Electrical Field Distribution Calculation And Analysis Of Effect Factors On Hydrophobicity Of 10kV Composite Insulator

Compared with traditional ceramic and glass insulators, a composite insulator has advantages of less weight, higher strength, more excellent anti-contaminated characteristic, easier to maintain. Therefore, the composite insulator is widely used by power utilities in many countries. However, as more and more composite insulators are put into service, there are some problems emerging, which indicate that the composite insulator also has some weakness. It is necessary to fully study the performance of composite insulator so as to solve these problems. The common study of composite insulator is focused on laboratory investigations, which can't explain un-certained-reason flashover reasonably. Therefore, based on the existence computation methods and the experiences in computing electrical field distributions of insulators, the program are making by the charge simulation method (CSM). By the program, the electric field distributions of a silicone rubber (SIR) rod and a SIR composite insulator under different contaminated condition are calculated. It is found that the electric field distribution of 10kV silicone rubber composite insulator is inhomogeneous. Under the condition of clean or dry polluted layer, the distribution of electric field along insulator surface has strong vertical. The maximum electric field stress is near the high voltage electrode. When polluted layer is moister, the normal value of electric field stress is dominant. The maximum electric field stress is on the edge of the skirt which near by the high voltage electrode and it is larger than that under the condition of clean or dry polluted layer, but it is less than the critical breakdown electric field stress. Meanwhile, the effect of ESDD on the electric field distribution is little in this process. When a dry belt appears near the high voltage electrode, the electric field stress of the dry belt is greater than that of others. It is the reason leading to create local arc that the tangential component of electric field stress exceeds the air critical breakdown stress. The width of a dry belt and ESDD on insulator surface have effect on the electric field stress of dry belt. In this process, the tangential stress of electric field is the crucial factor to cause local arcs to emerge. Moreover, in order to check up the calculated result, a test was done to determine the voltage distribution along the 10kV clean composite insulator. The test result can be accord with the computed result.Excellent un-contamination and wetting performance of a SIR composite insulator dues to its hydrophobicity of SIR on its low energy surface. Especially, when the surfaceof insulator is contaminated, the hydrophobicity can migrate from the bulk of SIR composite insulator to the contaminated surface. In this thesis, the factors which affect the hydrophobicity of composite insulators have been research, including immersion time in wetting conditions, pH value, ESDD and NSDD. It is found that the SIR composite insulator lose its hydrophobicity with the immersion time increased, and the effect of acid solution on its hydrophobicity is as much as the one of distilled water while the effect of alkaline solution is greater than that of distilled water. Moreover, with the increase of ESDD, the hydrophobicity of the contaminated surface reduce and the final hydrophobic classification is decreased, too. In addition, when the NSDD is less than 2.0mg/cm2,the hydrophobicity emigration speed of the composite insulator is slowed with the increase of NSDD, but the effect is not obvious. On the contrary, when the NSDD is greater than 3.0 mg/cm2,the hydrophobicity emigration time of composite insulator is obviously increased with increase of the NSDD.