Accelerated thermal deterioration test of insulators in air and test results on enamelled wires

摘要

A special assembly for accelerated thermal deterioration test of insulators in air was developed and the results on enamelled wires were shown. The results obtained are as follows: 1. It was shown that a new assembly using a gas circulating pump, a platinum filament, and a liquid nitrogen cold trap is very effective for collecting small amounts of gas generated from insulators heated in air. 2. The thermal deterioration of enamelled wires in air can be studied over a wide temperature range from high temperatures to normal working temperatures. The thermal deterioration characteristics of enamelled wires shown by the logarithm of the generation rate of (CO + CO2) versus 1/T is generally made of two offset line segments of differing slopes. The difference of slope would indicate a difference of thermal deterioration mechanism. 3. The slope of log(1/Δp) versus 1/T curve coincides with the slope of log(life) versus 1/T plot obtained in the measurements of the breakdown voltage. 4. According to the above results, the thermal life of enamelled wires in air at normal working temperatures can be estimated using together two type of information: a) the slope of log(1/Δp) versus 1/T, and b) the results of actual life tests made at much higher than normal temperatures. 5. The deterioration of enamelled wires in air will depend on the diffusion of atmospheric oxygen into the enamel films and the oxidation of the film by the diffused oxygen.