ABB REG670 - Page 777

X.21 A digital signalling interface primarily used for telecom
equipment
3I
O
Three times zero-sequence current.Often referred to as the
residual or the earth-fault current
3U
O
Three times the zero sequence voltage. Often referred to as
the residual voltage or the neutral point voltage
1MRK 502 071-UEN - Section 25
Glossary
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 771
Application manual