LED Light emitting diode
LNT LON network tool
LON Local operating network
MCB Miniature circuit breaker
MCM Mezzanine carrier module
MIM Milli-ampere module
MPM Main processing module
MVB Multifunction vehicle bus. Standardized serial bus originally
developed for use in trains.
NCC National Control Centre
NUM Numerical module
OCO cycle Open-close-open cycle
OCP Overcurrent protection
OEM Optical ethernet module
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 over-reaching
when the impedance presented to it is smaller than the
apparent impedance to the fault applied to the balance point,
i.e. 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
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
1MRK 504 088-UEN C Section 17
Glossary
229
Installation and commissioning manual
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