With the requirement of safe operation of power system and the continuous improvement of system operating voltage level, the insulation requirement is becoming higher and higher.Porcelain insulators were widely used in transmission lines in the past.In the middle and late 1990s, foreign tempered glass insulators gradually entered the Chinese market, and their excellent performance was gradually recognized.Especially with the continuous innovation of production technology and inspection means, tempered glass insulators have been widely used in the line in recent years.
1. Tempered glass insulator has excellent performance
Tempered glass insulators play two basic roles in overhead transmission lines, that is, supporting wires and preventing current from returning to the ground.These two functions must be ensured throughout the operating life of the line (usually 40 years) and the insulators should not fail due to various mechanical and electrical stresses caused by changes in environmental and electrical load conditions.In addition to the weight of the wire and metal accessories, the mechanical load of the insulator must also bear the wind load, snow load, wire dancing and shock load caused by improper operation during transportation and installation in bad weather.From an electrical point of view, insulators must not only insulate the wires from the ground, but also withstand the overvoltage impact caused by lightning and switch operation. Local overheating caused by flasticity due to voltage impact should not lead to the cracking of the tempered vitreous insulator.All the external factors will affect the performance of the insulator, so the design of the insulator is put forward higher requirements.
2. Excellent dielectric properties and no aging phenomenon
Dielectric properties refer to the electrical properties of a medium under the action of an electric field.The insulation performance of insulators is closely related to the internal molecular structure of insulating materials.Glass belongs to amorphous structure, is a silicate compound without fixed melting point, compact structure, uniform texture, produced in the continuous production process easy to control.SiO2 is the skeleton of glass, and other oxides are filled in the skeleton and connected by chemical bonds. With great interaction, SiO2 is not easy to be polarized by electric field, and shows good inertia, making it an ideal insulating material.Tempered glass insulator makes use of this characteristic, and its lightning impulse voltage is 3.8 times that of porcelain insulator.The aging here refers to the aging of electrical properties, that is, under the action of the electric field for a long time, some physical and chemical changes will gradually occur in the medium and make the medium irreversible deterioration, eventually leading to the breakdown of the medium.The tempered glass insulator has excellent anti-aging performance. According to the tracking test of the insulators on the 132kV transmission line in Malaysia after 27 years of operation by The French Company Sedivil, the mechanical and electrical properties of the insulators have not changed significantly.However, the mechanical and electrical performance of porcelain insulators used in the same period of time decreases obviously after running for a period of time.