ABB RET650 2.1 IEC Commissioning Manual page 124

Section 13
Glossary
118
TRM
TYP
UMT
Underreach
UTC
UV
WEI
VT
3I
O
3U
O
Transformer Module. This module transforms currents and
voltages taken from the process into levels suitable for
further signal processing.
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
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
1MRK 504 160-UEN -
Transformer protection RET650 2.1 IEC
Commissioning manual