Alstom MiCOM P846, Техническое руководство

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Symbols and Glossary P846/EN SG/D
MiCOM P846 (SG) 14-1
SG
Symbol 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.
Δ
“Delta”:
Used to indicate a step change.
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.
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.
CT Current transformer.
CTRL. Abbreviation of “Control”:
As used for the Control Inputs function.
CVT Capacitor-coupled voltage transformer:
Equivalent to terminology CCVT.
DDB Digital data bus within the programmable scheme logic:
A logic point that has a zero or 1 status. DDB signals are mapped in logic to customize
the relay’s operation.
DLO Open line detector function
Detects the open state of the line without the use of circuit breaker contacts
Dly Time delay.
DT Abbreviation of “Definite Time”:
An element which always responds with the same constant time delay on operation.