Generator Tripping

[TraderJoe80]

Another tug boat generator trip. Whenever we run our Port Generator and vessel is underway the generator trips. When sitting at anchor or along side the dock we have no trips.

Stbd generator is fine no matter what condition. Which leads us to assume some type of vibration is causing generator breaker to open.

This is what seems to be happening as observed by Chief Eng:
When load is placed from stbd to port gen say 80kw on port, it will immediately start to load to 90 then to 105kw and trip ( generator is a 150kw gen). Amps start at about 80 then gradually build to about 95-100 amps. Breaker finally trips at about 105kw and 155amps. I’m told the voltage stays at 480 the whole time, and the cycles are maintained at 60hz. Is this even possible? Do you think we could have a partial ground on the 480 line which is drawing some amps? The engineers aboard made no comment on the ground detection lights (which I’m waiting to hear back on). In E=IR if current is going up how come voltage isn’t dropping??? Is this possible?

I have an electrician going to visit the ship to take thermal imaging of the breaker and inspected contacts of main breaker. Do any of you have any other thoughts???

 

[alehman]

Sure it's possible. The generator would normally have a voltage regulator whose purpose is to maintain constant voltage output for load within its rated kW.

I suppose it's conceivable vibration is causing the trip, but something would have to be wrong with the breaker for that to be the case. I'm guessing the generator vibrates a fair amount itself, regardless of whether you're underway or not?

What is the amp trip rating of the circuit breaker? What else might change while underway? Are there any high inrush loads that occur under certain conditions?

 

[TraderJoe80]

No different loads that are on
While underway. The starboard generator is fine. That's what is throwing it off. We want to swap out breakers (port to stbd) to see if the problem switched, but I don't thinkit would have been the smart thing to do while we were out to sea. I don't know the amp rating right now. I will get back to you. If this posting is all weried its because I'm on my blackberry and the words aren't showing anymore?

 

[ScottyUK]

It's pretty much impossible for the power drawn by the load to change unless either the voltage or the frequency changes. That opens up a couple of possibilities: the power monitoring device is sick and thinks the power is increasing, causing the trip; the power really is increasing and either the voltage or frequency, or both, is changing but the instruments aren't detecting it. Verify your generator metering is behaving correctly against an independent instrument, and recalibrate the engineer's eyes if need be.


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If we learn from our mistakes I'm getting a great education!

 

[edison123]

I would check the CT's of the starboard generator for erroenous output.

 

[rbulsara]

Well, I still have some basic questions, seeking clarification:

1. Are you paralleling the two gens while transferring the loads, when the trip happens?

2. What do you mean by

Whenever we run our Port Generator and vessel is underway...

Is the vessel on the move when connected to port gen???? or you are paralleling the two gens?

3. What is meant by

When load is placed from stbd to port gen say 80kw on port, it will immediately start to load....

Sounds like you are paralleling the two gens.

Please clarify.

 

[TraderJoe80]

Port generator only trips when running on the board by herself. In parallel operations everything is fine. The trip occurs typically 30-45mins after being online.

"being underway" I mean the vessel is in transit, moving, not at anchor or tied along side the dock.

In response to the earlier guy recalibrating the Engineer's eyes....I think his eyes need more than recalibration! When we asked the Chief Engineer what had happened he said "I weren't never seen it before". I don't know what's worse, that he said that or that I knew what he was trying to say! haha.

Thanks for all your help guys!

 

[rbulsara]

traderjoe:

Sounds like you are stating a second hand account. You need to witness what is happening or get more facts.

Before you blame the chief engineer for ambiguity, you need to get your write up more clearer. At least I can't add up your description.

If the vessel is on the move, what loads are placed to the port gen?? How do you "place the load from std by to the port gen" when you are moving the load off of the port gen??

Does the port gen feed anything else on the port other than your vessel?

What is the normal operation? Meaning what is supposed to happen if the port gen was not tripping? Should it keep running or keep feeding some other load?

May be the guy who is disconnecting the "plug" is just throwing it in the water???

 

[ccjersey]

rbulsara, it sounds like a confusion between "port" side generator of the two generators in the tug and being in "port" tied alongside the dock.

What could cause some sort of circulating current within one generator and it's loads but not the other (identical???) one and the same loads? I would have thought this would happen while paralleled, but apparently the paralleling gear is taking care of the problem of circulating currents.

Probably eliminates basic problems with defective CT's etc if it will parallel, but isolating it changes some connection.

 

[waross]

Probably the breaker thermal trips on the Port generator breaker are failing.
This is based on the following information that I think we have,
The starboard genny works fine.
Parallel with both sharing the load works fine.
Running on the port generator the faulty breaker takes the full load current and due possibly to corrosion of the bimetal thermal trips, trips at less than full load current.
Change the breaker!!
Load build slowly. Probably a coincidence that also happens on the starboard generator also. But, with no problem on the starboard generator, no-one is sitting watching the ammeter.
Remember the immortal words we recently heard:
"I weren't never seen it before".



Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rbulsara]

ccjersy:

Thanks for the explanation. Still not all facts are clear. What is the actual load? Does the port gen ever runs OK on its own or it only trips when on the move, etc.

 

[rmw]

The way to solve this problem is to put her full astern and in that way the port generator becomes the starboard generator.

rmw

 

[oldfieldguy]

You don't add load when you swap to the port generator, and then you get -indication- of rising load before the port genny trips? I'd see if there was a way to monitor the load with a backup device, even a clampon meter to see if something validates the indication.

Easy trick--- does the prime mover sound like it's loading up? If visible, can you see the throttle moving to the higher power setting?

If these aren't happening, you have equipment giving you erroneous data.

It sounds like a control unit or generator breaker going bad

old field guy

 

[RRaghunath]

Could it be that the Over current release in the breaker is set low (lower than the generator rating)!!