AC TRACTION MANUAL PDF
Budget Estimates for Electric Traction. Electrical Department- Budget Demands. INDIAN RAILWAYS – AC TRACTION MANUAL- VOLUME 1. . The "A. C. Traction Manual" containing procedures and practices to be followed uniformly throughout Indian Railways, was published for the first time in Manual to Glued Insulated Rail Joints · Indian Railways Code for the Stores Department Volume - II · Indian Railways Manual of AC Traction Maintenance and.
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AC Traction Manual issued by IR on the field of Electric Traction is further detailed into various Volumes and Parts for covering the details of Installations and. kV ac traction and to avail high tension input power supply for TSS. vii) Consequential .. with locally operated manual isolating switches. should be a manual used by the staff who have been trained in the .. Plans and Sectioning Diagrams for 25 kV ac Traction issued by RDSO.
Currently produced modern locos generally use GTO thyristors Gate Turn-Off thyristors , but it is expected that soon insulated-gate bipolar transistors IGBTs , which offer extremely high switching speeds allowing for finer control over the waveforms generated, will be the switching technology of choice.
The 3-phase AC is fed to the AC traction motors, which are induction motors. As the voltage and the frequency can be modified easily, the motors can be driven with fine control over their speed and torque. By making the slip frequency of the motors negative i. There are various modes of operation of the motors, including constant torque and constant power modes, balancing speed mode, etc. AC motors have numerous advantages over DC motors.
DC motors use commutators which are prone to failure because of vibration and shock, and which also result in a lot of sparking and corrosion. Induction AC motors do not use commutators at all. It is hard to use a DC motor for regenerative braking, and the extra switchgear for this adds to the bulk and complexity of the loco. AC motors can fairly easily be used to generate power during regenerative braking.
In addition, DC motors tend to draw power from the OHE poorly, with a bad power factor and injecting a lot of undesirable harmonics into the power system. AC motors suffer less from these problems, and in addition have the advantage of a simpler construction. How are phase breaks AC or power gaps DC handled by the locomotives?
The catenary has breaks or gaps in its electrical continuity every once in a while at points where successive sections are connected to different substations. A neutral section of catenary is usually provided between the two live sections of different phases or connected to different substations. At such points, single locomotives do not drop their pantographs, although on-board equipment such as the traction motors, compressors, blowers, etc. The main circuit breaker DJ is also opened.
Warning boards at m and m before the neutral section are provided for this purpose. Earlier, locos used to routinely drop their pantographs for all neutral sections; this is no longer standard practice. In the case of multiple unit operation, however, pantographs are usually dropped on all the lashed-up locomotives, to avoid the possibility of short-circuiting adjacent sections of the catenary.
The possibility is remote, as normally there is no power flow between lashed-up units, hence the pantographs may not always be dropped, depending on the particular operational procedures of a division.
Why is the neutral section provided with a dummy neutral or electrically dead cable?
Why can't it be a real gap? Pantographs of electric locomotives have a spring mechanism or compressed-air assembly that keeps the pantograph pushing up against the contact wire with a certain specific pressure. If the neutral section were not wired and the contact wire simply ceased to exist, then then possibility exists that if the driver has not dropped the pantographs at the time the loco reaches the neutral section, then the pantograph will suddenly rise upwards unchecked; when the loco reaches the other end of the neutral zone, it is then likely to smash into the catenary where the next contact wire section begins.
It should be noted that in practice, at neutral sections where it is or was a requirement to drop the pantographs, it has been observed that IR crews almost never forget to do so.
But now with more locos and neutral sections coming up which do not require the pantograph to be dropped, this does become a concern. In time, when 25kV AC becomes the norm and DC traction is decommissioned, these transitions will be history and there will be no more traction changeovers!
Sad for railfans, but perhaps more efficient for IR. The catenary connected to the DC power supply does not reach all the way to the catenary connected to the AC power supply; there is a neutral section between them.
1. AC Traction Manual
This cable can be connected to either the DC or the AC power supply. Before the arrival of the DC loco, this section is connected to the DC supply.
Once the loco gets detached and goes off the main line a DC branch loop is provided for this purpose from the last DC section , the cable spanning the neutral section is switched over to the AC power supply and energized, so that the AC loco can now come in. Before entering neutral sections, electric locos often switch off power temporarily to the traction motors so as to prevent any transient disturbances and sparking.
Because the neutral section is switched between AC and DC supply, it is also known as the dynamic neutral section or the switched neutral section. Also see the article on Mumbai area electrification. The WCAM-1 has a selector on the rightmost side of horizontal control panel for selecting the pantograph. The DC pantograph has two shoes and is thicker in its contact area than the AC pantograph because it has to carry a larger current corresponding to the lower voltage.
In real life, the driver rarely gets a chance to see which pantograph is up; all he knows is the position of selector switch. Sometimes when a damaged pantograph is replaced, a pantograph of a different kind one shoe instead of two may be installed; the loco still works, although perhaps suboptimally. About the only time the driver must raise or lower the pantographs when the locomotive is in motion is at the AC-DC changeover point a little north of Virar on the Virar-Vaitarna section -- at a 'dead zone' or neutral section where there is a length of overhead catenary with no electricity supplied to it, between the AC and DC catenaries.
This usually extends for a length of about two or three catenary sections.
About a kilometer before this dead zone, a sign alerts driver with a ' meters' warning followed by another for ' meters' and then a sign saying 'Dead Zone'. Going from Mumbai towards Dahanu, the driver shuts most of the equipment in the loco off air compressor charged, traction motors cut off, motor generator switched off, etc.
At this point, he raises the AC pantograph. After about 30 seconds, the voltmeter shows 25 kV and he restarts the traction and other equipment. There, all locos have to stop and wait for the line voltage to be switched on in the intermediate neutral section.
The 'DS' is the main Disconnecting Switch, a manually operated circuit breaker in the DC supply path from the pantograph, that isolates and grounds the 1. This tricky manoeuvre is necessary when the speed is that low, because of the danger of losing momentum and stopping in the dead zone without power in case of any adverse conditions like emergency brake application, or brake pipe parting, etc.
The dead zone is one length of catenary and considering the cross-over structures on the DC and AC sides it is nearly two lengths, hence the loco and train have to have enough momentum for the loco to get across this distance.
What happens if the wrong selection has been made at the wrong time?
Not all IR locos have protection against incorrect line supplies, and the loco can be severely damaged in such cases. In some cases, this will blow a fusible link located near pantograph, and the driver will have to raise the appropriate ALT pantograph to continue. No further damage is possible because the only equipment that is live when pantograph is being raised is the voltmeter.
All others like the compressor, exhauster, and motor-generator have to be switched on manually after the pantograph is raised and the voltmeter shows the correct reading. What happens if the pantograph isn't lowered when the loco enters the dead zone? Usually there is no problem, if the master circuit breaker of the loco has been switched off.
Maintenance Handbook on Bonding Earthing for 25 KV AC Traction Systems(1)
In most cases of neutral sections, therefore, the driver does not have to lower the pantograph. If a live loco enters this section without its master circuit breaker turned off, then there is a possibility of sparking or transient disturbances, which can trip protective circuits in the loco and bring the train to a halt.
Rarely, it may trip breakers for the OHE and bring all the traffic to a halt. Regardless of this, and whether or not the pantograph is lowered, once the loco enters the dead zone it loses power and will grind to a halt once it loses its momentum, if it cannot coast all the way to the next live section.
When does the driver have to lower and raise a pantograph on the run? Normally, pantographs do not have to be lowered and raised on the run. Other than that, there are a few points where the catenary has a gap no cable physically present, not even a neutral or dead section , for instance at level crossings where there is provision for extra-tall road traffic, in which case the pantograph has to be lowered as the loco coasts through the gap.
The catenary may also be missing for short sections above diamond crossings or complex track configurations. Also, pantographs may be lowered and raised occasionally for troubleshooting if the driver suspects a problem.
In the AC sections, when the phase of the overhead cable's power supply changes at the 'phase breaks' the pantograph need not be lowered and raised at the dead zone. This happens in many places, e. Usually the driver will switch off and switch on the equipment in the loco in order to prevent transient effects from damaging the equipment.
Why do locos sometimes use the rear pantograph and sometimes the front pantograph? There is in principle no difference between using the front and the rear pantographs for most locos as each is fully capable of delivering the required electric current from the catenary to the loco.
The AC-DC locos are special in that each loco is intended for a different traction supply. Generally on IR there is no need for both pantographs to be raised at once since there are usually no unusual situations such as frost on the catenary or increased current collection requirements seen with other countries' railways.
Yet, it is often seen that there are some definite patterns in pantograph usage. It has been the practice in many areas for locos to always have their rear pantographs up. It is thought that this practice arises from the idea that entanglement of the catenary by the front pantograph may result in damage to the rear pantograph as well as the debris or broken equipment lands on it, and using the rear pantograph lessens the chance of this.
Considerable experience has since been gained in the operation and maintenance of electric traction assets. Technological upgradation has also been continuously taking place.
Microprocessor based SCADA systems for remote control of traction power supply have been introduced with telemetering facilities. Vacuum and SF6 gas circuit breakers have by and large replaced minimum oil circuit breakers.
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A pilot project of electrification with 2 x 25 kV State-of-art technology on Bilaspur-Bina-Katni section has also been taken up. While earlier supply was being availed at 25 kV from power supply authorities, Railway owned traction sub-stations and transmission lines have come up.
WAG5 freight locomotives HP. A sizeable fleet of dual brake locos has come up to offer better operational flexibility. These developments have given rise to a need for updating the Manual, The present Manual caters to this requirement and is the result of efforts put-in by a number of Electrical Engineers of Indian Railways.
I hope the Manual, in its revised form, will help towards developing better know-how of the prevalent system in respect of Maintenance and Operation and thereby improve reliability and safety.
Member Electrical Railway Board. The "Manual of AC Traction - Maintenance and Operation" covering the maintenance and operation of 25 kV ac 50 Hz single phase traction installations, electric locomotives and electrical multiple units and other connected matters including railway electrification - was issued in The Manual is generally procedural in scope and includes essential technical data of use to the operating and maintenance personnel but does not cover the theoretical and design aspects of the traction installations and electric rolling stock as these are contained in documents issued by the RDSO as well as the respective manufacturers.
In the preparation of the Manual all relevant documents, rule books, operating manuals and standing instructions issued by the electrified railways are considered together with the knowledge of procedures and practices as observed during inspections of various installations on the railways as well as discussions with Chief Electrical Engineers of the Railways and concerned officers and staff as also with RDSO.
In what is considered to be the greatest common measure of agreement in regard to the maintenance schedules and their periodicity, the forms and registers in use, the availability of staff and operating conditions obtaining on the Railways the bases have been standardised, subject, of course to the condition that the Chief Electrical Engineer of the Railway may, where considered essential, authorise deviations to the prescribed procedures and practices to the extent necessary.There are not many suppliers of this traction system.
If any of adjacent tracks whenever they exist at intervals of not less than m. Layout diagram of a typical traction substation is shown in Fig below.
Driver moves the power controller to the full power position 2. It consists of a rotating shaft, driven by the diesel engine.
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