Investigation on the Lightning Impulse Strength of Special Layered Silicone Dielectrics for HVDC Applications

摘要

In polymeric cables space charges tend to form, when they are submitted to high DC voltage stress. In order to reduce the formation of space charges, the insulation of DC cables is filled with conductive fillers. The insulating materials for cables are usually tested in the form of thin samples, where the volume effect is not considered. Therefore, in this contribution different material thicknesses are investigated by applying impulse breakdown voltage tests. For these tests, flat samples are prepared from silicone with 0.3 wt.% graphite filler. Additionally, samples made of pure silicone and layered silicone samples, one layer with graphite additive and the other without, were also investigated. The tests were performed according to the standard IEC 60243-3 [1] with positive impulse voltage at room temperature. The results with the electrodes of this test method show a high standard deviation, thus the tests are repeated using electrodes with a more homogeneous electrical field.