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.

Increased penetration of Distributed Generation (DG) from solar and wind plants has created challenges for network operators when it comes to power quality issues such as voltage regulation, power factor and harmonics.

The metal oxide surge arrester (MOSA) is a comparatively inexpensive component within a modern power system. Typically, it is specified, purchased and installed but later often overlooked when planning condition monitoring of assets in a substation.

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.