Abstract
High-voltage bushings play a crucial role in energy conveyance. Their specialized electric structure makes the bushing more vulnerable to surface discharge. However, the influence of a vertical electric field on the surface flashover of bushing structures remains unclear. To investigate this mechanism, four simplified bushing samples were built and the influence of pollution, leakage length, and the electric field component vertical to the dielectric surface on flashover properties of the bushing samples were tested. It was found that the surface pollution level was the decisive factor that influenced flashover voltage. When the leakage length and form factor were the same, the pollution flashover of the bushing structure was lower than that of the post structure. It was also found that increasing the leakage length was not very effective in improving the flashover voltage of bushings when the equivalent salt deposit density (ESDD) was high. No obvious correlation was found between pollution flashover voltage and electric field stress. Furthermore, the uneven wetting flashover performance of the bushings was tested. Under this condition, the flashover voltage decreased with an increase of the electric field component vertical to the dielectric surface. In addition, the electric field distribution of the samples was calculated and the results were in accordance with the experimental results.
Highlights
In high-voltage (HV) conversion substations, HV bushings play an important role
Till 3 s before the flashover and the surface resistance was about 30 MΩ, which indicated that the arc had not formed yet
The results demonstrate that the flashover voltage of the flashover voltage by increasing the leakage length
Summary
In high-voltage (HV) conversion substations, HV bushings play an important role. They convey current through walls or transformer tanks and act as insulation between lead wires and the ground. With the increase in voltage level, many flashover accidents in substations have been reported in the U.S, Canada, Brazil, and China [1,2,3,4]. More than 70% were related to HV wall bushings. The reported flashovers of HV bushings mostly happened under operational voltage on rainy days even when there was a relatively low equivalent salt deposit density (ESDD) As the configuration of a HV bushing is generally different from that of a line or post insulator, it is necessary to investigate their flashover mechanism in order to improve the bushing design and eventually avoid similar flashover accidents
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