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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.

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1. Gun enthusiasts in Canada seem to have used these old breaker bushings for target practice (photo INMR).
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Bad things can happen to insulators insulator Bad Things Can Happen to Insulators Bad things 2

2. Puncture near insulator’s live end in spite of special design featuring excess silicone material at ‘triple point’ (photo courtesy of Ofil Systems).
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3. Birds in northeastern Australia have used this line post to exercise powerful beaks (photo courtesy of Powerlink).
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4. Defective manufacture has made this 500 kV insulator housing crack (photo INMR).
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5. Pin post destroyed by radial cracking of porcelain body (photo courtesy of AltaLink).
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6. Birds in Brazil coat glass string in highly conductive excretions (photo courtesy of Cemig).
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7. Corroded pin on glass disc operating in contaminated coastal/desert environment (photo courtesy R. Znaidi/STEG).
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8. Porcelain bushing housing at polluted Ontario 230 kV substation shows impact from repeated pollution flashovers (photo INMR).
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9. Oil leaking onto RTV-coated transformer housing makes it suddenly more vulnerable to pollution accumulation (photo INMR).
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10. Corrosion of cap of glass disc at substation on Greek Island of Crete (photo INMR).
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11. Example of self-shattering of glass insulators on Danish DC line exposed to heavy maritime pollution (photo INMR).
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12. Mechanical fracture of 765 kV composite insulator at coastal thermal power plant in South Korea (photo courtesy of KEPCO).
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