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.

Cooling towers are a major source of pollution at substations located near thermal power plants. Moreover, their effect can become critical when prevailing winds blow from towers toward the substation.

It is common knowledge that composite insulators used at transmission voltages must be equipped with properly dimensioned corona rings to reduce risk of erosion to their housings. Nonetheless, situations still occur where such insulators are either installed without rings or where these detach and fall off due to conductor vibration and/or improper installation. The cases discussed in this past edited contribution to INMR by Cristian Gutierrez come from the 400 kV network in Venezuela and document what can happen to polymeric insulators when they are no longer protected by proper corona rings. Material failures or external factors such as environmental pollution can then severely reduce service life.

Finding ideal profiles for ceramic insulators has proven a challenging process, as demonstrated by the succession of numerous different designs over the past 100 years. All aimed to achieve some optimal combination of pollution flashover performance and self-cleaning properties.