ABB RELION REX640 Technical Manual page 1110

Section 5
Protection related functions
1104
TRIGG_T activation must be given after the initial earth-fault ignition
transients. Only one activation of TRIGG_T is allowed during an
earth fault. However, further activations are internally disabled.
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
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
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
and t
1
is taken at least one fundamental cycle before and t
1
1MRS759142 C
are determined by monitoring the
2
Technical Manual
at least
2
REX640