Research Of Materials And Properties Of Glass Insulators Of UHV Power Line

As the main supporting devices of the power lines, insulators are used to support wires, increase the creepage distance and prevent the current returning to the ground. Its properties and qualities have a very important influence on the stable operation of the power grid. Common insulators include ceramic insulators, composite insulators and glass insulators. Among them, glass insulators have the characteristics of uniform voltage distribution, shattering since zero, easy inspection, long service life etc. They are preferred by the HV, UHV, super UHV power line fields.The formula of glasses is the key to the properties of glass insulators. In this paper, aiming at meeting the demand of glasses with high properties of large tonnage of glass insulators, the components of traditional Na2O-CaO-SiO2 glasses is optimized and doped for modification, in order to improve the mechanical and dielectric properties. The effects of fundamental formula, doping of Nb2O5 and doping of rare-earth metal oxide on the structure, mechanical properties and dielectric properties have been studied systematically. And the formula of Na2O-CaO-SiO2 glasses suited with large tonnage of glass insulators has been optimized.(1) The effects of K/Na ratio, contents of CaO, Al2O3 on the structure and properties of glasses have been studied. When the K/Na ratio increases, the bending strength, the dielectric loss decreases and the buck resistance reach top in the middle, dielectric constants and the thermal expansion coefficient increases. The addition of CaO repairs the broken bond of the glass network. With the increasing of CaO, the maximum of the bending strength and the bulk resistance appear, and the minimum of dielectric loss appears in the middle, while the dielectric constants the thermal expansion coefficient increases. With the increasing of Al2O3, the thermal expansion coefficient, the dielectric loss and the dielectric constants increases, while the buck resistance decreases. When the amount of Al2O3 is small, Al3+ mainly exists in the form of [AlO4] which can repair the glass network and improve the bending strength. As the amount of Al2O3 increases, A1l3+ mainly exists in the form of [AlO6] which can broke the glass network and reduce the bending strength of glasses.(2) Nb2O5 has been used to improve the properties of Na2O-CaO-SiO2 glasses by doping. Nb2O5 has the effect of repairing the original structure of glasses. And bonds of Nb-O-Si and Nb=O have higher bond strength making the glass network more stable and compact. And the mechanical strength has been improved, the dielectric loss has been decreased. When the content of Nb2O5 is 3 wt.%, the bending strength is 117MPa, the relative dielectric constant is 8.78, the dielectric loss is 1.25×10-3, and the comprehensive properties is the best.(3) The effect of rare earth elements La, Y on the properties of Na2O-CaO-SiO2 glasses has been studied. The research shows that, with the increasing of the contents of La2O3, Y2O3, the glass network has been broken, the thermal expansion coefficient increases, the bending strength and dielectric properties decrease largely. Thus, the rare earth element is not suitable for the modified additive of insulator glasses.