Leakage Current Equalization via Thick Semiconducting Coatings Suppresses Pin Corrosion in Disc Insulators

Cong Zhang (), Hongyan Zheng, Zikui Shen, Junbin Su, Yibo Yang, Heng Zhong and Xiaotao Fu
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Cong Zhang: Key Laboratory of Physical and Chemical Analysis for Electric Power of Hainan Province, Haikou 570311, China
Hongyan Zheng: Key Laboratory of Physical and Chemical Analysis for Electric Power of Hainan Province, Haikou 570311, China
Zikui Shen: School of Electric Power Engineering, South China University of Technology, Guangzhou 510641, China
Junbin Su: Key Laboratory of Physical and Chemical Analysis for Electric Power of Hainan Province, Haikou 570311, China
Yibo Yang: School of Electric Power Engineering, South China University of Technology, Guangzhou 510641, China
Heng Zhong: Key Laboratory of Physical and Chemical Analysis for Electric Power of Hainan Province, Haikou 570311, China
Xiaotao Fu: Key Laboratory of Physical and Chemical Analysis for Electric Power of Hainan Province, Haikou 570311, China

Energies, 2025, vol. 18, issue 19, 1-13

Abstract: In coastal hot and humid regions, the steel pin of AC porcelain insulators often suffers from severe electrochemical corrosion due to surface contamination and moisture, leading to insulator string breakage. Contrary to the common belief that AC corrosion is negligible, this study reveals the significant role of the DC component in leakage currents and the synergy of this DC component with localized high current densities in accelerating corrosion, based on field investigations and experiments. Using a simulation model based on the Suwarno equivalent circuit, it is shown that non-linear contamination causes highly non-sinusoidal leakage currents, with total harmonic distortion up to 40% and a DC component of approximately 22%. To mitigate this, a conductive silicone rubber coating is proposed to block moisture and distribute leakage current evenly, keeping surface current density below the critical threshold of 100 A/m 2 . Simulations indicate that a 2 mm thick coating with conductivity around 10 −4 S/m effectively reduces current density to a safe level. Accelerated corrosion tests confirm that this conductive coating significantly suppresses pitting corrosion caused by high current densities, outperforming traditional insulating coatings. This study presents a practical and effective approach for protecting AC insulators in harsh environments, contributing to improved transmission line reliability in high-temperature and high-humidity regions.

Keywords: AC insulators; steel pin corrosion; leakage current; DC component; conductive coating; current density mitigation; Suwarno model; nonlinear conductivity (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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