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phonetic alphabet stands for "Z", which stands for
longitude zero.
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 511 394-UEN A
Section 6
Glossary
670 series 2.2 IEC
71
Communication protocol manual