P44x/EN SG/ Hb
MiCOM P40 Agile P442, P444
(SG) 13-
Logic Symbols used
Symbols Explanation
& Logical “AND”:
Used in logic diagrams to show an AND-gate function.
Σ
“Sigma”:
Used to indicate a summation, such as cumulative current interrupted.
τ
“Tau”:
Used to indicate a time constant, often associated with thermal characteristics.
< 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).
∆
Delta
∠
Angle
1 Logical “OR”:
Used in logic diagrams to show an OR-gate function.
1P / 3P One-pole trip / three-pole trip
21G/21P Phase and Earth Distance Protection
79/25 Autoreclosure with Check Synchronism
50N/51N Instantaneous and time-delayed neutral overcurrent protection
27 Undervoltage protection
46BC Broken conductor detection
49 Thermal overload protection
50BF Circuit Breaker Failure detection
59 Overvoltage protection
52a/52b A circuit breaker closed / open auxiliary contact
89a An Isolator closed auxiliary contact:
The contact is in the same state as the breaker primary contacts.
89b An Isolator open auxiliary contact:
The contact is in the opposite state to the breaker primary contacts.
A/R Abbreviation of “Autoreclose”
ACSI Abstract Communication Service Interface:
In IEC 61850, the ACSI provides abstract definitions of a hierarchical data model and the
services that operate on the data.
BAR Block auto-reclose signal.
BN> Neutral over susceptance protection element:
Reactive component of admittance calculation from neutral current and residual voltage.
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.
CLP Cold load pick-up.
CR Carrier Received
CS Carrier Send
CS Check synchronism
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