Dimensioning of a defined uneven silicone coating using the example of a glass cap and pin type insulator

Abstract:
This paper deals with the dimensioning of a partial silicone coating for glass cap and pin type insulators regarding the pollution flash over voltage. Therefore, the example of a 110 kV overhead line is chosen to determine parameters. The coating length is calculated based on these parameters and empirical data. The area for the further application of the silicone coating is chosen by means of numerical calculation of the electric field and potential distribution. The pollution flashover voltage of cap and pin type insulator units with the dimensioned silicone coating is experimentally verified, and turned out to be significantly lower than the calculated value. Liquid filaments bridging huge parts of the silicone coating cause this. Thus, the model is modified using an effective coating length. A salt fog test is carried out to investigate the hydrophobicity retention of the partially coated insulator in comparison to an overall coating. In suspension configuration no difference is recognized. In contrast to this in tension configuration higher leakage currents are measured and a local hydrophobicity reduction is shown after 1000 h. Finally a method for the optimization of the silicone coating length based on an empirical model was developed, which reduces material usage and coating cost. In future work the transferability to different insulator designs may be investigated.