Voltage endurance test at increasing voltage as a tool to express determinations of mathematical model parameters of electrical aging

摘要

Voltage endurance (VE) testing of insulation for high voltage machines has become a routine practice for qualification of winding reliability. The most typical VE test is a test conducted at one specific test level. Depending on both the electrical stress and the insulation quality, the test duration could last less than hour or could be a few years long. Standards with only Pass/Fail criteria provide only limited information about the insulation. A VE test that is conducted to the moment when at least 50% of the samples fail provides much more information about the insulation system. However, this type of VE test could take a very long time and is not practical for most industrial applications. At the other extreme, early failure would result in a very short test time and leave results about the test inconclusive. For conclusive test results, the applied electrical stress shall be selected so that test time is no more than 3 months but as a minimum, at least a few hours. The mathematical model for the electrical aging process is required to compare VE tests performed at different electrical stresses. This comparison is necessary in many cases to predict the test results at specified electrical stresses different from available reference data. It is also could be used to predict insulation life at the operational stresses.