Ship Power System

I don't know, but we know some guys that do.


Andy B.

Is the neutral typically distributed on ship power systems?

Often not, or at least so I gather. Ships systems are often IT systems and not distributing the N makes it easier to spot "earth" faults - which aren't then immediately disconnected but show up on an indicator and then fixed as a maintenance task. The logic being that many of the ship's electrical systems are critical to the safety of the vessel (everything from navigation to steering to propulsion) - so it's better that things keep working on first faults.


("earth" usually being the steel hull, rather than terra firma)


  - Andy.

Makes sense, understood.

Especially true on battleships, where the protective systems are isolated when entering battle. More people may die if the guns trip out and the ship sinks, rather than a few people being killed by shocks from equipment in fault

Generally the above comments are correct. The most common system on ships is IT (normally 440V 3 phase 3-wire 60Hz) but sometimes on smaller ships there will be a 380V 3 phase 4-wire (60Hz or 50Hz - I have seen both) system as this means that phase-neutral is 220V and therefore there is no need for a transformer.

The principle is that an earth fault on a circuit will be detected through mandated earth fault detection but leave the circuit operational rather than tripping a vital service (as has been said above). As added security certain circuits such as steering (which has duplicated systems) will have both running while in critical locations.

There are also requirements for certain ships such as tankers which prohibit a 3 phase 4 wire system (at least in the cargo area) to prevent an earth fault current returning through the metal structure of the cargo tanks (but don't get me started on the justification for that one....)

Alasdair

Its a pretty simple system, they use a number of isolating transformers to provide zoning of the sub systems. if its fed through an isolating transformer the power flows through bu the fault is kept isolated. Basically multiple IT systems with fault monitoring. You will see this in any safety critical system, by isolation of the system and removal of an earthed neutral the power system then floats. you can have a phase to earth fault and this will do nothing other than let the operators know. however a second fault then you will blow fuses and trip breakers, but it gives you that ride out capability, Also upon the reciept of a fault the operator will quickly remove the faulted item from the system if required. Or if in the middle of something important they can carry through until they are are a safe point to recover the issue.