Alstom MiCOM P545 - Page 931

Symbols and Glossary P54x/EN SG/La4
MiCOM P543, P544, P545 & P546 (SG) 14-3
SG
Symbols Explanation
I>3 Third stage of phase overcurrent protection:
Could be labeled 51-3 in ANSI terminology.
I>4 Fourth stage of phase overcurrent protection:
Could be labeled 51-4 in ANSI terminology.
I
0
Zero sequence current:
Equals one third of the measured neutral/residual current.
I
1
Positive sequence current.
I
2
Negative sequence current.
I2>
Negative sequence overcurrent protection (NPS element).
I2pol
Negative sequence polarizing current.
IA Phase A current:
Might be phase L1, red phase.. or other, in customer terminology.
IB Phase B current:
Might be phase L2, yellow phase.. or other, in customer terminology.
IC Phase C current:
Might be phase L3, blue phase.. or other, in customer terminology.
ID Abbreviation of “Identifier”:
Often a label used to track a software version installed.
IDMT Inverse definite minimum time:
A characteristic whose trip time depends on the measured input (e.g. current) according
to an inverse-time curve.
Im
Mutual current
IMx InterMiCOM
64
bit
(x=1 to 16)
IM64
InterMiCOM
64.
In The rated nominal current of the relay:
Software selectable as 1 amp or 5 amp to match the line CT input.
IN Neutral current, or residual current:
This results from an internal summation of the three measured phase currents.
IN> A neutral (residual) overcurrent element:
Detects earth/ground faults.
IN>1 First stage of ground overcurrent protection:
Could be labeled 51N-1 in ANSI terminology.
IN>2 Second stage of ground overcurrent protection:
Could be labeled 51N-2 in ANSI terminology.
Inh
An inhibit signal.
ISEF>
Sensitive earth fault overcurrent element.
Inst. An element with “instantaneous” operation:
i.e. having no deliberate time delay.
I/O Abbreviation of “Inputs and Outputs”:
Used in connection with the number of optocoupled inputs and output contacts within
the relay.
I/P
Abbreviation of “Input”.