Measurement and simulation of the electric field of high voltage suspension insulators Vassiliki T. Kontargyri, Ioannis F. Gonos * ,y and Ioannis A. Stathopulos High Voltage Laboratory, Electric Power Department, School of Electrical and Computer Engineering, National Technical University of Athens, 9, Iroon Politechniou Str., 15780 Zografou, Athens, Greece SUMMARY In this study, a method for the calculation of the electric field on high voltage insulators is presented. A model of the insulator string was set up using OPERA, an electromagnetic analysis program based on the Finite Element Method. In order to validate the accuracy of the method, simulated results have been compared with experimental results. Copyright # 2008 John Wiley & Sons, Ltd. key words: Insulators; electric field distribution; simulation software; finite element method 1. INTRODUCTION The insulator strings, which are used for the suspension of overhead transmission lines, constitute one of the most important parts of the transmission lines as they used to give support to electrical conductors and shield them from ground or other conductors as well as they provide the necessary mechanical supports for the transmission lines against the worst likely mechanical loading conditions. The number of the insulator units that consists the suspension insulator string depends on the operating voltage of the overhead transmission line. The calculation of the electric field and voltage distribution within and around high voltage insulators is a very important parameter for the design of the insulators. High levels of the electric field are possibly responsible for audible noise, electromagnetic pollution, partial discharge and premature aging of insulation. The assignment of the electric field distribution in an insulator string is useful as it is an indication for flashover propagation. Hampton’s criterion shows that flashover cannot occur if the surface electric gradient is sufficiently low [1]. The flashover effects in insulators can cause the breakdown of a transmission system. Furthermore, the knowledge of the electric field is helpful for the detection of defects in insulators [2]. Several methods such as finite difference method [3], boundary element method [4–6] and finite element method [7–13] have been developed for the computation of electric fields and potentials along an insulator string. The simulation methods give the possibility to examine the behaviour of models with very complex geometry without using analytical methods or experiments. The electric field measurement along the insulator can also be found in many previous literatures such as references [6,14]. In this paper, the electric field distribution of a high voltage suspension insulator has been measured. In addition, the electric field and potential distribution around and inside the insulator when it is stressed by power frequency voltage is examined using OPERA, which is a suite of programs for two and three dimensional electromagnetic field analysis [17]. The software package uses the finite element method to solve the partial differential equations that describe the behaviour of electromagnetic fields. The critical points affecting simulation accuracy are examined and the simulated results are compared with experimental results. EUROPEAN TRANSACTIONS ON ELECTRICAL POWER Euro. Trans. Electr. Power 2009; 19:509–517 Published online 5 March 2008 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/etep.238 *Correspondence to: Ioannis F. Gonos, High Voltage Laboratory, Electric Power Department, School of Electrical and Computer Engineering, National Technical University of Athens, 9, Iroon Politechniou Str., 15780 Zografou, Athens, Greece. y E-mail: igonos@ieee.org Copyright # 2008 John Wiley & Sons, Ltd.