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.
Gun enthusiasts in Canada seem to have used these old breaker bushings for target practice (photo INMR)Puncture near insulator’s live end in spite of special design featuring excess silicone material at ‘triple point’ (photo courtesy of Ofil Systems).Birds in northeastern Australia have used this line post to exercise powerful beaks (photo courtesy of Powerlink).Defective manufacture has made this 500 kV insulator housing crack (photo INMR).Pin post destroyed by radial cracking of porcelain body (photo courtesy of AltaLink).Birds in Brazil coat glass string in highly conductive excretions (photo courtesy of Cemig).Corroded pin on glass disc operating in contaminated coastal/desert environment (photo courtesy R. Znaidi/STEG).Porcelain bushing housing at polluted Ontario 230 kV substation shows impact from repeated pollution flashovers (photo INMR).Oil leaking onto RTV-coated transformer housing makes it more vulnerable to pollution accumulation (photo INMR).Corrosion of cap of glass disc at substation on Greek Island of Crete (photo INMR).
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Example of self-shattering of glass insulators on Danish DC line exposed to heavy maritime pollution (photo INMR).Mechanical fracture of 765 kV composite insulator at coastal thermal power plant in South Korea (photo courtesy of KEPCO).Evidence of severe pollution accumulation on cable termination bushing at Oteranga Bay, at southern tip of North Island in New Zealand (photo INMR).Fractured porcelain long rods in Eastern Europe due to defective cement attaching end fittings (photo courtesy of EGU HV Laboratory).Fracture of 500 kV suspension insulator in China due to excess water penetration into interface between rod and housing (photo INMR).Sheds on silicone line insulators show extensive damage due to onset of brittleness (photo INMR).Tearing of sheds on 750 kV silicone insulators due to high winds in Western China (photo INMR).Explosive failure of porcelain housing results in ejection of sharp projectiles at high velocities (photo INMR).Impact of repeated lightning strikes and flashovers (photo INMR).Bird pecking on sheds of 500 kV composite insulators (photo INMR).
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Arcing due to pollution seems about to overwhelm long rod insulators in Israel (photo courtesy of the late Radu Munteanu, Israel Electric).Biological growth on hollow composite insulator installed in Sweden. Note: insulator installed with shed tips facing upward and trapping moisture (photo INMR).Pollution from nearby cement factory overwhelmed these glass strings in Tunisia (photo INMR).Corrosion of metal cap on insulator operating in Florida (photo INMR).Self-shattered glass disc in South Africa (photo INMR).Erosion of sheds on silicone housing of improperly specified insulator in a heavily polluted region of Romania (photo courtesy of Transelectrica).Corrosion and self-shattering of glass insulator in Algeria (photo courtesy of R. Znaidi/Sonelgaz).Severe erosion of rubber along shank of composite insulator (photo courtesy R. Znaidi).Insulators barely visible through thick snow coating (photo courtesy of Hubei Electric Power Corp.).Effects of water penetration into internal interfaces of 765 kV composite insulator (photo courtesy of KEPCO).Pitting and cracking of cement of 115 kV porcelain disc insulator due to excessive corona (photo courtesy of Ofil).Explosive failure of porcelain arrester housing (photo source Entergy).Impact of lightning flashover on porcelain string (photo courtesy AltaLink).
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