Train Lighting system

Train lighting is one of the important passenger amenities which influence the image of Railways. Although 1 st train ran on 16 th Apr-1853 from Bori Bandar (present CSTM) to Thane, train lighting system came to Indian Railway in 1930 through Axle driven Dynamo pioneered by M/s J.Stone & Co.
Power supply system for trains are designed and developed to suit the requirement of AC and non-AC working in the train. Few factors considered for development of such systems are as under:

• Coach load
• Speed of the train
• Weight of the equipments
• Available technology for reliable equipments etc.

Indian Railways have been using following systems for power supply in mail/exp trains:

• Self-generating
• Mid-on-generation
• End-on-generation
• Head-on-generation

Self-generating

• Axle driven system working on 24 V DC
• Axle driven system working on 110V DC
1. Mid-on-generation
• MOG with 415 V, 3 phase generation and 110V AC utilization
2. End-on-generation
• EOG with 415 V, 3 phase generation and 110V AC utilization
• EOG with 750 V, 3 phase generation and 415 & 110V AC utilization
3. Head-on-generation (HOG)

Power feeding from OHE for for lighting loads (EMUs):

• 750 V DC -- light & fan works on 110 V AC
• 1500 V DC -- light & fan works on 110 V AC.
• 25 KV -- light & fan works on 141 V AC

Power feeding from HOG for Hotel Loads (Loco):

• Hotel load power taken from Electric / Diesel Locomotive.
• Hotel load power supply taken directly from OHE through a separate pantograph mounted on the power car.

Self Generation system:
The power supply arrangement of SG coach has under slung alternator, which is driven by the running axles of the coach with the belt of the coach. The voltage of the alternator which varies with the speed of the train is regulated with the help of RRU and converted to 110 v DC and is used for charging the battery. The electrical load of the coach is supplied through the 110 v DC battery at halt.
Advantages:

• The system is independent of mode of traction.
• As each coach has battery, so no additional source is required.
• The problem / defect in any particular coach do not affect the others.
• System can be designed to suit for its specific requirement.
• It gives better flexibility in rake formation; majority of SG type coach is more.

Disadvantages:

• The electrical load of the coach is restricted by the limitation of capacity of generation i.e. 2 x 25 kw per coach at present.
• The power is not generated during standing or slow movement of the train, therefore bulky batteries are provided.
• There is no standby source for alternator and batteries, so system became poor reliability.
• The system requires the extensive maintenance of alternator, batteries, belts, tensioning device etc.
• The system has very poor efficiency of 57% for power it receives from the locomotive.

EOG (End-on – generation)
The EOG system is used in Rajdhani and Shatabdi type trains which have only AC coaches and have large power requirement. Each EOG train has 2 power cars with 2 x 250 kw alternator each. The power is fed by any two DA sets through IVC. The power is supplied at 3 Φ, 750 V, which is stepped down in individual coach to 3 Φ, 415 v for supplying various loads like RMPU, WRA etc. The 110 v AC supply for lights and fans is obtained by further stepping down the 415 v supply. A 24 v battery is used for supplying a few emergency lights provided in the coach.
Advantages:

• With the development of high capacity power cars, 2 x 336 kw power is available from each power car.
• The system does not require use of bulky batteries and alternators in individual coaches.
• The system has higher reliability due to standby DA sets and reduced number of equipments.
• Due to elimination of heavy equipments, the dead weight of the coach is reduced.
• The system is independent of type of traction i.e. diesel or electric locomotive.
• The system has better energy efficiency as compared to self-generating system.
• Low maintenance.

Disadvantages:

• The cost of energy is high due to high fuel cost.
• Even with 750 V, 3 Φ , there is still an effect of voltage drop at farthest end of the train.
• Noise and smoke pollution is generated from power cars.
• The passenger carrying capacity of the train is reduced due to provision of power car.

MOG (Mid-on–generation)
The MOG system was adopted by IR for slow moving passenger trains which have very low generation to non-generation ratio. These trains had one power car in the middle of the train, which fed power supply to the coaches at either side of power car. The power car coach had two DA set of 30 KVA each out of which one was used as standby. The power car coach also had one 3 Φ, 30 kva step down transformer of 415/110 v. The 110 v AC supplied to the coaches through couplers.
The system has discontinued after introduction of EMU and DMU service.
Advantages:

• The system was most suitable for slow moving branch line passenger trains.
• Light and fan of all the coaches had centralized control in power car coach.
• Fan and lights were working on AC supply.
• There was no need for stand by batteries in the coaches.

Disadvantages:

• There was noise and smoke pollution due to DA set working.
• The operator was required in power car coach.
• Some valuable passenger spaces was occupied by DA sets.

HOG (Head- on- generation ):

• The HOG scheme is widely used power supply by Railways world over. The power supply system for the coaches is either received from locomotive or it is directly tapped from traction overhead lines into the power cars.
• The system is considered to provide cost effective, reliable and energy efficient supply system for coaches.

The HOG scheme can be considered with following two options:

• Hotel load power taken from Electric / Diesel Locomotive.
• Hotel load power supply taken directly from OHE through a separate pantograph mounted on the power car.

Second system is not considered technically feasible for Indian Railways due to some limitations.
HOG scheme where power is taken from Electric / Diesel Locomotive:
The power supply is received directly from locomotive through couplers. The supply from locomotive can be a 750 v, 3 Φ supply or a 1 Φ supply at variable voltage of 750 V. The power supply received from loco is regulated and stepped down in individual AC coaches, with the help of converters to provide a regulated 415 v, 3 Φ supply. Similarly in AC coaches, power supply from locomotive can be stepped down and regulated to provide 1 Φ, 110 v AC supply. One power car with stand by DA sets is also used in the train, which can supply power to the coaches in case of failure of locomotive.
Advantage:

• Cheaper cost of power as compared to EOG & SG system.
• Pollution is less as compared to EOG system.
• One power car may be replaced by trailer coach, revenue increased.
• Escorting staff will be reduced for one power car.
• Net dead weight of the train is reduced as compared to SG sys.
• HOG type AC coaches can be used in EOG type trains.
• This system is compatible for diesel and electric traction.
• Maintenance cost of HOG system coaches is lower as compared to SG coaches.

Disadvantages:

• While working with electric locomotive there are power interruptions for short durations to various electrical equipments except lights while through neutral section.
• One power car is still required for supplying power during failure of OHE supply or locomotive etc.
• HOG type coaches require rake integrity of coaches similar to EOG system.

Conclusion:
This HOG scheme is under development. The following options for developments of HOG scheme can be considered for adoption:

• HOG scheme with individual coach converter.
• HOG scheme with bulk converter.