Characteristics of streamer propagation along the insulation surface: influence of dielectric material

Research on dynamics of streamer propagation along different dielectric materials under a uniform electric field is presented. In the three-electrode arrangement, the variation of the streamer propagation probability, velocity and light intensity with electric field in the air and along the different dielectric materials was measured through three photomultipliers. The photographs of the streamer propagation in the air and along the different dielectric materials were taken with an ultraviolet camera. The test results have shown that the electric field required for streamer propagation in air alone is less than along the insulation surface. Furthermore, for electric fields higher than streamer `stability' propagation fields, the streamer propagates along insulation surface with a `fast' and a `slow' component. However, the streamer propagates in air alone without a `fast' component, only with a `slow' component. The velocity of the streamer propagating in air alone is significantly less than the velocity of the `fast' component, and is higher than the velocity of the `slow' component. The streamer `stability' propagation field and velocity depend upon the nature of the dielectric material. Specifically, higher electric fields are required for streamers to propagate along a dielectric material with larger permittivity. The velocity of streamer propagation along the dielectric material is also affected by attachment of charge to the surface and photoemission of secondary electrons from the surface so much. Consequently, under the same electric field, the relationship between streamer propagation velocity and permittivity of dielectric material is not very evident, roughly inverse proportion.