An engineering approach to computational prediction of breakdown in air with surface charging effects

Atle Pedersen,Andreas Blaszczyk

doi:10.1109/tdei.2017.006650

Atle Pedersen, Andreas Blaszczyk

Open Access

https://doi.org/10.1109/tdei.2017.006650

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Abstract

This paper presents a dielectric simulation approach for predicting withstand voltage of air insulated power devices. The paper gives an overview of typical evaluation procedures for the basic discharge stages including inception, streamer propagation and leader transition. For selected test arrangements, we compare the results of lightning impulse tests with simulations. The simulations utilize a new approach that combines the well-established empirical procedure with numerical computations for arbitrary geometries. We introduce a new formulation for evaluation of saturation charge density, which enables a revision of the streamer inception conditions due to surface charging and an estimation of the leader transition characteristics including the surface capacitance.

Highlights

The goal of dielectric designing of high voltage equipment is to predict the necessary withstand voltage Uw in order to pass the required tests
We describe the concept of saturation charge and apply it to evaluation of restrikes, changed inception conditions as well as leader transition
This result indicates that the layer of surface charge accumulated during the first few microseconds of the lightning impulse on the horizontal surfaces of both rods is large enough to cause a re-inception of the streamer discharge after a few hundred microseconds

Summary

Introduction

The goal of dielectric designing of high voltage equipment is to predict the necessary withstand voltage Uw in order to pass the required tests. It involves quantitative assessment of the discharge process including inception and propagation of streamers, which are the basic precursors for dielectric breakdown in inhomogeneous electric fields. Designers of high and medium voltage equipment typically utilize semi-empirical behavioural rules characterizing the discharge, described in engineering handbooks [1 - 3]. [4]); such complex approaches are rarely usable for simulation procedures in industrial design of real devices. The focus in this study is on an engineering approach that combines the empirical observations with numerical computations

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