ABB Relion Technical Manual page 776

Section 22
Glossary
770
UV
WEI
VT
3I
O
3V
O
Coordinated Universal Time is expressed using a 24-hour clock,
and uses the Gregorian calendar. It is used for aeroplane and
ship navigation, where it is also sometimes known by the
military name, "Zulu time." "Zulu" in the phonetic alphabet
stands for "Z", which stands for longitude zero.
Undervoltage
Weak end infeed logic
Voltage transformer
Three times zero-sequence current. Often referred to as the
residual or the ground-fault current
Three times the zero sequence voltage. Often referred to as the
residual voltage or the neutral point voltage
1MRK 502 048-UUS A
Technical manual