Technical data

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
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
1MRK 511 261-UUS A Section 10
Glossary
650 series ANSI 129
Engineering Manual