The introduction of series capacitors presents a number of
technical challenges when setting distance protection relays,
because of the combined effects of the series capacitor’s
compensating reactance and the series capacitor’s own
protective equipment, on the measured impedance to a short-
circuit fault. During a short-circuit fault, the fault current
through the capacitor produces overvoltages across the
terminals of the series capacitor. Therefore, protection is
provided to limit voltage across the series capacitor. In the mid
1970s a MOV was announced as a means of series capacitor
protection, which superseded spark gaps previously used to
protect series capacitors [9], [10]