ABB 650 series Engineering Manual page 124

Section 10
Glossary
118
SDU Service data unit
SMA connector Subminiature version A, A threaded connector with constant
impedance.
SMT Signal matrix tool within PCM600
SMS Station monitoring system
SNTP Simple network time protocol – is used to synchronize
computer clocks on local area networks. This reduces the
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.
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.
TNC connector Threaded Neill-Concelman, a threaded constant impedance
version of a BNC connector
TPZ, TPY, TPX, Current transformer class according to IEC
TPS
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
1MRK 511 261-UEN -
650 series
Engineering Manual