Abstract
In order to improve the insulating performance of air-insulated high voltage electrical apparatuses, solid barriers are always introduced in the interelectrode gaps. The breakdown paths and conditions of air-insulated rod-plane gaps in the range of 2–5 cm under alternating voltages were investigated for three different sizes of polyvinyl chloride barriers inserted at different gap positions. The breakdown processes were observed using two cameras placed in orthogonal directions, and two typical breakdown paths were captured. The statistical results showed that the occurrence probabilities of the two typical breakdown paths were related to the barrier position, but that the breakdown voltages were very similar in all breakdown events. Further, formulae to predict the breakdown voltage were deduced using a linear regression method. The results provide a reference for improving the insulation performance of gas–solid hybrid insulation systems based on the barrier effect as well as for modelling gas discharges in hybrid gaps.
Highlights
Atmospheric air has been widely used as an insulation medium for high voltage electrical apparatuses
The barrier effect has clear advantages when used in nonuniform electrode configurations, and in such situations the strength of the effect is associated with the barrier position, barrier size, and barrier material
We present the results of an experimental investigation into the alternating current breakdown paths and voltages of air-insulated rod–plane gaps with polyvinyl chloride (PVC) barriers of different sizes and positions
Summary
Atmospheric air has been widely used as an insulation medium for high voltage electrical apparatuses. compared with apparatuses that use SF6 gas, those that use air are far larger because of the lower insulation performance of air. To combat this problem, the breakdown voltage of the gas-insulated gap under a nonuniform electric field can be increased by inserting a barrier in the inter-electrode gap. This can reduce the size of the apparatus by reducing the volume of air required, and improve the reliability of the insulation.When a barrier is used in a non-uniform field in air, it increases the flashover voltage. Compared with apparatuses that use SF6 gas, those that use air are far larger because of the lower insulation performance of air.3–5 To combat this problem, the breakdown voltage of the gas-insulated gap under a nonuniform electric field can be increased by inserting a barrier in the inter-electrode gap.. The breakdown voltage of the gas-insulated gap under a nonuniform electric field can be increased by inserting a barrier in the inter-electrode gap.6 This can reduce the size of the apparatus by reducing the volume of air required, and improve the reliability of the insulation. When a barrier is used in a non-uniform field in air, it increases the flashover voltage This is referred to as the barrier effect; its influence on the performances of gas-insulated gaps depends on many factors. The barrier effect has clear advantages when used in nonuniform electrode configurations, and in such situations the strength of the effect is associated with the barrier position, barrier size, and barrier material. Further, the barrier effect plays a significant role under other types of applied voltages and in various gaseous media. it has been observed that the barrier effect is greater when two barriers are inserted in the air-insulated point– point gap compared with only inserting one barrier. A series of discharge spreading and reignition phenomena in the air-insulated point–plane gap with two barriers have been simulated using a fluid model. it is difficult to put forward a generalized law to evaluate the breakdown voltage of gas–solid hybrid insulation systems because of the many influencing factors
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