Page 216 - Practical Power System and Protective Relays Commissioning

216 Practical Power System and Protective Relays Commissioning

FIGURE 18.6.9 Special distance relay characteristic used as a remedial for load encroach-
ments and arc fault resistance effect.
transmission line and will not trip for a fault which it is required to trip
on (refer to Fig. 18.6.10).
As a fault on the transmission line with fault impedance Z with the effect
of fault resistance, R f will be seen by the relay as Z x and cause the relay not
to trip on this fault.
To avoid this problem of arc fault resistance we use the quadrilateral
characteristic as shown in Fig. 18.6.9.
In general, distance relay has different characteristics depending on the
application as shown in Fig. 18.6.11.