Transmission line surge arresters (TLSAs) have become an important design and mitigation alternative to improve grounding and reduce investment in overhead ground wire. However, they have also been known to experience a number of mechanical problems in service.

As in places such as Japan where lightning accounts for more than 50% of power system failures, a high proportion of all transmission line trippings in China are due to lightning strike. For example, operating data for 500 kV lines across five provinces within the China Southern Power Grid showed that, of the 62 total trip-outs registered during one year, 87% were linked to lightning.

Transient Recovery Voltage (TRV) of a circuit breaker is voltage difference measured between each side of the circuit breaker to ground. The most severe TRV from an amplitude point of view follows interruption of the first phase to clear an ungrounded three-phase fault.

The 400 kV Gutinas-Brasov overhead line is located in a mountainous area of Romania that has mostly rocky soil. Thick ice covers conductors during winter and in the past caused breakage of shield wire such that it had to be dismantled in the most severely affected sections.

Power system engineers all face a similar dilemma at one time or other when trying to identify which product offers the quality they require – especially in today’s global market with its many competing suppliers.

As surge protective devices, arresters mitigate the impact of events that might otherwise trigger outages and monitoring them has become part of an industry-wide trend toward greater condition assessment of key network components.