Improved Isothermal Relaxation Current Measurement Based on Isolated Circuit for Nondestructive Evaluation of High-Voltage Cable Insulation

Huangjing Gu, Yongkang Zhang, Bin Shen, Ziqi Liu, Yunjie Zhou, Xiaodi Wang, Xinyang Zhu and Yalin Wang ()
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Huangjing Gu: State Gid Shanghai Cable Company, Shanghai 200122, China
Yongkang Zhang: State Gid Shanghai Cable Company, Shanghai 200122, China
Bin Shen: State Gid Shanghai Cable Company, Shanghai 200122, China
Ziqi Liu: State Gid Shanghai Cable Company, Shanghai 200122, China
Yunjie Zhou: State Gid Shanghai Cable Company, Shanghai 200122, China
Xiaodi Wang: State Gid Shanghai Cable Company, Shanghai 200122, China
Xinyang Zhu: Department of Electrical Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Yalin Wang: Department of Electrical Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Energies, 2023, vol. 16, issue 23, 1-18

Abstract: The Isothermal Relaxation Current (IRC) method, as a non-destructive condition evaluation method based on insulation dielectric response, has been applied in the maintenance of power cables. However, the relaxation current is usually conducted through the outer shield of the high-voltage wire, which will introduce the extra depolarization current into the test circuit, affecting the accuracy of the test results. Furthermore, most IRC cable measurements are single-phase, which means depolarization currents are measured for each cable separately. In order to improve the measurement accuracy and efficiency of the IRC test, this paper proposes an improved IRC measurement method based on an isolated circuit, which discharges the interference current from the high-voltage insulated wire back to the earth and reduces the measurement error of depolarization current. At the same time, a three-phase IRC simultaneous test system is designed, and the control software is developed. Furthermore, by verifying the accuracy of the test system, the independence of the single-phase circuit and the consistency of the three-phase circuit is achieved. The effect of depolarization time and temperature on the relaxation current is then explored to determine the suitable parameter of the IRC test. Finally, the IRC system is used to evaluate the aging state of 10 kV cables with various aging conditions in the air and water for the longest 12 months. Critical parameters such as aging factor and time constants are compared to investigate the aging characteristics of tested cables with various aging conditions in the air and water. The proposed method and research conclusions can provide helpful references for the non-destructive condition evaluation for high-voltage cable insulation.

Keywords: high-voltage cable insulation; condition evaluation; non-destructive measurement; isothermal relaxation current; isolated circuit (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: 2023
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