Synergistic effect of SF<sub>6</sub>/N<sub>2</sub> gas mixtures on surface partial discharge under DC voltage
Zhiqiang Hou, Ruochen Guo, Cong He, Junhao Li, Xiu Yao
Abstract
With the development of high-voltage direct-current (HVDC) transmission, DC gas insulated lines (GIL) with SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas mixtures as insulating medium have been successfully adopted. Space is typically the weak link of equipment insulation where surface discharge is one of the common discharge forms in power equipment. Therefore, research on the surface discharge characteristics of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> under DC voltage can contribute to insulation design of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> insulated DC GIS, GIL and other power equipment. In this paper, a DC high-voltage experimental system is established to study partial discharge (PD) along insulation surfaces. The characteristics at the initial discharge and the discharge development stages are analyzed in detail. Additionally, the synergistic effect of mixed gas is investigated based on the discharge characteristics and the synergistic effect coefficient is introduced. The experimental results show that the synergistic effect of mixed gas partial discharge inception voltage (PDIV) under high pressure is more obvious compared to low pressure and the discharge quantities of mixed gas is smaller than that of pure SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> at the discharge development stage. This study on the multiple influencing factors of synergistic effect is expected to provide important insight for exploring the SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> discharge mechanism and helps decreasing the usage SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> .