Switchboard Safeties onboard Ships
The main switchboard (MSB) on a ship is a critical component of the electrical power distribution system. To ensure safe and reliable operation, various safety devices and measures are implemented. Here are the key switchboard safeties and their functions:
Electrical Safety Devices
Circuit Breakers
Circuit breakers are automatic shutdown devices that activate during electrical abnormalities. They protect the system by opening the circuit during overloads or short circuits, isolating the fault from the rest of the network.
Fuses
Fuses provide short circuit protection and come in various ratings. When current exceeds the safe value, the fuse material melts, isolating the faulty system from the MSB. Typically, fuses are rated at 1.5 times the full load current.
Over Current Relay (OCR)
OCRs protect against high currents on local panels and the MSB. They are set to trip at full load current with a time delay, providing protection where low power signals are used as controllers.
Earth Fault Indicators
These devices detect and indicate any ground faults in the electrical system, helping to prevent potential hazards.
Under Voltage Relay
This relay protects equipment from damage due to low voltage conditions.
Reverse Power Trip
This safety feature prevents power from flowing back into the generator, which can cause damage.
Preferential Trip
This system automatically sheds non-essential loads during power shortages to maintain critical systems.
Short Circuit Trip
This protection activates during short circuit conditions to prevent damage to the electrical system.
Physical Safety Measures
Dead Front Panel
This safety feature prevents access to live parts from the front of the switchboard. The panel cannot be opened until the power is switched off.
Insulated Rubber Mats
Anti-skid, insulated rubber mats with a minimum thickness of 15 mm are placed in front of and behind the MSB to provide electrical insulation for operators.
Interlocked Door Mechanism
The door opening mechanism is interlocked with the power supply, preventing access to live components.
Proper Earthing
The MSB and its components must be properly earthed to prevent electrical shock hazards.
Ebonite Rod
This non-conductive rod is used to remove static charges from the switchboard.
Additional Safety Measures
Proper Ventilation and Illumination
The MSB location should have good ventilation and lighting to ensure safe operation and maintenance.
No Water or Oil Pipes Nearby
Water, steam, or oil pipelines should not pass in the vicinity of the switchboard to prevent potential hazards.
Safety Charts and Signage
Charts indicating procedures for electric shock treatment and danger signs should be prominently displayed near the MSB.
By implementing these safety devices and measures, ship operators can significantly reduce the risk of electrical accidents and ensure the reliable operation of the ship’s power distribution system.
