Performance evaluation of insulator creepage extender at heavy magnetite polluted 230 kV substation

摘要

Pollution, if it is industrial, can create a lot of problems, mainly on air insulated insulators. Regarding to this issue, A 230 kV substation located at a vicinity of steel mill factory in Iran is considered as a case study. In this substation wind drives magnetite airborne contaminant particles from steel mill factory onto the insulator surfaces. A continuous flow of power to the steel mill plant is critical in terms of safety and economic impact on the entire company. Those who have lost it can best appreciate the importance of a reliable source of power in a steel mill. Phrases such as "safety hazard," "loss of production," "damaged mill," do not begin to impart the sense of agony and loss such an event can conjure up in certain minds. [1] The continuous deposition of these particles increases the thickness of these deposits. After a long time (months, years) the deposits are stabilized and a thin layer of solid deposit will cover the insulator. Surface contamination make pollution induced flashovers a much broader problem. In this substation the industrial contamination condition is severe and periodic insulator hand cleaning is performed in substations, which involve de-energized manual wiping. A replacement insulator having greater electric strength may be installed but the costs of this are very high especially when a complete assembly, like a bushing, is involved. Common palliatives include hand cleaning which reduces the contamination level, or surface treatments like silicone rubbery coatings, or both. These palliatives have disadvantages in cost and effectiveness. The frequency of cleaning can be unacceptable and Coatings especially in this condition are very difficult to apply and are also very difficult to remove when eroded. Another remedy, which is not so common for pollution flashovers nowadays, is using creepage extender on existing apparatus type insulators. Creepage Extenders increase the flashover performance of insulators by reducing the surface electric stress, reducing the leakage current and increasing the electric strength of the insulators. In order to investigate the influence of magnetite pollution on the performance evaluation of creepage extender in such this heavy industrial contamination areas, NRI carried out a series of field tests. In this paper the result of this site test research will be discussed and different aspects of application of this equipment will be presented.