IRF
Internal failure signal
IRIG-B:
InterRange Instrumentation Group Time code format B, standard 200
ITU
International Telecommunications Union
LAN
Local area network
LIB 520
High-voltage software module
LCD
Liquid crystal display
LDD
Local detection device
LED
Light-emitting diode
MCB
Miniature circuit breaker
MCM
Mezzanine carrier module
MVB
Multifunction vehicle bus. Standardized serial bus originally developed for
use in trains.
NCC
National Control Centre
OCO cycle
Open-close-open cycle
OCP
Overcurrent protection
OLTC
On-load tap changer
OV
Over-voltage
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
PISA
Process interface for sensors & actuators
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
Section 4
1MRK 511 244-UUS A
Glossary
48
DNP, 650 series
Point list manual
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