Evaluation of Dynamic Hydrophobicity Properties with the Dynamic Drop Test under AC and DC stress and the Hydrophobicity Transfer Test

Summary

This paper deals with the development of two test procedures for evaluating the dynamic properties of hy-drophobicity of polymeric insulating materials for high voltage outdoor application. These properties include the retention, the recovery and the transfer of hydrophobicity onto accumulated pollution layers. The Dy-namic Drop Test (DDT) for evaluating the retention and recovery as well as the Hydrophobicity Transfer Test (HTT) have proven to be suitable test methods and the ongoing investigations are intended to im-prove their repeatability and reproducibility. The paper presents test results of the DDT and HTT performed in two independent laboratories with a variety of relevant polymeric insulating materials. The scatter of DDT-results is reduced compared to previous investigations. Possible reasons for discrepant test results, like the influence of the test setup, the cleaning and storage of samples etc., are discussed. For a further reduction of the scatter a test procedure with stepwise increasing test voltage and flow rate is investigated. The recovery of hydrophobicity is evaluated by using the DDT with discontinuous stress. After a defined period of stress the specimen is allowed to recover its hydrophobicity before it is stressed again. This pro-cedure is repeated until the specimen's hydrophobicity is lost temporarily. The ability of the investigated insulating materials to transfer their hydrophobic properties onto artificial pollution layers is also evaluated. Correlations of the transfer and the retention capabilities are discussed.

Additional informations

Authors

Baer Christiane, Baersch Roland, Hergert Alexander, Kindersberger Josef