American Transmission Company (ATC) own and operates transmission lines in the States of Wisconsin, Michigan, Minnesota and Illinois. The system originally belonged to local utilities that had different standards and this resulted in a variety of different line surge arrester installations at 69 kV and 138 kV.

Integration of renewable energy sources into the electrical system in Germany has required adapting and expanding the existing grid. At the same time, public opposition to added infrastructure has meant that system operators face lengthy approval processes for new overhead lines.

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.