![]() According to the paper’s authors, it is very difficult to distinguish low quality from high quality insulators relying on standard IEC tests since insulators are usually ‘specially selected’ for type and sample testing. These organizations reported on the poor performance of certain families of low quality glass cap & pin insulators. This was pointed out, for example, in paper B2.209 presented during the past CIGRE general session by power companies and test laboratories from the Czech Republic, Sweden, Norway and Finland. Service experience as well as laboratory research has revealed that there can be great variance in the manufacturing quality of insulators from new producers – even though these may have formally passed standard IEC test requirements. in terms of additional required diagnostics and/or more unscheduled maintenance. ![]() ![]() As a result, some of the power utilities who have purchased them have been underestimating their impact on total life cycle costs in service, e.g. Most products from such new players are offered at a lower price than brands with a quality track record. New players have also entered the business, some supplying insulators of questionable quality. Due to market forces, certain manufacturers have re-located production and opened new factories in low cost countries – sometimes accompanied by a corresponding loss of manufacturing experience. Indeed, over the past years there has been large-scale restructuring of the industry supplying toughened glass as well as porcelain line insulators. If anything, the above observations seem truer today than back in 1988 when Looms first wrote them. They start to consider true costs rather than merely purchase price …” However, a change of attitude towards insulators is now becoming apparent in some supply utilities. The emergence of insulator production in parts of the world where labour costs are much lower than in the industrial North has further increased the downward pressure on purchase price and upon the level of quality. In other words: insulators are absurdly cheap. In his landmark (but now hard to find) book Insulators for High Voltages, J.S.T Looms offered the following insight: “ The purchase price of insulators, especially those of glass or porcelain, is totally dominated by market forces and bears no relation either to technical importance of insulation on transmission lines or to the cost of replacement and revenue loss in case of failure. Tests that have been carried out in this regard are described below: Therefore, when it comes to HV terminations equipped with composite insulators, either a test procedure has to be agreed upon between manufacturer and user or some specification from the purchaser must be made available. As a result, the only standardized test procedure for hollow composite insulators is the tracking and erosion test according to IEC 62217, which is really a test of the housing material and not of pollution performance. While a cable termination can basically be regarded as a bushing, meaning that both applicable standards can apply, care has to be taken to avoid internal breakdown.Ĭomposite insulators are excluded from the scope of the standards referred to above since the test procedures were developed for hydrophilic surfaces and hydrophobic silicone results in certain unwanted effects. In both cases, however, the scope of the standards does not include terminations as the test object. For glass and porcelain insulators, pollution tests have been standardized in IEC 60507 for AC and IEC/TS 61245 for DC. Housings can be either hollow porcelains or, as increasingly being used, hollow composite insulators with different silicone rubber material. With increasing nominal voltage, terminations become larger and therefore installation is often made in discrete steps with the various elements installed individually. Due to their relatively limited size, the weight of medium voltage terminations is typically low enough that no additional mechanical support is required. field grading, heat-shrinkable tube, weathersheds) installed separately. MV terminations are directly installed onto cable ends, either with all components integrated into a single piece or with the individual elements (i.e. Housings of HV terminations employ either porcelain or composite insulators.
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