CST – Computer Simulation Technology

Electroquasistatic Simulation of a High Voltage Insulator

This example shows the behavior of the electric field on the surface of a high voltage insulator with conductive contamination. The model consists of a dielectric cylindrical insulator (epoxy resin) which is capped by two electrodes and contaminated by seven water drops. The frequency of the alternating voltage is 50 Hz and a voltage gradient of 500 V/mm is applied. Further details of the application and the simulation method can be found in [1, pp. 224-231].



Figure 1: High voltage insulator model setup for electroquasistatic simulation

Figure 1 shows the model geometry. The structure generation involves the creation of three cylinders (representing the insulator and the electrodes) and several spheres (representing the waterdrops). The cylinders are inserted into the spheres by a Boolean operation. The generation of the spheres is performed by a VBA macro which allows for the creation of an arbitrary number of randomly distributed waterdrops....

The blue line is the path along which the electric field is be evaluated for both the E-Static and Electroquasistatic fields.



Figure 2: Electroquasistatic electric field plot at 50 Hz

The model is solved with the electroquasistatic solver with a solver accuracy 1e-6. In Figure 2 the resulting E-fields are superimposed on the partially-refined tetrahedral mesh used. This model can also be solved with the electrostatic solver which, however, does not take into account the conductivity of the waterdrops. An inherent systematic error is therefore made with the electrostatic solver. The difference in the results is best quantified by inspecting the field values at particular points or along predefined curves such as the one shown in Figure 1. The difference between the electric field along the curve for the electro- and electroquasistatic cases can be clearly seen in Figure 3.



Figure 3: Comparison between the EQS (red) and E-Static (green) field results

This article has demonstrated the importance of the EQS Solver in CST EM STUDIO® and its application to the simulation of a high voltage insulator. The difference between the Static and Quasistatic solvers has been shown.

Reference

[1] Van Rienen, Ursula, Numerical Methods in Computational Electrodynamics : Linear Systems in Practical Applications, Berlin: Springer-Verlag, 2001.

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