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Study On Moisture Absorption Characteristics And Dielectric Properties Of Silicone Rubber Material

Posted on:2016-08-03Degree:MasterType:Thesis
Country:ChinaCandidate:B GongFull Text:PDF
GTID:2272330470470899Subject:High Voltage and Insulation Technology
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In recent years, a local heating phenomenon of composite insulators in service has been found in China. Moisture plays an important role in the local heating phenomenon. In this paper, proceeding from the moisture induced local temperature rise phenomenon of composite insulator, reason of local temperature rise is analyzed. The primary heat source of local temperature rise and the effect of relative humidity combining with the silicone rubber on local temperature rise are put forward. According to the possible aging factors, corona aging and ultraviolet aging experiments are designed and conducted. Taking the silicone rubber material before and after corona or UV aging as test samples, moisture absorption and dielectric property tests are carried out under different relative humidity. By analyzing the effect of aging on the moisture absorption characteristics and dielectric properties of silicone rubber material, the primary origin of moisture induced composite insulator local temperature rise phenomenon is proposed.For the moisture induced local temperature rise phenomenon of Lingshen line AC 500 kV composite insulators, reason of local temperature rise is analyzed. Electric property of the local temperature rise section is found obviously different from other part of the composite insulator. Heat caused by conductivity and the dielectric loss of FRP rod material is too weak to induce local temperature rise. The local temperature rise is mainly derived from dielectric loss of the aged high-voltage end housing material, especially in the surface layer of housing material whose thickness of about 1 mm.Moisture absorption and dielectric property test results show that moisture absorption rate, dielectric constant and dielectric loss factor of silicone rubber material basically rise with the increasing of relative humidity, and the volume resistivity is on the decline. Moisture absorption rates of samples after corona aging are higher than the new sample. The reason is that electron bombardment, nitric acid and ozone aging cause physical defects (such as holes, cracks, etc.) and chemical degradation, so the free volume and hydrophilic groups in silicone rubber material increase. The moisture absorption rate of material rises as a consequence.When the corona voltage is constant, moisture absorption rate, dielectric constant and dielectric loss factor of material after aging increase with the increasing of aging time, and the volume resistivity decreases with aging time. These trends become more obvious and regular with the increasing of corona voltage. When the corona aging time is constant, effect of corona voltage on the moisture absorption and dielectric properties are similar to the ageing time.As to the moisture absorption characteristics and dielectric properties, the differences between silicone rubber specimens before and after 3000 h UV aging are not significant. UV aging of this intensity cannot obviously cause the local temperature rise of the composite insulator. Corona aging significantly affects the moisture absorption characteristics and dielectric properties of silicone rubber material, and it is deduced to be the primary origin of moisture induced composite insulator local temperature rise phenomenon.
Keywords/Search Tags:Composite insulator, local temperature rise, aging, moisture absorption, dielectric property
PDF Full Text Request
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