what is the difference between high impedance REF & REF,
same high impedance differential protection & differential
protection for Power transformer?



what is the difference between high impedance REF & REF, same high impedance differential prote..

Answer / guest

REF protection can be implemented as High Imp or Low imp.
In high imp scheme, the CT ratios needs to be same but in
low the CT ratios may be different. Same is for the
differential protection. If the CT ratios are same the high
imp scheme can be implemneted as in busbar differential
protection.Key advantage of High imp tech is its immunity
to CT saturation . Key adv of low imp is to use CT with
different ratios for differentail / REF schemes.

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