Research On Composite Insulators Internal Air Gap Influence On The Electric Field Distribution Impact

With the fast speed of national social and economic development, lead to the demand for electric energy is more and more heavy, the HV and UHV transmission lines play its key role of the energy delivery. For composite insulator has more superior performance which is widely used in HUV transmission line gradually, however, some operation experience show that the inherent defects of composite insulator have been exposed, including aging, mandrel and sheath interface carbonization, which are all hot topic, and the aging is directly related to field intensity distribution of composit insultor, the distortion of field intensity distribution lead to partial discharge, and the carbide channel formation is source of partial discharge. Also,composite insulator partial discharge occurs inside the micro gap, the Mirco-gap may form under the following several factors: 1) Due to the manufacturing process injection pressure and liquid rubber technology demand are very high, so the Micro-gap can appear if technology are not strict.Another reason is sheath processing interface bonding, moulding, injection temperature, material when characteristics of material producing heat bilges cold shrink, which are hard to avoid building gap in hardware, mandrel, an umbrella skirt suites formed local gap. 2) under the condition of abnormal natural conditions or various overvoltage, hardware port will produce a corona, the N2 on the surface of sheath will be generated NO2 by the role of corona in the air, and nitric acid is generated by NO2 reaction with water medium, acid medium will be adsorpted, infiltrated, diffused continuously into the internal core rod, then the resulting of a gap is built in a paritial location. 3) About 6% of the length of the umbrella skirt of insulator high port will bear 25% ~ 30% of the operating voltage, over voltage or abnormal natural conditions may appear discharge within the composite insulator or umbrella skirt, a local micro-gap will formed by local electric corrosion perforation; 4) Due to composite insulator is bended by the process of installing, make the interface pressure drop which make in a Micro-gap, and a long-term operation under line effect of the mechanical force which is easy to make a local micro mechanical cracks in some parts of the insulator interface, tiny cracks is the air gap, and provide the hiding place for water molecules, the over voltage or under the action of other factors that provides a internal discharge channel. The emergence of local micro-gap, may influence a field strength and potential distribution of composite insulator, electric field of the local focus is the source of production and development of local discharge, severe field intensity may result in partial discharge. The discharge of the composite insulator interface with a micro-gap is lead to accelerated aging of the insulating material, insulation breakdown. Aslo,the discharge occure between the electric hardware,core rod, and the umbrella skirt sheath will directly corrosion the mandrel, aging, corrosion umbrella skirt sheath, which reduce the mechanical properties of mandrel, cause the brittle fracture of rods, drops line, make major blackouts, and even lead to system collapse. So, after the presence of composite insulator with a partical micro-gap, the safe and stable operation of composite insulator may be effected by a certain security hidden danger,so the related work of this subject study is meaningful. In this paper, the key is to deeply research different micro-gap size, different position of composite insulator, study the influence of the potential distribution in the whole field Repeatedly, the characteristics are extracted and summarized, then all datas are collected for finding the corresponding regularity.