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.

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.

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.

Thermal imaging has for years served as a practical and cost-effective means of assessing the condition of surge arresters. But comparatively little effort has been made to determine what constitutes a ‘healthy’ versus a ‘suspect’ surface temperature profile.