Study of importance of line entrance arrester for a composite transmission circuit

The installation of surge arresters on the line side of circuit breakers is proved to provide an effective protection to the substation equipment against overvoltage surges including lightning faults. It is applied to both air insulated substation (AIS) and gas insulated substation (GIS). These arresters have not yet been provided on a large scale in Tamil Nadu State of India in spite of its merits. As a result the connected substation equipment are subjected to life threatening overvoltage surges. The urgency of this situation has prompted to bring these cases to spot light. The protective role played by these arresters is focused with the aid of case studies involving composite transmission circuits. Suitable remedial measures are suggested to ensure that the safety and security of the equipment in the stations covered by this study.