Harmonic resraint
Harmonic resraint
(OP)
I had a question concerning harmonic restraint for differential relaying. The question concerns an auto transformer with a delta tertiary. I was told that there would be no need to have harmonic restraint for this particular transformer due to the presence of the delta tertiary. I do not see how the two are similar. I thought that harmonic restraint was for energizing a transformer and restraining for second and fifth harmonic current. I thought the only purpose of a delta tertiary in an auto transformer was to reduce fundamental harmonic. Any clarification would be appreciated. Thanks






RE: Harmonic resraint
Alan
"The engineer's first problem in any design situation is to discover what the problem really is." Unk.
RE: Harmonic resraint
By the way, if you have in your relay setting option "cross blocking" for charmonic restrain, don't forget to ckeck it. I had a case in the past when left it unchecked and old 25 MVA transformer tripped when level of 2-nd charmonic of 2 from 3 phases dropped under setting level.
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It may be like this in theory and practice, but in real life it is completely different.
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