Protection Engineering Basics and Schemes Protection Engineering | Page 88

in next drawing we are observing the Neutral unbalance
CT and PT circuit.
One neutral unbalance CT via Test block is connected to
C-70 relay, in C-70 relay there is function named as 46UB,
which is unbalanced detection relay due to negative
sequence current.
Basically these relays equipped with two stage of
tripping, 1st one is activate when value increase up to
pg. 88