Dynamic AC surface discharge characteristics of PMMA and LDPE

Polymeric materials such as Low Density Polyethylene (LDPE) and Polymethylmethacrylate (PMMA) have properties that are ideal for use as electrical insulating materials within a wide range of commercial products. They have good mechanical properties and the advantages of high electrical breakdown strength, high electrical resistivity and low dielectric loss. In many practical applications involving the use of insulation, high electrical stresses can be generated at the edges of the interface between a conductor and the solid insulation by the existence of a non-uniform electric field. This may cause local sparking and or corona along the surface of the insulation. The presence of surface discharge activity is a significant problem for polymeric insulators. Any discharge can cause a slow deterioration of the insulator surface in the long term through three mechanisms: firstly through slow erosion by ionic bombardment of ions in the sparks, secondly by chemical degradation of the insulation material and thirdly from carbonisation of the material surface. Conducting deposits are formed on the surface and this will influence the electrical characteristics of the insulator. The development of a suitable method to monitor surface discharge behaviour of high voltage insulating materials is therefore of particular interest