Ship distribution system
The main elements of a marine distribution system are the main and emergency switchboards, power panels / boards, motor controllers, lighting and small power panels / boards.
The system is generally designed such that under all normal conditions of operation, power is distributed from the main switchboard.
The distribution system is designed to keep cable costs to a minimum by distributing supply to power panels located close to the user services.
The main switchboard is generally located near the centre of the distribution system and this is normally the main engine room or machinery control room.
These locations are normally below the ship’s waterline or below the uppermost continuous deck of the ship i.e. the bulkhead or main deck.
Consequently, in the event of a fire or flooding it is likely that the main generators and switchboard would be disabled.
Protective system for main Switchboard
For shipboard installations specific protective systems are required to shut down all ventilation systems and all fuel oil systems in the event of a fire.
When motor auxiliaries are grouped together and supplied from a Motor Control Centre (MCC) or a grouped distribution panel, this can best be achieved by providing the MCC supply feeder’s circuit breaker with an under-voltage tripping device and connecting this to the ventilation or fuel system’s: trip unit.
When grouped MCCs or grouped distribution panels are not used, separate cables must be installed for each motor controller; this leads to increased cable costs and increases the system’s susceptibility to failure.