Term Description
LAN Local Area Network
LCD Liquid Crystal Display: The front-panel text display on the relay.
LD Level Detector: An element responding to a current or voltage below its set threshold.
LDOV Level Detector for Overvoltage
LDUV Level Detector for Undervoltage
LED Light Emitting Diode: Red or green indicator on the front-panel.
LLDB
Live-Line Dead-Bus : In system synchronism check, indication that the line is energized whilst the
bus is de-energized.
Ln Natural logarithm
LN Logical Node
LoL A Loss of Load scheme, providing a fast distance trip without needing a signaling channel.
LPDU Link Protocol Data Unit
LPHD Logical Physical Device
MC MultiCast
MCB Miniature Circuit Breaker
MCL MiCOM Configuration Language
MICS Model Implementation Conformance Statement
MMF Magneto-Motive Force
MMS Manufacturing Message Specification
MRP Media Redundancy Protocol
MU Merging Unit
MV Measured Value
N Neutral
N/A Not Applicable
N/C A Normally Closed or "break" contact: Often called a "form B" contact.
N/O A Normally Open or "make" contact: Often called a "form A" contact.
NERC North American Reliability Corporation
NIST National Institute of Standards and Technology
NPS Negative Phase Sequence
NVD Neutral voltage displacement: Equivalent to residual overvoltage protection.
NXT Abbreviation of "Next": In connection with hotkey menu navigation.
O/C Overcurrent
O/P Output
Opto A generic term for a digital input.
OSI Open Systems Interconnection
PCB Printed Circuit Board
PCT Protective Conductor Terminal (Ground)
PDC Phasor Data Concentrator
Ph Phase - used in distance settings to identify settings that relate to phase-phase faults.
PICS Protocol Implementation Conformance Statement
PMU Phasor Measurement Unit
PNG Portable Network Graphics – a file format for a computer graphic
Pol Polarize - typically the polarizing voltage used in making directional decisions.
POR Permissive Over Reach
MiCOM P747 Appendix A - Symbols and Glossary
P747-TM-EN-1 411
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