P54x/EN SG/La4 Symbols and Glossary
(SG) 14-4
MiCOM P543, P544, P545 & P546
SG
Symbols Explanation
km Distance in kilometers
kZm
The mutual compensation factor (mutual compensation of distance elements and fault
locator for parallel line coupling effects).
kZN The residual compensation factor:
Ensuring correct reach for ground distance elements.
LCD Liquid crystal display:
The front-panel text display on the relay.
LD Abbreviation of “Level Detector”:
An element responding to a current or voltage below its set threshold.
LDOV
Overvoltage level detector, used in the distance aided channel schemes.
LED Light emitting diode:
Red or green indicator on the relay front-panel.
LoL
A loss of load scheme, providing a fast distance trip without needing a signaling
channel.
MCB A “miniature circuit breaker”:
Used instead of a fuse to protect VT secondary circuits.
mi
Distance in miles.
N Indication of “Neutral” involvement in a fault:
i.e. a ground (earth) fault.
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.
NPS
Negative phase sequence.
NXT Abbreviation of “Next”:
In connection with hotkey menu navigation.
NVD Neutral voltage displacement:
Equivalent to residual overvoltage protection.
O/P
Abbreviation of “output”.
Opto An optocoupled logic input:
Alternative terminology: binary input.
P1 Used in IEC terminology to identify the primary CT terminal polarity:
Replace by a dot when using ANSI standards.
P2 Used in IEC terminology to identify the primary CT terminal polarity:
The non-dot terminal.
PCB
Printed circuit board.
Ph Abbreviation of “Phase”:
Used in distance settings to identify settings that relate to phase-phase faults.
Pol Abbreviation of “Polarizing”:
Typically the polarizing voltage used in making directional decisions.
POR
A permissive overreaching transfer trip scheme (alternative terminology: POTT).
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