SRY Switch for CB ready condition
ST Switch or push button to trip
Starpoint Neutral/Wye point of transformer or generator
SVC Static VAr compensation
TC Trip coil
TCS Trip circuit supervision
TCP Transmission control protocol. The most common transport layer protocol used
on Ethernet and the Internet.
TCP/IP Transmission control protocol over Internet Protocol. The de facto standard
Ethernet protocols incorporated into 4.2BSD 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 gound-fault protection function
TLS Transport Layer Security
TM Transmit (disturbance data)
TNC connector Threaded Neill-Concelman, a threaded constant impedance version of a BNC
connector
TP Trip (recorded fault)
TPZ, TPY, TPX, TPS Current transformer class according to IEC
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
1MRK 504 165-UUS Rev. J Section 16
Glossary
Transformer protection RET670 321
Commissioning manual
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