Technical Documentation
KSR-Z – Capacitor-Bank Protection Relay
Rev. 04
Page
6
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36
2.2 Protection Elements
2.2.1 Overload and Unbalance protection
Current I
L1
I
L2
I
L3
and I
UB
elements provide Overload and Unbalance protection respectively. Each
element is pre-programmed to have two independent stages (Alarm and Trip) for current setting and
DTL (definite time lag) characteristic or trip characteristic as described in section 3 and Appendix B.
For Overload protection the current can be monitored as follows:
OL = current as trms value
OL
th
= current as thermal damped value
OL
f
= current as fundamental value (Only ground wave 50 or 60 Hz)
Samples of the current input signals are taken at a frequency of 6,4 kHz. This enables KSR-Z to
act as a True RMS measuring device (TRMS) over a wide frequency range.
2.2.2 Overvoltage and Undervoltage Protection
Voltage V
L1
V
L2
V
L3
elements provide Over-voltage and Under-voltage. Each element can is pre-
programmed to have two independent stages (Alarm and Trip) for current setting and DTL (definite
time lag) characteristic or trip characteristic as described in section 3 and Appendix B.
Samples of the voltage input signals are taken at a frequency of 6,4 kHz. This enables KSR-Z to act
as a True RMS measuring device (TRMS) over a wide frequency range.
2.2.3 Voltage asymmetric protection
The KSR-
Z is monitoring the deviation between all line voltages. For the monitoring function it’s
possible to adjust an allowed deviation from 1% -99.99%. To calculate the Voltage asymmetry the
IEEE formula is used:
PVUR =
max voltage deviation from the avg. phase voltage
*100
Avg. phase voltage
