Insulators are among the few components in a power system that are continuously exposed to a spectrum of service stresses that can cause failure. These stresses can include: high electric field, pollution, wetting events, corona, temperature variation, mechanical shock, interaction with birds and other wildlife, wind, solar radiation, oil leaks, lightning and switching impulses, biological growths, vibration and vandalism. If factoring in the risk that an insulator is defective during manufacture or has been damaged during transport and installation or was improperly specified for its intended service environment, today’s low failure rate for insulators is indeed an accomplishment. In fact, the reliability and durability of modern insulators speak to how well engineered and manufactured most of them now are.
Still, a lot can go wrong. Given their huge populations on power networks, even low failure rate is no guarantee that there will not be serious problems. And, unfortunately, when something bad does happen to an insulator, there will likely be reliability and cost consequences. The following images depict examples of what can go wrong with insulators and why they are so deserving of careful selection and scrutiny.