data and failure is Safe.  e) If Current Limiting Resistance R1 is Open: Relay Drop condition: Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1101’. Fault is detected as invalid data and failure is Safe.  Relay Pick-up condition : Current  passes through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘0’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  f) If Current Limiting Resistance R2 is Open: Relay Drop condition: Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1101’. Fault is not detected data and failure is Safe.  Relay Pick-up condition : Current  does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is also at ‘1’. Output  to Port will be ’1011’. Fault is  detected  as invalid and failure is Safe.  g) If Current Limiting Resistance R5 is Open: Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘0’ and U1 pin 5 is  aI ‘1’. Output  to Port will be ’0101’. Fault is not detected data and failure is Safe.  Relay Pick-up condition : Current  does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘1’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  h) If Current Limiting Resistance R6 is Open: Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘0’ and U1 pin 5 is  aI ‘1’. Output  to Port will be ’0101’. Fault is not detected data and failure is Safe.  Relay Pick-up condition : Current  does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘1’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  i) If Protection Diode D1 is open: Normal operation of the cct is not affected. But a reverse voltage of more than 6V during Drop condition would damage the Diode of Opto coupler OC1. During Pick-up condition, there is no effect. j) If Protection Diode D2 is open: Normal operation of the cct is not affected. But a reverse voltage of more than 6V would damage the Diode of Opto Coupler OC2 during Pick-up. There is no effect during  Drop condition. k) If Protection Diode D1 is short: Relay Drop condition: Opto coupler OC1 will be OFF since current will  be bypassed via D1. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘1’. Output  to Port will be ’1101’. Fault is detected as invalid data and failure is Safe.  Relay Pick-up condition : Opto coupler OC1 will be OFF since current will  be bypassed via D1. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘1’. Output  to Port will be ’1010’. Fault is not detected failure is Safe.  l) If Protection Diode D2 is short: Relay Drop condition: Opto coupler OC2 will be OFF since current will  be bypassed via D2. U1 pin 1 is at ‘1’ and U1 pin 5 is  also at ‘1’. Output  to Port will be ’ 0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Opto coupler OC2 will be OFF since current will  be bypassed via D2. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1011’. Fault is detected as invalid data and failure is Safe. m) If Input Diode of Opto Coupler OC1 is open: Relay Drop condition: Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  aIso ‘1’. Output  to Port will be ’1101’. Fault is detected as invalid data and failure is Safe.  Relay Pick-up condition : Current does not pass through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  at ‘0’. Output  to Port will be ’1010’. Fault is not detected  and failure is Safe.  n) If Input Diode of Opto Coupler OC2 is open: Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin 5  is at ‘1’ and U1 pin 1 is at ‘0’. Output  to Port will be ’0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Current  does not pass through input of Opto Coupler OC2. U1 pin 1 is at ‘1’ and U1 pin 5 is  also at ‘1’. Output  to Port will be ’1011’. Fault is  detected  as invalid data. o) If Collector in Opto Coupler OC1 is open: Relay Drop condition: Due to the pull up Resistor 5, Current does not pass through input of Opto Coupler OC1. U1 pin 5  is at ‘1’ and U1 pin 1 is at ‘0’. Output  to Port will be ’0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Opto Coupler OC2 starts conducting  and port input becomes 0101. Fault is not detected  and failure is Safe.  p) If Collector in Opto Coupler OC2 is open: Relay Drop condition: Current does not pass through input of Opto Coupler OC2. U1 pin5  is at ‘1’ and U1 pin 1 is at ‘0’. Output  to Port will be ’0101’. Fault is not detected and failure is Safe.  Relay Pick-up condition : Current  passes through input of Opto Coupler OC1. U1 pin 1 is at ‘1’ and U1 pin 5 is  also at ‘1’. Output  to Port will be ’1011’. Fault is  detected  as invalid data. q) If Collector and Emitter of OC1 is short: Relay Drop condition: We get  1 in Pin 1 of U1 and port gets data 0101. Fault is not detected and failure is Safe.  Relay Pick-up condition : Both pins 1 and 5 get 1 and we get 0110. Fault is  detected  as invalid data. r) If Collector and Emitter of OC 2 is short: Relay Drop condition: We get  1 in Pin 5 of U1 and port gets data 1010. Fault is not detected and failure is Safe.  Relay Pick-up condition : Both pins 1 and 5 get 1 and we get 0110. Fault is  detected  as invalid data. s) If Pull up Resistor R3 is open: Relay Drop condition: Since Opto Coupler OC1 is in operated condition, we get  0 in Pin1 of U1 and port gets data 0101. Fault is not detected and failure is Safe.  Relay Pick-up condition : If there is large leakage current from Supply and Ground, the Collector of Opto coupler OC1 will be at level ‘0’. So data to  port will be 0110. Fault is  detected  as invalid data. t) If Pull up Resistor R7 is open: Relay Drop condition: Since Opto Coupler OC2 is in operated condition, we get  0 in Pin5 of U1 and port gets data 0110. Fault is detected as invalid data and failure is Safe.  Relay Pick-up condition : If there is large leakage current from Supply and Ground, the Collector of Opto coupler OC1 will be at level ‘0’. So data to  port will be 1010. Fault is  not detected.  u) If S-a-0 fault is at Pin 1 of U1: Relay Drop condition: Pin 3 of U1 will be ‘1’ and Port Input is 0101. Fault is not detected. Relay Pick-up condition : Port Input will be 0110, which is invalid. v) If S-a-0 fault is at Pin 5 of U1: Relay Drop condition: Pin 6 of U1 will be ‘1’ and Port Input is 0110 which is invalid. Relay Pick-up condition : :Port Input will be 1010. Fault is not detected. w) If S-a-1 fault is at Pin 1 of U1: Relay Drop condition: Pin 1 and Pin 5 of U1 both will be ‘1’ and Port Input remains 0101. Fault is not detected. Relay Pick-up condition : Port Input will be 1010. Fault is not detected. x) If S-a-1 fault is at U1-5: Relay Drop condition: Pin 6 of U1 will be ‘0’ and Port Input is 0101.  Fault is not detected. Relay Pick-up condition : Pin 1 and Pin 5 of U1 both will be ‘1’ and Port Input remains 1010. Fault is not detected. y) If S-a-0 fault is at U1-3: Relay Drop condition: Pin 3 of U1 will be ‘0’ and Port Input is 0011, which is invalid. Relay Pick-up condition : Port Input is 1010. Fault is not detected. z) If S-a-0 fault is at U1-6: Relay Drop condition: Port Input is 0101. Fault is not detected. Relay Pick-up condition : Port Input is 1100, which is invalid. aa) If S-a-1 fault is at U1-3: Relay Drop condition: Port Input is 0101. Fault is not detected. Relay Pick-up condition : Port Input is 1101, which is invalid. ab) If S-a-1 fault is at U1-6: Relay Drop condition: Port Input is 0111, which is invalid. Relay Pick-up condition : Port Input is 1010. Fault is not detected. ac) If R4 is Open: Relay Drop condition: LED 1 will not glow. Since LED 2 also does not glow, fault can be usually detected. Relay Pick-up condition : Since LED 2 glows, fault cannot be detected. ad) If R8 is Open: Relay Drop condition: Since LED 1 glows, fault cannot be detected. Relay Pick-up condition : LED 2 will not glow. Since LED 1 also does not glow, fault can be usually detected . ae) If LED1 is faulty: Relay Drop condition: LED 1 will not glow. Since LED 2 also does not glow, fault can be usually detected. Relay Pick-up condition : Since LED 2 glows, fault cannot be detected. af) If LED2 is faulty: Relay Drop condition: Since LED 1 glows, fault cannot be detected. Relay Pick-up condition : LED 2 will not glow. Since LED 1 also does not glow, fault can be usually detected. In summary, Invalid Input is obtained in Relay Drop condition if OC1 Output is Short OC2 Input or Output is Open U1-3 S-a-1 U1-6 S-a-0 Similarly, Invalid Input is obtained in Relay Pick-up   condition if OC1 Input or Output is Open OC2 Output is Short U1-3 S-a-0 U1-6 S-a-1 It also shows that a single fault cannot lead to Unsafe Failure. After the completion of FMECA, we are to perform Fault Tree Analysis (FTA) of the Circuit to identify the causes of Safe and Unsafe Failures .                                                        Fault Tree Analysis (FTA) We shall now learn how the Circuit can fail to operate. So, we shall make a Fault Tree Analysis as shown below. Fault trees are individually made for both Safe as well as Unsafe Failures. Safe Failure can occur due to Two simultaneous Faults --- Open Cct Fault in Opto Coupler OC2 as well as Short Cct Fault in Opto Coupler OC1. Unsafe Failure can occur due to Two simultaneous Faults --- Open Cct Fault in Opto Coupler OC1 as well as Short Cct Fault in Opto Coupler OC2.     Unsafe Failure can happen only due to simultaneous Faults in Open cct in Relay NO path and Short cct in Relay NC path.         CCT UNSAFE FAILURE (0101 is read as 1010)               Once we prepare the Fault Tree, we are to calculate the Failure Rate of the Card .               For this, we are initially to find the Basic Failure Rate for each component as per Calculations given in MIL Std 217F . Then we are to Calculate the actual Failure Rate under environmental stress.   The environmental stress factors are : λ C =  Contact Constitution Factor λ Q = Quality Factor λ E =  Environmental Factor. We consider Ground Fixed λ T =  Temperature Factor λ s =  Electrical Stress Factor λ R =  Resistor Value factor λ CV = Capacitor Value Factor   Typical Calculations for a Components are showed in Chapter. The following Table shows the individual Component Failure Rates for the Input Interface Cct. We have seen that Unsafe Failure can be caused only by 2 simultaneous failures – Open Circuit in OC 1 and Short Circuit of OC 2 Output. So, the Failure Rate will be the Product of Individual Failure Rates of the 2 Opto Couplers. From the table above, we find that the Failure Rate of an Opto Coupler is 0.0257 X 10 -6 . So, the Unsafe Failure Rate will be ( 0.0257 X 10 -6 ) 2 = 6.6040 X 10 -16.  This is far above the requirement of SIL 4. Total Failure Rate of the Card is 3.375477 X 10 -6 giving a Mean Time Between Failure of 296254.4 Hours. Reliability after a period of One year (8760 Hrs) i s R = e – λt     = e - 0.0000033754 X 8760    = e – 0.029568    = 0.97086   Designed Life with 99% Reliability = (- ln 0.99) / 0.0000033754 = 0.01005033585 / 0.0000033754 = 2977.5 Hrs. Preventing Common- Mode Failures: To reduce Common- mode failures, we can feed U1 outputs in two different Ports and that too at different Input Pins . For example, if Pin 3 of U1 is fed to D0 of Port A, Pin 6 of U1 should be fed to D7 of Port B . Then we can match them through Software in Processor Card. See the Diagram of the connection in Fig 4 A Program for the same task is written below in 8085 Assembly language. START:          IN Port 1                     :   Read Drop Contact Data                        MOV D, A                  :    Save Data                        IN Port 2                     :    Read Pick-Up Contact Data MATCH:         PUSH D                     :    Save Drop Contact Data                        CMA                           :    Invert Pick-Up Contact Data                        MOV B, A                  :   Save Data                        MVI C, 00                  :   Initialize Register ‘C’                        LXI H, 0180                :   Initialize Registers : ‘H’ and ‘L’                        MVI E, 08                  :    Load Count (8) for the Loop Iterator LOOP  :         ANA H                        :    Mask Unconcerned Bits of the Pick-Up* Data                        JNZ ONE                    :    If Data Bit is Not 0, Go to Label ONE                         MOV A, L                   :    Transfer Data from Register ‘L’ to ‘A’.                         CMA                           :    Invert Data of Accumulator                         ANA C                        :    Mask Unconcerned Bits                         JMP ZERO                 :    Go To Label ZERO . ONE    :          MOV A, C                  :    Copy Contents of ‘C’ to Accumulator                       ORA L                        :    Make MSB ‘1’ and progress with other bits ZERO  :          MOV C, A                  :    Save the new value in Register C                      MOV A, H                  :    Load Bit Position Indicator in Accumulator                      ADD H                       :    Shift Left for Next Bit indicator                        MOV H, A                  :   Save the Bit Indicator Data.                                     MOV A, L                   :   Load Bit Position in Accumulator                            RRC                           ;    Go to Next Bit Position                        MOV L, A                :    Save Updated Bit Position Data                        MOV A, B                :    Read saved Pick-up* Contacts Data                        DCR E                    :    Check for completion of all 8 Bits           JNZ LOOP             :  Repeat Rearranging for all 8 Bits                         MOV A, C              :  Save Rearranged Pick-up* Data                         POP D                   :  Restore Saved Drop Contact Data                        RET                       :  Go back to Main Programme                        CMP D                   :   Compare Drop and Pick-up* Data                       JNZ FLT                 :   If not Matched, Go to Fault This Subroutine is Executed in 34.5 μs, considering that each State in 8085 generally takes 330 ns for execution .   Toggling of Input data to detect Opto Coupler Faults Instead of keeping the Emitter of Opto Coupler permanently Grounded, we feed ‘0’ from Processor through Port C of Programmable Peripheral Interface 8255, to the Emitters as showed in Fig 5.   After reading the input and analysing, we momentarily feed ‘1’ to the Emitters. Now, all the opto-couplers should be OFF. That means, Opto-coupler outputs should follow the Toggling input from the microprocessor. Now, we again feed ‘0’ from the Processor and analyse the Opto-coupler Outputs finally. We take inputs from Drop Contacts of 4 different relays along with the Output of U1 Pin 3 of their De-bounce circuits, via Port ‘A’ of 8255. Similarly, the pick-up Contacts of the same four Relays and Output from U1 Pin 6 are taken through Port ‘B’. For 16 relays, Interface to the Card, 4 numbers of 8255 ICs PPI 8255   1 are needed. The Programme for the Toggle Operation is given below:   MVI A, 92                 Programme Four PPIs (8255) having     OUT 03                           PORT A -- INPUT OUT 07                           PORT B -- INPUT OUT 0B                          PORT C -- OUTPUT OUT 0F                           LXI H, 1100               Starting Location to keep Drop Contacts Data SUB A                       Enable Opto Couplers in PPI 1 OUT 02 IN 00                         Read Drop contact Status from PPI 1 MOV M, A                 Save in Location 1100 IN 01                         Read Pick-up contact Status from PPI 1 CALL MATCH          Rearrange Bits and Match them. INX H                        Go to Next Location SUB A                       Enable Opto Couplers in PPI 2 OUT 06 IN 04                        Read Drop contact Status from PPI 2 MOV M, A                Save in Location 1101 IN 05                        Read Pick-up contact Status from PPI 2 CALL MATCH         Rearrange Bits and Match them. INX H                       Go to Next Location SUB A                      Enable Opto Couplers in PPI 3 OUT 0A IN 08                        Read Drop contact Status from PPI 3 MOV M, A                Save in Location 1102 IN 09                        Read Pick-up contact Status from PPI 3 CALL MATCH         Rearrange Bits and Match them. INX H                       Go to Next Location SUB A                      Enable Opto Couplers in PPI 4 OUT 0E IN 0C                        Read Drop contact Status from PPI 4 MOV M, A                Save in Location 1100 IN 0D                        Read Pick-up contact Status from PPI 4 CALL MATCH         Rearrange Bits and Match them.                            STA 1100                Bring Drop Contact Data from Location 1100 LXI H , 1200             Initialize Flag Location for First Relay of PPI 1 IN 00                       Read Drop contact Status from PPI 1        CPI 55                      Check if this Data is same as the Saved Data JZ PPI 2 CALL DELAY 1ms  Wait for 1 milli second MVI A, FF                 Disable Opto Couplers OUT 02 IN 00 CALL DELAY 1ms  Wait for 1 milli second CPI FF JNZ FLT                   If not, Go to Fault SUB A                      Again Enable Opto Couplers OUT 02 IN 00 CPI 55 CNZ PROCESS PPI 2    :             STA 1101                   Bring Drop Contact Data from Location 1101 LXI H , 1204                 Initialize Flag Location for First Relay of PPI 2 IN 04                           Read Drop contact Status from PPI 2 CPI AA JZ PPI 3 CALL DELAY 1ms     Wait for 1 milli second MVI A, FF                    Disable Opto Couplers OUT 06 IN 04                            Read Drop contact Status from PPI 2 CALL DELAY 1ms     Wait for 1 milli second CPI FF                        Check if Opto Couplers are Disabled JNZ FLT                      If not, Go to Fault SUB A                        Again Enable Opto Couplers OUT 06 IN 04                           Read Drop contact Status from PPI 2 CPI AA CNZ PROCESS PPI 3       :        STA 1102                   Bring Drop Contact Data from Location 1102 LXI H , 1208                Initialize Flag Location for First Relay of PPI 3 IN 08                          Read Drop contact Status from PPI 3 CPI 55                   JZ PPI 4 CALL DELAY 1ms   Wait for 1 milli second MVI A, FF OUT 0A IN 08                         Read Drop contact Status from PPI 3 CALL DELAY 1ms   Wait for 1 milli second CPI FF                      Check if Opto Couplers are Disabled JNZ FLT                   If not, Go to Fault SUB A                       Again Enable Opto Couplers OUT 0A IN 08                        Read Drop contact Status from PPI 2 CPI 55 CNZ PROCESS PPI 4    :             STA 1103                 Bring Drop Contact Data from Location 1104 LXI H , 120C              Initialize Flag Location for First Relay of PPI 4 IN 0C                        Read Drop contact Status from PPI 4 CPI AA   JZ NXT_CARD CALL DELAY 1ms  Wait for 1 milli second MVI A, FF                 Disable Opto Couplers OUT 0E IN 0C                         Read Drop contact Status from PPI 4 CALL DELAY 1ms  Wait for 1 milli second CPI FF                       Check if Opto Couplers are Disabled JNZ FLT                   If not, Go to Fault SUB A                       Again Enable Opto Couplers OUT 0E IN 0C                         Read Drop contact Status from PPI 4 CPI AA CNZ PROCESS   PROCESS   :    MOV B, A     MVI C, 04                MVI D, 40                              CHK             :     MOV B, A               ANA D               JNZ PICK-UP               MVI A, FF               MOV M, A PICK-UP       :  MOV A, D RLC MOV D, A ANA D JNZ FLT SUB A MOV  M, A INX H MOV A, D RLC MOV D, A DCR C JNZ CHK   dELAY 1 ms :   PUSH D BACK           :    LXI B , 0BB1                            DCX B JNZ BACK POP D RET  This Programme to check the Status of the Relays Interfaced in One Card takes about 9.64 ms . Thus to check all 16 Input Cards, a total time of 154 ms is needed. It covers up the Transition periods for QN1 Relays. Card AcCcess Whenever an Input Card is inserted into one of the I/O Slots, it gets the I/O Slot address , which is Hardwired in Back-plane . Processor Card sends Motherboard Slot addres s through the I/O Bus. When the two addresses match, the Comparator Output Pin gets low and a Decoder and Data Buffer are enabled. The arrangement is showed in Fig 6 .    The FMECA of this sub- circuit is given below. a) If Pin 19 of Comparator UA is s-a-1: The Decoder UD and Buffer UC will not be enabled. Processor cannot read ID andID* of Input Card. b) If pin 19 of Comparator UA is s-a-0: The fault will not be detected. c) If any Input Pin of P or Q Comparator of UA is s-a-0 / s-a-1 : Software data sent by Processor will not match with Hardware data from the Backplane. Failure is same as (a). d) If any Pull- up resistor for Backplane is Open: The corresponding Pin may float to either 0 or  1. Depending on that the Hardware and Software addresses may or may not match. e) If any Input Pin of Buffer UB is s-a-0 or s-a-1. Software data will be faulty and may or may not match with Hardware data. f) If Pin 19 of Bus Driver UC is s-a-1: UC will not be enabled. Card ID and ID* cannot be read. g) f) If Pin 19 of Bus Driver UC is s-a-0 : UC will be permanently enabled and the fault will remain undetected while accessing the Card. h) If Pin 1of Bus Driver UC is s-a-1 : UC will not allow reading Card ID and ID*. i) if any Data Pin of Bus Driver UC is s-a-0 or s-a-1 : Processor will get wrong ID and ID*. j) If Pins 1 and 19 of Buffers UE or UF are s-a-1 : Processor will not get ID or ID* depending on whether UE or UF has got the fault. j) If Pins 1 and 19 of Buffers UE or UF are s-a-0 : UE or UF will be permanently enabled . There will be Bus contention while reading ID and ID*.    

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Somnath Pal -
Posted 321 days Ago

QUANTIFIED RAMS BASED RAILWAY ASSET MANAGEMENT

Rail Asset

  Railway Asset Management provides Sustainable Infrastructures through evidence-based decision making to achieve the optimum performance with Economic benefit while ensuring Safety and Integrity. It covers defining Asset Management Policy, Strategy and Framework. Key factors to consider are the physical deterioration, obsolescence, operation and maintenance of the system. Corrective Actions are based on management Data Reviews. Asset Managers must perform Risk Analysis and Predictive Analysis for Maintenance planning. In addition, a Qualitative Vulnerability Analysis and Managerial Oversight Risk Analysis should be performed to evaluate System Safety Robustness.  After defining the System Reliability, Reliability Allocation to sub-systems are fixed and various Design and Manufacture criterions are followed with trade-off between Performance and Service life-cycle Cost. Failure probabilities are calculated after Mitigation of critical Failure Modes. Cost models on maintenance optimization can be based on Markov model with Inspection and Replacement policy. Incentive on improved Reliability and Supply of specific Reliability Data for the Equipment must be implied in Supply Contract, considering other performance aspects.  Acceptance Testing should comply with Reliability Targets and specify Accelerated Stress Test Duration, including Burn-in periods, if any. Maximum Likelihood Estimation for Failure is calculated before Asset acceptance. While increasing Reliability, Preventive Maintenance reduces Availability and might introduce new failures. So, Predictive Maintenance using Diagnostics and Prognostics is a better Option. Comparisons between Repair and Renewal are chosen to maximize Availability. MTTR must comply with 95% Confidence that Repairs are performed within defined duration. Optimum Inspection Interval must be calculated from Failure Rates, Inspection duration and Repair time. Adequacy of Spare Parts and Location of Stores, whether Centralized or Distributed, are to be specified after calculations to provide maximum Availability.  Reliability Growth testing must be done to verify stipulated MTTF. To avoid any lapse during On-site Maintenance Activities due to Human Errors, specific Checklists, Maintenance Tools and, Drawings must be available. Proper updated Training is mandatory for the Concerned men-at-site. Cloud-based Intelligent Safety Asset Management can implement Expert Systems, Video Conferencing with Experts during emergency and Video Surveillance of Construction Sites. Finally, Asset Management Audits check whether the specified strategies are being followed.

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Suman Pathak -
Posted 93 days Ago

POWER QUALITY ISSUES IN RAILWAY ELECTRIFICATION

Rail Electrification

  POWER QUALITY ISSUES IN RAILWAY ELECTRIFICATION The power quality issues through electric railway development are overviewed as follows :    Voltage Unbalance Voltage imbalance (also called voltage unbalance) is defined as the maximum deviation from the average of the three-phase voltages or currents, divided by the average of the three-phase voltages or currents, expressed in percent. The most frequent problems of voltages are associated with their magnitudes. The major problem is unbalanced currents produce unbalanced voltages. Traction motors and other related loads in trains are designed to function properly with reduced voltage amplitude by 24% or increased amplitudes by 10% than the nominal voltage of electric railroad drives. System imbalance System imbalance is the most serious problem in electric railway power quality because most trains are single phase, and a single-phase load produces a current NSC (Negative Sequence Current) as much as a PSC (Positive Sequence Current). A new traction power supply system adopting a single-phase traction transformer and active power flow controller (PFC) is proposed. In the new system, the power quality problems caused by single-phase traction load are solved on the grid side and the continuous power can be Arcing The interaction between the pantograph/catenary of overhead systems or between brushes and the third or fourth rail causes arcs because of dynamic latitudinal tolerance between the wheels and rail. Arcs will occur, which can distort voltages and currents and produce a transient dc component in the ac systems causing a breakdown of dielectrics. Flicker As the train passes between two adjacent substations voltage sag may happen and affect other customers electrical light performance so-called flicker. EMI/EMC The movement of rolling stock along an electrified track produces Electromagnetic interference in the system. EMC covers a wide range of phenomena, including inductive noise in parallel communication lines, impulse noise from lightning and traction transients, the production of hazardous voltage under step and touch conditions, and the appearance of stray currents. EMI and EMC are very complicated for high-speed railway systems. Nowadays, the investigation in EMI/EMC high-speed railway is highly relying on simulation and measurement. Waveform Distortion Waveform distortion is defined as a steady-state deviation from an ideal sine wave of power frequency. There are five primary types of waveform distortion :  1. DC offset     The presence of a dc voltage or current in an ac power system is termed dc offset  2. Notching    Notching is a periodic voltage disturbance caused by the normal operation of power electronic   devices when current is commutated from one phase to another.    3. Noise    Noise is the unwanted electrical signal with broadband spectral content lower than 200 kHz  superimposed upon the power system voltage or current in phase conductors, or found on neutral  conductors or signal lines.   4. Interharmonics  Voltages or currents having frequency components that are not integer multiples of the frequency  at which the supply system is designed to operate (e.g., 50 or 60 Hz) are called inter harmonics.   5. Harmonics Harmonics can be best described as the shape or characteristics of a voltage or current waveform relative to its fundamental frequency. The ideal power source for all power systems is smooth sinusoidal waves. These perfect sinewaves do not contain harmonics. When waveforms deviate from a sinewave shape, they contain harmonics. These current harmonics distort the voltage waveform and create distortion in the power system which can cause many problems. In short (Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate.) Types of Harmonics: Odd and Even Order Harmonics: As their names suggest, odd harmonics have odd numbers (e.g., 3, 5, 7, 9, 11) , and even harmonics have even numbers (e.g., 2, 4, 6, 8, 10) . Harmonic number 1 is assigned to the fundamental frequency component of the periodic wave. Harmonic number 0 represents the constant or DC component of the waveform. The DC component is the net difference between the positive and negative halves of one complete waveform cycle. Total Harmonic Distortion (THD) is defined as the measurement of the harmonic distortion present in a waveform. The power quality of a power system is inversely proportional to THD. More harmonic distortion in the system, lower will be the power quality and vice versa. THD is equal to the ratio of the RMS harmonic content to the fundamental:   Where Vn-rms is the RMS voltage of nth harmonic in the signal and Vfund-rms is the RMS voltage of the fundamental frequency. The Destructive Effects of Harmonic Distortion A power system’s ability to perform at optimal levels is compromised when harmonic distortion enters the system. It creates inefficiencies in equipment operations due to the increased need for power consumption. The increase of overall current required creates higher installation and utility costs, heating, and decreasing profitability. Harmonics in Electrified Railways It is well known that the rapid spread of power electronics brought along not only great advantages but also some drawbacks as they are the main sources of harmonics and voltage waveform distortion. Harmonic has emerged as a matter of great interest for electrical power system engineering. The electrified railway is one of the main harmonic sources in utility. Because electrified railway is supplied by High Voltage (HV) power system directly, lots of harmonic (mainly including 3rd, 5th, and 7th) produced by electric locomotive penetrate in the whole utility from HV. Compared with normal load, the most characteristics of traction are random time-varying and non-symmetry. So, the harmonic of traction load is very different from the normal load of utility. In an electrified railroad, the traction power is delivered to the catenary by substations, which in turn receive their supply from the utility network. For the electric utility transmission systems, the alternating current catenary is an unfavorable consumer.  Two major reasons for this are: i)    the catenary is a single-phase load, which power consumption unbalances the main supply three-phase system, ii)   the use of power electronics converters to drive traction motors, generates harmonic currents that perturb interconnection busbar voltage. Basically, the power quality issues in railway electrification systems include the studies of the influence of traction loads on three-phase utility systems. Most of the high-speed trains are single-phase loads. Due to a large amount of power electronics application to the motor driving circuits of trains, they contribute to the high harmonic currents flowing to the railway catenary system.  Traction load is varying dynamically, and arcs may occur because of pantograph/catenary and switching actions. Modern drive trains rely on power electronic converters combined with transformers, which inject low amounts of current harmonics into the supply system. Therefore, power quality must be considered in all aspects of the design for every system dealing with electric power systems. Some especially connected transformers are widely used, such as V-V, Scott, Le Blanc, and Modified Woodbridge connection schemes have been utilized in traction substations to compensate for negative sequence current (NSC) of the grid-side. Due to the nature of time-varying traction loads, it is almost impossible to compensate the whole NSC in all loading conditions.  Passive filters have been adapted to suppress harmonics in electrical railway systems. Among derivations of filters, a C-type filter (CTF) introduces no power loss at the fundamental. frequency and performs as a first-order high-pass filter at tuned resonance frequency. Accordingly, the CTF is generally used to mitigate high-order harmonics caused by the PWM converters of the traction trains and prevent harmonic resonance. Although passive devices are affordable with a simple configuration, their performance is not satisfactory when operational conditions are varying. Therefore, active devices in AC electric railways have been proposed to resolve this issue. Static VAR compensators (SVC ) and static synchronous compensators (STATCOM) were proposed to compensate the load reactive power of trains dynamically. Since electric locomotives introduce harmonic contents, there is no chance to compensate harmonics by these devices, concurrently.  Many other strategies have been also proposed for power quality improvement in electric railways, investigated in a comprehensive historical perspective. Nowadays, power quality improvement strategies have developed to a mature degree for new electric railway systems, among which Railway static Power Conditioners (RPC) and its alternatives (e. g. APQC, HBRPC, HPQC) have the main place.  These compensation schemes are connected to the TSS secondary, as shown in Fig. , and theoretically operate based on instantaneous active/reactive power theory, in which the three-phase currents at the TSS primary side are supposed to be:  (i)    three-phase symmetrical, (ii)    fully sinusoidal with no relevant harmonic content (iii)    aligned with the three-phase voltage featuring negligible reactive power.  Thereafter, the difference between the load currents and the ideal currents must be generated by the compensator, called compensation currents. The compensator operates as an independent three-phase current source, generating the desired compensation currents. The RPC consists of two single-phase back-to-back converters sharing the same DC-link capacitor through which active and reactive power are applied compensates voltage, NSC, total harmonic distortions (THD), and PF simultaneously and each AC side of inverters are connected to the two phases of the secondary side of feeding transformer, main phase, and teaser, respectively. These inverters work as effective power balancers and reactive power compensators. For example, if a load of the main phase is larger than that of the teaser, the RPC transfers effective power from the teaser bus to the main phase bus. This system works to balance the effective power of different phases and compensate for reactive power to reduce voltage unbalance and fluctuation. The various structures of the RPC such as active power quality conditioner (APQC), half-bridge RPC (HBRPC) and Hybrid power quality conditioner (HPQC) were presented. These devices can perform at a full compensating method which results in grid-side power factor unity, zero current unbalance, and harmonics.   DIFFERENT COMPENSATORS USED IN SCOTT CO-PHASE SYSTEM  Hazards of Poor Power Quality Problems in Railways Impacts on Signaling and Communications: Track circuits are designed to work with a special frequency that must not have any interference with the power frequency. But in presence of harmonics, communication signals may be affected by harmonic frequencies, resulting in erroneous signals and faulty train positioning, which lead to a disaster. Also, high-order harmonics may cause an interference problem between communication and power systems. Malfunction of the protective system: Protection relays may operate incorrectly in the presence of harmonics and NSCs of currents and voltages. Traction load injects many harmonics and NSCs resulting in the malfunction of the protective system. Decreased Utilization Factor: Since the traction load is a large single-phase load, it results in high current NSCs, which will flow in only two phases, and it decreases the utilization factor of the transmission line. Incorrect Operation of Transmission Line Control Systems: Voltages and currents sampling is based on fundamental components of either voltage or current. Every control system in the transmission line would work not appropriately because traction loads inject large amounts of harmonics and NSC current into the transmission lines.     References: " IEEE Paper 10.1109/TIE.2014.2386794”, IEEE Paper 10.1109/TVT.2017.2661820, IEEE Std 519-1992    

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Kathy Shen -
Posted 41 days Ago

Pantograph CCTV Intelligent Analysis System for rolling stock

Communication Systems

  1. Overview By the arrangement of the Ministry of Machinery and Vehicles of the National Railway Group on the intelligent analysis of the pantograph video monitoring system, the existing pantograph video monitoring system intelligently analyses the installation requirements, identifies pantograph mechanical structure abnormalities, electrical faults, and other problems, and assists mechanics in judging pantograph faults. Through the analysis of the failure mode of the existing vehicle and the vehicle protection logic, mainly for pantograph failures that cannot be detected by the car itself, such as pantograph tilt, pantograph structure deformation, etc. Such failures are not easily identified during operation and lead to more severe consequences. The intelligent analysis function of the pantograph video monitoring system can analyze the pantograph video monitoring images, identify pantograph faults and make alarm prompts to assist the mechanic in judging and taking effective measures to avoid more significant hazards. 2. Pantograph CCTV System composition The pantograph CCTV system is used to monitor the operational status of the pantographs and contact network on the roof of the train in real-time during operation. The intelligent analysis function adds intelligent identification technology to the original video monitoring system to achieve automatic real-time identification of abnormal pantograph conditions. Save videos of the working state of the pantographs during train operation and pictures of structural abnormalities in the pantographs to provide supplementary surveillance videos and analysis images for the accompanying mechanics to deal with abnormal bow network faults. The intelligent analysis function of the pantograph CCTV system for rolling stock consists of the following main components: pantograph video monitoring server, intelligent analysis host, pantograph camera, and monitoring screen. 3. Application conditions of the intelligent analysis function of the pantograph CCTV system   The intelligent analysis function of the pantograph video monitoring system mainly identifies pantograph faults during vehicle operation. For significant pantograph faults, such as ruptured ducts and dislodged carbon skids, the pantograph will be automatically lowered without further judgment and operation by the mechanic. This intelligent analysis function alerts for bow abnormalities that are not easily detected directly, such as pantograph tilting and pantograph structural deformation, with priority given to identifying bow structural abnormalities as they have the most severe impact. Combined with the technical item analysis of pantograph faults in the high voltage system of the rolling stock, the application items for which the intelligent analysis function of the pantograph video monitoring system assists the mechanic in making judgments were identified as follows. 1. The pantograph is tilted during operation. At this time, the pantograph duct does not break and will not automatically lower the bow. If no alarm is provided, the tilted pantograph may be pulled by the contact network or knocked out by other foreign objects, causing severe secondary damage, so fault identification and alarm are required under this working condition. 2. Structural deformation occurs during the pantograph operation; the types of structural deformation include missing bow angles and bending deformation of the bow structure, etc., when the duct is not broken. Alarm failure may result in problems such as drilling bows, so fault identification and alarming are required for this condition. 3. Foreign objects caught in the pantograph during operation. Identification and alarm for foreign objects hanging on the bow structure and identification and notice for foreign objects on the support frame. 4. When large sparks are generated during pantograph operation, and the sparks occur in the working area, intelligent analysis functions are required to effectively identify the large sparks and provide alarms to avoid secondary accidents. Tiny sparks generated during operation are not identified, and alarm for the time being because they are not a significant hazard. 5. There is a small amount of dirt in the pantograph CCTV system camera, with a small portion at the bow structure captured by the camera when the intelligent analysis is required to allow for chunking and identification without interference from foreign objects. 4. Pantograph structure anomaly identification 4.1 Pantograph structure deformation alarm There is a small amount of dirt in the pantograph CCTV system camera, with a small portion at the bow structure captured by the camera when the intelligent analysis is required to allow for chunking and identification without interference from foreign objects.                                                           Picture of pantograph in normal condition After running for some time, the vehicle pantograph is subjected to structural deformation by foreign object impact; it is necessary to effectively identify this type of fault and alarm through the pantograph video monitoring system; the identification picture is shown below.                                                         Pantograph structure failure picture 4.2 Pantograph tilt alarm Pantograph tilt faults can occur during operation and need to be brought to the mechanic's attention in time for judgment and action. However, the structure of the pantograph and the position of the pantograph camera installed on different models are different, so the decision of the tilt angle of the pantograph is different. Combined with the relevant video of the pantograph tilt, the tilt angle of the alarm needs to be given.                                                 Intelligent identification of pantograph tilt angle pictures 4.3 Pantograph angle break alarm There are two scenarios for pantograph angle breakage, one in which the angle is broken and suspended but not dislodged, and one in which the angle is broken and dislodged. Both scenarios require testing the bow integrity and sending an alarm signal to the monitoring screen when the pantograph form is incomplete. The difference lies in the trade-off threshold settings needed in both cases to reduce the rate of missed alarms. It also needs to be combined with video testing to define that an image above 40 frames in 3 seconds is a fault that will send an alarm condition.                                                            Pictures of the pantograph lowering process   (1)Bow horn fracture not detached The situation is as shown in the diagram below when the pantograph angle is broken and not dislodged from the fault.                                             Picture of pantograph with broken bow angle not dislodged Intelligent analysis of such situations requires correct identification of faults and alarms and actual testing of breakage without dislodging video detection. (2)Bow angle completely broken This type of pantograph fault needs to be identified when a complete break in the pantograph arch angle occurs, as follows.                                             Intelligent identification of complete pantograph angle breakage Intelligent analysis of such situations requires correct identification of faults and alarms and actual testing of breakage without dislodging video detection.   4.4 Pantograph foreign object intrusion alarm False alarms caused by various factors are considered when the pantograph intelligent analysis mainframe identifies foreign object intrusion faults in the pantograph. Analysis from the intrusion results currently only identifies foreign object intrusion faults hanging from the bow for a long time. (1)Pantograph body For the intrusion of foreign objects into the bow of the pantograph, it is necessary to identify whether there is a foreign object intrusion, as shown in the diagram below, which requires the apparent detection of a foreign object in a plastic bag hanging from the pantograph of the “Fuxing” D1702.                        Intelligent identification of foreign objects hanging from the pantograph body 4.5 Pantograph spark alarm Currently, tiny pantograph sparks are not analyzed for identification due to their minor impact on vehicle safety. Pantograph intelligent analysis of pantograph sparks identifies only significant spark faults (Spark area > half of the pantograph head area; this indicator can be modified for configuration). The spark is judged to be in the working area of the carbon skid (x1 to x2, as shown in the picture below) to avoid false alarms. The large pantograph sparks intelligent identification alarm result is shown in the following picture of the large spark intelligent identification alarm.                                Image of the coordinates of the area where the spark occurred                                  Pantograph large spark intelligent identification alarm result picture 5.Intelligent pantograph fault recognition and alarm for particular operating conditions In opening the intelligent analysis function of the pantograph video monitoring system, special working conditions can have a significant impact on the intelligent analysis function, resulting in missed and false alarms. The following special conditions are required. 5.1 Tunnel mode alarm During the process of entering and exiting the tunnel and running in the tunnel, the camera's exposure and the influence of the environment in the tunnel will affect the intelligent analysis function, as follows. When entering and leaving the tunnel, algorithms need to be designed to recognize the tunnel entry and exit patterns and filter out false exposure alarms for the entry and exit tunnel entrance process. The diagram below shows that the exposure images need to be filtered out, and no warnings are made.                                                 Instant exposure picture of entering the tunnel In the tunnel, it is necessary to identify whether the current environment is suitable for detection, i.e., whether the pantograph video monitoring screen is blurred or not. If the screen is blurred due to insufficient fill light intensity or fill light failure, then the intelligent identification detection function is switched off. If it is not confusing, then detection is activated, as shown in the picture of the system generally operating in the tunnel. In addition, false alarm scenarios caused by reflections from fill lights are recommended to be included in the category of unsuitable detection, with the alarm function turned off, as shown in the picture of the bow blur caused by reflections from fill lights in the tunnel.                                                 Pictures of the system in operation in the tunnel                                          Image of bow blur caused by reflections from fill light in the tunnel 5.2 Background mode alarm (1)Background factors such as bridges, power supply equipment Interference caused by background factors such as bridges, power supply equipment, etc., are a few frames that will occasionally be detected as anomalies during intelligent analysis. The alarm will be triggered when there is an anomaly greater than a certain number of frames so that false images can be effectively filtered out. The specific algorithm needs to be set up in conjunction with the vehicle's speed, the time consumed by the car to pass background objects at different rates (i.e., the number of frames) is counted, and the thresholds are optimized to exclude such interference ultimately. For example, by analyzing the background railings shown below, it was found that the train took up a total of about 4 frames as it passed through the above background facilities. The pantograph detection result is normal after 4 frames, so set that for this type of railing background. It is possible to set more than 20 frames in 1 second for normal recognition without alarm.                                                          Background pattern interference picture (2)Background factors for train stops For train stops, the speed threshold needs to be set to 0, i.e., the intelligent identification function is switched off when the speed is 0. The pantograph video monitoring picture of the train stop is shown below. The image on the left shows background interference, which will give rise to false alarms. In the picture on the right, if the pantograph stops on the railing behind the image after the train has ceased to produce an overlap, false alarms will occur, so setting the speed to 0 when the intelligent analysis function is switched off will filter out such interference.                                             Video surveillance images of pantographs at train stops (3)Train entry contextual factors During the train's progress, the intelligent analysis function can be affected by false alarms due to changes in the background of the station. Due to the low-speed state, pantograph abnormalities have less impact on vehicle operation safety, and the low-speed state is less likely to cause abnormal pantograph structure problems. A certain speed threshold must be set to shield the station from false interference alarms. The pantograph video monitoring intelligent analysis function is switched off below a specific operating speed. According to the vehicle in and out of the station speed limit, tentatively set lower than 40 km / h, the speed threshold can be adjusted according to the application of the analysis to minimize the occurrence of false alarm problems. 5.3 Dirty mode alarm The dirty mode affects the clarity of the pantograph CCTV system camera and thus the alarm of the intelligent identification function. Intelligent analysis can be switched off directly to reduce false alarms for dirty stains with a significant impact, such as sand, dust, heavy rain, or snow. For less impactful dirt, such as small smear spots, false alarms need to be reduced. The judgment of the influence of dirt can be realized by identifying whether the video picture is blurred.                                                     Pantograph video image clarity comparison image The amount of dirty intrusion needs to be identified for judgment. For example, as shown in the diagram below, if you set the intelligent analysis to turn off when the rainwater intrusion exceeds 30%. The graph below does not identify the pantograph as a whole, i.e., rainwater soiling encroaches on the pantograph area by more than 30%. The rain is judged to be too heavy, and the intelligent analysis is switched off. If the rainwater dirt encroaching on the pantograph area is less than a certain threshold, the intelligent identification function is not switched off.                                      Pantograph video surveillance images under heavy rain conditions For cases where the soiling is minor, the video image is identified as edge soiled, and the overall structure of the bow is not affected; therefore, no alarm is made, as shown below.                                        Pictures of pantograph video surveillance affected by dirty edges For more minor dirty cases, the dirty area of the lens is primarily fixed.   6.Client   when the intelligent analysis function detects an abnormality in the pantograph, an alarm box pops up directly on the interface of the pantograph video monitoring screen, which contains the type of pantograph fault and the fault picture. At the same time, you can click on the "Associated Video" button in the alarm box to call and play the 2-minute video where the fault picture is located (1min before and 1min after the fault alarm picture), as shown in the figure below.                                            Pantograph monitoring screen fault video alarm picture    

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Calvin Barrows -
Posted 138 days Ago

METRO In-tunnel Overheating: Problem defined… Solution proposed…

Civil

Authors: Calvin R Barrows, BSc (Hons), CEng, MICE & Sylvia J Telatycka, BA (Hons) 1.  Big Picture Findings Metro Railways, which are mixed underground/overground networks like London’s Tube, gain more heat on the surface in the summer – the source of which, rationally, can only be attributed to the sun [1] . Such mixed underground/overground networks are “open systems”, and subject to the Laws of Thermodynamics [2] . These points are absolutely fundamental to understanding all that follows and are easily verifiable. 2.  The Macro Evidence [3] Underground-only trains/networks (c.f. Glasgow, Prague and Warsaw Metros) DO NOT overheat due to operational heat, nor due to the sun, as they remain below ground. (However, it should be noted that underground only lines in a generally mixed over/underground network do NOT share the same benefits because of the Laws of Thermodynamics – but see further below!) Overground-only trains/networks (c.f. urban and intercity networks) are clearly affected by ambient surface temperatures, requiring heating in colder seasons and air conditioning [AC] when the weather becomes hotter. Such networks are not affected by operational heat loads because these are readily disbursed to atmosphere, including the heat generated and disbursed outwards by controlling summer temperatures in the saloons.  A summer cooling solution (e.g. AC) is required for passenger comfort but the failure of AC in this context potentially exposes passengers and staff to very serious health, safety and welfare risks, as past incidents have graphically shown [4] . As identified under 1., mixed underground/overground networks DO NOT share any of the above advantages because of the Laws of Thermodynamics! Overheating is seasonal: LU’s own data confirm this [5] [6] . Even Metro train carriages require heating in winter. Passengers confirm these symptoms through their seasonal choice of clothing. “Operational” heat sources, (which LU/TfL are now describing as “base load”), like braking, traction, auxiliary systems (station and tunnel), etc are year-round sources of heat load, so cannot be implicated in a seasonal problem [7] . In the earliest days of networks like London’s Tube overheating was not a problem.  It was only later, when such networks were extended overground and on into the suburbs (defined above as “mixed underground/overground networks”), that over time the increasing underground heat load was flagged up as a concern that would become a danger if not addressed.  On the London Tube in a stalled train event below ground during the hotter months, with saloon temperatures reaching 40°C+, forced ventilation (by piston effect) is absent causing passengers and staff to be exposed to unacceptable risks [8] . The effects and consequences of solar irradiation from the sun on the surface was already recognised and addressed back in the mid-1970s by Parsons Brinckerhoff [PB], in their seminal subway design handbooks and associated software [9] [10] .  [For easy reading the reference made here is to Volume 1 in its Second Edition, since in the First Edition copy that we located, published in 1975, the print is very faint and hard to read.  However, we have verified that in the relevant pages quoted, there is no difference in the actual text between the First and Second Editions.] Despite becoming the go-to resource for tunnel design, nevertheless over the last 40+ years successive rail engineers have failed to explore these heat transfer mechanisms.  By 1993 the New York Subway had air-conditioned 99% of its cars but in 2021 they still suffer from summer overheating below ground – evidencing that AC in a mixed underground/overground network environment is hardly the way forward [11] . Progress resolving this problem has been negligible and today’s generation of engineers, including LU as network operators of London’s Tube, other consultants, academics, and even PB themselves, are still narrowly focussed on “operational” heat load and especially the “brakes”.  Astonishingly, however, they have overlooked any significant operational contribution from traction, and no one seems to agree on which and to what extent all these sources are culpable [12] .  Unfortunately, through unrelenting repetition, these (erroneous) views have become widely accepted, stifling any creative, investigative efforts or constructive debate by others.  Undoubtedly, this is not a successful way to resolve such a seemingly challenging problem. 3.  Understanding the Cyclical Heat Transfer Mechanisms The sun irradiates everything exposed to it on the surface [13] , comprising: - The entire external fabric of the train, including the undercarriage; plus The entire rail track and ballast, which in turn…. Re-irradiates and convects to the undercarriage of the entire train. This summer heat from the overheated trains is dissipated into the tunnel via thermodynamic action [14] . The more specific discussions about this process and potential impact were elaborated on by PB in consultation and collaboration with the US rail industry leaders [15] [16] [17] [18] in their afore-mentioned design handbooks.  New York Subway and other US rail networks were experiencing similar problems to those of London’s Tube and when many networks in the USA were surveyed, the Southeastern Pennsylvania Transportation Authority [SEPTA] reported very explicitly that the cars on the Market Street Line were absorbing solar heat whilst above ground and bringing this heat into the subway [19] .  However, this key finding appears to have been “lost” over time and, whilst all the LU/TfL’s cooling team, their consultants and academic advisers appear to have subconsciously recognised the seasonal nature of the problem and most of the press reports have also alluded to it, no one seems to have asked the questions: “why should this be?” and “what is the mechanism that is causing it?”  Seasonal symptoms can only result from seasonal causes! 4.  The Metro Overheating Consequences The cumulative consequences of increasing tunnel heat load as summarised below is illustrated by reference to a useful infographic (Appendix H below) that clarifies the consequential outcome of solar irradiation in mixed underground/overground networks [20] . The carriages heated by the sun leave the surface sections and enter the underground tunnel section of the network. Like storage radiators they re-irradiate and convect their heat into the tunnel environment. As each individual train service begins its run along the overground and underground sections of the network and then back to its starting point, the heat load of the carriages increases cumulatively throughout the day with each new loop. As the hotter summer months progress, the heat load within the underground part of the network, carried in from the surface, also increases day on day throughout the season – until external ambient temperatures start to moderate in the autumn. 5.  The Remedial Proposals [21] There is still a prevailing and mistaken assumption in the industry that AC is a viable solution for London’s Tube.  However, AC is NOT an option in mixed underground/overground networks since its hot discharge cannot be satisfactorily vented to free air, so that this heated air is added to the overall, in-tunnel heat load [22] . Viable remedial solutions could include the following:- Solar-reflective paint, which these days can reflect up to 98% of solar irradiation (carriages, undercarriages, and non-wearing surfaces of the rails) [23] . Solar-reflective glass, which these days can already restrict about 70% of the sun’s heat passing through the train windows into the saloons [24] . Solar barriers on the undercarriage. This could be a specially designed, robust reflective paint for surfaces where oxidation of the metal may be an issue, or the chosen base material could have low oxidation properties.  “Therma-Light” manufactured by Blocksil may be an option.  It is an aerogel product in an acrylic solution.  Because aerogels disperse heat quickly, the heat cannot penetrate the surface, so keeping everything at a constant temperature.  For example, if you have a surface temperature of 170°C, with the application of 2mm of the aerogel product the reverse side will stay at a constant 39°C.  Blocksil have confirmed that reduced surface temperatures deliver pro-rata benefits [25] . Reduction of absorbed heat in the track environment could be achieved by green planting (e.g. sedum) as a protective screen for traditional ballast and sleepers [26] . It has become clear that the only effective, straightforward solutions are those that mitigate the ever-increasing heat load absorbed by the trains on the surface, and which at present is carried into the tunnel sections of the network.  These various EXISTING technologies could be readily “retro” applied and should certainly be specified at the point of manufacture going forward. 6.  Environmental / Climate Change Benefits of Remedial Proposals Network Rail’s Chief Track and Lineside Engineer, John Edgley, reporting to the House of Commons Adaptation [to Climate Change] Sub-Committee, which was examining how climate extremes affect public transport, noted service breakdown events were expected to increase four to five times by the 2050s with a predicted eight-fold increase in related costs by the 2080s [27] .  TfL’s Policy Manager for Environment, Sam Longman, also expressed the concerns in relation to London Underground, around the effect of excessive heat on equipment causing failures and delays to services, which could lead to people being trapped in tunnels, and their consequential overheating [28] . The public have been conditioned by LU/TfL and the industry’s erroneous PR regarding the causes of in-tunnel heat load and so there is increased public demand for AC, but no one troubles to explain publicly that AC will exacerbate the in-tunnel, heat load problem, not to mention it would negatively affect climate change [29] .  Despite LU/TfL’s statements to Parliament regarding AC in para 109 [30] , AC has now been mooted by LU for new rolling stock on some lines – in complete contradiction to their previous stance and that of others regarding the negative outcomes for heat load in the tunnelled sections of the network [31] . LU/TfL continue seeking to resolve the relatively small problem of reducing operational heat, including significant investment in the futile, flawed Bunhill heat recovery project, which cannot deliver the advertised solution, since in wintertime when heat is needed, there is no surplus heat in the tube tunnels available to be exported commercially to provide the heating for above ground spaces [32] [33] . It is an absurdity that LU/TfL are totally resistant to climate being implicated in the historic and present tunnel overheating problem, whilst at the same time being cognisant of the longer-term climate change consequences – at least to the extent it could affect their short-term bottom line.  In the present time, they continue to address the symptoms that will give negligible positive results and significant detrimental climate change implications, instead of addressing the major cause and seeking to implement the readily available, one-time, preventative solutions. We have mentioned some specific solutions for London’s Tube – solar-reflective paint [34] , perhaps combined with flexible “peel and stick” solar panels [35] on train roofs.  Since Cooling the Tube’s inception, our fellow Europeans have not been idle, building a railway tunnel topped and walled with solar panels, both delivering power to run trains, whilst also providing protective overground shading for trains [36] . There are myriad innovative and climate-friendly options available, which would not only mitigate the Tube’s “immediate” heat load problem but can also deliver major long-term economic benefits.  It should not be so difficult to engage in fruitful (truly open-minded) dialogue to answer these questions accurately:- WHAT the prime cause of elevated in-tunnel heat load? WHETHER it is indeed “base load” increase, or WHETHER (OR NOT) the action of the sun on the surface part of the line could be the principal cause of this challenge [37] [38] ). This work should NOT be about professional egos and fear of “losing face”, nor indeed about blame or scapegoating.  Such concerns are reprehensible.  It is more about the importance of “black box thinking” – collaboration, a willingness to seek an understanding of what causal evidence the symptoms are revealing, and to define the problem properly, to constantly RE-EVALUATE as necessary, which in turn will uncover potentially sound and innovative solutions. Regardless of who originally said it, the following point is very valid and sadly is certainly applicable in this context of “Cooling the Tube” . "Insanity is doing the same thing over and over again and expecting different results" [39] . Appendix A LU-average-monthly evening peak temperatures by line (Jan 2013 to Dec 2020) A graphical representation of LU-average-monthly evening peak temperatures by line (Jan 2013 to Dec 2020) Appendix B Why will Air Conditioning not work in the Deep Tube? The answer to this question is one that we have arrived at over time, developing the theory through several short papers, examining different elements of the high heat load in metro networks like London’s Tube to identify the root cause(s). We believe the hitherto, generally accepted proposition within London Underground [LU]/Transport for London [TfL] of air conditioning in the underground being unviable is still the case.  LU’s expressed intention to bring air conditioning into use for the new Deep Tube lines is an act of desperation and ignores everything that could help them resolve this seemingly intractable heat load issue – including the laws of physics. Thinking all this through brought to light for us several questions:- What is the problem? (Ever increasing tunnel heat load); When does it occur? (Seasonally in the hot weather); Where does it arise? (On the surface prior to entering the underground sections); Why (aka how) does it occur? (Thermodynamics)! Our first paper Cooling the Tube still on ice [40] covered most of these questions but subsequent papers went on to develop these themes, especially in the light of seeming wilful blindness on the part of LU/TfL and their various consultants and academic advisers. Regarding the first question, LU/TfL have focused on analysing the heat IN the tunnels, brakes, passengers/stations, mechanical losses, tunnel systems, drive losses, etc etc.  These are OPERATIONAL heat sources, that are produced YEAR-ROUND – LU’s “engineers” are now describing as “base load”.  All this has led them down a blind alley.  See Pie Chart and associated text referred to in the link in Endnote 1. The second question of when? is explained by LU’s own data gathering [41] , which unequivocally confirms that the problem is SEASONAL – the tube gets progressively hotter as the outside temperature warms up.  It does not overheat in winter, as can also be seen by passengers’ winter clothing and the fact that train saloons are heated. This connects to the third question of where it arises?  London’s Tube is a mixed over overground and underground NETWORK, unlike (e.g.) Glasgow’s, Warsaw’s and Prague’s, which are entirely UNDERGROUND and do not overheat.  This leads to the inevitable conclusion that the heat from the SUN must have something to do with this overheating – see infographic and associated text referred to in the link in Endnote 1.  It is instructive to note from David Attenborough’s “Perfect Planet” series, episode 2 where at minute 38, Attenborough reminds us: “The solar energy that strikes our planet in just an hour contains more power than that used by all of humanity in an entire year! ” [42] On the fourth question of how? – if every part of the surface of the track, and every part of the train saloons is being irradiated by the sun, including the undercarriage which is re-irradiated by the track bed, then when a train enters the underground section of the network, that heat load is re-radiated into the tunnels, attempting to reach equilibrium.  This is where the Laws of Thermodynamics come in – see again the infographic and associated text referred to in Endnote 1 and in more detail in our paper: A Reflective Perspective: The Whys and Wherefores of Metro Overheating [43] pp2-3.  The overheating cycle is cumulatively repeated by every train for every “round trip” journey throughout the day and so the tunnel heat load increases….. So, why does installing AC on the metro train not work for combined over/underground Metro Networks? Once one has got one’s head around the thermodynamics of mixed networks like London’s, it is not too great a leap to understand why the use of air conditioning in this context will not only fail to achieve its objective, but it will also simply add to the overall tunnel heat load. As with all air conditioning systems the principle remains the same, whereby the heat is removed from one area and replaced with chilled dry air, and the hot air is expelled, normally to the outside atmosphere via an outside unit.  In the outside air conditioning unit, the ambient air is drawn over the condenser that can best described as a ‘radiator’ as seen on motor vehicles but instead of water running through the system it contains a refrigerant gas. On its journey around the AC system, it has three main stages:- The evaporator contains the sub-cooled refrigerant and air blows through its fins to release the chilled dry air into the saloon; The condenser contains the high temperature gas and air is blown through the heat exchanger matrix collecting the expelled saloon heat as it passes through; and The hot exhaust air is then expelled outside. For AC to work, there must be a difference between the incoming and outgoing air in the outside AC unit (aka a ΔT – Delta T).  If the air that is blown through is too hot because of the severely overheated tunnels, then the heat cannot be dispersed, because ΔT is near or at zero. As one of our scientist colleagues said, the simple explanation is that AC simply adds two additional heat sources to the already overheated tunnel: The extracted heat from the saloon and Heat from the energy required to run the AC. As far back as 2016, LU’s George McInulty from the Cooling Project Team confirmed in RAIL Magazine [44] (about halfway through the article) the unworkability of AC in this context. Moreover, the New York Subway have had air-conditioned trains for the last 30 years, but they still suffer from summer overheating below ground [45] . Appendix C Heat Loads…? and so what happened to traction energy? CONCLUSION: So, on that theoretical basis, it takes two to three times the energy to accelerate the train from 0-40mph than it does to decelerate the train from 40-0mph, but in terms of total energy, we must add in the energy to maintain the train at 40mph.  The precise figures might be debatable and need formal calculation – but the concept is not! DISCUSSION: The starting assumption is that it takes the same amount of energy to accelerate a resistanceless / frictionless train from 0-40mph as it does to decelerate a train from 40-0mph as the mass remains constant! The London South Bank University [LSBU] claimed in their report “Underground railway environment in the UK Part 2: Investigation of heat load” [46] that braking energy contributes 60% of the heat load in the London Underground [LU] Network! The above concept diagram demonstrates that traction energy must contribute a significantly greater heat load than braking energy.  Despite this predictable and blatantly obvious conclusion, traction has never figured in the thinking of Transport for London’s [TfL’s] cooling team, their consultants and academic advisers! We believe this exercise has uncovered a monumental weakness in their argument – you cannot have more than 100% heat load!  On further examination, using the LSBU's 60% braking energy contribution, which did not consider any other heat sources, the above concept diagram indicates that the total heat load from brakes and traction might be 240% using a comparative 3:1 ratio.  Even using the “measured” comparative ratio of 2:1 it might be 180%. This contrasts with later figures released by TfL, published in "Rail Engineering" [47] , which give a somewhat different picture.  TfL’s claim is that only 38% of the heat is caused by braking energy, so with a 3:1 comparative ratio, it then produces 152% of the heat load.  At a comparative ratio of 2:1 it is 114%.  If these TfL statistics were to include the other heat sources, which were part of the same information release, the heat load including traction increases to176%. We believe that this is further evidence of the flawed data and irrational propositions that TfL, its consultants, and advisors have endlessly peddled!   Appendix I Harnessing heat from the Tube 11 May 2020. Available at: https://www.newcivilengineer.com/innovative-thinking/harnessing-heat-from-the-tube-11-05-2020/ Comments 27 August – 7 September 2020.   Calvin Ronald Barrows 27 Aug, 2020 at 1:28 pm (This is the full text of my letter, which is published in the September 2020 issue. Unfortunately due to insufficient space the omissions very much watered down my reasoning as to why the Bunhill 2 System/Concept is flawed!  This was then included in the e-article as a comment, which raised subsequent reactions!) Harnessing “HOT AIR” from the Tube. I was intrigued to read your article “Harnessing heat from the Tube”. I happened on the root cause of LU’s overheating several years ago and went on to develop a hypothesis that clearly fits the evidence as to the seasonal nature of the problem. LU’s official temperature monitoring indicates that the Northern Line below ground temperatures vary from about 20°C in the winter to about 28°C in the summer; similarly, it indicates on the Jubilee Line the temperature ranges generally from about 18°C to 26 °C between winter and summer. However, it should be noted that these seasonal data for tunnel temperatures clearly proves it cannot be the brakes nor indeed any other operational heat causing the overheating in the tunnels, as these happen year-round. Moreover, if operational heat does NOT cause overheating in underground-only networks like the Warsaw’s metro system, then why would it cause overheating in mixed networks like LU’s? As a logical extension of these observations, extracting heat from the tunnels in winter seems to me to be a fool’s errand. So, it is necessary to examine the myth that the Tube is always hot! In the first instance, it begs the question at which locations these LU temperatures were taken, since they do not fit with my experiences of travelling underground in winter. Whilst discussing the myth with an engineering colleague, he relayed his experience of a station where a vent shaft was close to the platform tunnel. It was snowing outside, and he could see the snow fluttering down onto the rails and track bed – and it was settling, not melting immediately! Interesting also is that Rachel Holdsworth of the Londonist prepared a video cum article entitled  ( “How Warm is a Tube Train in Winter?” ). This monitoring was undertaken on the Jubilee Line, in the direction of Stanmore to Stratford. In February 2016 she recorded temperatures on the surface of 6-9°C and in the tunnel 9-13°C. So, there was not that much waste heat at that time of year when Bunhill 2 would most need it! With the heat pumps commissioned to provide District Heat to the London Borough of Islington at 70°C and with the benefit of waste heat from the tunnels in winter likely to be only 3-4°C above ambient, it would appear that these heat pumps are going to have to top up most of the required District Heat – circa 55-60°C. This being the case, I wonder:- What was the extra-over investment cost of the infrastructure and associated plant required to raise the slightly warmer than ambient air up the vent shaft; and What is the likely return on investment for the extra-over costs, compared to a conventional Air to Water Heat Pump using ambient air? Moreover, the necessary requirement to incorporate two gas-fired Combined Heat and Power [CHP] engines (smaller than those used in Bunhill 1) both to provide heat and to supply electricity to the heat pumps when electricity from the power grid is most expensive, raises further questions about the environmental effectiveness of this scheme. So, it seems to me that, because of a perverse, ongoing lack of understanding of the temperatures underground in London’s Tube Network, there is a fundamental flaw in the Bunhill 2 concept since:- In a report by the University of Cambridge, Engineering Department (UCED) for TFL/LU “Thermal Modelling and Parametric Analysis of Underground Rail Systems” their plotted graphs of platform and tunnel temperatures both demonstrate an almost linear relationship when set against overground ambient temperature; and At the time the system requires the most waste heat, it has the least; yet when there is little or no demand for heat, there is masses available. Regarding its summer operation, a heat pump works by extracting heat from where it is not needed and transferring it to where it is needed. So, the method of passing air over the cooled heat pump coil then blowing it into the tunnel is far less effective than Air Conditioning. Ventilation does not equal cooling, though it will be slightly better than blowing in ambient air at 30°C. So, using a fan will always give the impression of cooling because of the “wind chill factor”, however, it will have a limited range and when it is turned off the temperature will immediately climb. Moreover, the passage of trains causes a wave effect, which will alternately push and suck the air within the vent shaft. In summary, the whole engineering approach has slavishly followed TfL’s flawed historic interpretation of the evidence, rather than analysing and confirming the prevailing, below ground conditions. As a result, with very little of the district heat produced in winter being derived from tunnel waste heat, most of the heat is going to be produced by a combination of heat pumps and gas-fired CHP engines – not the environmentally-friendly project it has been assumed or made out to be. I believe this Project will eventually be seen as a vanity project rather than an environmentally and financially viable source of heat – especially when extracting what little available heat there is in the underground network in the winter season will:- leave the travelling public colder, and the train saloons requiring more heating than might have otherwise been the case….. In my opinion, Bunhill 2 is unlikely to provide the environmentally-friendly district heating project it was intended to and is likely to be yet one more of a number of multi-million-pound projects carried out by the Cooling the Tube team that has completely failed to improve the well-being of passengers in the summer heat! Andrew Simkin 01 Sep, 2020 at 8:53 am The industry doesn’t make capital investment decisions such as this based on subjective beliefs and casual observations. Watching snow falling on lines and how commuters ‘feel’ isn’t particularly useful data. The industry undertakes detailed scientific measurements and surveys and uses modelling developed from scientifically based reasoning and the laws of physics. Heat pumps are not a new invention, and their application is well understood. Referring to the results of surveys and science as myths is akin to Trumps ‘fake news’ mantra which gets used when he doesn’t like an alternative view to his own. Commuters come in all different shapes and sizes and wear a huge variety of clothing. Some arrive at the tube heart racing from a brisk walk, others are still asleep! My vote is with scientific data and the laws of physics. Calvin Ronald Barrows 06 Sep, 2020 at 9:22 pm @ Andrew. Thank you for responding to my comment above on the Bunhill 2 article. You may not have known that I have been involved directly and indirectly with these issues for some length of time, so I am not coming to my conclusions without a considerable amount of research and discussion with other engineers and specialists, both within and outside the rail industry, because the challenge facing TfL/LU and other similar networks around the world needs more than those specialising in rail engineering to resolve it. With that in mind, you may find it helpful first to read my most recent papers on this topic, which will lay out for you how I arrived at my ultimate conclusions over time .  I do not question the technology of the heat pump; I use one to heat my own home, so I am very familiar with their workings and capabilities and the use of them to heat these homes is not in question. However, although the initial data provided to the Bunhill 2 Project suggest that the heat in the tunnels in winter is around 18-20°C and could therefore be used as a free source of heat for these particular homes, this is dubious at best, since there is a wealth of empirical evidence to confirm that tunnel temperatures are indeed seasonal, so I maintain winter temperatures are much lower than this. Moreover, whilst I did not comment above on the physical variety of commuters and their clothing, the difference in what they wear in summer versus winter as shown in this link confirms (albeit subjectively!) the existence of this seasonal temperature variation acting on the saloons, trains and the tunnel itself and demonstrates the hard reality of how in winter there is little practical or financial benefit in extracting this negligible “waste” heat in the tunnels to heat Bunhill 2 homes. You have taken issue with what you refer to as [my] subjective beliefs and [another’s] casual observations, reminding us all that “the industry does not make capital investment decisions such as this based on subjective beliefs and casual observations”. Of course, it doesn’t. However, all the modelling, science-based reasoning, and laws of physics and thermodynamics in the world cannot help to provide the necessary understanding of the problem, if the problem itself is not properly defined at the outset and the right questions are not raised. For example, when the New York Subway said the cause of overheating was the brakes, TfL/LU did not assess that claim scientifically, and so allowed themselves to be led up the wrong track. Even the below ground monitoring TfL/LU have done confirms that tunnel overheating is seasonal. However, since the primary problem is neither a “tunnel problem”, as this defies the laws of thermodynamics, nor a year-round “operational heat” one, chasing solutions along these lines will go nowhere in dealing with the overheating. It is necessary to identify the CAUSE of the overheating and consider ways to treat it at source, such as can be seen here . On the back of my papers and discussion with the Research and Development arm of The Rail Safety and Standards Board (RSSB), they believe investigating my theories on train, track and tunnel overheating could well merit further research, which would likely be funded by the Department for Transport, and they are currently undertaking an initial knowledge search of the industry’s extensive databases to that end. It is worth remembering that part of scientific research is about observation and logic, which then needs to be empirically tested in order to substantiate it before moving on to the next step in the process. I have never claimed to have the last word on this topic. Through my publications I have sought to encourage the industry (and TfL/LU in particular) to engage in open-minded exchanges of views with me and other engineers and specialists around the world, urging them to undertake programmes of monitoring to test such hypotheses as mine and to identify solutions. Regrettably, the evidence shows that every project CTP have ever done, except one, has been unintentionally based on opinion and subjective beliefs, and not a true interpretation of the evidence. The one success is the partial use of solar barriers on the Central Line! Unfortunately, the appointment of the new Managing Director for London Underground, who has embraced my theories with enthusiasm, came too late for Bunhill 2. In conclusion, the Cooling the Tube Project has been in existence since 2005 and lamentably after 15 years they are no nearer a solution now than they were then. Rather than my albeit rudimentary research as a regular passenger being compared with Trumpian “fake news”, I am sure the readers of NCE would find it far more useful if you could provide links to your own research or information resources, where you have identified key points that we can all benefit from.   ENDNOTES [1] Barrows, C. R. 24 Jan 2019. Cooling the Tube still on ice . [Online]. Available from: https://www.tunneltalk.com/Discussion-Forum-Jan2019-Considering-the-issue-of-metro-system-climate-control.php [Accessed 19 October 2021].  Based on Barrows, C R. 2018. Cooling the Tube –  on Ice till 2030? [2] Barrows, C. R & Telatycka, S. J. 3 August 2020. A Reflective Perspective: The Whys and Wherefores of Metro Overheating . Available from: https://news.railbusinessdaily.com/a-reflective-perspective-the-whys-and-wherefores-of-metro-overheating/ [Accessed 19 October 2021]. [3] Ibid. [4] Near disaster on sweltering Tube 23 January 2003. BBC News [Online]. Available at: http://news.bbc.co.uk/1/hi/england/2686441.stm [Accessed 19 Oct 2021], and   Cool the Tube and win £100k 16 July 2003. BBC News [Online]. Available at: http://news.bbc.co.uk/1/hi/magazine/3069037.stm [Accessed 19 Oct 2021], and    Commuters led off stalled train 16 June 2006. BBC News [Online]. Available at: http://news.bbc.co.uk/1/hi/england/london/5086396.stm [Accessed 19 Oct 2021]. [5] London Underground Average Monthly Temperatures 2019 [Updated 2021]. [Online]. Available from: https://data.london.gov.uk/dataset/london-underground-average-monthly-temperatures then open CSV file. [Accessed 19 October 2021]. [Appendix A]. [6] Barrows, C R. 2019. A graphical representation of LU-average-monthly-evening peak temperatures (Jan 13 to Dec 20). Based on data from: London Underground Average Monthly Temperatures. 2019 [Updated 2021]. [Online}. Available from: https://data.london.gov.uk/dataset/london-underground-average-monthly-temperatures (then open CSV file). [Accessed 19 October 2021]. [Appendix A].   [7] Ibid. [8] Op. cit. 2. [9] Parsons, Brinckerhoff, Quade & Douglas, Inc. March 1976. Subway Environmental Design Handbook, Volume I: Principles and Applications, Second Edition , reproduced by U.S. Dept of Commerce, National Technical Information Service. Available at: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB254788.xhtml [Accessed 19 October 2021]. [10] Parsons, Brinckerhoff, Quade & Douglas, Inc. October 1975. Subway Environmental Design Handbook, Volume II: Subway Environment Simulation Computer Program (SES) , reproduced by U.S. Dept of Commerce, National Technical Information Service. Available at: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB254789.xhtml [Accessed 19 October 2021]. [11] Barrows, C. R. & Telatycka, S. J. April 2021. Why will AC not work in the Deep Tube . [Appendix B]. [12] Barrows, C. R. & Telatycka, S. J. April 2021. Heat Loads…? and so what happened to traction energy? [Appendix C]. [13] A Perfect Planet. Series 1: Episode 2 ‘The Sun’ Minute 38 . 3 January 2021. Available on BBC iPlayer at: https://www.bbc.co.uk/iplayer/episode/p08xc2x7/a-perfect-planet-series-1-2-the-sun [Accessed 19 October 2021]. [14] Op. cit. 2. [15] Op. cit. 9, pp 2-8, 4-56, 4-65, 4-66, 4-67, 4-68 and C-15 original text page references but e-pp 68, 268, 277-280, 363. [Appendix D]. [16] Op. cit. 10, pp 5-1 and 14-110 original text page references but e-pp 130, 1206. [Appendix E]. [17] Op. cit. 9, p C-15 original text page reference but e-p 363. [Appendix F]. [18] Op. cit. 9, pp xvi – xviii.  (e-pp26-28). [Appendix G]. [19] Op. cit. 17, p C-15 original text page reference but e-p 363. [20] Barrows, C. R. & Telatycka, S. J. May 2021 Cumulative Daily Heat Transfer Cycle of Multiple Round Trip Train Journeys on a Mixed Under-Overground Network in Summer . [Appendix H]. [21] Op. cit. 2. [22] Op. cit. 11 [23] Whitest ever paint reflects 98% of sunlight 16 April 2021. BBC News [Online]. Available at: https://www.bbc.co.uk/news/science-environment-56749105 . [Accessed 19/10/2021]. [24] Bouvard, O., Burnier, L., Oelhafen, P. et al. 2018. Solar heat gains through train windows: a non-negligible contribution to the energy balance . Available at:   https://www.researchgate.net/profile/Olivia-Bouvard/publication/323592680_Solar_heat_gains_through_train_windows_a_non-negligible_contribution_to_the_energy_balance/links/5dd65ec5a6fdcc2b1fa96c1e/Solar-heat-gains-through-train-windows-a-non-negligible-contribution-to-the-energy-balance.pdf . [Accessed 19/10/2021]. [25] Thermally Efficient Coatings. No date. Available at: https://blocksil.co.uk/solutions/thermally-efficient-coatings/ [Accessed 22 October 2021]. [26] Green Tracks . 2021. Available at: https://www.sempergreen.com/en/solutions/green-ground-covering/green-tracks [Accessed 21 October 2021]. [27] Productivity during heatwaves 26 July 2018. Parliamentary Business [Online] Paragraph 106. Available at: https://publications.parliament.uk/pa/cm201719/cmselect/cmenvaud/826/82607.htm [Accessed 20 October 2021]. [28] Productivity during heatwaves 26 July 2018. Parliamentary Business [Online] Paragraph 107 & 109. Available at: https://publications.parliament.uk/pa/cm201719/cmselect/cmenvaud/826/82607.htm [Accessed 20 October 2021]. [29] Productivity during heatwaves 26 July 2018. Parliamentary Business [Online] Paragraph 109. Available at: https://publications.parliament.uk/pa/cm201719/cmselect/cmenvaud/826/82607.htm [Accessed 20 October 2021]. [30] Ibid. [31] Op. cit. 5 [32] Productivity during heatwaves 26 July 2018. Parliamentary Business [Online] Paragraph 111. Available at: https://publications.parliament.uk/pa/cm201719/cmselect/cmenvaud/826/82607.htm [Accessed 20 October 2021]. [33] Harnessing heat from the Tube 2020. Available at:  https://www.newcivilengineer.com/innovative-thinking/harnessing-heat-from-the-tube-11-05-2020/ [Accessed 22 October 2021]. [See Appendix I for reproduction of comments 27 August – 7 September 2020 with accessible links] [34] Op. cit. 24. [35] FLEXTRON Flexible Solar Module 2020.  Available at: https://www.specifiedby.com/bipvco/flextron-flexible-solar-module [Accessed 19 October 2021]. [36] 16,000 solar panels 4 train tunnel from Paris 2 Amsterdam No date. Available at: https://www.dailymotion.com/video/xj4psq [Accessed 20 October 2021] [37] Op. cit. 1. [38] Op. cit. 2 [39] Did Einstein really define insanity as 'doing the same thing over and over again and expecting different results? 2018. Available at: https://www.quora.com/Did-Einstein-really-define-insanity-as-doing-the-same-thing-over-and-over-again-and-expecting-different-results [Accessed 19 October 2021]. [40] Op. cit. 1. [41] Op. cit. 5. [42] Op. cit. 13. [43] Op. cit 2. [44] Paul Stephen. 3 February 2016. Cooling the Tube . Available from: https://www.railmagazine.com/infrastructure/stations/cooling-the-tube [Accessed 27 October 2021] [45] A Brief History of Air-Conditioning on the New York Subway 15 August 2012. Bloomberg CityLab [Online]. Available at: https://www.bloomberg.com/news/articles/2012-08-15/a-brief-history-of-air-conditioning-on-the-new-york-subway . [Accessed 27 October 2021]. [46] F. Ampofo, G. Maidment, and J. Missenden 2004. Underground railway environment in the UK part 2: Investigation of heat load . Applied Thermal Engineering 24 pp 633-645. Available for purchase at https://www.sciencedirect.com/science/article/abs/pii/S1359431103003375 for $37.95 [Accessed 19/10/2021]. [47] Brian Tinham November/December 2007. Cooling the Tube in Plant Engineer pp8-11. Website no longer available. Republished November 2018. Available from: http://www.operationsengineer.org.uk/article-images/23757/cooling.pdf [Accessed 19/10/2021].   BIBLIOGRAPHY Ampofo F., Maidment G., & Missenden J. 2004 Underground railway environment in the UK part 2: Investigation of heat load ’ Applied Thermal Engineering 24. Available for purchase at https://www.sciencedirect.com/science/article/abs/pii/S1359431103003375 Bouvard, O., Burnier, L., Oelhafen, P. et al. 2018. Solar heat gains through train windows: a non-negligible contribution to the energy balance. Available at: https://www.researchgate.net/profile/Olivia-Bouvard/publication/323592680_Solar_heat_gains_through_train_windows_a_non-negligible_contribution_to_the_energy_balance/links/5dd65ec5a6fdcc2b1fa96c1e/Solar-heat-gains-through-train-windows-a-non-negligible-contribution-to-the-energy-balance.pdf Barrows, C. R. 24 Jan 2019. Cooling the Tube still on ice . [Online]. Available from: https://www.tunneltalk.com/Discussion-Forum-Jan2019-Considering-the-issue-of-metro-system-climate-control.php . Based on Barrows, C R. 2018. Cooling the Tube –  on Ice till 2030? Barrows, C R. 2019. A graphical representation of LU-average-monthly-evening peak temperatures (Jan 13 to Dec 20). Based on data from: London Underground Average Monthly Temperatures. 2019 [Updated 2021]. [Online}. Available from: https://data.london.gov.uk/dataset/london-underground-average-monthly-temperatures (then open CSV file). [Accessed 19 October 2021]. [Appendix A] Barrows, C. R & Telatycka, S. J. 3 August 2020. A Reflective Perspective: The Whys and Wherefores of Metro Overheating . Available at: https://news.railbusinessdaily.com/a-reflective-perspective-the-whys-and-wherefores-of-metro-overheating/ . Barrows, C. R. & Telatycka, S. J. April 2021. Why will AC not work in the Deep Tube . [Appendix B]. Barrows, C. R. & Telatycka, S. J. April 2021. Heat Loads…? and so what happened to traction energy? [Appendix C]. Barrows, C. R. & Telatycka, S. J. May 2021 Cumulative Daily Heat Transfer Cycle of Multiple Round Trip Train Journeys on a Mixed Under-Overground Network in Summer . [Appendix I]. BBC iPlayer 3 January 2021. A Perfect Planet - Series 1: 2. The Sun. Available at: https://www.bbc.co.uk/iplayer/episode/p08xc2x7/a-perfect-planet-series-1-2-the-sun . BBC News [Online] 23 January 2003. Near disaster on sweltering Tube . Available at: http://news.bbc.co.uk/1/hi/england/2686441.stm . BBC News [Online] 16 July 2003 Cool the Tube and win £100k . Available at: http://news.bbc.co.uk/1/hi/magazine/3069037.stm . BBC News [Online] 16 June 2006. Commuters led off stalled train . http://news.bbc.co.uk/1/hi/england/london/5086396.stm . BBC News [Online] 16 April 2021. Whitest ever paint reflects 98% of sunlight . Available at: https://www.bbc.co.uk/news/science-environment-56749105 . BiPVco 2020. FLEXTRON Flexible Solar Module . Available at: https://www.specifiedby.com/bipvco/flextron-flexible-solar-module . Blocksil Thermally Efficient Coatings. No date. Available at: https://blocksil.co.uk/solutions/thermally-efficient-coatings/ . Bloomberg CityLab [Online] 15 August 2012. A Brief History of Air-Conditioning on the New York Subway . Available at: https://www.bloomberg.com/news/articles/2012-08-15/a-brief-history-of-air-conditioning-on-the-new-york-subway . Data.london.gov.uk 2019 [updated 2021]. London Underground Average Monthly Temperatures . Available from: https://data.london.gov.uk/dataset/london-underground-average-monthly-temperatures then open CSV file. Dailymotion.com 16,000 solar panels 4 train tunnel from Paris 2 Amsterdam No date. Available at: https://www.dailymotion.com/video/xj4psq . Green Tracks. 2021. Available at: https://www.sempergreen.com/en/solutions/green-ground-covering/green-tracks . New Civil Engineer 11 May 2020 Harnessing heat from the Tube. Available at: https://www.newcivilengineer.com/innovative-thinking/harnessing-heat-from-the-tube-11-05-2020/ . Parliamentary Business 26 July 2018 Productivity during heatwaves. Available at: https://publications.parliament.uk/pa/cm201719/cmselect/cmenvaud/826/82607.htm . Parsons, Brinckerhoff, Quade & Douglas, Inc., March 1976 Subway Environmental Design Handbook, Volume I: Principles and Applications , Second Edition New York reproduced by U.S. Dept of Commers, National Technical Information Service. Available at: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB254788.xhtml . Parsons, Brinckerhoff, Quade & Douglas, Inc., October 1975 Subway Environmental Design Handbook, Volume II: Subway Environment Simulation Computer Program (SES) , New York, reproduced by U.S. Dept of Commers, National Technical Information Service. Available at: https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/PB254789.xhtml . Quora.com (updated 2018). ‘Did Einstein really define insanity as 'doing the same thing over and over again and expecting different results?'. Available at: https://www.quora.com/Did-Einstein-really-define-insanity-as-doing-the-same-thing-over-and-over-again-and-expecting-different-results . Rail Magazine (2016) ‘Cooling the Tube’ https://www.railmagazine.com/infrastructure/stations/cooling-the-tube Tinham, Brian 2007 Cooling the Tube November/December issue Plant Engineer. Available from: http://www.operationsengineer.org.uk/article-images/23757/cooling.pdf  

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Innovative PantoSystem Prevents Service Disruptions to Paris RER Network of RATP

Automatic Train Supervision

      The customer RATP is a state-owned public transport operator and the biggest transport company in Paris with 60,000 people responsible for engineering, exploitation, and maintenance. The company provides multiple transport modes such as metros, buses, trams, and regional express rail (RER) network. RATP has a total of 28 lines of metro, trams, and RER in the Parisian metropolis.   The challenges/problems Within a two-week interval, incidents related to the spring box of two separate pantographs running on opposite train tracks, were identified. In one of the incidents, the abnormal wear of the carbon strip kept deteriorating, and when the carbon strip finally had a pitch angle between -3,8° and -3,4°, the PantoSystem generated a level 1 alarm in one of RATP´s RER networks, indicating a warning of high importance. After examining the 3D images of the pantograph, the PantoInspect team urgently sent an e-mail to warn RATP about the carbon strip, which had clearly been bended. Immediately after, the exploitation team of RATP took the train off the track and when the problem was investigated by the maintenance team, they confirmed that the horn of the pantograph was hit by an unknown object, causing the spring box to twist on one side.   The solution As the PantoSystem has not yet been validated by formal tests, the RATP does not yet have a dedicated team to handle the train alarms and take appropriate action, and that is why, they were very pleased to receive a direct warning from PantoInspect, that a train required attention. The company was also very satisfied that the PantoSystem enabled them to detect the consequences of the twisted or broken spring box, by accurately measuring the geometry of the pantograph. The automatic system is important due to the fact that RATP has about 90 km of tracks on each direction, a total of 180 km track on both directions, and since this type of problem does not happen frequently, manually identifying this type of defect throughout the RATP fleet would have been very time-consuming and costly for RATP as it is not visible from the ground. Additionally, to manually investigate if more trains were affected would again require a major effort.                Figure 3: Broken spring box             About PantoInspect PantoInspect was the first company world-wide to develop an automated pantograph inspection system, in partnership with Banedanmark, the Danish railway infrastructure owner, around 2008. Today, PantoInspect is one of the world’s most recognized and respected brands, and a market-leading manufacturer and supplier of automated and real-time Wayside Pantograph Monitoring systems to the global Railway industry. We have supplied several pantograph monitoring systems to some of the world’s leading infrastructure owners and rolling stock operators such as Deutsche Bahn, RATP, Infrabel, Sydney Trains, Network Rail and TRA.   PantoInspect Titangade 9C Copenhagen 2200, Denmark www.pantoinspect.com Email: contact@pantoinspect.com Tel: +45 3318 9120

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