Transformer Differential Protection
Transformer Differential Protection
(OP)
A customer has installed a solid state transformer differential relay to protect a small pad mount transformer. All of the hardware is installed. This is a non-critical application. I have never set a transformer differential relay, so this might be an excellent opportunity to learn how to properly set one. Can someone give me some guidance (or refer me to a good book) on how to set Percent differential and the corresponding slopes along with the energization inhibit features.
Regards,
Dave
Regards,
Dave






RE: Transformer Differential Protection
Quite a few settings that seem to be popular are:
Pickup (87R) ~ 0.3 x Tap
Slope 1 ~ 25%
Slope 2 ~ 40-50%
87U ~ 8
2nd Harm ~20-25%
GE has a free online book called The Art and Science of Protective Relays, that is also a very good start.
ht
RE: Transformer Differential Protection
Protecting a small padmount transformer with differential relays is unusual. Mainly because it would be unusual to have CTs to use on both sides and a high side device that can be tripped by the relay (instead of fuses).