Response of metal oxide arrester in gas-insulated substation and methods to improve its dynamic characteristics

It is well known that the metal oxide arrester (MOA) has the inability to operate against very fast transient overvoltage (VFTO). The aim of this paper is to study the dynamic performance of MOA in gas-insulated substation (GIS). A 230 kV GIS is taken from a local utility and the system is modelled for very fast transients. The dynamic performance of arrester is analysed for current surges of different front times, varying from microsecond to nanosecond using electromagnetic transient program. The dynamic characteristics can be obtained for front time, more than 1 s. However, there is a deviation in it when front time is less than 1 s, showing failure of arrester conduction because of delay in its initial response, especially under VFTO. The dynamic characteristic is improved by making modifications in the system as well as in the arrester. A dynamic hysteresis curve is constructed to confirm the delay between the residual voltage and current surge. By decreasing the delay, it is possible to improve the dynamic characteristics of the arrester so that the effective utilisation of MOA can be enhanced in VFTO applications.