Electric circuit theoretical insulation diagnosis for XLPE power cables

The author is studying an insulation diagnosis system for XLPE power cables by applying an AC voltage on test specimens to detect frequency signals lower than the AC frequency, and has found that signals are generated not only by insulation defects. This paper discusses the new concept that signal sources in the test voltage pass through deteriorated parts of insulation and defective parts more easily. The origin of the signal and how it functions are discussed based on electric circuit theory.