MVAL
Value of measurement
MVB
Multifunction vehicle bus. Standardized serial bus originally developed for
use in trains.
NCC
National Control Centre
NOF
Number of grid faults
NUM
Numerical module
OCO cycle
Open-close-open cycle
OCP
Overcurrent protection
OEM
Optical Ethernet module
OLTC
On-load tap changer
OTEV
Disturbance data recording initiated by other event than start/pick-up
OV
Overvoltage
Overreach
A term used to describe how the relay behaves during a fault condition. For
example, a distance relay is overreaching when the impedance presented
to it is smaller than the apparent impedance to the fault applied to the
balance point, that is, the set reach. The relay “sees” the fault but perhaps it
should not have seen it.
PCI
Peripheral component interconnect, a local data bus
PCM
Pulse code modulation
PCM600
Protection and control IED manager
PC-MIP
Mezzanine card standard
PELV circuit
Protected Extra-Low Voltage circuit type according to IEC60255-27
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
PRP
Parallel redundancy protocol
PSM
Power supply module
PST
Parameter setting tool within PCM600
PTP
Precision time protocol
PT ratio
Potential transformer or voltage transformer ratio
PUTT
Permissive underreach transfer trip
RASC
Synchrocheck relay, COMBIFLEX
RCA
Relay characteristic angle
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
1MRK 506 377-UEN Rev. K
Section 13
Glossary
Railway application RER670
177
Commissioning manual
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