Minimising the risk of cross-country faults in systems using arc suppression coils

Arc suppression coil systems are able to improve the high-voltage system reliability and safety. One of the reasons why these systems are not more widely used is the occurrence of simultaneous faults caused by the neutral voltage displacement combined with the transient voltages at the time of the initial earth fault. These transient over-voltages are analysed in detail and the capability of system components to withstand the over-voltages is assessed. Simple methods to estimate the transient voltages on overhead power systems are developed. Testing of the ability of power system components to withstand transient over-voltages and a new method of minimising the transient over-voltages is proposed.