6–62
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
NEG SEQ TOC RESET
Range: Instantaneous, Linear
Default: Instantaneous
The reset of the negative sequence timed overcurrent can be selected as either
“Instantaneous” or “Linear”. If Instantaneous reset is selected, the Negative Sequence
TOC element will reset instantaneously providing that the current drops below 97-98%
of the Neg. Seq. TOC PKP level, before the time for operation is reached. When Linear
reset is selected, the time to reset is calculated based on the following linear equation:
Eq. 3
where:
T
RESET
- reset time in seconds;
E
- energy capacity reached (per unit);
M
- curve
multiplier;
C
R
- characteristic constant (5 for ANSI, IAC, Definite Time, and Flexcurves
TM
; 8
for IEC).
The 100% “energy capacity” for the TOC element is defined by the selection of PKP, TDM
and points from the inverse curve. A memory variable based on actual values currents is
monitored for accumulation of energy capacity, where if it reaches a level of 100% of
the set energy capacity level, the element operates, and if it goes below 97-98% of this
level, the element will tend to reset. The accumulated energy capacity is used as an
input for computation of the reset time, when the “Linear” reset is selected as a setting.
OUTPUT RELAY X
For details see
BLOCK 1/2/3
For details see
