Water is a threat to the insulation of oil (or ester) insulated power transformers. It leads to reduced breakdown strength of the oil and an accelerated aging of the cellulose insulation. Dielectric frequency response analysis is a suitable and accurate way to assess the water content of the insulation and it helps to determine the condition and remaining lifetime of the transformer.
Prior drawbacks of this technology, such as long measurement times and complex assessment, can be eliminated using modern software. This paper introduces the new PDC+ technique, an improved version of the polarization depolarization current (PDC) measurement. This new technique reduces the measurement time up to a factor of 20. Further automation of the whole measurement and assessment process makes the PDC+ technique easy and reliable for all users.