Study on the aging properties of silicone fluid in GIS cable terminations

摘要

Silicone fluid is an important insulating material that has been used in cable or GIS terminations for many years. However during operation the insulation may be subjected to an electric discharge due to abnormal operation of the high voltage equipment or external faults. Service engineers recently found that aging occurred after years of the operation, for example darken the color of in-service-aged oil and gaseous decomposition products formed. Using a needle-plate configuration electrode, this paper reports the effect of electrical discharge quantity to the electrical, physical and chemical characteristics of the low viscosity fluid. Silicone fluid gets aging gradually with the accumulation of discharge quantity and the cumulative discharging quantity is directly related to the aging degree of silicone fluid which can be characterized by dielectric loss tangent, volume resistivity and ultraviolet spectrogram. 2×10⁹pC and 5×10⁹pC are drafted as two threshold values which respectively divide the mild aging and moderate aging, moderate aging and serious aging of insulated fluid.