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Study on the Influence of Temperature, Moisture and Electric Field on the Electrical Conductivity of Oil-Impregnated Pressboard

1
College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
2
State Key Laboratory of Power Grid Environmental Protection, Wuhan 430074, China
*
Author to whom correspondence should be addressed.
Energies 2019, 12(16), 3136; https://doi.org/10.3390/en12163136
Received: 8 July 2019 / Revised: 25 July 2019 / Accepted: 9 August 2019 / Published: 15 August 2019
(This article belongs to the Section Electrical Power and Energy System)
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PDF [4264 KB, uploaded 15 August 2019]
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Abstract

The main insulation of converter transformers consists of transformer oil and oil-impregnated pressboard. Under operating conditions, the valve-side winding of the converter transformer is subject to DC voltage components. Therefore, studies on the characteristics of oil-impregnated pressboard conductivity are necessary. In this paper, the temperature, moisture and electric field dependency of pressboard conductivity are investigated based on a specially designed three-electrode experimental chamber, which allows for a variation in temperature ranging from 25 °C to 120 °C and an electric field strength ranging from 0 to 30 kV/mm. The experimental results show that, within the experimental conditions, the conductivity of oil-impregnated pressboard increases exponentially with increasing moisture and temperature. High moisture and temperature will increase both the carrier concentration and carrier mobility, which explains the exponential correspondence. Furthermore, the electric field dependency of the conductivity is more obvious for wet pressboard than for dry pressboard. Protons in the wet pressboard are more easily accelerated by the electric field than the impurity ions in the oil of the dry pressboard, which leads to an obvious electric field dependency of the wet pressboard conductivity. View Full-Text
Keywords: converter transformer; electrical conductivity; oil-impregnated pressboard; ion concentration; ion mobility converter transformer; electrical conductivity; oil-impregnated pressboard; ion concentration; ion mobility
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Li, Y.; Zhou, K.; Zhu, G.; Li, M.; Li, S.; Zhang, J. Study on the Influence of Temperature, Moisture and Electric Field on the Electrical Conductivity of Oil-Impregnated Pressboard. Energies 2019, 12, 3136.

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