tailieunhanh - Extending analyzed frequency range in interpretation of frequency responses measured on a distribution transformer
The test object in this paper is a 200 kVA kV Yy6 distribution transformer whose measurement. To facilitate the investigation with the distributed circuit development, after all measurements were carried out, the transformer was disassembed to measure its geometrical parameters. | TAÏP CHÍ PHAÙT TRIEÅN KH&CN, TAÄP 18, SOÁ K6- 2015 Extending analyzed frequency range in interpretation of frequency responses measured on a distribution transformer Dinh Anh Khoi Pham Thi Minh Thai Pham Ho Chi Minh city University of Technology, VNU-HCM, Vietnam (Manuscript Received on July 15, 2015, Manuscript Revised August 30, 2015) ABSTRACT In the field of diagnosis of mechanical failures in power transformer’s active part, ., windings, leads and the core, the technique of Frequency Response Analysis (FRA) has been recently approved as the main application tool. Mechanical failures in transformer windings reflect changes on measured terminal frequency responses normally in medium frequency range, from several to hundreds of kHz, which is in fact not easy to interpret for diagnosis. The authors proposed a new method based on simulation of a lumped three-phase equivalent circuit of power transformers to interpret frequency responses effectively, but only within low frequency range. This limitation is due to the fact that, the circuit cannot reflect well physical phenomena at medium and higher frequencies. To improve the FRA performance of the proposed method at medium frequencies for transformer failure diagnosis purpose, the paper introduces an investigation on a distributed three-phase equivalent circuit of a 200 kVA kV Yy6 distribution transformer. Result of the investigation is a simplified procedure in determination of electrical parameters associated with the distributed circuit for better simulation based FRA interpretation at medium frequencies. Keywords: Failure diagnosis, power transformer, Frequency Response Analysis, lumped equivalent circuit, distributed equivalent circuit. 1. INTRODUCTION To understand what happens in transformer’s active part after a suspected through fault or during transportation for diagnostic purpose, measurement of terminal frequency responses of voltage ratios (end-to-end, inductive and capacitive .
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