selected, an immediate reset occurs. The
START
output is deactivated when the
reset timer has elapsed.
The setting
Time multiplier is used for scaling the IDMT operation and reset times.
The setting parameter
Minimum operate time defines the minimum desired
operation time for IDMT. The setting is applicable only when the IDMT curves are
used.
The
Minimum operate time setting should be used with great care
because the operation time is according to the IDMT curve but always
at least the value of the
Minimum operate time setting.
The Timer 1 module calculates the start duration value START_DUR, which indicates
the percentile ratio of the start situation and the set operation time. The value is
available in the monitored data view.
In a typical double-Y-connected configuration (
), there are two branches
in every phase and hence six individual counters COUNT_BR1_A, COUNT_BR2_A,
COUNT_BR1_B, COUNT_BR2_B, COUNT_BR1_C and COUNT_BR2_C are maintained.
Based on the phase angle of the compensated unbalance current I_ANGL_COMP,
the phase and the branch of the element failure location is detected. However,
the element failure location also depends on the type of capacitor banks, that is,
whether internal or external fuses are used. The setting
Fuse location is used to set
the capacitor bank type as “External” or “Internal”.
For an external fuse capacitor bank, the element failure location and corresponding
counters to be incremented are determined based on the phase angle of the
compensated unbalance current.
Table 749: Element failure location and counters to be incremented for external
fuse case
Phase angle of the
compensated unbalance
current (degrees)
Phase and branch of the
element failure
Counters to be incremented
-15...+15
Phase-A branch 1
COUNT_BR1_A
-15...-45
Phase-A branch 1
Phase-C branch 2
COUNT_BR1_A
COUNT_BR2_C
-45...-75
Phase-C branch 2
COUNT_BR2_C
-75...-105
Phase-B branch 1
Phase-C branch 2
COUNT_BR1_B
COUNT_BR2_C
-105...-135
Phase-B branch 1
COUNT_BR1_B
-135...-165
Phase-B branch 1
Phase-A branch 2
COUNT_BR1_B
COUNT_BR2_A
-165...-180
Phase-A branch 2
COUNT_BR2_A
+165...+180
Phase-A branch2
COUNT_BR2_A
+135...+165
Phase-C branch 1
Phase-A branch 2
COUNT_BR1_C
COUNT_BR2_A
+105...+135
Phase-C branch 1
COUNT_BR1_C
Table continues on the next page
Protection functions
1MRS757644 H
786
620 series
Technical Manual
