Technical Documentation
KSR-Z – Capacitor-Bank Protection Relay
Rev. 04
Page
7
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36
2.2.4 Earth fault protection
The KSR-Z calculates the earth fault current as the RMS value of the vector sum from the three
currents I
L1
I
L2
I
L3
. All values are taken from the fundamental wave.
EF
is compared with two
adjustable thresholds
, EF trip
and
EF alarm.
For each threshold it’s adjustable to use an
adjustable time delay or select a trip characteristic.
2.2.5 Protection against repetitive overload and over voltage
To avoid damages of the capacitors due to repetitive overload or over voltage which is to short to
be detected by the normal monitoring functions, the KSR-Z has an additionally timer to detect such
repetitive events. If an adjusted threshold is exceeded, the time for the threshold violation is stored
and subtracted from the delay time respective the trip characteristic to get an alarm or trip event if
this violation occurs multiple during a critical time frame. To switch off this additional timer set “T-
RESET” to “0” in the protection settings.
2.2.6 Hysteresis of threshold values
For the adjusted alarm thresholds the KSR-Z uses depending on the trigger a pickup respectively a
dropout ratio. In case of monitoring a value "greater than", the device triggers an alarm at the
adjusted value and go back to normal at value * 0,97. For the monitoring of values "less than", the
function works vice versa (value * 1,03).
