A series compensating capacitor reduces the net fault
impedance for all faults behind it; consequently such a fault
appears closer to the relay depending on the amount of series
compensation, fault current and the fault location. A
comprehensive depiction of the effect of fault resistance and
the MOV-series capacitor impedance characteristic on a
distance relay is illustrated in figure 11 on the R-X plane.
The RF shifts the impedance seen by the relay to the right
and lowers the fault impedance angle to δ’. The MOV and
series capacitor combination also reduces the impedance seen
by the relay and lowers the fault impedance angle further to
δ’’. This shifting of the fault impedance seen by the relay
could affect the relay’s performance.