Patterns and Development of the Surface Discharge of High Frequency Power Transformer Insulation Under Frequency-Dependent Electric Stress
Liu Tao1, Han Shuai2, Li Qingmin1, Lu Xu3, Huang Xuwei4
1.State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2.China Electric Power Research Institute Beijing 100192 China; 3.State Grid Beijing Shijingshan Electric Power Supply Company Beijing 100043 China; 4.Beijing Key Laboratory of High Voltage and EMC North China Electric Power University Beijing 102206 China
Abstract Surface discharge is one of the main causes of insulation failures.In order to investigate the patterns of surface discharge and its evolution process in high frequency power transformers,an experimental platform with high frequency voltage source was built.First,the surface discharge inception voltage,the flashover voltage,and the insulation life were tested under sinusoidal voltage of different frequencies from 10 kHz to 40 kHz.Then,with the constant sinusoidal voltage value,surface discharge tests were conducted to observe the entire evolution process of the surface discharge including its initiation,development,and the ultimate flashover,along with the characteristic parameters and phase resolved spectra at different discharging stages. At last,the evolution process was analyzed based on the secondary electron emission avalanche model and the trap theory.Experimental results and analyses indicate that:the surface flashover voltage and the insulation life will be decreased with the increase of the voltage frequency;the surface discharge of polyimide film approximately develops in a straight line under high frequency;the discharge amplitude,discharge number,phase resolved spectrum,and corresponding statistical parameters show specific variation trend at different evolutionary stages,which can utilized as the evaluation index of the development degree for surface discharge; the charge distribution and the trap parameters on the insulation surface are the key issues to reveal the inherent mechanism of surface flashover,since they have important effects on surface discharge characteristics.
Liu Tao,Han Shuai,Li Qingmin等. Patterns and Development of the Surface Discharge of High Frequency Power Transformer Insulation Under Frequency-Dependent Electric Stress[J]. Transactions of China Electrotechnical Society, 2016, 31(19): 199-207.
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2016, Vol. 31 
