> Auxiliary and emergency services are supplied by the Main generators during normal operating conditions. In the event of an emergency, only the emergency services are supplied by the Emergency generator.
> The main generators are connected to the main bus bar via air circuit breakers. The main bus bar supplies 440V directly, 220V via transformers and 24V DC via transformers and rectifiers.
> The main bus bar is connected to the emergency switch board via the tiebreaker.
> Emergency generator is also connected to the emergency switch board.
> Arrangements are also made for shore supply to be connected.
> The general scheme of a ship’s electrical power system is common to nearly all ships. The below figure shows a typical electrical distribution system of a vessel.
Bus Tie Breaker Interlock
Interlocks are provided such that power is supplied from only one source at a time to the emergency switchboard i.e. mains supply or emergency generator, so that the circuit breakers of the two supplies cannot be closed together.