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user-deleted-1076
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Join Date: Oct 2010
Location: Hyd - IND
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Synchronising of DG

02/23/2011 2:08 AM

In our project we installed 5x500kVA DG's with synchronising panel thro Comap controller(Inteligen Sys), during the test run process i have observed following

1. when O/G ACB's are OFF position the Ammeter shows in each phase around 20Amps to 70Amps (Average) in each phase of the DG's with out any connected load, (how it is possible?) i have checked CT's and the control wiring also everything is fine and correct.

we have connected the neutral of the DG's thro O/G bus bar to 02nos. (parrallel) of Copper Plate earthing and value of earth resistance also in the specified limits.

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 Shaju Khan
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Anonymous Poster
#1

Re: Synchronising of DG

02/23/2011 2:41 AM

Did you megger it?
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loadshare
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Engineering Fields - Electrical Engineering - New Member Engineering Fields - Mechanical Engineering - New Member

Join Date: Jan 2011
Location: Jakarta
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#2

Re: Synchronising of DG

02/23/2011 2:52 AM

Hi,

Some question need clarification and suggestion:

1. Did all DG read amp before CB close ? if no, please check actual with amperemeter, if amp'er read no amp, you must callibrate measuremet display on comap.

2. You must do megger test bus of phase to ground and breaker itself, but try remove/disconnect power cable on DG and run the set, if ampere exist on DG then problem on the set, but when no amp read then problem on your panel or system distribution, you could review installation

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user-deleted-1076
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Join Date: Oct 2010
Location: Hyd - IND
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#3
In reply to #2

Re: Synchronising of DG

02/23/2011 10:15 AM

Dear Mr. Loadshare

1. after closing of DG CB (i.e after charging the common bus bar) the Ammeter shows / read amps in each DG. i took measurment from the DG outgoing cable (i.e to sync. panel) with clamp meter the amps reading remain same, instantaneuos values of current in amps.

2. i did not megger between common bus to ground.

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67model
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#4

Re: Synchronising of DG

02/23/2011 12:52 PM

You have not clarified how many DG are running in parallel when you make the measurement. You write DG's - do you mean 2 or more? Different makes of generator in parallel may have slightly different waveform. Does adjusting manual governor up or down on one unit have an effect on current - if one unit is slightly throttled-back, synchronizing power flow demands a reactive current.

And you have not clarified how many earths you have - if you earth two DG star points at same time, you get circulating harmonic currents without any load.
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loadshare
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#5

Re: Synchronising of DG

02/23/2011 7:46 PM

1. You mentioned ampere read when CB Off, now you mentioned amp read when after sync and CB close. If that case, its very common issue when DG parallel. The ampere read on meter is caused of different voltage between the DG. No worry about that as long as the amp not too high, if you have so you will get reverse power.

2. No need to megger.

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Dave Simpson
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#6

Re: Synchronising of DG

02/24/2011 10:09 AM

Is there a device that measures phase angle between DG's? And cos.phi? Are output V's all exactly the same? Are the ammeters electronic or straight 'moving iron' type? The latter is preferable in this application.
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