tweeky
Marine/Ocean
- Nov 27, 2008
- 4
- 0
- 0
I work for a ferry company with 30 ships. All our ships have a three phase 440v insulated neutral system. So basically the neutral terminal at the generators are not used with only the three phase wires going to the main breakers in the control room. The ships hull is being used as a 'floating earth'. I know this system is used as it has better reliability for essential gear on vessels. This is because if an earth fault appears on one phase it will not trip the breaker as there would not be a path back to neutral. If an earth fault appears on two of the phases then the breaker would trip.Having earth meters on board gives the engineer time to solve problems before the breaker trips. I know also some ships have a neutral earthed system as well, which would trip the breaker if a fault appeared on any one phase.
My concern is that with all the new earth friendly regulations some of our vessels are planning on using shore power to stop generators running all night. If the vessel uses shore power what would be the best way to connect the earth cable from shore to stop electrolysis happening.
The shore power box on certain vessels have the earth tag from the box connected straight onto the ships hull. I dont think this is correct! As the vessel is an insulated neutral system it probably is not as bad as it would be if it was a neutral earthed system.
As the PD of the shore power earth will be different to the ships hull this would cause electrolysis.
What i need to know is if there is anybody with any experience in this matter and suggestions regards the best way to earth the vessel safely.
My concern is that with all the new earth friendly regulations some of our vessels are planning on using shore power to stop generators running all night. If the vessel uses shore power what would be the best way to connect the earth cable from shore to stop electrolysis happening.
The shore power box on certain vessels have the earth tag from the box connected straight onto the ships hull. I dont think this is correct! As the vessel is an insulated neutral system it probably is not as bad as it would be if it was a neutral earthed system.
As the PD of the shore power earth will be different to the ships hull this would cause electrolysis.
What i need to know is if there is anybody with any experience in this matter and suggestions regards the best way to earth the vessel safely.
