Each insulator user hopes that the polymer insulator may have long service life replacing porcelain and glass insulators. Aging Tests for polymer insulator is necessary.

Aging Tests for polymer insulator

The method designated by IEC 61109 for accelerated aging tests of the housing material of composite insulators specifies evaluation of short specimens that satisfy unit electrical stress levels. In this case, however, to examine the effect both of the material and of the structure, the procedures used in the loading exposure tests being carried out in Okinawa were followed for both the test specimens and the voltage (77 kV AC (to ground). To serve as a suitable site for these tests, a large fog chamber was built measuring 4.4 m square by 3.3 m in height.)

In order to be able to investigate the temperature change, humidification, precipitation, salt exposure and UV irradiation set forth in IEC 61109, at the same time as performing accelerated aging tests on the adhesion of the end-fitting and terminal portion of the housing rubber, this facility is provided with equipment for applying a steady load of 20 kN.

This method of acceleration provides a test that promotes electrical degradation by simulating, reproducing in a short period of time, and then repeating the stress caused by changes in weather under electrical stress.

Evaluation of the test results was carried out by continuous measurement of leakage current, regular measurements of the hydrophobicity of insulator surfaces, and analysis of surface conditions after the completion of the tests using scanning electron microscopy (SEM) and Xray photoelectron spectrometry (XPS).

As the tests, hydrophobicity was adequately maintained after the specified period of 5000 hr, despite a minor decline from the initial conditions.

Visual observation of insulators after test completion revealed a certain degree of gray discoloration, but SEM results showed no difference from the initial conditions.

XPS observation of coupling energy also showed no change from initial rubber coupling, thus confirming that no aging occurred.

Thus we see that in actual-dimension accelerated aging tests conducted in accordance with IEC 61109 Annex C, the composite insulators showed no great leakage current and no tracking or erosion of the insulator surface. Tests of withstand voltage characteristics conducted separately also showed satisfactory results. It was accordingly concluded that these insulators would satisfactorily stand up to use at the ordinary level of pollution prevailing in Taiwan.

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