Symbols and Glossary P54x/EN SG/La4
MiCOM P543, P544, P545 & P546
(SG) 14-1
SG
Logic symbols
Symbols Explanation
< Less than:
Used to indicate an “under” threshold, such as undercurrent (current dropout).
> Greater than:
Used to indicate an “over” threshold, such as overcurrent (current overload)
& Logical “AND”:
Used in logic diagrams to show an AND-gate function.
1 Logical “OR”:
Used in logic diagrams to show an OR-gate function.
o
A small circle on the input or output of a logic gate:
Indicates a NOT (invert) function.
52a A circuit breaker closed auxiliary contact:
The contact is in the same state as the breaker primary contacts.
52b A circuit breaker open auxiliary contact:
The contact is in the opposite state to the breaker primary contacts.
“Sigma”:
Used to indicate a summation, such as cumulative current interrupted.
“Tau”:
Used to indicate a time constant, often associated with thermal characteristics.
ABC
Anti-clockwise phase rotation.
ACB
Clock-wise phase rotation.
BAR
Block auto-reclose signal.
BOP
Abbreviation of “Blocking Overreach Protection”. A blocking aided-channel scheme.
BU Backup:
Typically a back-up protection element.
C/O A changeover contact having normally closed and normally open connections:
Often called a “form C” contact.
CB
Circuit breaker.
CB Aux. Circuit breaker auxiliary contacts:
Indication of the breaker open/closed status.
CBF
Circuit breaker failure protection.
Ch
Abbreviation of channel - usually a communications or signaling channel.
CNV
Abbreviation of Current No Volts
CRx Channel Receive:
Typically used to indicate a teleprotection signal received.
CS
Check synchronism.
CT
Current transformer.
CTRL. Abbreviation of “Control”:
As used for the Control Inputs function.
CTS Current transformer supervision:
To detect CT input failure.
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