Designing overhead lines and substations that will perform reliably for decades has always been a remarkable challenge. So many things can go wrong over such a time frame, especially given increasing levels of pollution, more weather extremes linked to climate change, growing interactions with both humans and wildlife – all potentially culminating in problems linked to flashover, mechanical or other types of failure.

Selection of hollow composite insulators for application on equipment such as bushings, surge arresters, breakers and instrument transformers has increased worldwide. For example, where reduced weight or superior pollution performance are the key decision criteria, the majority of such apparatus is now being ordered equipped with this type of insulator.

Application of gapped (EGLAs) or non-gapped (NGLAs) transmission line surge arresters (TLSAs) offers perhaps the best opportunity for power engineers to improve system reliability. However, as important as this may be, the value of using them transcends this one objective alone.

Protection against overvoltages using gapless zinc oxide surge arresters has been accepted and adopted worldwide. In particular, assets such as transformers, cables and gas-insulated substations are highly vulnerable to transient surges from lightning and switching.

Transmission lines the world over often have to traverse mountain ranges or plateaus situated at least 1000 m above sea level. In China, for example, it is estimated that some 60% of the country lies at this altitude or higher.

Building overhead lines and substations that perform reliably for decades has always been a challenge. Many things can go wrong over such a time frame, especially given increasing pollution, more weather extremes linked to climate change, growing interactions with humans and wildlife – all potentially culminating in problems linked to flashover, mechanical or other types of failure.