Analysis of inrush current and delta winding circulating current in three‑phase transformers with different core structures

Authors

Jimin CHAI, School of Electrical and information Engineering, Changzhou Institute of Technology, Changzhou 213032, China; College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, ChinaFollow
Yuping ZHENG, College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, China; NARI Group Corporation (State Grid Electric Power Research Institute), Nanjing 211106, China; State Key Laboratory of Smart Grid Protection and Control，Nanjing 211106, China
Shuyan PANG, NARI Group Corporation (State Grid Electric Power Research Institute), Nanjing 211106, China; State Key Laboratory of Smart Grid Protection and Control，Nanjing 211106, China

Keywords

transformer, inrush current, circulating current, zero-sequence component

Abstract

The magnetic circuit characteristics and operating equations of transformers with three different core structures: three-phase banked, five-limb, and three-limb are utilized. A numerical method is proposed to fit the circulating current in the delta windings using the zero-sequence current and voltage on the wye side. Through this approach, a deeper understanding of the characteristics of current in the delta windings and magnetizing inrush current in transformers with different core structures is gained. To validate the effectiveness of the proposed numerical method, software simulations and field waveform recordings are conducted. The results show that for three-phase banked and five-limb transformers, the differential current in each phase winding corresponds directly to the magnetizing inrush current of that phase; however, for three-limb transformers, the differential current in a phase winding is not directly correspond to its excitation current. Further theoretical analysis and simulation verification indicate that during no-load closing from the wye side of transformers with these three types of core structures, the difference between the line currents of any two phases on the wye side can be regarded as the difference in magnetizing inrush current between the two equivalent magnetic circuits. This finding provides a new basis for identifying the magnetizing inrush current of three-phase transformers with different core structures.

DOI

10.19781/j.issn.1673-9140.2024.02.011

First Page

91

Last Page

100

Recommended Citation

CHAI, Jimin; ZHENG, Yuping; and PANG, Shuyan (2024) "Analysis of inrush current and delta winding circulating current in three‑phase transformers with different core structures," Journal of Electric Power Science and Technology: Vol. 39: Iss. 2, Article 11.
DOI: 10.19781/j.issn.1673-9140.2024.02.011
Available at: https://jepst.researchcommons.org/journal/vol39/iss2/11