Design of corona mitigation device and application of ZnO microvaristor on 66kV insulators by finite element method

Abstract

Insulators play a vital role in electrical power system. Due to continuous energisation and presence of various pollutions in the atmosphere, electrical stresses on the surface of the insulator are becoming high. Insulators will degrade and fail due to presence of these higher electrical stresses on its surface. Electrical stresses can be minimized with the placement of corona rings at end fittings. As per IEC standards corona rings need to be preferred for above 220kV insulators only. But below 220kV transmission line insulators like 66kV and 132kV are also degrading due to high pollution contaminations and high electrical stresses. Most of the utility companies in India are recommending corona rings for 66kV and 132kV insulators. But electrical stresses can also be minimized with usage of microvaristor component on the surface of the insulator. In this paper, with the help of FEMM 2D software package corona rings are designed for 66kV ceramic and polymer insulators and electric field was analyzed by finite element method. Application of ZnO microvaristor on the surface of the polymer insulator was evaluated and results are compared between with and without microvaristor. Results proved that insulators with ZnO microvaristor give better field results.