A New Approach to the Voltage-Endurance Test on Electrical Insulation

After examining the life-testing theories for both thermal and electrical aging, a new theory, starting from an extension of the chemical reaction one, is proposed. However, the new theory is quite different from the latter, because it ignores the aging mechanism, considering only its effects. Through this theory, electrical aging is investigated and the fundamental law governing the time behavior of electrical insulation is derived on the hypothesis that the voltage-life law has the form of an inverse-power law. This result suggests a new procedure for the voltage endurance test. Short-time dielectric strength of specimens, prestressed for different times by an ac voltage of the same value, is measured and plotted against the aging time. Using this procedure a great deal of information about the time behavior of insulating materials can be obtained in a short time. Experimental data, pertinent to plastic insulating materials for medium-and high-voltage cables, are given in support of the theory. Since the theory proposed is quite general, it can be extended to the study of aging in other systems subject to degradation.