GE P741

Symbols and Glossary
P74x/EN SG/N
a7
MiCOM P74
1, P742, P743
(SG) 14-
1
SG
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).
1 Logical “OR”:
Used in logic diagrams to show an OR-gate function.
50BF Breaker Failure protection
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.
87BB Differential Busbar protection
87BBN Phase differential Busbar
87BBP Neutral differential Busbar
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.
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 cur
rent 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.
CS
Check synchronism.
CT
Current transformer.