Indian Railways AC Traction Manual Volume 1 PDF

CHAPTER II GENERAL DESCRIPTION OF FIXED INSTALLATIONS 1. POWER SUPPLY ARRANGEMENTS AT SUB-STATIONS 10200 Power Supply 25 kV, ac, 50 Hz single phase power supply for electric traction is derived from the grid system of State Electricity Boards through traction sub-stations located al...

CHAPTER II GENERAL DESCRIPTION OF FIXED INSTALLATIONS 1. POWER SUPPLY ARRANGEMENTS AT SUB-STATIONS 10200 Power Supply 25 kV, ac, 50 Hz single phase power supply for electric traction is derived from the grid system of State Electricity Boards through traction sub-stations located along the route of the electrified sections at distances of 35 to 50 km apart. The distance between adjacent sub-stations may however be even less depending on intensity of traffic and load of trains. At present there are broadly four different arrangements in existence as under :- 1. The Supply Authorities supply power at 220/132/110/66 kV Extra High Voltage (EHV) at each traction sub-station which is owned, installed, operated and maintained by the Railway'; 2. The Railway receives 3-phase power supply from the Supply Authority at a single point near the grid sub- station, from where the Railway runs its own transmission lines providing its own traction sub-stations; 3. All EHV and 25 kV equipment is owned, installed, operated, and maintained by the Supply Authority, except 25 kV feeder circuit breakers which are owned, installed, operated and maintained by the Railway; 4. All EHV and 25 kV equipment is owned, installed, operated and maintained by the Supply Authority but 25 kV feeder circuit breakers alone are operated on remote control by the Traction Power Controller (TPC). 10201 Duplicate Supply 1. Fig. 2.01 shows schematically the arrangement at a typical traction sub-station. 2. To ensure continuity of supply under all conditions, the high voltage feed to the traction substations is invariably arranged either from two sources of power or by a double circuit transmission line, so that even if one source fails, the other remains in service. Suitable protective equipment is installed at the sub-stations to ensure rapid isolation of any fault in transmission lines and sub-station equipment, so that the power supply for electric traction is maintained under all conditions. 3. At each traction sub-station, normally two single-phase transformers are installed, one of which is in service and the other is 100% stand by. The present standard capacity is 21.6 MVA (ONAN)/30.2 MVA (ONAF). However transformers of capacity 13.5 MVA (ONAN)/I0.8 MVA (ONAN) have also been used at many of the sub-stations. These transformers step down the grid voltage to 25 kV for feeding the traction overhead equipment (OHE). 25 kV feeders carry the power from the sub- stations to feeding posts located near the tracks. Each feeder is controlled by a single-pole circuit breaker equipped with protective devices. 10202 Voltage Regulation The permissible variation of the bus bar voltage on the busbars at the grid sub-station is+ 10% and –5% i.e., between 27,500 V. and 23,750 V. The tappings on the transformers are on the secondary winding and are set to ensure that the voltage is maintained as high as possible but not exceeding 27.5 kV at the feeding post at any time. 10203 25 kV Supply at Traction Sub-stations 1. On the secondary side, one transformer circuit breaker and one feeder circuit breaker are installed with associated double pole isolator, the busbar connections being such that full flexibility of operation is assured. INDIAN RAILWAYS AC TRACTION MANUAL - VOLUME (14) 2. The traction sub-station is designed for remote operation. 3. The facilities exist to change over from one feeder to the other by means of isolator/bus coupler. 4. One end of the secondary winding of the transformer is solidly earthed at the sub-station and is connected to track/return feeder through buried rail. 10204Feeding and Sectioning Arrangements 1. The generation and transmission systems of Supply Authorities are 3-phase systems. The single- phase traction load causes unbalance in the supply system. This unbalance has undesirable effects on the generators of the Supply Authorities and equipment of other consumers, if its value becomes excessive. 2. The permissible voltage unbalance at the point of common coupling on the grid supply system should not exceed the following limits:- Voltage Unbalance (%) Instantaneous 5 2 hours 3 Continuous 2 3. To keep the unbalance on the 3-phase grid system within the above limits, power for ac single phase traction is tapped off the grid system across the different phases at adjacent sub-stations in cyclic order. 4. Thus it becomes necessary to separate electrically the overhead equipment systems fed by adjacent sub- stations. This is done by providing a 'Neutral Section' between two sub-stations on the overhead equipment to ensure that the two phases are not bridged by the pantographs of passing electric locomotives/EMUs. 5. To ensure rapid isolation of faults on the OHE and to facilitate maintenance work, the OHE is sectioned at intervals of 10 to 15 km along the route. At each such point a 'switching station interruptors' usually rated at 600A are provided. The shortest section of the OHE, which can be isolated by opening interruptors alone is called a 'sub-sector'. Each sub-sector is further sub-divided into smaller 'elementary sections' by provision of off-load type manually operated isolator switches. 6. At some stations with large yards, alternative feeding arrangements are provided so that the power for feeding and yards may be drawn from alternative routes. Normally the switch is locked in one position, being changed to the other when required after taking necessary precautions. 7. To meet requirements at electric loco running sheds isolators with earthing device in the ‘off’ positions is provided. At watering stations manually operated interrupters and isolator with earthing heels are provided to enable switching off of the power supply locally and earthing the OHE to enable working on roofs of rolling-stock. There are several types of switching stations as detailed in the following paras. 10205 Feeding Post (FP) Each feeder supplies the OHE on one side of the feeding post through interruptors controlling supply to the individual lines. Thus, for a two track line, there will be four interruptors at each feeding post. 10206 Sectioning and Paralleling Post (SP) These posts are situated approximately midway between feeding posts marking the demarcating point of two zones fed from different phases from adjacent sub-stations. At these posts, a neutral section is provided to make INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME (16)  it impossible for the pantograph of an electric locomotive or EMU train to bridge- the different Phases of 25 kV supply, while passing from the zone fed from one sub-station to the next one. Since the neutral section remains 'dead', warning boards are provided in advance to warn and remind the Driver of an approaching electric locomotive/EMU to open locomotive circuit breaker (DJ) before approaching the 'neutral section', to coast through it and then switch 'on' on the other side. Special care is taken infixing the location of neutral sections, on level tangent tracks far away from signals, level crossing gates etc. to ensure that the train coasts through the, neutral section at a sufficiently high speed, to obviate the possibility of its stopping and getting stuck within the neutral section. A paralleling interruptor is provided at each 'SP' to parallel the OHE of the up and down tracks of a double track section. 'bridging interruptors' are also provided to permit one feeding post to feed beyond the sectioning post upto the next FP if its 25 kV supply is interrupted for some reasons. These bridging interruptors are normally kept open and should only be closed after taking special precautions as detailed in these rules. 10207 Sub-Sectioning and Paralleling Post (SSP) One or more SSPs are provided between each FP and adjacent SP depending upon the distance between them. In a double track section, normally three interruptors are provided at each SSP i.e. two connecting the adjacent sub-sectors of up and down tracks and one for paralleling the up and down tracks. 10208 Sub-Sectioning Post (SS) These are provided only occasionally. They are similar to SSPs with provision for sectioning of the OHE but not paralleling. 10209 Certain Equipment at Switching Stations Certain equipments are installed at various points to protect the lines, to monitor the availability of power supply and provide other facilities. These are generally as under :- 1. Lightning arresters are provided to protect every sub-sector against voltage surges. 2. Auxiliary transformers are provided at all the posts and also at certain intermediate points to supply ac at 240 V, 50 Hz required for signalling and operationally essential lighting installations. To ensure a fairly steady voltage, automatic voltage regulators are also provided where required. 3. Potential transformers are provided at the various switching stations for monitoring supply to each sub-sector. 4. A small masonry cubicle is provided to accommodate remote control equipment, control panel, telephone and batteries and battery chargers required for the control of interruptors and other similar equipments. II. POWER SUPPLY FOR SIGNALLING 10210 Supply Arrangements 1. To ensure reliability of ac 240V, supply through 25 kV/240V auxiliary transformer by tapping 25 kV OHE is made available at following places: (a) At each way side station for CLS. (b) Level crossings located more than 2 km.away from Railway Station. (C) At IBH. (d) At all the power supply installations. INDIAN RAILWAYS AC TRACTION MANUAL VOLUME 1 (17) 2. In the event of power block being given on both the OHE sub-sectors from which the signal supply is derived, electric traffic would necessarily have to be suspended on the line. During such periods, colour light signalling will not also be in operation. Such cases are likely to arise very rarely at any station and the duration of the block is not likely to exceed-one hour at a time. Therefore, no additional power supply arrangement need be made by the Electrical Department at wayside stations. However, to cater for this condition, portable-generating sets should be kept by the S&T Department to be operated until 25 kV supply is restored. At large stations with considerable shunting movements, a stand-by diesel generator set may be installed by the S&T Department to meet emergencies, if considered essential. 10211 Voltage Regulators The fluctuating nature of traction load causes perceptible fluctuation on the ac 240 V supply affecting operation of signalling equipment. To overcome this, static type voltage regulators are provided by the S&T Department to limit voltage fluctuations to + 5%. These voltage regulators are installed either in separate kiosks inside the remote control cubicles, inside the ASM's room, or inside the cabins depending upon the position of various load centres. III. REMOTE CONTROL AND COMMUNICATION ARRANGEMENTS 10212 Remote Control The interruptors at the various switching stations as well as the feeder circuit breakers (and other switch gear owned and operated by the Railway) at the traction sub-stations are controlled from a Remote Control Centre (RCC) manned throughout the 24 hours of the day. During each shift there is one or more number of Traction Power Controllers (TPC), depending upon the work load. All switching operations on the system are thus under the control of one single person, namely TPC, who is responsible for maintaining continuity of power supply on all sections of the OHE. He also maintains continuous and close liaison with the Section Controllers in regard to train operations on electrified sections. Further details regarding Remote Control are given in Vol. II of this manual. 10213 Communication Facilities All aerial telecommunication lines running by the side of the tracks are replaced with under-ground cables/ microwave to overcome the interference caused by 25 kV single phase ac traction. The cables contain adequate number of pairs of conductors for the various types of Railway telecommunication circuits on ac traction. For technical details reference may be made to Indian Railways Telecommunication Manual. In an electrified section it is essential, in the interest of efficiency, to provide several independent telephone circuits to facilitate quick communication and to achieve necessary co-ordination between different branches of the Railway. In an emergency several alternative telephone channels will be available for communication should any one fail. The various telephone circuits provided in electrified sections are described below briefly :- 1. Train Control/Section Control : This circuit is operated by the Section Controller and is used mainly for controlling train movements within his jurisdiction. It has connections with Signal Cabins, ASMs Offices, Loco Sheds and Yard Masters' Offices. 2.Dy. Control Telephone This circuit is operated by the Deputy Controller and is used for directing traffic operations in general. It has connections with the important Station Masters' offices, Yard Masters' Offices, Loco Sheds and Signal Cabins. INDIAN RAILWAYS AC TRACTION MANUAL - VOLUME 1 (18) 3. Stock Control Telephone: This circuit is operated by the Stock Controller and is mainly used for keeping a continuous watch and to maintain control over the movements of wagons. It has connections with Yard Masters and important Station Masters' offices. 4.Traction Loco Control : This is a circuit provided for ac traction and is operated by the Traction Loco Controller who is responsible for movements of electric locomotives and Electric Multiple Unit (EMU) stock. It has connections with Electric Loco Sheds, EMU Sheds, important Station Masters, Yard Masters, Divisional Officers such as Sr. DEE/DEE, AEE (RS), Sr DEE/DEE/AEE- (OP), Traffic Control Offices, Traction Foreman and important crew booking points. 5.Traction Power Control: This is a special circuit on ac traction and is used by TPC for all communications in connection with power supply, switching operations and ‘permit-to-work'. It has connections with Station Masters' offices, cabins, Traction sub- stations, feeding posts, sectioning and sub-sectioning posts, traction maintenance depots, important Signal Cabins, Divisional Officers such as Sr. DEE (TrD), Sr. DEE/OP and Traffic Control Offices. 6. Emergency Control Circuit This circuit is provided to facilitate the traction maintenance gangs and electric train crew to get in touch with TPC with the least possible delay in emergencies. It is also used by train crew in times of accidents for communication with the Control Office. This circuit is operated by TPC and is located in the RCC. Emergency telephone socket boxes are provided along the track at an interval of 0.75 to 1 km and also near the signal cabins, sub-sectioning and sectioning posts, insulated overlaps and feeding posts etc. Portable emergency telephones are given to maintenance gangs, train crew and Station Masters. By plugging the portable telephone into an emergency socket it is possible to communicate with the TPC. 7. Hot Line Communication: Hot line communication circuit should be provided between the HQ, divisional HQ traction loco controller and electric loco sheds. These would be provided in the HQ with CEE, CEE/Loco, Dy. CEE/RS, Sr. DEE/RS in the sheds and Sr. DEE/OP in the divisions. 8. Walkie Talkie sets Every maintenance depot of OHE should have adequate numbers of walkie-talkie sets to be available with them during their normal maintenance work as well as break-downs so that not only effective communication is available at site but also to increase the efficiency and productivity of the work during power blocks. These walkie-talkie sets are to be used primarily for the following purposes: a) To communicate to the maintenance/breakdown gangs/parties that power block has been sanctioned; b) To direct and supervise work during the period power block is in force; c) Confirmation regarding cancellation of power block by each individual party and cancellation of power block. 9. Other Communication Facilities: An independent inter-communication 'circuit is also provided between the various Section Controllers and the Chief Controller for local communication between themselves. Facilities are also provided for the Chief Controller INDIAN RAILWAYS AC TRACTION MANUAL VOLUME I (19) to talk to any station on train control, deputy control, stock control and traction loco control circuits. Similarly, facilities are provided to TPC to talk to any station on the train control and traction loco control in an emergency. However, it will not be possible for the Chief Controller or TPC to ring independently any station on any control circuit as this ringing facility is only provided to the respective Controllers. IV OVERHEAD EQUIPMENT 10214 Catenary and Contact wire 1. The overhead equipment above the tracks comprises of the following:- a) A standard cadmium copper wire of about 65 mm2 section or standard aluminium alloy wire of about 116 mm 2 section for catenary. b) A grooved hard drawn copper contact wire of 107 mm 2 cross-section (when new) supported from the catenary by means of droppers of 5 mm diameter spaced not more than 9 m apart. 2. The catenary and contact wire together have an equivalent copper section of 157 mm 2. The current normally permissible on a single track is 600 A approximately, because of equivalent cross-sectional area of OHE. This current limit is based on the temperature limit of 850 C in contact wire. Certain sections in Waltair-Kirandul section have the catenary and contact wires together having an equivalent copper section of 200 mm 2. 3. For loop lines, sidings, yards and spur lines excluding the main running lines and first loop or lines taking off from main running line, tramway type OHE having only grooved hard drawn copper contact wire of 107 mm2 section is provided. 10215 Height of Contact wire The normal height of contact wire for regulated OHE is 5.60 m (with 10 cm presag for 72 m span) above rail level. For unregulated OHE in areas with a temperature range of 40 C to 65 0 C, this figure is 5.75 m and in areas with a temperature range of 15 0 C to 650 C, it is 5.65 m. In certain cases, such as under over-line structures, the height may be as low as 4.65 m on BG and 4.02 m on MG. For passing oversize consignments on such lines, special precautions have to be taken. 10216 Span of Supporting Mast/Structures The span normally used for supporting the OHE from masts/structures using the cantilever type bracket assembly varies from maximum 72 m on straight track to 27 m on curved track, the spans depending upon the degree of curvature. The catenary system is normally supported on straight tracks at maximum intervals of 72 m ( 63 m on MG) by cantilever type arms fixed to galvanized broad flange or I section steel masts or fabricated steel structures. On curves the catenary is supported at closer intervals, the spans adopted depending upon the degree of curvature. 10217 Stagger The contact wire is staggered so that as the pantograph glides along, the contact wire sweeps across the current collecting strips of the pantograph upto a distance of 200 mm on either side of the centre line on straight runs and 300 mm on one side on curves. This ensures a uniform wear of the current collecting strips of the pantographs. 10218 Overlaps The OHE conductors are terminated at intervals of about 1.5 Km with an overlap generally as shown in Fig. 2.02, the conductor height being so adjusted that the pantograph glides from one conductor to the other smoothly. There are two types of overlap spans as under :- a) Uninsulated overlap spans where the distance of separation between two contact wires is 200 mm and INDIAN RAILWAYS AC TRACTION MANUAL-VOLUME I the two conductors are permanently connected together electrically by suitable jumpers. b) Insulated overlaps, where the two OHE systems are kept apart at a distance of 500 mm. Normally the electrical discontinuity at insulated overlaps is bridged by interrupters or isolator except at neutral sections. 10219 Regulated and Unregulated OHE OHE with automatic tensioning called 'regulated OHE' is generally provided for all main lines, but for large isolated yard and unimportant lines, automatic tensioning is dispensed with in the interest of economy and only unregulated OHE is used. 10220 Section Insulator Assembly Section insulators are provided to insulate the OHE of one elementary section from the OHE of the adjacent elementary section such as at cross-overs. When the pantograph of a locomotive passes from one track to another along a cross- over/turnout, current collection changes from one OHE to other and therefore the runners of the section insulators overlap with contact wire so that there is no arcing. On double line sections with runners trailing, the section insulator assembly using porcelain insulators are fit for speeds upto 120 km/h provided it is installed between the first one-tenth and one - third of the span. In case the runners of the section insulator assembly are in the facing direction cr it is not installed within the first one third of the span, the speed should be restricted to 80 km/h. 10221 Mechanical Independence of OHE Track - Structures By providing independent structures for supporting the OHE of each track, complete mechanical independence of each OHE is secured. Any irregularity or damage or maladjustment of the OHE of one track will not, therefore, affect the performance of the other. INDIAN RAILWAYS — AC TRACTION MANUAL - VOLUME 1 10222 Flexible Head-Span and Rigid Portals. In large yards, where difficulty is experienced in locating individual supporting structures between the tracks, a cross catenary wire system called flexible head-span is provided to maintain two or more catenaries and their contact wires at the appropriate heights and locations. Where the OHE has to be regulated, rigid portal structures are used. 10223 Maximum Speed The OHE with maximum span of 72 m and with presag of that span of 10 mm and with tension of 1000 kgf in contact and catenary wire is designed for a speed potential of up to 160 km/h. The existing system is generally fit for 140 km/h with AM-12 pantographs now in use on ac locomotives. V. SPECIAL WARNING SIGNALS 10224 Signal Marking the end of Catenary Certain loops and sidings at a station may not be wired. An electric locomotive should not be taken into an unwired track as its pantographs and the OHE may get damaged and it will require a diesel or steam engine to pull the electric locomotive out of the unwired track. Caution boards as per Fig. 2.03 are provided for warning the Drivers of the unwired tracks taking off from wired tracks. In addition special indication boards are provided where the OHE ends on a track. Point levers controlling the movement of trains from the wired track to the unwired track are fitted with warning tablets (Boards) as per Fig. 2.04 painted yellow, to warn the cabinman not to admit electric locomotives on the unwired track. 10225 Warning Signals for Neutral Sections To indicate to the Driver that he is approaching a neutral section and should be in readiness to open DJ, two warning boards as per Figs. 2.07 & 2.08 are fixed 500 m and 250 m ahead of the neutral section. The point where DJ is to be opened is indicated by a signal shown in Fig. 2. 05. Indication that the neutral section has been passed and DJ may be switched on again is given by another signal shown in Fig.2.06. 10226 Temporary Signals Occasionally it becomes necessary to lower the pantograph on certain sections when OHE is not properly adjusted so as to avoid damage to the pantographs. In such cases temporary warning boards as shown in Fig. 2.09 are placed ahead of the section, facing the direction from which locomotives normally approach for this purpose. On reaching such a warning board, the Driver shall open DJ and lower pantograph/s of his electric locomotive/s. He may raise the pantographs after passing the section and reaching the signal provided for the purpose as per Fig. 2. 10. After a break-down on OHE normally only temporary repairs permitting electric locomotives to pass with their pantographs lowered are carried out in attending to break-downs, so that the traffic may not be dislocated unduly. Permanent repairs are done as soon as possible thereafter by taking a prearranged block in consultation with the Operating Department. 10227 Special features of Traction Installations in Waltair - Kirandul section of S. E. Railway Waltair -Kirandul section of South Eastern Railway is about 471 km long , having large number of tunnels and gradients as high as 1 in 60 and sharp curves of 8 degree. The configuration of traction distribution system in the section is as under: - i) OHE- About 329 km of the section has got 19/2.10 mm HDBC catenary and 150 mm2 contact wire. The tension in catenary is 800 kgf while contact wire has got 1200 kgf tension. INDIAN RAILWAYS AC TRACTION MANUAL - VOLUME 1 (22)