The Effect of Insulator Angles on Leakage Current Characteristics In Wet Fog

Composite insulators have been designed to isolate high voltage conductors from their support structures while retaining the conductors in a specific position. These insulators may be used in orientations that are neither vertical nor horizontal - typically these non-standard angles are seen in railway applications but also increasingly in new forms of aesthetically pleasing overhead line towers that are designed to make better use of space. As a result of the unusual installation angle, the ways in which the insulators are subject to contamination and the way water flows over the surface, wetting the pollution and then cleaning the insulator will be different. As a result, the leakage current and partial discharge activity that will be seen on the insulator is likely to be altered with resulting implications for life. A high voltage test under an artificial fog was performed using a simple fibre-glass reinforced in silicone rubber rod as a sample which was set at different orientations. The discharge activity was imaged by a camera. The current was monitored and collected by a data acquisition system. The leakage current magnitudes and harmonic components were analysed. In general, the current magnitude is low at the beginning of the test while the rod is clean and dry. As the level of moisture on the sample grows, the current increases at different rates depending on the angles with third and fifth harmonic components being clearly visible. The highest current magnitude is seen in the case of the vertical sample. Discharges are clearly seen when the current flow is higher than 1 mA and occur at different positions on the rod surface. Based on the experimental results, the positions of discharge and the magnitude of the leakage current flowing on the rod surface are directly influenced by the orientation of insulator core.