Cable accessories perform the key function of ensuring required insulation either at the connection points of cables (straight joints) or at their ends (terminations). These accessories have to be easy and safe to install over a broad range of different cable cross-sections and ideally should consist of as few components as possible.

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.

At some point, all electrical equipment has an end-of-life-event (EOLE). Sometimes this event can be as benign as being removed and replaced with a newer device, but it can also be the by-product of a thunderous overload. In the case of distribution surge arresters, such a thunderous overload can trigger either a short or long-term outage.

Lightning accounts for about 60% of all transmission line trippings in China and is closely linked to season as well as region. Based on the physical processes, lightning overvoltages can fall into two broad categories: those caused by direct strike to the tower, shield wire or conductor; and those where lightning strikes the ground near lines, generating an induced overvoltage on conductors.

Composite insulators have become the dominant type selected for use on overhead lines and have also been growing rapidly in application at substations.