Unix. TCP/IP was developed by DARPA for internet working
and encompasses both network layer and transport layer
protocols. While TCP and IP specify two protocols at specific
protocol layers, TCP/IP is often used to refer to the entire US
Department of Defense protocol suite based upon these,
including Telnet, FTP, UDP and RDP.
TEF
Time delayed earth-fault protection function
TNC connector
Threaded Neill Concelman, A threaded constant impedance
version of a BNC connector
TPZ, TPY, TPX,
TPS
Current transformer class according to IEC
Underreach
A term used to describe how the relay behaves during a fault
condition. For example a distance relay is under-reaching
when the impedance presented to it is greater than the apparent
impedance to the fault applied to the balance point, i.e. the set
reach. The relay does not “see” the fault but perhaps it should
have seen it. See also Overreach.
U/I-PISA
Process interface components that deliver measured voltage
and current values
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 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
3IO
Three times zero-sequence current. Often referred to as the
residual or the earth-fault current
3UO
Three times the zero sequence voltage. Often referred to as the
residual voltage or the neutral point voltage
Section 15
Glossary
RET 670
Operator's manual
1MRK504049-UEN rev. D
91
