Insulation Online Monitoring Method for Dry-Type Current Transformers Based on Virtual Voltage

Junjie Zhang, Yu Peng, Xiaohui Hu, Zhipeng Li, Li Yan, Can Ding () and Ruihua Zhao
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Junjie Zhang: Shaoguan Power Supply Bureau, Guangdong Power Grid Co., Ltd., Shaoguan 512000, China
Yu Peng: Shaoguan Power Supply Bureau, Guangdong Power Grid Co., Ltd., Shaoguan 512000, China
Xiaohui Hu: Wuhan Kangda Electric Co., Ltd., Wuhan 430070, China
Zhipeng Li: Wuhan Kangda Electric Co., Ltd., Wuhan 430070, China
Li Yan: Wuhan Kangda Electric Co., Ltd., Wuhan 430070, China
Can Ding: College of Electrical Engineering and New Energy, China Three Gorges University, Yichang 443000, China
Ruihua Zhao: College of Electrical Engineering and New Energy, China Three Gorges University, Yichang 443000, China

Energies, 2025, vol. 18, issue 13, 1-16

Abstract: To improve the accuracy of insulation state online monitoring for capacitive dry-type current transformers (CTs) and to address the limitations of traditional methods relying on potential transformer (PT) voltage signals and reference devices, a virtual voltage-based online monitoring method is proposed. First, the leakage current is collected through a core-type current transformer on the end-screen grounding line. Combined with group measurement data from surge arresters and dry-type CTs on the same busbar, phase constraints are established, and a least mean square (LMS) algorithm is utilized to iteratively train the virtual voltage reference phase. Subsequently, the resistive current and dielectric loss factor (tan δ) are calculated based on the virtual voltage reference phase to achieve online insulation state monitoring. Simulation results demonstrate that the proposed method can accurately obtain the virtual voltage reference phase and effectively identify the degradation trend of dry-type CTs. Field applications validate the feasibility of the method, with monitoring data fluctuations (±20 μA for the resistive current and ±0.002 for the dielectric loss) meeting engineering requirements. This method eliminates the need for PT signals and reference devices, thus providing a novel approach for the online insulation monitoring of dry-type CTs.

Keywords: dry-type current transformer; phase constraints; virtual voltage; resistive current measurement; insulation state monitoring (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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