REDUCTION OF INSULATION LEVEL BY UTILIZATION OF METAL OXIDE SURGE ARRESTERS

Most of the circuit breakers installed in Extra high voltage network of Iran are equipped with closing resistors. The delicate mechanisms of the closing resistors and lack of specialized maintenance personnel cause very often maloperation and sometimes even explosion of the circuit breakers. Wide application of metal oxide (ZnO) surge arresters and their impact on overvoltages in the networks leads to eliminate the closing resistors in the circuit breakers. This paper presents the results of the computer modelling of the case studies with different overvoltage limiting techniques.