transformers in the feeder circuit (for example, in the transformer bushings). It is often
required to separate the protection zones that the feeder is protected with one scheme
while the T-zone is protected with a separate dif
ferential protection scheme. The 1Ph
high impedance differential HZPDIF (87) function in the IED allows this to be done
efficiently, see Figure
52.
1MRK 511 401-UUS A Section 7
Differential protection
Bay control REC670 2.2 ANSI 139
Application manual