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
3I
O
Three times zero-sequence current.Often referred to as the residual or
the earth-fault current
3U
O
Three times the zero sequence voltage. Often referred to as the
residual voltage or the neutral point voltage
1MRK 514 027-UEN D
Section 10
Glossary
650 series
65
Installation manual
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