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DC supply system in a generating station

Short answer

DC supply system provides reliable power for protection, control, breaker trip/close, emergency lighting, and field flashing. Typically 220/110 V DC from battery banks (lead-acid or Ni-Cd) with redundant float-cum-boost chargers, distribution with earth-fault monitoring, sized per duty cycle with ageing margin.

Discuss briefly about requirements of DC supply system in a power generating station.

The DC supply system gives a reliable, uninterrupted power source for the vital control, protection and emergency loads of a power station, even when all AC supply is lost.

Requirements

  • Loads served: relay and protection circuits, breaker trip and close coils, control and SCADA, alarms, emergency lighting, field flashing, DC emergency oil pumps (governor, bearing lube), communication (often 48 V).
  • Voltage levels: typically 220 V or 110 V DC for control and switchgear, 48 V DC for telecom/PLCC, 24 V for some electronics.
  • Battery bank: lead-acid (VRLA or flooded) or Ni-Cd, sized for the duty cycle (e.g. 1–3 hours of emergency load plus trip and close surges at the end), with ageing and temperature factors (IEEE 485).
  • Battery chargers: float-cum-boost chargers fed from the station AC. Usually two chargers and two battery banks for redundancy in large stations.
  • Distribution: DC distribution board with separate feeders, fuses/MCBs, and earth-fault monitoring because the DC system is unearthed.
  • Reliability: separate battery room with ventilation (hydrogen), voltage monitoring and alarms, and regular capacity tests.

✓ Answer checked by Claude Opus 5.5 (high effort)

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