Evaluation of temperature rise of distribution transformers in the presence of harmonics and distortion

• Published in: Electric power systems research Vol. 20; no. 1; pp. 15 - 22
• Main Authors: Girgis, Adly A., Makram, Elham B., Nims, Joseph W., O'Dell, Larry K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.1990; Elsevier
• Subjects: Applied sciences; Electrical engineering. Electrical power engineering; Exact sciences and technology; Transformers and inductors; Harmonic; Energy loss; Load distribution; Experimental result; Temperature; Frequency spectrum; Daily variation; Harmonic distortion; Power transformer; Modeling; Distribution system
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/0378-7796(90)90021-T

Core and copper losses of a distribution transformer increase in the presence of harmonics and distortion. In most of the cases, an indication of total harmonic distortion is known. Expressions for the transformer core and winding losses as a function of the total harmonic distortion are obtained experimentally using a harmonic generator, a 10 kVA 7200/120 V distribution transformer, and a digital oscilloscope equipped with digital processing software. The selection of the harmonics is based on actual recorded data. A thermal model of a distribution transformer is used to evaluate the temperature rise both with and without harmonics. The evaluation indicates that there is a significant increase in the operating temperature in the presence of high order harmonics, as compared with the operating temperatures when no harmonics are present. This paper presents the nature of the actual recorded data, the method of evaluation, and the results.