Investigation of Partial Discharge and Surface Flashover Characteristics of Spacers in High-Voltage Dividers

Summary

High voltage dividers are commonly used for metering, measurement, controlling, and protection purposes in HVDC systems. To meet these demands voltage dividers have to fulfil the requirement of accurate measurement of high voltage signals in a wide frequency range from DC up to some kHz. Depending on used construction technique solid dielectric spacers are inserted to support the inner stack of components mechanically against the enclosing insulator during assembly and transport. Spacers constructed with holes, known as “communicating insulators”, are used in gas insulated transmission lines to ensure the gas continuity between the adjacent enclosures. Similar spacers may also be used in high voltage dividers with non-modular design for the same reason. Applying spacers with holes in high voltage dividers assures a better heat convection and consequently a more uniform temperature distribution in the gas-filled enclosure. This minimizes the voltage measurement uncertainties and fulfils the mechanical requirements at the same time. From the electric point of view spacers are generally known as critical components in high voltage gas-insulated components, limiting the electric performance of the systems. In this paper the partial discharge and the surface flashover characteristics of disc-type spacers have been investigated for various N2-gas pressures. The experiments were carried out with AC and impulse voltages using a coaxial electrode system consisting of a pressure vessel with an inner electrode. The test spacers were made from glass fiber reinforced polymer composite. The influence of hole geometry and hole distribution on the flashover performance of the disc spacer was examined in comparison to that of a solid disc. The focus of this investigation was worst case only, namely applying a tangential field being responsible for surface flashover. Furthermore the electrostatic field distribution and field strength were calculated using finite-element-methods.

Additional informations

Authors

Kouzmine Oleg, Seiler Johannes, Rüdinger Bernd, Pachin Juriy