Anneberg was the name of a now-closed insulator research station located in south-eastern Sweden and operated for years by Chalmers University of Technology. This was also the site of one of the first installations of composite-housed bushings, mounted in different configurations during the 1980s. The rainy and damp environment in the region soon resulted in appearance of substantial biological growths on the shaded lower portion of sheds. A similar problem – although more severe – was reported in the mid 1990s on 230 kV composite breaker bushings by a rural power utility in Florida. Research over the years by Professor Stanislaw Gubanski and colleagues, demonstrated that such growths should ideally be removed by water washing followed by alcohol since they create localized sites of moisture accumulation. However, notwithstanding their menacing appearance, these growths do not present any longterm danger of degrading the silicone housing material.

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Photo: INMR ©

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This one image has made composite insulator manufacturers around the globe shudder since it reveals in an instant the‘ Achilles heel’ of this otherwise brilliant technology. Australia is home to many species of exotic birds that sometimes find insulators a convenient place to sharpen and exercise powerful beaks. The problem has been so severe in certain areas that large numbers of insulators on new lines were found critically damaged even before energization. A number of techniques have been proposed to shield composite insulators from severe bird-pecking damage during the period between installation and energization, when this problem apparently lessens due to high electric fields that keep birds away. But none seems to have yet become industry standard.

Photo: Courtesy Powerlink

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