ABB RED670 - Page 305

UV Undervoltage
WEI Weak end infeed logic
VT Voltage transformer
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 505 378-UEN A Section 15
Glossary
Line differential protection RED670 2.2 IEC 299
Commissioning manual