Flashover of polluted high voltage insulators is a major problem for operation of power lines in Egypt. In 2010, insulators' pollution was the cause of several interruptions in the Egyptian electric network. Variations of climatic conditions and large industrial developments in the last few years call to update the pollution map of Egypt. To achieve this, six sites in northern Egypt with different types of pollution (industrial, desert, marine and their mixtures) have been investigated. To asses the pollution behavior of line insulators, IEC standard cap-pin suspension insulators were hanged for a time zone of 5 months. The study was conducted through measurements of: Equivalent salt deposition density (ESDD), Surface Conductivity, Maximum leakage current and Flashover voltage. The results are useful to assess the insulation performance in different environmental situations and as well to provide an updated pollution map in Egypt.
Presence of water droplets on a polluted outdoor high voltage insulator surface modifies the electric field flux and the equipotential distribution along the insulator surface. The water droplet may appear in different forms and sizes. The form is defined, here, by the angle shape between the water droplet surface and that of the insulator, which is kept constant at 90 degrees. The droplet size is specified by the diameter. The water droplet may measure from less than 90 degrees (hydrophilic) up to greater than 90 degrees (hydrophobic), depending on the properties of insulator surface. The present work describes a detailed numerical computation of the electric field and the potential distribution in the surroundings of water droplet on a polluted insulator surface. The computations are carried out using the Femlab package 3.1, which is based on the finite element method. The parameters used in the numerical analysis are the size of the water droplet and the pollution layer permittivity which describes the possible wetting conditions of the layer (i.e. clean, semi-wetted, and fully-wetted polymer surface). Detailed plots of the potential and field distribution in the inter electrode space, with and without the presence of a water droplet, were generated. The results showed that the electric field close to the water droplet tends to be higher as the diameter of the droplet increases, and lower as the relative permittivity of the pollution layer increases.
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