A moisture-in-oil model for power transformer monitoring - Part II: Experimental verification

For Part I see ibid., p.1417-22, 2005. In the companion paper, a model to detect failures leading to an increase of the water content in transformer oil was proposed. In this paper, the experimental verification of the model is presented. The model was tested in a 1500-kVA test transformer constructed as a reduced scale model of a 60-MVA 220-kV transformer. In order to load the transformer to have the capability of varying load and power factor over a wide range, the opposition method described in IEC 60076-2 Standard was used. Sensors to measure temperature and moisture in oil were installed in the test transformer. The model was adjusted and validated using a set of data corresponding to different operating conditions. The transformer was submitted to an accelerated aging process studying the model response in such a case. In order to verify the model´s ability to detect failures, a water ingress in the transformer was simulated.