ABB RET670 Commissioning Manual page 325

1MRK 504 165-UUS -
Transformer protection RET670 2.2 ANSI
Commissioning manual
TYP
UMT
Underreach
UTC
UV
WEI
VT
X.21
3I
O
3V
O
Type identification
User management tool
A term used to describe how the relay behaves during a fault
condition. For example, a distance relay is underreaching when
the impedance presented to it is greater than the apparent
impedance to the fault applied to the balance point, that is, the
set reach. The relay does not "see" the fault but perhaps it should
have seen it. See also Overreach.
Coordinated Universal Time. A coordinated time scale,
maintained by the Bureau International des Poids et Mesures
(BIPM), which forms the basis of a coordinated dissemination
of standard frequencies and time signals. UTC is derived from
International Atomic Time (TAI) by the addition of a whole
number of "leap seconds" to synchronize it with Universal Time
1 (UT1), thus allowing for the eccentricity of the Earth's orbit,
the rotational axis tilt (23.5 degrees), but still showing the
Earth's irregular rotation, on which UT1 is based. The
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
A digital signalling interface primarily used for telecom
equipment
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
Section 16
Glossary
319