Simple Method to Visualize Surface and Space Charges by Specially Processed Colour Pigments

Abstract

HVDC applications are getting globally more and more important for the energy transport in the high voltage networks. To design apparatus properly it is important to understand the space and surface charges that are accumulating under DC stress in certain areas. Existing methods to measure or visualize such charge accumulations like “Pressure Wave Propagation Method”, “Thermal Step Method”, “Pulsed Electro Acoustic Method” or “Electro Static Volt Meters” show often limitations applied to full size apparatus. Sometimes the resolution or specimen thickness is limited or the application can be rather time consuming or complex. A simple method to visualize surface charges is known as “Lichtenberg’s dust figures”. It is known since hundreds of years but rarely practiced as the best working chemicals (yellow sulphur and red lead) are not health save. In this paper a fresh view is given to charge visualization by colour pigments. It is shown that different pigments attach to positive or negative charges. The application of this method is easy and takes just a view seconds. E.g. tree type structures can be visualized with a resolution of less than 1 mm. Hover the value of the charge magnitude cannot be obtained. The surface charge behaviour on different materials like Epoxy, PE-HD, Silicone is shown. In addition, the possibility of space charge visualization on specimen cross sections is discussed.