Sites: GlobalSpec.com | GlobalSpec Electronics | CR4 | Electronics360
Login | Register
The Engineer's Place for News and Discussion®

Previous in Forum: Type of Cables for Fire Safety Devices   Next in Forum: Link Box Problem
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







4 comments
Member

Join Date: Apr 2012
Posts: 7

Diesel Generator Over Current

05/03/2012 7:24 AM

our diesel generator 4.0MVA capacity, 6.3kV voltage faced over current just after synchronization with the bus and resulted in damaging one of the excitation rotating diode due to over excitation.

what is reason of over current just after synchronization?

Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain - possibly to become "South Scotland" or "Non-Caledonia" from September 2016. Kettle's on.
Posts: 22589
Good Answers: 579
#1

Re: Diesel generator over current

05/03/2012 7:26 AM

Incorrect setting of the overcurrent protection device(s) prior to commissioning.

__________________
"The problem with quotes on the internet is that it is extremely difficult to establish that they are genuine." - Abraham Lincoln.
Register to Reply
Guru

Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 2347
Good Answers: 60
#2

Re: Diesel Generator Over Current

05/03/2012 12:57 PM

Is this the same disel generator as in your earlier post?

__________________
Give masochists a fair crack of the whip
Register to Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 1687
Good Answers: 223
#3

Re: Diesel Generator Over Current

05/03/2012 3:40 PM

If this is the same generator as your previous post then thanks for confirming my analysis. Now it's time for you to read everyone's responses and get some competent help instead of starting a duplicate thread. If your operating/tagging/relaying procedures are so lax that they allow for closing a breaker on to a dead generator then it's time to get some engineers out there before you close a breaker onto a dead bus that just happens to have live people (maybe even you) working on it.

To answer your question, the diode(s) failed because of the huge current that was induced in the stationary rotor, kind of like the current that is induced in the rotor of an induction motor that is started DOL, except that instead of having welded end-turns to handle the current induced in the field you had diode junctions and fuses. As an exercise you might try calculating what those currents might be; it can be done with the information that you can get from the manufacturer.

If this is yet another generator under your watch then you failed to follow the three basic requirements for proper synchronization; matched frequencies, matched voltages, and matched phase sequence. My guess is that you closed way off speed or out of phase, the huge current draw was the system trying to instantly get the rotor up to speed and/or in phase; be glad that your overcurrent protection took you out.

__________________
Curious minds want to know, engineering minds get answers....
Register to Reply Score 1 for Good Answer
Commentator

Join Date: May 2012
Posts: 56
#4

Re: Diesel Generator Over Current

05/13/2012 6:26 AM

hello fiaz6555 , the reason of that is he take somuch load that is why diod is damage to avoid that happen again you to turn of all output load before you start your generator and when it start wait 2min and then turn on one by one your CB , hope that will make you happy. and you can repair the broken diod to here is the wesite to get diod http://www.powersupply-parts.com/sdp/1198946/4/pd-5469021/9773278-2125666/Stamford_rectifier_diode_RSK2001.html

at your service O&M GENTECH,

__________________
i want ot helf piple need assistance and to share my knowleged in technical
Register to Reply Off Topic (Score 5)
Register to Reply 4 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

Codemaster (1); PWSlack (1); RAMConsult (1); toink (1)

Previous in Forum: Type of Cables for Fire Safety Devices   Next in Forum: Link Box Problem