Influence of surface state and thin dielectric coating on the insulation properties of a coaxial electrode arrangement in SF6

The improvement of the dielectric strength of SF6 insulated systems by using a thin dielectric coating to change the surface state of electrodes was studied. The paper deals with the breakdown probability of a coaxial aluminium electrode arrangement with different surface roughness in pressurized SF6. Thin epoxy resins with different thickness were used as coating material on the inner conductor. The outer conductor of the electrode arrangement was polished and uncoated. The surface roughness of the inner electrode was varied. To determine the cumulative frequency function of the breakdown voltage the progressive stress test of stepwise voltage increase was applied for positive and negative lightning impulse. Charge measurements have been carried out to investigate the influence of the first breakdown and of the root points after a breakdown. With the applied charge measurement the influence of the rising voltage test on the breakdown probability could be evaluated. The influence of repairing the root point of the surface by a second coating procedure (emplatrification) has been investigated.      «

The improvement of the dielectric strength of SF6 insulated systems by using a thin dielectric coating to change the surface state of electrodes was studied. The paper deals with the breakdown probability of a coaxial aluminium electrode arrangement with different surface roughness in pressurized SF6. Thin epoxy resins with different thickness were used as coating material on the inner conductor. The outer conductor of the electrode arrangement was polished and uncoated. The surface roughness o...     »