requirement to have accurate hardware clocks in every
embedded system in a network. Each embedded node can
instead synchronize with a remote clock, providing the
required accuracy.
SPA
Strömberg protection acquisition, a serial master/slave
protocol for point-to-point communication
SRY
Switch for CB ready condition
ST
Switch or push button to trip
Starpoint
Neutral 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 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
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
1MRK511240-UEN B
Section 10
Glossary
670 series
97
Engineering Manual
