ASTM D2275-14 PDF Download

ASTM D2275-14 is a standard test method used for evaluating solid electrical insulating materials in terms of their voltage endurance under corona conditions. The purpose of this test is to measure the ability of these materials to withstand prolonged AC stress in the presence of corona, which is a visible glow at the edge of the electrode interface resulting from partial discharge. The test method is particularly useful for comparing different materials or comparing materials of the same relative thickness.

The standard provides guidelines for analyzing the data generated during the test, which is in the form of a set of values of lifetimes at a specific voltage. The dispersion of failure times can be analyzed using various methods such as Weibull Probability Plot, statistical analysis, or truncating the test at a specific failure time. The variability of the time to failure is also considered and the Weibull slope factor (ß) is recommended as a measure of variability.

The standard also highlights the potential factors related to failures caused by corona, such as erosion of insulation, carbonization of the insulation surface, formation of compounds, treeing within the insulation, and changes in the physical properties of the material. It is important to note that a poor result on this test does not necessarily indicate that the material is unsuitable for high voltage use in the absence of surface corona.

The test is typically conducted in open air at 50% relative humidity, but additional information can be obtained by conducting tests in circulating air at lower humidity levels. It is important to monitor the consistency of test parameters, such as voltage levels, in order to accurately assess the voltage endurance of the insulating materials. The shape of the Weibull Probability Plot can also provide additional insights, potentially indicating multiple failure mechanisms or the presence of defective specimens within a lot.