Insulation Withstand Testing on Surge Arresters and the Influence of Voltage Grading
Abstract
In order to reduce the risk of insulation failure to an economically and operationally acceptable level, the insulation withstand and clearances for substation equipment is selected with regard to anticipated overvoltages; taking into account the expected protective characteristics of nearby surge arresters in the station. Insulation coordination standards further recognize that, since the primary function of a surge arrester is to limit, and thereby render harmless, overvoltages to which the protected equipment is exposed, the arrester’s own insulation is obviously the best protected of all. In contrast to other HV apparatus, the insulation level for surge arresters therefore does not need to fulfil a standardized insulation class since the arrester will effectively protect its own insulation against overvoltages.
An intensive review of the surge arrester standard IEC 60099-4 resulted in the release of Edition 3.0 during 2014. Amongst other matters, this introduced a new procedure for verifying the dielectric withstand of the external insulation on an arrester. Equations were defined which consider the relationship between dry arcing distances and withstand voltages and thereafter the need to perform a specific insulation withstand test or not. For arresters intended for use on systems of Us > 245 kV, lightning and switching impulse voltage tests on complete arrester assemblies based on the arrester’s protective level can be especially defining. During the tests the nonlinear metal-oxide (MO) resistors are replaced by linear resistors, capacitors or high gradient MO resistors in order to achieve the supposed voltage distribution along the arrester during impulses. The MO resistor distribution within a multi-unit arrester as well as the grading ring configuration used may impact the withstand voltage of the arrester, and arresters with similar appearance or with the same arcing distance can potentially perform differently.
This paper discusses the requirements for insulation withstand on surge arrester housings and evaluates the role voltage grading plays on arrester performance, both during dielectric testing and normal operation.
Keywords
Surge arrester Insulation withstand voltage Insulation coordinationReferences
- 1.IEC 60071-2, Edition 4.0, 2018-03, Insulation co-ordination - Part 2: Application guidelinesGoogle Scholar
- 2.IEC 60099-4, Edition 3.0, 2014-06, Surge arresters - Part 4: Metal-oxide surge arresters without gaps for a.c. systemsGoogle Scholar
- 3.IEC 60099-5, Edition 3.0, 2018-01, Surge arresters - Part 5: Selection and application recommendationsGoogle Scholar
- 4.IEC 60071-1, Edition 8.1, 2011-03, Insulation co-ordination - Part 1: Definitions, principles and rulesGoogle Scholar
- 5.Stenström, L., Taylor, J., Westerlund, H.: An optimal surge arrester for EHV air insulated stations utilizing high-gradient MO resistors. In: IEEE Electrical Insulation Conference (EIC), Ottawa (2013)Google Scholar
- 6.Martin, M., Taylor, J., Popic, M.: Optimisation of air-insulated substations by consideration of surge arrester protective characteristic. HRO CIGRÉ Session, Cavtat (2013)Google Scholar
- 7.IEC 60099-4, Edition 2.2, 2009, Surge arresters - Part 4: Metal-oxide surge arresters without gaps for a.c. systemsGoogle Scholar
- 8.IEC 60060-1, Edition 3.0, 2010-09, High-voltage test techniques – Part 1: General definitions and test requirementsGoogle Scholar
- 9.Csendes, Z.J., Hamann, J.R.: Surge arrester voltage distribution analysis by the finite element method. IEEE Trans. Power App. Syst. PAS-100(4), 1806–1813 (1981)CrossRefGoogle Scholar
- 10.Oyama, M., Ohshima, I., Honda, M., Yamashita, M., Kojima, S.: Analytical and experimental approach to the voltage distribution on gapless zinc-oxide surge arresters. IEEE Trans. Power App. Syst. PAS-100(11), 4621–4627 (1981)CrossRefGoogle Scholar
- 11.Valsalal, P., Usa, S., Udayakumar, K.: Effect on stray capacitance on surge arrester performance, In: Lecture Notes in Engineering and Computer Science, vol. 2178, no. 1, pp. 541–544 (2009)Google Scholar
- 12.Haddad, A., Naylor, P.: Finite-element computation of capacitance networks in multiple electrode systems: application to ZnO surge arresters. IEE Proc. Sci. Meas. Technol. 145(4), 129–135 (1998)CrossRefGoogle Scholar
- 13.Sjöstedt, H., Stenström, L., Pusch, D., Ostrowski, J.: Voltage grading design of UHV surge arrester using 3D transient capacitive-resistive field simulations. In: International Conference on High Voltage Engineering and Application (ICHVE), New Orleans, pp. 32–35 (2010)Google Scholar
- 14.He, J.L., Hu, J., Gu, S.Q., Zhang, B., Zeng, R.: Analysis and improvement of potential distribution of 1000-kV ultra-high voltage metal-oxide arrester. IEEE Trans. Power Del. 24(3) (2009)Google Scholar
- 15.CIGRÉ TB 696: MO Surge Arresters – Metal Oxide Resistors and Surge Arresters for Emerging System Conditions. CIGRE WG A3.25 (2017)Google Scholar