SUMMARY

Interest is increasing in replacing the traditional way for determining moisture content in pressboard and paper in insulation of power transformers, based on chemical analyses of oil, by new methods utilising dielectric response measurements. One of the main reasons driving ahead the development of the new techniques is related to the inferior accuracy of the former methodology, especially at lower temperatures. In response to the conclusions of CIGRE TF 15.01.09 – Dielectric Response Methods for Diagnostics of Power Transformers [1], a European project, named REDIATOOL (Contract no. NNE5/2001/472), was initiated in 2003. The project involved collaborations among researchers and engineers from Sweden, Poland and Germany. The project in its part related to the evaluation of dielectric response methods concentrated on (i) investigations using laboratory models to improve calibration (interpretation of results) of the methods based on dielectric response measurements, on (ii) verifications performed on different types of the transformers sent for repairs, and finally, on (iii) gathering experiences from investigations of transformer insulation on-site. REDIATOOL combines theory and laboratory methods, computer and physical modeling as well as testing real units in field conditions. This paper presents and summarises the project results, to be use