Influence of Pretreatment on the Results of Space Charge Measurements on Silicone Rubbers

Space charge studies are an important aspect when investigating the suitability of insulation materials for High Voltage Direct Current (HVDC) applications. During such investigations at the TU Berlin, space charge measurements using the Laser Induced Pressure Pulse (LIPP) method on silicone rubbers showed a varying space charge profile, which seems to be dependent on some influences such as pretreatment. The aim of this work is to determine the influence of pretreatment and to look for a method to improve the repeatability and reliability of space charge measurements. To determine the influence of such pre-treatments, the results of space charge measurements with different settling times are compared by determining the variance of individual measurement curves and using the deviation as a criterion for evaluation. It was found that the accumulation of space charges in liquid silicone rubber (LSR) is not significantly influenced by the settling time. Other parameters such as surface roughness, type of silicone rubber or electrode material may dominate the observed differences between measurement series of several samples of one type of silicone rubber and should be investigated further.