Natural, rotationally asymmetric ageing of composite insulators

The market for polymeric insulators has existed for over 20 years and the possibility now exists to compare good quality service-aged products with the original expectations of performance. This paper presents investigations of field-aged insulators, which have been deployed for 6-7 years on a variety of distribution lines. The insulators are all from coastal regions of the UK. In each case evidence is presented of non-rotationally symmetric ageing. Such a pattern of ageing is not widely reported in detail. Accelerated testing of materials and systems is a key part of product development and approval regimes. Certainly such tests do not provide for uneven ageing of insulators, more usually every effort is made to reduce such effects. Data from the UK is compared to equivalent reports in the literature. In addition to the role of electrical discharges and corona in ageing, solar radiation and pollutants appear critical on distribution systems. It is also suggested that wind direction, may also be an important consideration. The implications of the rotationally asymmetric ageing found on these insulators is considered. ©2008 IEEE.