The challenge of protecting the grid and maintaining system reliability depends on proper inspection and testing of insulators, particularly as system voltages and criticality of lines increase.

What is the kJ/kV Uc rating of a Class 1, 10 kA arrester? This type of question has often been asked when it comes to distribution arresters. Yet finding an answer was never easy since these arresters (formerly referred to as Class 1) never had energy ratings.

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.

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.

While metal oxide arresters are comparatively modern devices, they have nonetheless undergone rapid development. For example, such arresters were among the first apparatus in power systems to be equipped with polymeric insulation. Progress has also been achieved in improving MO resistor performance

Silicone coatings have traditionally been applied mainly to mitigate insulator contamination problems at substations but the past 25 years have seen their application to overhead lines grow significantly. As this process evolved, coating line insulators moved progressively from something performed mostly in the field to industrial scale application in specialized factories to allow for greater consistency, reliability and economy.