Influence of DC Voltage Component on Surface Flashover of Insulating Screw under Composite AC and DC Voltage

In order to deeply understand the flashover problem of insulating screw under composite AC and DC voltage in converter transformer, an experimental electrode satisfying the electric field distribution characteristics of insulating screw surface was designed on the basis of simulation. By building an AC-DC superimposed power system in which the DC voltage component can be adjusted arbitrarily, the influence law of DC component on the flashover characteristics of insulating screw along the surface under composite voltage was studied. The results show that the flashover voltage along the surface of insulating screw increases with the increase of DC voltage. However, space charge accumulates on the surface of insulated screw under DC voltage, which distorts the electric field and leads to the decline of AC component, which decreases continuously with the increase of DC component.