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How does differential protection work in generators? What is the purpose of baising?
How is the scheme implemented in protection schemes. Do numerical relays offer this protection??

Responding to Santan’s 13-Jan (14:21) questions:

1) The fundamental operation is based on comparing current-in to current-out of each phase-winding, thus any unbalance or difference operates the protection device!

2) Not all circuit elements are perfect, that is, current transformer curves are not exact over the entire operating range, nor are secondary burdens (impedances) the same. Then, in order to prevent unwarranted operation due to the maximum error current that could exist. This is accomplished by biasing, as well as other methods!

3) Biasing is one way to desensitize the protection system so errors are precluded from from false trips, especially in the higher fault-current range!

4) Presuming you are differentiating (please excuse the pun) between hardware versus soft-ware based systems, the answer is yes!

If you need additional information, contact me on or off-list!

Regards, Phil Corso (cepsicon@aol.com)