ABB Relion 650 Series Point List Manual page 56

Section 4
Glossary
Underreach
U/I-PISA
UTC
UV
WEI
VT
X.21
3I
O
50
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.
Process interface components that deliver measured voltage and current
values
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
-fault current
Three times the zero sequence voltage. Often referred to as the residual
voltage or the neutral point voltage
© Copyright 2011 ABB. All rights reserved
1MRK 511 244-UUS A
DNP, 650 series
Point list manual