Hi the reason that the star point on a ships generator is not connected to the hull of the ship is because the circulating currents from other boats combined with the one with the star point connected to its hull will cause the hull of the ship to be eaten away by electrolyictrolis. Putting it simply means that the hull would eventually fail to to the metal being very thin.
Hi in New zealand we use the M.E.N system which is multiple earth neutral were the earth and neutral are return paths for fault currents to flow back to the protective devices and esures that the equipment is isolated from the fault. On the super yAchts I worked the Generator earth was connected to the hull but allDC equipment was Isolated from the hull to prevent corrision of the hull and test equipment setup so no dc paths were present. David Grey
@ David : you can do that if the Yacht is a non metal hull (epoxy or wood) if it is metal even AC will start erroding the hull or the bearings.
@Kifayat :it is the unballance that you always have that starts corrosion so if you connect the star point to ground you will have stray currents in the hull. A potential of more than -300mV (that is mili Volt) and active corrosion starts or +50mV and you have paint failure. So as you understand you dont want to do that.
p.s. i am a marine corrosion engineer nad on a every day base i see the results of people that do not understand that corrosion is a electro/chemical function.
Just as a guess: in the presence of (electrically conductive) salt water, this would greatly reduce the risk of electrocution in the event of a fault developing, as there would be no complete current path through a grounded person. (Although some degree of shock could still be experienced.)
