ABB RET670 Commissioning Manual page 315

1MRK 504 165-UEN A
Transformer protection RET670 2.2 IEC
Commissioning manual
UV
WEI
VT
X.21
3I
O
3U
O
Undervoltage
Weak end infeed logic
Voltage transformer
A digital signalling interface primarily used for telecom
equipment
Three times zero-sequence current.Often referred to as the
residual or the earth-fault current
Three times the zero sequence voltage. Often referred to
as the residual voltage or the neutral point voltage
Section 16
Glossary
309