Protection Engineering Basics and Schemes Protection Engineering | Page 203
6.3.2 Biased Differential Protection: It is technique in which Pick up current of Differential Protection relay will rise with through current.
From this point the concept of slope is come in differential relay, where protection relay produce different response on different amount of fault or differential current,
If I assigned 10 % slope and 30 % slope in differential relay, then response with respect of time is different in both slope condition.
There is two current input on which relay will work, I biased and I operation