Study Of RTV Coating Hydrophobicity And Its Influence On Insulator Electric Field And Pollution Flashover Characteristic

Hydrophobicity is an important characteristic of room temperature vulcanization (RTV) silicone rubber coating, which has a great influence on the electric field and the pollution flashover characteristic of insulator, so it is necessary to be studied. In this dissertation, hydrophobicity measurement method of RTV coating and the hydrophobicity loss and recovery caused by corona were studied, and electric field and pollution flashover characteristic of insulator with different hydrophobicity was analyzed. The main content and contributions are presented as following:1. A silicone rubber hydrophobicity measurement method based on dynamic contact angle was proposed, which greatly improved the accuracy in hydrophobicity measurement of the immersed and contaminated silicone rubber. A globule edge measurement method based on level set was brought forward, which effectively improved the accuracy and anti-interference capacity of edge detection. Contact angle calculation accuracy was improved based on the use of circle and ellipse fitting algorithm. Based on Matlab, a silicone rubber dynamic and static contact angle automatic calculation system was built, which can obtain the dynamic and static contact angle automatically and exactly, and the calculation time reduced to one forty of the original, the work load was saved greatly accordingly, which ensured the hydrophobicity measurement successfully. The influences of globule volume, water conductivity, inclination, environmental temperature and delay time on contact angle measurement result were analyzed carefully, which contributed to the accuracy and steady in the silicone rubber hydrophobicity measurement.2. The rule of the AC corona influencing on the hydrophobicity of silicone rubber surface was studied. It was first found that whether releasing surface charge after AC corona will influence seriously static contact angle measurement result (error may reach 70°), the mechanism of silicone rubber generation surface charge after AC corona was analyzed. For improving the accuracy of hydrophobicity dectecting, the charge releasing method such as grounding and water was adopted. The influence of the silicone rubber types, temperature and repeated corona on hydrophobicity loss and recovery caused by corona was investigated respectively. The influence of corona on silicone rubber hydrophobicity loss and recovery caused by immersion was researched. Through research, some rules were put forward. The hydrophobicity loss speed of high temperature vulcanization (HTV) is faster than that of RTV, but the hydrophobicity recovery speed of HTV is slower than that of RTV. The slower hydrophobicity loss speed caused by corona will decrease at high temperature. If the corona is take placed at high temperature, then the hydrophobicity loss speed becomes slower. If hydrophobicity is recovery completely, corona has nothing to do with hydrophobicity loss and recovery speed caused by immersion.3. The influence of electric field type, far field, axisymmetric simplified analysis mode on electric field analysis result of insulator was studied respectively, which found that wrong setting could bring on error as high as -66%, and the research result effectively improved the accuracy of insulator electric field analysis based on finite element method. The influence of RTV coating and its thickness, resistivity and dielectric constant on the insulator electric field distribution was studied respectively, and the result indicated that their influence is very little. The influence of dry band of hydrophilic insulator and its position, width, resistivity, number on insulator electric field distribution was investigated respectively. Several laws were concluded. If the dry band locates in cylinder or upper surface of shed, the narrower of dry band, the more serious distortion of the field strength. If the dry band locates in lower surface of shed, the surface maximal field strength unnecessarily decreases with the increasing of the dry band width. The dry band position has a little influence on the field strength. The surface maximal field strength is increasing with the increasing of the dry band resistivity, and trends to a steady value. Finally, the influence of separated globules and its contact angle, conductivity and globule interval on electric field distribution was studied respectively. The result indicates that the surface field strength increases with existing of separated globule and surface field strength changing speed becomes fast, the surface maximal field strength will increase with the globule contact angle increasing or the globule interval decreasing, water conductivity has nothing to do with field strength.4. The applicability of Hampton criterion in the Obenaus AC pollution flashover model was studied, the suitable critical flashover criterion for the Obenaus AC pollution flashover model was given, which effectively improves the accuracy of pollution flashover voltage predication. Based on the Obenaus model, the influence of arc float, air arc, arc number and arc restoration condition on the pollution flashover voltage is studied respectively wherever the insulator has hydrophilicity or hydrophobicity. The research result tells that, the pollution flashover voltage is a approximately proportional to the equivalent creepage distance, the arc restoration condition has obviously influenced on the pollution flashover voltage, and the pollution flashover voltage grows with the increase of arc number.