Numerical Analysis of Electric Field in Oil-Immersed Current Transformer with Metallic Particles Inside Main Insulation

Wei Lou, Bo Lu, Youxiang Pan, Zhou Han and Lujia Wang ()
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Wei Lou: State Grid Corporation of China, East China Branch, Shanghai 200120, China
Bo Lu: State Grid Corporation of China, East China Branch, Shanghai 200120, China
Youxiang Pan: Anhui Nanrui Zhongtian Electric Power Electronics Co., Ltd., Hefei 230061, China
Zhou Han: Anhui Nanrui Zhongtian Electric Power Electronics Co., Ltd., Hefei 230061, China
Lujia Wang: School of Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, China

Energies, 2025, vol. 18, issue 14, 1-16

Abstract: During the manufacturing process of oil-immersed current transformers, metallic particles may become embedded in the insulation wrapping, and the resulting electric field distortion is one of the primary causes of failure. Historically, the shape of metallic particles has often been simplified to a standard sphere, whereas in practice, these particles are predominantly irregular. In this study, ellipsoidal and flaky particles were selected to represent smooth and angular surfaces, respectively. Using COMSOL Multiphysics ® (version 6.2) software, a three-dimensional simulation model of an oil-immersed inverted current transformer was developed, and the influence of defect position and size on electric field characteristics was analyzed. The results indicate that both types of defects cause electric field distortion, with longer particles exerting a greater influence on the electric field distribution. Under the voltage of a 220 kV system, elliptical particles (9 mm half shaft) lead to the maximum electric field intensity of main insulation of up to 45.1 × 10 6 V/m, while the maximum field strength of flaky particles (length 30 mm) is 28.9 × 10 6 V/m. Additionally, the closer the particles are to the inner side of the main insulation, the more significant their influence on the electric field distribution becomes. The findings provide a foundation for fault analysis and propagation studies related to the main insulation of current transformers.

Keywords: oil-immersed current transformer; metallic particles; insulation defects (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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