Electrical
Electrical
(OP)
IN OLTC we observed "OUT OF STEP" Alarm, we have two different transformer, when both are in parallel this type of alarm observed. what's the meaning of this alarm and why it occurs???
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Electrical
You may have a problem with the transducer on one of the transformers which tells the control circuit what tap it is on. It could also be a problem with the tap changer itself not making a solid connection to the tap.
You said the alarm doesn't come in when only one transformer is in service. Have you tried single service to your station with both transformers? If you haven't and you put the unit that hasn't been tested into service as a single supply and you get the same out of step alarm it is likely to be a problem with the tapchanger.
RE: Electrical
Regards
Marmite
RE: Electrical
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Electrical
Thanks for you comment.
what I observed, Primary voltage of both the Transformers are not exactly same, around 2000-3000V difference observed.
secondly AVR operate Tap changer to compensate secondary voltage. and beacuse of tap positions are different it gives Out of step alarm, is it right????? or actually problem in Tap changer???
Thanks once again.
RE: Electrical
What Scotty told you is correct. With 2 paralleled transformers (primary and secondary), if one of the tap changers is out of step with the other, you develop large circulating currents.
RE: Electrical
RE: Electrical
RE: Electrical
The master/follower or master slave schemes are intended to be applied where trfrs primaries are connected to the same busbar. If this is not the case then it would be unwise to use these OLTC philosophies as circulating currents are definitely possible even with the trfrs on the same tap.
Note also, that impedance does not play such an important role as turns ratio! Trfrs differing in impedance by up to 50% can still be paralleled, the only issue is that they will not be sharing the load current in proportion to their ratings. If the units are not heavily loaded this should not be a problem.
If the source voltages differ then I recommend you consider a tapchanging algorithm such as those found in the REG-D relay (from Eberle) which seeks to minimuse the circultaing current based on various principles. In your case the algorithm that regulates when the source voltages are different is based on the power factor of the system.
Here's their website:
http://www.a-eberle.de/index.php?lang=english
Hope this helps
RE: Electrical
Your "OUT OF STEP" alarm may possibly need to be turned off in this application.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrical
Thus my recommendation that an algorithm such as those in the REG-D or similar is required.
Regards.