Temporal Stability of Modified Surfaces of Insulating HV Devices Using Atmospheric Pressure Plasma

Plasma discharge at atmospheric pressure can be used to modify the surface electrical strength of insulators made of dielectric materials, thermosets and thermoplastics. The methodology of surface treatment by plasma discharge was published and applied to typical samples of materials with dimensions of 100 × 100 mm. To make the methodological procedure for influencing and predicting the desired change in the dielectric surface industrially applicable, it was necessary to develop a diagnostics methodology for applying plasma discharge at atmospheric pressure. This method was tested on previously selected and tested types of materials on samples of two types (thermoset, thermoplastic). The effects of measuring and evaluating the RF spectrum, along with the corresponding long-term change in the surface strength Ep of the dielectric sample, were demonstrated. This work presents repeated extension tests with statistical evaluation of the effects of surface treatment of dielectric samples using a slot plasma chamber in Ar, N2 and O2 atmospheres. The surface structure was modified using precursor-free plasma discharge according to the developed methodologies with the addition of radiometric evaluation of the plasma discharge. Changes in surface properties were measured and evaluated as a function of exposure time and the stability of the modification was evaluated with a prediction of the expected long-term surface properties.