ABB Relion 670 series, Technical Reference Manual

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RS422 A balanced serial interface for the transmission of digital data
in point-to-point connections
RS485 Serial link according to EIA standard RS485
RTC Real-time clock
RTU Remote terminal unit
SA Substation Automation
SBO Select-before-operate
SC Switch or push button to close
SCS Station control system
SCADA Supervision, control and data acquisition
SCT System configuration tool according to standard IEC 61850
SDU Service data unit
SLM Serial communication module. Used for SPA/LON/IEC/
DNP3 communication.
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.
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/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.
1MRK505222-UUS C
Section 23
Glossary
1221
Technical reference manual