Phase angle of the
compensated unbalance
current (degrees)
Phase and branch of the
element failure
Counters to be incremented
Phase-C branch 1 COUNT_BR1_C
-45...-75 Phase-C branch 1 COUNT_BR1_C
-75...-105 Phase-B branch 2
Phase-C branch 1
COUNT_BR2_B
COUNT_BR1_C
-105...-135 Phase-B branch 2 COUNT_BR2_B
-135...-165 Phase-B branch 2
Phase-A branch 1
COUNT_BR2_B
COUNT_BR1_A
-165...-180 Phase-A branch 1 COUNT_BR1_A
+165...+180 Phase-A branch 1 COUNT_BR1_A
+135...+165 Phase-C branch 2
Phase-A branch 1
COUNT_BR2_C
COUNT_BR1_A
+105...+135 Phase-C branch 2 COUNT_BR2_C
+75...+105 Phase-C branch 2
Phase-B branch 1
COUNT_BR2_C
COUNT_BR1_B
+45...+75 Phase-B branch 1 COUNT_BR1_B
+15...+45 Phase-A branch 2
Phase-B branch 1
COUNT_BR2_A
COUNT_BR1_B
After
Alarm delay time
has elapsed, the corresponding counter value is incremented
based on the magnitude of the unbalance current. If I_AMPL_COMP is less than
1.5 times the set
Alarm value
, the counter is incremented by one. Furthermore, if
I_AMPL_COMP is between 1.5 and 2.5 times the set
Alarm value
, the counter is
incremented by two and so on.
Normally, the setting
Alarm value
is about 0.1 percent lower than the
value of the unbalance current which is caused by one faulty element.
This setting value has to be chosen carefully because a slightly lower
value may lead to a situation where the counters show more failures than
the actual. Too high setting leads to a situation where a fault is not
detected.
The counter values COUNT_BR1_A, COUNT_BR2_A, COUNT_BR1_B, COUNT_BR2_B,
COUNT_BR1_C and COUNT_BR2_C are available in the monitoring data view.
The total number of element failures in double-Y-connected capacitor banks,
FAIL_COUNT, is available in the monitored data view.
The ALARM output is activated, when the value of FAIL_COUNT exceeds the setting
Element failure limit
.
The counter values can be reset via
CUBPTOC counters
which is located under the
Clear menu.
1MRS759142 F
Protection functions
REX640
Technical Manual
1125
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