ABB RELION REX640 Technical Manual page 1202

Protection related functions
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
the change of the resistive component of Io current using admittance calculation
during the earth fault and comparing the magnitude of change to setting
Curr change . Time instance t
t at least one fundamental cycle after the change in the resistive component of Io
2
exceeding the start value (setting
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
1202
and t
1
is taken at least one fundamental cycle before and
1
Zero Ris Curr change ). The value for setting Zero
1MRS759142 F
are determined by monitoring
2
Technical Manual
Zero Ris
REX640