The Analysis of the Hydrophobicity Performance of the Composite insulator′s Shed Surface
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In order to achieve a better understanding of the Hydrophobicity performance of the composite insulator′s surface, an analysis is carried on according to the specific feature of the composite insulator′s insulation design.It is found that the coagulated water drops, at different positions on the insulation structure′s surface, have obvious different shapes due to the gravity.As the result, the water drops coagulated along the creepage distance of the operating composite insulator will change their shapes periodically.This behavior helps to improve the product′s flashover voltage, and to avoid the flashover accident.Keywords:
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The flashover characteristics of composite insulator are analyzed by using Obenaus model.Flashover voltage tests are carried out by using the different run length samples and in the different electrical conductivity of water,the test results showed that flashover voltage decreases exponentially with water conductivity increases,but the change variation of sample with bad hydrophobicity is not obviously. By the calculation of the model and the test results,found that there was a certain relationship between the voltage drop of the total anode and cathode arc and hydrophobicity,the numerical size of voltage drop decreases with the weakening of hydrophobicity. The results of research showed that the hydrophobicity is the main reason of the flashover voltage of composite insulator,because the voltage drop of the total anode and cathode arc was directly determined by hydrophobic;the flashover voltage is also influenced by the water conductivity,water conductivity was depend on the pollution accumulation degree of the insulator surface.
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According to the test results carried in the artificial climate chamber, this paper analyzes the flashover process and the effects of ice amount, icing water conductivity and ice-covering appearance on AC flashover performance of l0 kV composite insulator The test results show that because icic1es bridge the air gaps between the sheds, the ice flashover voltage will decrease, and that because intermittent partial arcs between ice and insulator's surface burn, the unrecoverable comedown of hydrophobicity of silicon rubber material of the insulator surface cause the reduce of the flashover.
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Silicon rubber
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Composite insulating material, silicone rubber primarily, is widely used in the field of high voltage outdoor insulation. The higher pollution flashover voltage of line insulators benefits from the hydrophobicity and hydrophobicity transfer of silicone rubber. However, silicone rubber served over many years shows partial degradation which leads to uneven hydrophobicity on surfaces of insulators. It's of great research significance for effect of uneven hydrophobicity on antipollution flashover performance of line insulators. Base on the uneven distribution characteristics of hydrophobicity along composite insulators and hydrophobicity on upper or lower surfaces of RTV coated insulators, anti-pollution flashover performance is measured with artificial pollution flashover test and saturated wetting test. Experimental results indicate that the hydrophobicity of high-voltage end has a great impact on anti-pollution flashover performance. In addition, for pendent insulators, the integral wetting state is depended on the saturated wetting time of both surfaces and the situation of contamination loss. Therefore, the hydrophobicity of lower surface is crucial for anti-pollution flashover performance. According to the above test results, the hydrophobicity of high-voltage end for composite insulators and lower surface for pendent insulators should be paid more attention in operation state assessment.
Silicone rubber
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Environmental Pollution
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In order to investigate the influence of parameters of composite insulator on flashover performance and to put forward the reference for the selection and the design of composite insulator for the extra or ultra high voltage transmission projects,we presented the artificial pollution test results for 31 kinds of composite insulator in natural high altitude areas(1970 m),and adopted the up-and-down method.With different shed overhang and shed spacing,the leakage distance and the utilization ratio of leakage distance differ greatly.Results show that the parameters of composite insulator have remarkable effects on flashover voltage.There is a maximum flashover voltage with the increasing of the shed spacing or the shed radius.The shed spacing has a more remarkable effect on the flashover voltage of composite insulator with one large shed and one small shed,and the shed radius had a more remarkable effect on the flashover voltage of composite insulator with one large shed and two small shed.
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Leakage (economics)
High Voltage
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With the development of the power system, composite insulators are widely used in China. However, the contamination flashover caused by the loss of the hydrophobicity of silicone rubber remains a threat to the insulation, especially in EHV and UHV transmission lines. The statue variations of the composite insulator surface were studied in this paper. Based on the cluster analysis method, the leakage current was also investigated. And 16 parameters were extracted to characterize the surface state. It was showed that these parameters could be used to recognize the degree of hydrophobicity loss over the composite insulator surface. The discharge model spectrum diagram of composite insulator surface was also established, which could be used for the diagnosis of the degree of hydrophobicity loss and salt deposit density over the insulator surface. This work can enrich the recognition methods of surface statue of composite insulators and may provide useful reference for performance evaluation of composite insulators in service.
Silicone rubber
Arc flash
Silicon rubber
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Due to its outstanding anti-flashover characteristic, composite insulator has been extensively applied in power system. A lot of research has investigated flashover characteristics of hydrophobic specimens with artificial water droplets on. However, the phenomenon is not consistent with that of the contaminated composite insulators. On the test specimens covered with water droplets, there is no obvious leakage current before the flashover and no obvious relationship between flashover voltage and the conductivity of water droplets. On the contaminated composite insulator surface, there are short continuous arcs on the insulators before critical flashover, making insulators look like a luminous lantern. Considering that under these two conditions, the proportion of water along the insulation distance is different, the flashover characteristic of band-water on hydrophobicity surface was analyzed in the present study. The influence of the water band parameter (including length, width, and conductivity) as well as the length of dry band was studied. On this basis, the arc generation and development process of the surface covered with Band-water was analyzed. The research results can deepen the understanding of flashover process on contaminated composite insulator.
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Leakage (economics)
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The polymer composite insulator had been used to increase flashover gradient in order to solve the phenomenon of flashover bottle bomb and breakdown leakage of polymer composite insulator appeared in cold ice,freezing rain,fog,wet weather.The safety and reliability had been improved and the service life had been extended by changing skirt concave to increase creepage distance and increasing joint strength reasonably.
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Flashover performance of composite insulator is restricted by material hydrophobicity and hydrophobicity transfer.The influence of environmental factors and component of non-soluble materials in contamination on hydrophobicity of heat vulcanized rubber was analyzed.Quantitative contrast experiment to study the relationship between DC flashover performance of composite insulators and component of non-soluble materials as well as hydrophobicity time was carried out.The test results show that,the increasing percentage of Kieselgur leads to the quicker rate of hydrophobicity transfer,as a result of which,the contact angle turns larger,and all these further contribute to the higher DC flashover voltage.The result of this paper can be taken as a reference for hydrophobicity transfer analysis of silicone rubber,and as the foundation of establishment of artificial pollution DC test standard of composite insulators.
Silicone rubber
Arc flash
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Studying the state of hydrophobicity and its influential factors of different areas of a composite insulator is of guiding significance for hydrophobicity tests and discrimination of the whole insulator.Thus,we selected four series of silicone rubber composite insulators in service to perform hydrophobicity tests on these whole strings of insulators by means of the static contact angle method.The test results showed that hydrophobicity of whole composite insulators was uneven,which could be seen in terms of different sheds along one string and different areas on the same shed.The distribution of hydrophobicity along one string agreed with that of electric field strength.Meanwhile,the upper and lower surfaces of one shed had quite different hydrophobicity.The difference in hydrophobicity was also found in different oriental areas of one shed,and the worst hydrophobicity characteristics of the shed surfaces of one string existed in one certain radial direction.Further analyses indicate that insulator surface discharge is the main reason leading to the uneven hydrophobicity of the sheds;long-time ultraviolet radiation and contamination accumulation are also figured to be account for the hydrophobicity degradation of composite insulators sheds.
Silicone rubber
Ultraviolet
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