Activation of input TRIGG_REC is required in case of external triggering to record
the calculated estimates for fault distance. TRIGG_REC should be activated during
the earth fault after the switching of the parallel resistor.
In case of internal triggering, time instances t
1
and t
2
are determined by monitoring
the change of the resistive component of Io current using admittance calculation
during the earth fault and comparing the magnitude of change to setting
Zero Ris
Curr change
. Time instance t
1
is taken at least one fundamental cycle before and
t
2
at least one fundamental cycle after the change in the resistive component of Io
exceeding the start value (setting
Zero Ris Curr change
). The value for setting Zero
Ris Curr change should be chosen based on the rated current value of the parallel
resistor with proper margin:
Zero Ris Curr change
< Ipar_rated [A] · q
where q = 0.5–0.7
For example, if the rated current value of the parallel resistor is 10A@20kV and In =
100 A for Io channel, then
Zero Ris Curr change
< 0.05–0.07xIn
Protection related functions
1MRS759142 F
1202 REX640
Technical Manual
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