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

Yuan Li, Kai Zhou, Guangya Zhu, Mingzhi Li, Shiyu Li and Jiangong Zhang
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Yuan Li: College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
Kai Zhou: College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
Guangya Zhu: College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
Mingzhi Li: College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
Shiyu Li: College of Electrical Engineering, Sichuan University, No. 24 Yihuan Road, Chengdu 610065, China
Jiangong Zhang: State Key Laboratory of Power Grid Environmental Protection, Wuhan 430074, China

Energies, 2019, vol. 12, issue 16, 1-13

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.

Keywords: converter transformer; electrical conductivity; oil-impregnated pressboard; ion concentration; ion mobility (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: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (4)

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