ABB RELION RET670, Applications Manual

Page: 1013 / 1016

TRM Transformer Module. This module transforms currents and
voltages taken from the process into levels suitable for further
signal processing.
TYP Type identification
UMT User management tool
Underreach 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.
UTC 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.
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 ground-fault current
3V
O
Three times the zero sequence voltage. Often referred to as
the residual voltage or the neutral point voltage
1MRK 504 163-UUS A
Section 26
Glossary
Transformer protection RET670 2.2 ANSI 1007
Application manual