Electrical field computation of polymeric insulator using reduced dimension modeling

In recent years, electrical field distribution is the area of major concern in the service life of Polymeric Insulators. Several methodologies are proposed to analyze the electrical field along the insulators both experimentally and numerically of which the former might be very time consuming requiring a number of trial-error tests to determine the optimum dimensions. The advent of super computers makes numerical analyses feasible on any complex geometry modeled in 3-D and the overall optimization techniques to control the electrical field become quite easier. However, the main drawbacks in 3-D analyses are the more computation time and memory, making it desirable to simplify the structure. Hence a methodology based on relationship between electrical field profiles of 2-D (axi-symmetry model of insulator with corona ring) and 3-D model (insulator with corona ring, tower, 3 phase hardware fittings and conductors) for a dimension and location of corona/grading rings is proposed. Based on the relationship, electrical field profiles of 3-D models are predicted for different dimension and location of rings using its equivalent 2-D model electrical field profile. Commercially available 2-D and 3-D finite element based electrostatic field computation program is used. A 220 kV suspension type I string assembly is used for this study. Later, the approach is validated for 132 kV and 400 kV insulators. The type of tower, string configuration is kept constant throughout the analyses.