Abstract
Flashover at gas/insulator interface acts as a vital challenge to the safe and stable operation of gas-insulated system especially when involved with surface metallic particle. In this paper, flashover characteristics at SF<sub>6</sub>/epoxy insulator interface were investigated concerning on the tracking property based on image analysis. DC flashover experiments were operated for basin-type spacer with metallic particle at various locations. Flashover voltage was obtained and tracking on the surface after successive flashover was captured. Improved image analysis method based on fractal theory was carried out to evaluate tracking pattern quantitatively. The relation between the fractal dimension of tracking and field distribution at particle tip was revealed. Obtained results showed that flashover voltage decreased due to severe field distortion with moving particle from ground to HV electrode. Meanwhile, fractal dimension of tracking covering the area from particle to ground electrode indicated centralized tendency. Simulation result confirmed this variation as the consequence of centralized field distribution at the tip of particle. The quantitative relation between fractal dimension and field distribution suggests new sight to estimate the influence of metallic particle on insulation property in the gas-insulated system.
Highlights
Solid insulators are widely applied in gas-insulated apparatus including gas insulated switchgear (GIS) and gas insulated transmission lines (GIL) functioning as the main supporting and isolating components with insulating property [1], [2]
This article investigated the DC flashover property of basintype insulator in SF6 gas considering the influence of surface metallic particle
Tracking pattern due to successive discharge was analyzed based on fractal theory
Summary
Solid insulators are widely applied in gas-insulated apparatus including gas insulated switchgear (GIS) and gas insulated transmission lines (GIL) functioning as the main supporting and isolating components with insulating property [1], [2]. Metallic particle which may be introduced in manufacture, transportation or operation would be adhered on the insulator surface under electric field stress [4], [5]. This may cause severe field distortion and contribute to the initiation of flashover and is reported as a vital issue for the system [6]-[8]. Damage due to successive discharge may promote surface deterioration by providing possible propagation path for continuous discharge and lead to the decrease of surface strength. Tracking indicates the propagation property of discharge and may provide potential approach to reveal the propagation and probability characteristics of surface discharge. Tracking taken from insulator surface via off-line method performs as a possible approach to diagnose and analyses flashover characteristics
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