Yachts 3 phase smoothing transformer

Thread Starter

ChiefEngineer

Joined Jul 28, 2014
3
Good day all!
I'm an engineer on board a 50m Benetti built in 1996. When I arrived on the boat 3 years ago the Atlas shore power converter had already been removed and there was only a direct connection from the phase sequencing box to the smoothing transformer. Transformer is a 150kva rated transformer at 380VAC 50Hz. When changing to shore power and back to boats generator power I have to go dead ship in order to do so. Currently have a new issue with the power now. When I connect to shore power and the AC power goes to the transformer only (boat still not connected and drawing power, only the transformer connected) the earth leakage on the shore power breaker on the dock supply trips. I have megged the shore power cable and there are no faults. I've checked all connections within the phase rotation or sequencing unit and have found no faults.
My question is as follows, when I read the the ohms between each of the phases on the incoming side of the smoothing transformer and to ground, I have 5-6ohms on each of the phases to ground, is this correct?

Furthermore I know the cabling on the boat is old and each year that passes I find the earth leakage on the boat going up. Is there any way to reduce the leakage other than replacing cabling? Have been through the entire boats earth straps and replaced them all this past year, however it has made no difference to the total earth leakage..... any help or assistance would be greatly appreciated.
Regards
 
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