What are common maintenance procedures for earth faults prevention and troubleshooting?
10 Mar '18, 21:04
Class rules require a minimum insulation resistance of 1 mega ohm (1 million ohms). Good practice suggests that a much higher standard, as near to infinity as possible, but not less than 5 mega ohms, should be aimed for.
Any earth fault in an electrical equipment can lead to short circuiting and spark a FIRE on board. There is also an electrocution hazard due to low insulation.
There are few common areas which are detected with Earth Fault, e.g. Galley Hot plate, Laundry Room (Washing machine/Iron), Navigation lights, deck lights, etc. which can be easily rectified.
The following action can be taken to avoid earth fault on board vessel:
Watch keepers must check for earth fault every watch by pressing the Test button on the respective switch board (440v/220v/110v). Any low insulation alarm activated must be verified by pressing the Test button.
Any earth faults detected must be immediately rectified.
Watch keepers must investigate any downward trend of insulation readings.
All deck fittings especially deck light covers must be intact and watertight integrity maintained.
Cable glands for all the light fittings must be regularly checked and ensured that it is watertight and secured.
Galley hotplate must be maintained dry and clean.
Electrical contacts serving laundry machines and dryers must be maintained moisture free.
Perform Megger test on all the electrical motors periodically (3 monthly).
If an earth fault arises due to low insulation on a critical machinery(440v), the standby machinery must be first taken on load before the running machinery is isolated for investigation.
Low insulation in the 110/220V circuit or the 440V circuit or both is one of the most repetitive observation. Any earth fault requires immediate attention.
10 Mar '18, 21:10