It is very important to isolate any type of fault in an electrical system supplied from the main switchboard (MSB), or else, it will affect all the other systems connected to the same. If such isolation is not provided then short circuit in even a smaller system can cause blackout of the whole ship.
The main switchboard is an intermediate installation in the ship’s power distribution circuit, connecting the power generators and power consumers. The power generators on ships are auxiliary engines with alternators and the different engine room machineries such as motors, blowers etc. are the consumers.
Variety of safety devices are used on board ships and installed on the main switchboard (MSB) and electrical distribution panels. This ensures safe and efficient running of machinery systems and safety of the seafarers from electric shocks.
The Important safety devices fitted on main switchboard are:
Circuit breakers:
A circuit breaker is an auto shutdown device, which activates during an abnormality in the electrical circuit. Especially during overloading or short circuit, the circuit breaker opens the supplied circuit from MSB and protects the same. Different circuit breakers are strategically installed at various locations on the ship.
Fuses:
Fuses are mainly used for short circuit protection and comes in various ratings. If the current passing through the circuit exceeds the safe value, the fuse material melts and isolates the MSB from the default system. Normally, fuses are used with 1.5 times of full load current.
Over current relay:
OCR is used mainly on the local panel and MSB for protection from high current. It is installed where a low power signal is a controller. Normally relays are set equivalent to full load current with time delay.
Dead front panel:
It is also a safety device provided on the main switchboard individual panels, wherein you cannot open the panel until the power of that panel is completely switched off.
Maintenance and operational safety plays an important role for the overall safety of the main switchboard.
