Ship Power

[mbrooke]

Do ship power systems use a neutral? I see a lot of diagrams without them:

 

[PaulMmn]

They have a hard time finding a 'ground.' :lol:

 

[mbrooke]

They have a hard time finding a 'ground.' :lol:

There is ground, its the ship's haul. :thumbsup:

 

[winnie]

There is ground, its the ship's haul. :thumbsup:

So only bulk transport ships carrying soil

Seriously, I honestly know next to nothing about ship power, but I recall reading that there are sometimes issues with stray current causing corrosion when connected to grounded shore power.

-Jon

 

[mbrooke]

So only bulk transport ships carrying soil

Seriously, I honestly know next to nothing about ship power, but I recall reading that there are sometimes issues with stray current causing corrosion when connected to grounded shore power.

-Jon

It gets complicated, this I know. Wish an expert would chime in.

 

[Hv&Lv]

Not an expert but I know a guy that was an engineer in the Navy.
he said it’s an insulated neutral system. If you have a ground fault it turns on a light and the equipment keeps working. Only if you have a second fault will something trip.
he said when someone noticed a light on, they would trip the breakers until the light went off to identify the faulted line. The critical circuits were checked next to last, and the circuits to the captains quarters were very last...

 

[mbrooke]

Not an expert but I know a guy that was an engineer in the Navy.
he said it’s an insulated neutral system. If you have a ground fault it turns on a light and the equipment keeps working. Only if you have a second fault will something trip.
he said when someone noticed a light on, they would trip the breakers until the light went off to identify the faulted line. The critical circuits were checked next to last, and the circuits to the captains quarters were very last...

Would make sense.

 

[LarryFine]

That diagram is a one-line drawing, not even showing phases (three probably), so you can not tell whether there is a neutral from it (yes, probably).

 

[tom baker]

Charlie B was an electrical engineer on the Nimitz, see if he answers

 

[iceworm]

Puget sound Naval Shipyard - 1973 - 1980, Refueling overhauls, surface ships and submarines.

All were 480D, ungrounded - even the reactor coolant pumps

Except the last carrier that I cant remember, cause when it came - I was leaving. The Reactor Coolant Pumps were 4160D, ungrounded

I have no clue about civilian ships

 

[mbrooke]

Was the 120 ungrounded? I once heard of 120 volts ungrounded delta.

 

[petersonra]

I can tell you that all the gensets for navy vessels I have seen are wye systems. My understanding is no comnection from wye to hull. Dont want ground fault to trip anything. Bad juju to trip main cb during surface battle.

 

[Besoeker3]

Not an expert but I know a guy that was an engineer in the Navy.
he said it’s an insulated neutral system. If you have a ground fault it turns on a light and the equipment keeps working. Only if you have a second fault will something trip.

Yes, neutral and ground are two different things although there seems to be a tendency on here to use them interchangeably. I suppose on a ship, the hull would be used as the ground.

My only experience on ships was a series of Canadian icebreakers where we supplied and commissioned variable speed drives for deck machinery. The supply was, from memory, 575Vac. We didn't need a neutral. We had an internal control transformer for relays and the main contactor. One leg of that was connected to the chassis. I don't where or whether the chassis was connected to an external "ground". We didn't do the installation.

Forgive me mods. An aside. It was an interesting application and experience. I remember the load testing on one of the vessels. It was to pick up a 25 tonne load from the dock. I could hear our drive running, saw the winch winding in, and the load not moving. Light bulb moment. The ship was moving. It heeled over about 15 degrees to the starboard before that load moved off the dock. I know 15 deg doesn't sound like much but if you are trying to walk across a slippery deck.............

 

[charlie b]

Charlie B was an electrical engineer on the Nimitz, see if he answers

And on the Eisenhower, a sister ship to the nuclear-powered carrier Nimitz, and the nuclear-powered cruiser Arkansas as well. But that part of my work life ended 35+ years ago. So don't rely too heavily on my memory.

The carriers had a 4160 volt delta connection for shore power service, and their generators produced the same voltage. There were step-down transformers to 480 volts for the large motors, but I don't recall whether the secondary windings were WYE or Delta. The cruisers had a 480 volt delta connection for shore power service, and their generators produced the same voltage. Both classes of ships had step down transformers with 120/208V WYE secondary windings. The neutral point of the transformers were not connected to any "ground," and in particular not to the ship's hull.

This was for reliability, as has already been mentioned. If a phase conductor contacted a metal enclosure, for example, it would not result in a short circuit, and no equipment would be out of service. A second phase-to-metal enclosure from a different phase would cause a breaker or fuse to terminate the short circuit. So it was important to discover and fix the first, before the second could happen.

I would like to clarify something said in post #6. The ships on which I served did have a ground detection system. But the ground indicator light did not immediately come on when a phase wire contacted a metal enclosure. Rather, an operator would push a "ground test" button once an hour, during the routine recording of temperatures, pressures, levels, and all other parameters that are monitored throughout the engineering plant. Once a ground fault was noticed, we did turn off circuits one-by-one until the fault was isolated.

 

[charlie b]

I have no clue about civilian ships

I have a slight clue. I spent a year (05-06) working in Naval Architecture and Marine Engineering. I did design work on several types of vessels, including tug boats, ferries, and oil tankers. All of them had an ungrounded distribution system. The tankers had a requirement that I had not encountered before. Any circuit that served an outlet of any kind in the vicinity of the oil storage tanks had to originate from a 2-pole breaker. One pole was for the phase conductor, and the other pole was for the neutral.

 

[mbrooke]

I have a slight clue. I spent a year (05-06) working in Naval Architecture and Marine Engineering. I did design work on several types of vessels, including tug boats, ferries, and oil tankers. All of them had an ungrounded distribution system. The tankers had a requirement that I had not encountered before. Any circuit that served an outlet of any kind in the vicinity of the oil storage tanks had to originate from a 2-pole breaker. One pole was for the phase conductor, and the other pole was for the neutral.

So it was a 4 wire system? Why not 3 wire since they got 2 poles already? And how did they get the noodle through the two pole breakers- switching neutral like in gas stations? How were ground faults detected? And why not HRG- ungrounded systems have transient over voltages.

 

[mbrooke]

And on the Eisenhower, a sister ship to the nuclear-powered carrier Nimitz, and the nuclear-powered cruiser Arkansas as well. But that part of my work life ended 35+ years ago. So don't rely too heavily on my memory.

The carriers had a 4160 volt delta connection for shore power service, and their generators produced the same voltage. There were step-down transformers to 480 volts for the large motors, but I don't recall whether the secondary windings were WYE or Delta. The cruisers had a 480 volt delta connection for shore power service, and their generators produced the same voltage. Both classes of ships had step down transformers with 120/208V WYE secondary windings. The neutral point of the transformers were not connected to any "ground," and in particular not to the ship's hull.

This was for reliability, as has already been mentioned. If a phase conductor contacted a metal enclosure, for example, it would not result in a short circuit, and no equipment would be out of service. A second phase-to-metal enclosure from a different phase would cause a breaker or fuse to terminate the short circuit. So it was important to discover and fix the first, before the second could happen.

I would like to clarify something said in post #6. The ships on which I served did have a ground detection system. But the ground indicator light did not immediately come on when a phase wire contacted a metal enclosure. Rather, an operator would push a "ground test" button once an hour, during the routine recording of temperatures, pressures, levels, and all other parameters that are monitored throughout the engineering plant. Once a ground fault was noticed, we did turn off circuits one-by-one until the fault was isolated.

Ok, that answered some of the above :lol: Way cool you got to work on such a system

 

[charlie b]

So it was a 4 wire system? Why not 3 wire since they got 2 poles already? And how did they get the noodle through the two pole breakers- switching neutral like in gas stations? How were ground faults detected? And why not HRG- ungrounded systems have transient over voltages.

Keep in mind that my tour of duty in Naval Architecture and Marine Engineering was 13+ years ago. I believe the power systems were 4-wire, 120/208V, for general power and lighting. They were ungrounded neutral, for the reliability reasons mentioned above. I believe they has the same ground detection system as the navy ships, with a push-to-test-for-ground button. I might have used the phrase "2-pole breaker" incorrectly. I meant to convey that the neutral was switched, and the neutral is disconnected at the same moment the phase conductor is disconnected.

 

[mbrooke]

Keep in mind that my tour of duty in Naval Architecture and Marine Engineering was 13+ years ago. I believe the power systems were 4-wire, 120/208V, for general power and lighting. They were ungrounded neutral, for the reliability reasons mentioned above. I believe they has the same ground detection system as the navy ships, with a push-to-test-for-ground button. I might have used the phrase "2-pole breaker" incorrectly. I meant to convey that the neutral was switched, and the neutral is disconnected at the same moment the phase conductor is disconnected.

Switching the noodle is good thing :thumbsup:

 

[electrofelon]

Switching the noodle is good thing :thumbsup:

I was at sea for 30 days several years ago on RV Sikuliaq. The generators we're 690V, but I don't know if delta or wye. I also don't know what the low voltage system was. I did see a fault detector during a tour of the ships systems so something was ungrounded. (I did ask if the system was grounded or not and I got laughed at. :ashamed1: The ships Electrician was not present during the tour)