PC-MIP
Mezzanine card standard
PMC
PCI Mezzanine card
POR
Permissive overreach
POTT
Permissive overreach transfer trip
Process bus
Bus or LAN used at the process level, that is, in near
proximity to the measured and/or controlled components
PSM
Power supply module
PST
Parameter setting tool within PCM600
PT ratio
Potential transformer or voltage transformer ratio
PUTT
Permissive underreach transfer trip
RASC
Synchrocheck relay, COMBIFLEX
RCA
Relay characteristic angle
RFPP
Resistance for phase-to-phase faults
RFPE
Resistance for phase-to-earth faults
RISC
Reduced instruction set computer
RMS value
Root mean square value
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
Section 10
1MRK511240-UEN B
Glossary
96
670 series
Engineering Manual