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Reference: ISH2015_71

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Current State of Analysis and Comparison of Atmospheric and Altitude Correction Methods for Air Gaps and Clean Insulators



The dielectric strength of air gaps is affected by both: air density (determined by temperature and pressure) and humidity. In order to normalize external insulation strength of power equipment under different conditions, such effects need to be taken into account when external insulation is designed and tested. There are three main applications for atmospheric and altitude corrections: insulation coordination, equipment design and equipment testing. The existing correction methods for the different applications can lead to large differences in the applied correction factors and a need for harmonization between the standards was recognized. This paper presents the continued work of CIGRE WG D1.50 “Atmospheric and altitude correction factors for air gaps and clean insulators”, some preliminary results were already published earlier [1,2,3]. It summarises the current knowledge on the effect of air density and humidity on large and short gaps and presents the results in recent years of typical rod-plane tests up to 4300 m in relation to the correction curves in IEC 60060-1 [4] (exponent m in relation to factor g) and IEC 60071-2 [5] (exponent m in relation to voltage UCW) for rod plane gaps. These new test results combined with the results which were the base for the current correction methods could provide the basis for formulating new or revising the existing atmospheric and altitude correction methods.

File Size: 515,6 KB

Year: 2015

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