Simulation of Electric Field Strength and Force Density on Contaminated H-V Insulators
This paper reports on the simulation of the behavior of single water droplets on a horizontally arranged polymeric surface under the influence of an applied electric a.c. field. The goal of this investigation are predictions for the aging performance of c
- PDF / 1,149,704 Bytes
- 8 Pages / 439.37 x 666.14 pts Page_size
- 38 Downloads / 160 Views
S. Keirrr", and U. van Rienen!
Institute of General Electrical Engineering, Rostock University, Albert-Einstein-Str. 2, D-18051 Rostock, Germany High Voltage Laboratory, Darmstadt University of Technology, Landgraf-Georg-Str. 4, D-64283 Darmstadt, Germany
Abstract This paper reports on the simulation of the behavior of single water droplets on a horizontally arranged polymeric surface under the influence of an applied electric a.c . field. The goal of this investigation are predictions for the aging performance of contaminated insulators in high-voltage power problems.
1
Introduction
High-voltage insulators are stressed by the applied electric field as well as by other environmental factors. As a result of this stress, the surface of the insulating material gets aged and the dielectric material looses it's hydrophobic and insulating characteristics. The contamination of the object with water droplets accelerates the aging process. Experimental investigations have shown that with increase of applied voltage, droplets vibrate first, they are then extended to the direction of the applied electric field and finally flashover bridging water droplets occurs (see [6]). To improve the understanding of aging phenomena it is advisable to observe single droplets on an insulating surface. The shape of the droplets supplies more information about the status of the insulating material. This paper presents first the calculation of electric field strength and force density around the droplets. We model our problem as an electro-quasistatic 3D-problem (see [9]) . For discretisization we use the Finite Integration Theory (FIT, see [10]). FIT was especially developed to solve Maxwell's equations. It guarantees a consistent conversion of Maxwell's equations on a staggered grid, the so-called Maxwell-Grid-Equations. Our insulator problem leads to an almost singular complex symmetric system of linear equations. We investigate various solution methods for our complex symmetric system in order to compare these methods and find sufficiently robust ones . Second, we simulate our water droplet as a rotational ellipsoid with geometric values from experiments. We are looking for a relation between force density at the droplets and the measured shape of the ellipsoid. The goal is to predict the droplet behavior without experiments. * supported by Deutsche Forschungsgemeinschaft
U. van Rienen, et al. (eds.), Scientific Computing in Electrical Engineering © Springer-Verlag Berlin Heidelberg 2001
80
U. Schreiber , S. Keirn, U.v. Rienen
Figure!. The unaged solid epoxy resin sample with horizontally embedded electrodes and two wat er droplet s on t he t op of the t est object .
2
Figure2. Two wat er droplets afte r 20 min applicat ion of high voltage (8 kV). The droplet s are deformed during t he experiment .
Modelling for Electro-Quasistatics
The considered devices are driven with 50 Hz a.c, high-voltage, i.e. the electromagn etic field is slowly varying. The displacement cur rent plays a cru cial role. It 's density aD/at is linked u
Data Loading...
