In high voltage technology, vital parts are usually covered with insulating material. However, detrimental breakdown still can occur in the gas region outside the solid insulation. In many cases, a discharge creeps along an insulator surface where it can propagate over longer distances than in the bulk of the gas. The underlying physics is poorly understood, and control and prevention is usually based on empirical design rules or on oversimplified engineering models, or even on trial and error.

But experimental and theoretical methods are now ripe to analyze these creeping sparks as a fundamental physics problem and to understand how they depend on gas and insulator properties. How and where does the discharge start in the absence of electrodes? How do discharge channels grow over surfaces or through the gas? When do they heat up and create an electric short-circuit?

Discharges creeping over insulator surfaces frequently dominate the break-down, because the surface can modify the local electric field, it can store surface charges, and it can release electrons. We will quantify these microscopic effects with new experimental diagnostics and we will characterize the macroscopic discharge evolution. Finally, the project will provide design tools predicting how surface break-down depends on materials, geometries and applied voltage.



This project is sponsored by STW with the project title Creeping Sparks - Understanding the mechanisms of surface flashover: towards an efficient and reliable electric power grid. The work will be done in cooperation with the Centrum Wiskunde & Informatica in Amsterdam and ABB Corporate Research in Baden-Dttwil, Switzerland.

Project focus:

Both PhD candidates will:
Study the start of the discharge with a nanosecond fast ICCD-camera and accurate current measurements. Characterize the various stages of discharge evolution with detailed optical, electrical and spectroscopic measurements.