Porcelain or glass material in the various atomic is by ionic bonds through electrostatic attraction combined together, so the stability of porcelain and glass is very good. This also means that porcelain and glass which two materials have higher surface energy, high thermal capacity, so surface materials have strong water absorption ability. In other words, porcelain or glass surface is easy to damp wet. In terms of porcelain or glass insulators, in order to damp dirty environmental conditions can still make the insulator have higher surface resistance, you need to make a relatively large leakage distance and more complex structure and the shape of the insulator.
Porcelain and glass are very dense material, larger proportion, so electric porcelain and glass insulators are very bulky, the compressive strength of the two materials are higher than tensile strength. But these two kinds of materials are brittle materials, to be careful in transportation and installation, avoid breakage.
Composite insulator umbrella group of the sheath material is the organic material, compared with the porcelain or glass and other inorganic materials, organic molecular material elements are combined by covalent bonds, the keys and the force between the elements is relatively weak, constitute a large molecular organic material is easy to break, so in the corona, ultraviolet radiation, moisture, temperature and chemical factors, organic insulating materials is easy to aging. Electrical properties and mechanical properties of the composite insulators will be gradually decreased with the running time, and the performance degradation is not recovered. If the decline in the performance of a material is recoverable, known as fatigue, the decline in performance is not recoverable, it is called aging. All of the insulator materials have aging problems, but there is a great difference in the aging speed of different materials. Although electric porcelain and glass also has the problem of aging, but because of the very low rate of aging does not become serious problems in the operation of, so rarely discussed porcelain or glass insulator aging problem. Under the action of voltage and external factors, the aging of composite insulators is a serious problem, so it is a frequently discussed topic in the discussion of the use of composite insulators.
