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Participant

Join Date: Sep 2014
Posts: 3

MV DG Sync. Issue

05/19/2015 3:18 AM

Dear All,

We have 3No's. 11 DG's MTU Sets running parallel.Our problem is any two Dg's parallel operation with load sharing is ok with in min.will happened. but when we want third set its taking more time to Sync. & aswell as load shearing by the time dg's will trips in reverse power.

We tried all the possibility like checking of governors, Droop setting etc. nothing is happenining

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Engineering Fields - Power Engineering - New Member

Join Date: May 2007
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#1

Re: MV DG Sync. Issue

05/19/2015 9:45 AM

You have not "...tried all possibility like checking of..." all the sensing wiring, PT, CT polarities, cross current compensation, etc. etc. When you do check the wiring you will most likely find that somewhere two wires were crossed.

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Member

Join Date: Aug 2010
Posts: 9
Good Answers: 1
#2

Re: MV DG Sync. Issue

05/19/2015 10:21 PM

What load are you running at ? if its too low then you could get the symptoms that you are discribing

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Guru

Join Date: Jun 2007
Location: chennai,India
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#3

Re: MV DG Sync. Issue

05/19/2015 10:45 PM

If this problem persists from commissioning then you have to check wiring,CTs etc.

If it is recent one developed after normal running for quite some time, check the third set for proper operation, check controller., check independent operation of the set.

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Guru
Engineering Fields - Mechanical Engineering - New Member

Join Date: May 2008
Location: CHENNAI, TAMIL NADU, INDIA.
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#4

Re: MV DG Sync. Issue

05/20/2015 12:24 PM

Dear Mr. Kn_murali2001,

Pl. try the 3rd set independently and load it fully. If it takes full load, the Mechanical Performance of the engine is OK.

When you are synchronising, 3rd set trips mean some problem in the Excitation Circuit, CT related issues.

Pl. post the information how the problem was solved, as I am eager to know the cause and remedy.

DHAYANANDHAN.S

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Associate

Join Date: May 2008
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#5

Re: MV DG Sync. Issue

05/23/2015 5:30 PM

My guess is that there is nothing wrong with your wiring or the generators.

Every generator (until it is synced) will wander a bit in frequency. That isn't too much of a problem with one generator.

When you put the second generator on, it will sync with the first, but then both of them will wander together. Each will contribute a little to the wandering. That can mean that they wander twice as fast, but perhaps not as far. It also will wander more erratically.

Now, you put the third one on. It's controls are tuned to slowly bring it to sync, but the target is moving faster than it can deal with. Finally, by some great chance, it manages to get frequency and phase together and finally things work out. By then, it's too late.

The solution may be to detune the frequency and phase tolerance a little bit so that it isn't quite so picky about when it declares that it is synced. The other solution is to have a single strong signal which declares what the current frequency and phase should be and have all the units sync to that. Usually, that strong one is the utility.

This is going to be a problem whenever you have generators that are about the same size. If you have one really big one, and a few little ones, the big one will set the pace, and the others will pick up on it.

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