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It is no odd coincidence that while composite insulators now strongly dominate suspension applications on Chinese transmission lines( especially at UHV), associated tension strings are almost all either of porcelain or glass. The reason for this anomaly can be seen in this image since Chinese engineers worry that composite tension strings – and particularly the long ones – will suffer permanent damage due to linemen crossing them to access the conductor for repairs. Research at a Chinese university simulated the impact of lineman boots crossing insulators several times and found no trace of damage. But perception is often a more powerful motivator than demonstration and this situation does not seem likely to change soon.
Photo: Courtesy of China Southern Power Grid
Rainfall is often seen as a natural cleaning mechanism for porcelain insulators. But it can also act as a trigger for problems the first time it occurs after prolonged dry periods, particularly in areas with heavy maritime pollution. This image, taken at a new 90 kV substation of a wind power plant along the North African coast, captures just a small example of arcing that almost overwhelmed the substation’ s insulation one rainy September day – the first rainfall after the long dry summer. The event also highlighted that insulators at the substation may not have been ideally dimensioned for this challenging service environment.
Photos: INMR ©
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Recent service experience across several countries suggests that as much as 70 to 80 % of all outages affecting overhead lines can be directly attributed to birds. At the same time, countless birds succumb each year to electrocution on power networks across the globe. This image of pole top equipment and components, taken near the beach in the Chinese coastal city of Qingdao, shows at a glance that there are effective ways to deal with both problems.
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Combining different technologies in a single insulator string is not common but, as this image taken in northeastern Brazil shows, is still utilized for special situations. In this case, the motivation for this strange configuration was vandalism with the porcelain discs installed to ensure that the entire string would not be destroyed by rock throwing.
Part 2 of this article will appear in Q3, 2013
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