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Topic Title: Secondary Injection tests on
Topic Summary: Negative Sequence overcurrent relay (46) and Loss of Field (40)
Created On: 22 May 2010 12:36 PM
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 22 May 2010 12:36 PM
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bobramsey

Posts: 26
Joined: 17 December 2003

To carry out the secondary injection tests on a Negative Sequence overcurrent (46) and Loss of Field (40) protection relays is just a case of injecting the required current for "tripping" as overcurrent and differential relays?
I have performed the test on these with no problem.
 22 May 2010 05:09 PM
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sfchew

Posts: 589
Joined: 10 December 2002

You may have to indicate the loss of field relay working principle. Generally you require injection of both current and voltage simultaneously. Negative sequence can be current injection only. Regards Chris Chew
 22 May 2010 05:27 PM
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ArthurHall

Posts: 735
Joined: 25 July 2008

Feild failure requires the use of phase shifting equipment.
NPS requires a three phase test set, rough checks can be made with a single phase test set but you will have to use about three times the setting to get it to pick up
 22 May 2010 06:51 PM
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bobramsey

Posts: 26
Joined: 17 December 2003

Thank you, sfchew and ArthurHall
I've managed to "trip" the NPS in the Alarm mode setting, but the Trip point setting will not operate - I suspect the relay is faulty inside the electronics.
So far no sucess with the FF, I have the AC voltage connected (100V) and trying to phase - shift the injected current (-90) - but so far I haven't managed it.
The test unit is supposed to allow this - it is a ISA DTRS unit, working with X-Test software - and it is a very old version!
I will keep trying different settings, of course the FF relay could be bad!
They both are 23 years old - Delle-Alsthom units!

The reason for the tests, is that there was a major SC on the main busbars coming from the generator (11Kv, 21Mva unit).

Thanks again guys
 22 May 2010 08:29 PM
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ArthurHall

Posts: 735
Joined: 25 July 2008

Bob
you need to predict the operating point then check that the relay operates at that point, otherwise it is not a complete test.
Could you not hire a suitable test set for a couple of days?
You say that they are 23 years old, thats not that old, but given the importance of the protection have they not been tested in that time? I would say every 3 to 5 years. If the protection was working properly it might have minimised the damage caused by your fault.

Arthur
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