Performance comparison of porcelain, glass and composite insulators
A variety of porcelain or glass material atoms in the body is composed of an ionic bond through electrostatic attraction together, so the stability of porcelain and glass is very good. This also means that the surface electric porcelain and glass of the two materials have higher energy, thermodynamic quantity higher, therefore material surface adsorption water strong. In other words, porcelain or glass surface is easier to damp humid. The porcelain or glass insulators, in order to damp dirty conditions can still make the insulator surface resistance is higher, it is necessary to make the insulator leakage distance is very large and complex shape.
Porcelain and glass are very dense material, a larger proportion of porcelain and glass insulators, therefore are very heavy, the compressive strength of the two kinds of materials are higher than the tensile strength. But these two materials are brittle materials, should be handled with care in transportation and installation, avoid breakage.
The umbrella group of sheath material of composite insulator is the organic material, compared with the porcelain or glass and other inorganic materials, organic materials in molecule elements is through the covalent bonding phase, key and force elements are relatively weak, composed of large molecular organic material is easy to break, so in the corona discharge, UV radiation, moisture, changes of temperature and chemical factors such as the role of organic insulating materials, easy to aging. Composite insulator of electric properties and the mechanical properties with the running time and gradually decreased, but the performance is not recoverable. If the decline in some properties of materials can be recovered, is called the fatigue; a decline in performance is not restored, is called aging. Insulator materials all have a problem of aging, but the aging rate of different materials have different. Although porcelain and glass also has the problem of aging, but due to the aging of the speed is low, does not become a serious problem in the operation, so little discussed problem of aging of porcelain or glass insulator. Composite insulators in voltage and external factors, aging is a serious problem, therefore the discussion on the use of composite insulators, aging is a frequently mentioned topic.