Abstract
The voltage distribution across gas insulated surge arrester (GISA) is highly non-uniform as compared to conventional porcelain-clad surge arresters. The aim of the present paper is to optimize design of grading shield in such a way that the non-uniformity voltage factor across GISA must be less than ±10%. To achieve this order of non-uniformity factors, special grading shields like window based cylindrical and conical shields are proposed. In the present paper, 245 kV GISA model has been considered to analyze voltage distribution across the metal-oxide (MO) blocks. The electrostatic field and voltage distribution analyses are carried out on surge arrester by considering various shield configurations using numerical techniques. Further, design of shield and development is verified by performing dielectric duties on GISA assembly without MO blocks as per IEC 62,271–203. The lightning and switching impulse discharge current tests were carried out on the developed 245 kV GISA residual voltages were recorded. These voltage levels for above discharge currents are found to be in the order of 2.8 – 3.2 p. u. and are at acceptable levels as per IEC 60,099–4. Finally, protection level or V-I characteristics of GISA is established by measuring residual voltages for the entire current range.
Published Version
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