People Shocked in U.S. Swimming Pool.

The real problem is not the TT or not but the fact that most ships/boats are IT so an earth fault doesn't manifest itself until there is a fault on the/an other phase/pole. There is normally an earth connection to the propeller shaft or engine which when connecting to a shore supply is connected to earth and will cause a trip if there is an earth fault on the vessel, provided the earth conductor is intact. If you read the article I provided a link to they say that the problems have been where there is an earth fault and the earth conductor in the connection (or ground conductor, being Yanks) is broken then the return path is through the water. I think the biggest problems have been with people swimming near the boat propellers (you normally board a moored/anchored boat via steps at the stern) where the voltage gradient is greatest. As the problem is a broken earth connection I think it is probably irrelevant what the earthing scheme on shore is, though no doubt someone will correct me.

Alasdair

The real problem is not the TT or not but the fact that most ships/boats are IT so an earth fault doesn't manifest itself until there is a fault on the/an other phase/pole. There is normally an earth connection to the propeller shaft or engine which when connecting to a shore supply is connected to earth and will cause a trip if there is an earth fault on the vessel, provided the earth conductor is intact. If you read the article I provided a link to they say that the problems have been where there is an earth fault and the earth conductor in the connection (or ground conductor, being Yanks) is broken then the return path is through the water. I think the biggest problems have been with people swimming near the boat propellers (you normally board a moored/anchored boat via steps at the stern) where the voltage gradient is greatest. As the problem is a broken earth connection I think it is probably irrelevant what the earthing scheme on shore is, though no doubt someone will correct me.

Alasdair