Development of a Simple Experimental Setup for the Study of the Formation of Dry Bands on Composite Insulators

This paper introduces a new geometry for the study of dry band formation. Firstly, a thermoelectric simulation of a 69 kV uniformly polluted composite insulator was performed. The results obtained show that thermal stress is greater at the rod surface where current density is maximum. In order to experimentally reproduce the constriction of current density lines on the insulator rod surface, which is the cause of dry band formation, the development of a new simple geometric setup, which was then tested experimentally, was proposed. For this purpose, an ESDD value corresponding to a high level of pollution was used for each polluted sample, and the samples were placed in a climate chamber at constant 90% relative humidity and a constant ambient temperature of 20 °C. Low-voltage tests permitted the determination of the wetting duration, which corresponds to the maximum surface conductance of the polluted layer. The values obtained agree with the 10–40 min duration recommended in IEC 60507. Moreover, the tests performed at a higher voltage demonstrated the efficiency of the proposed setup to simulate the complex process of dry band formation in a reproducible way in terms of leakage current and temperature behavior. The proposed setup is a new and simple method that can be easily used by the electrical industry to develop new material for the next generation of overhead line composite insulators without requiring costly HV equipment.