The significance of corona measurements on electrical insulation systems

There has developed in the past 10 to 15 years an increasing conscience about corona in electrical apparatus. This has come about because of the experimental evidence for the degradation and erosion effects of electrical discharges, which gives to many organic insulating materials a finite life under electric stress in the presence of such discharges. This has led to the increasing use of corona testing of apparatus of various types, but without a complete understanding of the significance of the test results.