There are some methods for flashover Mitigation of porcelain and polymer material, porcelain and polymer material uses different method as below having detail introduction.
Users can utilize several counter - measures to reduce flashover with porcelain insulating housings. They are:
1. Creepage extenders – polymer sheds (Figure 2) are installed directly over porcelain insulator weathersheds to increase the creepage distance.
2. Extra-creepage housings – housings with extra-creepage, more creepage than typically used for the specific system, will reduce flashover risk.
3. Washing – insulators may be washed live or de-energized with high pressure water or with solid materials such as ground up walnut shells. This is a costly process which may need to be carried out on a regular schedule to be effective. In addition, the use of solid cleaning materials may abrade away the protective glaze of the porce lain, exposing the underlying substrate to the environment, which can then hold contamination.
4. Complex weathershed profiles – protected creepage and fog-type weathershed profiles are available, at a premium cost, which have profiles which resist contamination deposition in the protected areas. Such shapes, however, do not lend themselves to live line washing.
5. Surface coatings - greases or polymer coatings may be applied to the porcelain housing to improve the pollution performance. Coatings have a finite life, are costly to install, and potentially very costly to reapply because of the need to clean and/or remove prior applications. Performance improvement and time necessary for recoating are highly dependent upon the quality of the coating application.
Separate or retrofit flashover countermeasures for polymer are rarely used. The development of standard products for a wide range of applications and conditions requires careful attention to the material formulation and insulator housing design.
One important contamination application consideration is if a polymer product can be washed, either intentionally or unintentionally, along with porcelain insulators. Polymer products which are not firmly secured to the underlying layer, such as insulators or arresters which rely on grease as the housing interfacial sealing system, may not be suitable for high pressure washing. Such products may fail prematurely from washing, and users need to consider the use of such products in their specific service environment, if the supplier does not recommend washing.
Polymer insulating housings need leakage current control. While some degradation over service is likely to occur, one defense mechanism against flashover is retention of leakage current control. If the leakage current is insufficient then the flashover mechanism cannot progress. This is a result of the interaction of the polymer material and product design.
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