Power Supply Arrangement & Protection Scheme For Passenger Coaches:
Code of practices for prevention of fire for the different type of rolling stock is issued by RDSO and updated time to time for railways for implementation. The salient features of power supply arrangement are summarized below:
- 110 V DC two wire insulated system with each wire placed in a separate conduit to prevent any short circuit is adopted.
- In 110 V system, the fault current is 10 times more than the load current hence the faults are promptly cleared (24 V system had very narrow discrimination between fault and load current).
- 110 V DC system has reduced the load current to approx. 1/5th as compared to 24 V DC system and so the overheating at various junction points has also reduced.
- All the circuits are protected by suitable sizes of fuses.
- It does not cause shock to any person due to the floating system.
- Use of overvoltage protection has been provided to prevent any damage to the equipment.
Insulation scheme for alternators has been upgraded.
- Cables from the alternator to RRU/ERRU have been changed to copper from aluminum, along with fire retardant molding compound cleats.
- Supply scheme has a multi-level protection system in the event of short circuit & more than two earth faults.