Insulators are probably the only components in a power system that find themselves continually exposed to the full spectrum of possible service stresses, any one of which can cause them to fail.
These include: high electric field, pollution, wetting events, corona, temperature swings, mechanical shock, interactions with birds and other wildlife, winds, solar radiation, oil leaks, lightning and switching impulse, biological growths, vibration and vandalism. Into this potentially lethal cocktail of stresses, one also has to factor in several added risks: namely that the insulator is defective during manufacture, has been damaged during handling or was not well specified for its service conditions.
Based on all these dangers, today’s low failure rates for insulators might seem nothing short of miraculous.
But miracles have nothing to do with it. The reliability and durability of modern insulators speaks to how well engineered and manufactured most of them now are.
Still, a lot can go wrong and, given their huge population on electrical networks, even low failure rate is no guarantee that there will not be serious problems. And, whenever something bad happens to an insulator, there will invariably be reliability and cost consequences for the affected power system operator.
In this column, I keep words to a minimum and instead present images from our archive that depict some of the many things that can go wrong with insulators. These images, better than words, illustrate why components that account for only some 5 to 8 percent of the total investment in power infrastructure always deserve a disproportionately high level of scrutiny.