Diagnostic measurements of high voltage polymeric cable insulation

This paper describes two techniques that can help to diagnose the operating conditions of polymeric cable insulation. The first, the oxidative induction time (OIT) measurements, requires obtaining specimens of the insulation and performing tests in a laboratory. Insulation samples can be taken, for example, after the first cable failure. The second technique, which measures the harmonic distortion of an ac loss component of the current flowing through the insulation, could evolve into an in situ diagnostic technique.