ABB RELION REX640 Technical Manual page 1109

1MRS759142 C
REX640
Technical Manual
The algorithm requires three independent time instances, which are assumed to be
known by the algorithm:
• t = time instance before the fault
0
• t = time instance before the change during the earth fault
1
• t = time instance after the change during the earth fault
2
The effect of loads is considered by applying "Load modelling" algorithm.
The required settings of the algorithm are:
• R1 = Positive-sequence resistance of the protected feeder [ohm, prim]
• X1 = Positive-sequence reactance of the protected feeder [ohm, prim]
• R0 = Zero-sequence resistance of the protected feeder [ohm, prim]
• X0 = Zero-sequence reactance of the protected feeder [ohm, prim]
• s = Equivalent load distance [pu]
Determining timings of changes: determination of earth fault occurrence and
time instance t
0
Timing t is needed to store the current and voltage phasors right before the occurrence
0
of the earth fault. Timing t
either "Internal" or "External"). Pre-fault (indicating healthy network) phasors are
continuously updated and stored at intervals of 300 ms until the earth fault is indicated.
When the earth fault is detected (internal detection), the pre-fault phasor is stored at
least 300 ms before the detection of the earth fault. This time instance before the earth
fault is noted as t (see Figure
0
Determining timings of changes: determination of changes during an earth fault
due to parallel resistor switching, time instances t
• Time instance t equals the time during earth fault, right before the switching of
1
the parallel resistor of the coil (see
• Time instance t equals the time during earth fault, just after the switching of the
2
parallel resistor of the coil (see
In case of external triggering, time instances t
TRIGG_T and delay setting Time delay. TRIGG_T input should be activated when
the parallel resistor is switched ON. Time instance t
cycle before TRIGG_T rising edge. Time instance t
delay after the rising edge of TRIGG_T signal. Setting Time delay should be few
hundreds of ms and it is needed due to oscillations in currents and voltages after the
switching of the parallel resistor.
Protection related functions
is common to both triggering types (Calculation Trg mode
0
598).
Figure 598)
Figure 598)
and t
1
Section 5
and t
1 2
are determined using input
2
is taken at least one fundamental
1
is taken according to the set Time
2
1103