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Transformer Insulation Condition Assessment by Evaluation of High Voltage IFRA Measurements

Abstract:

An experimental evaluation of the insulation condition of a 50 kVA three-phase oil-immersed transformer is presented in this document by applying high-voltage standard atmospheric impulses to obtain its frequency response, also known as Impulse Frequency Response Analysis (IFRA). The evaluation is based on comparing two different conditions of the insulation on a transformer. For instance, in this article, one insulation condition is obtained when the transformer uses deteriorated dielectric oil, and the second condition is obtained by replacing this deteriorated oil by a new one. A general evaluation of the transformer is performed in both conditions through the execution of routine tests. Frequency response analysis is implemented by obtaining the transformer response in the two insulation conditions, and under different measurement configurations. Then, the results are evaluated qualitatively and quantitatively through a graphic comparison between the measured frequency responses, and relating them to the dielectric oil insulating condition. The experimental methodology is provided as an alternative to the use of specialized frequency response analysis equipment, through the application of standard high voltage atmospheric impulses, using the equipment available in the High Voltage Laboratory of the National Polytechnic School for lightning impulse test.