If intermittent earth fault protection would be set for optimal operation, sensitive pick-up settings should
be avoided. General setting parameter values are presented below.
Setting parameter
Value
U
0
Detect spike >
60 %
I
0
Detect spike >
0.5 × I0
n
FWD reset time
0.250 s
REV reset time
0.250 s
Spikes to indicate >
2
The best veri cation for the settings is a eld test with a test system capable of intermittent earth faults.
One network characteristic may vary signi cantly from another. By following the basic rules presented
in this chapter it should be easier to de ne the correct setting range.
It is also important to check that the reset time settings are never set longer than the desired operating
time delay setting.
Measured input
The function block uses analog current measurement values from the residual magnitudes. The
residual voltage has to be measured for this function to operate correctly. Either the I01 or the I02
channel can be selected for residual current samples.
Table. 5.3.5. - 60. Measurement inputs of the I0int> function.
Signal
Description
Time base
U0 samples
U
0
residual voltage circular buffer of samples (in p.u.)
5 ms
I01 samples
I
0
residual voltage circular buffer of samples (in p.u.)
5 ms
I02 samples
I
0
residual voltage circular buffer of samples (in p.u.)
5 ms
The selection of the AI channel in use is made with a setting parameter.
Pick-up
The setting parameters
U0 Detect spike>
and
I0 Detect spike
> control the pick-up of the
I0int> function. They de ne the maximum allowed measured residual current and voltage before action
from the function. The function constantly calculates the ratio between the setting and the maximum
value of the circular buffer.
Table. 5.3.5. - 61. Pick-up settings.
Name
Range
Step
Default
Description
U0 Detect spike >
1.00…100.00 %U0
n
0.01 %U0
n
80.00 %U0
n
Pick-up setting U
0
I0 Detect spike >
0.05…40.00 x I0
n
0.01 x I0
n
0.50 x I0
n
Pick-up setting I
0
The pick-up activation of the function is not directly equal to the START signal generation of the
function. The START signal is allowed if the blocking condition is not active and if the threshold of the
admittance delta calculated by the input signal exceeds these settings:
I0 Detect spike > = set admittance delta threshold
U0 Detect spike > = set admittance delta threshold.
AQ-E215
Instruction manual
Version: 2.01
© Arcteq Relays Ltd
84
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