Purpose/Aim

Under the action of the impressed voltage, the condensation and the contamination composed of dust and charged particles on the surface of the insulating material will distort the electric field distribution on the surface of the insulating part. Thus, condensation and contamination will cause corona discharge which will gradually develop into surface flashover, resulting in serious accidents. Therefore, it is of great significance to research the condensation model and discharge initiation characteristics on the surface of contaminated insulating materials to improve the operational reliability of insulating parts.

Experimental/Modeling methods

Condensation tests were carried out in an artificial climate chamber to determine the influence of relative humidity, condensate depression and pollution degree on the various processes of condensation on the surface of insulating materials. Based on the existing condensation growth model, a new model considering contamination conditions is established, and MATLAB software is used to program the visualization dynamic image of the whole process of condensation growth. Use Solidworks software to build a physical model of the condensation on the surface of the insulating material and use the finite element method (FEM) to calculate the electric field distribution on the surface and around it. An experimental platform was built to test the corona inception voltage under the condition of condensation on the surface of the contaminated insulating material, and the corona inception voltage was determined by measuring the number of photons. A prediction method of corona onset voltage based on photoionization criterion under condensation conditions is proposed, and the validity of the prediction method is verified.

Results/discussion

The condensation growth model established in this paper is in good agreement with the condensation test results, and the error between the predicted value of corona onset voltage and the experimental value is small.

Conclusions

This research will help to improve the surface discharge mechanism of wet and dirty insulating materials, and provide basic theoretical as well as key technical support for the performance improvement of insulating materials in special operating environments.