Fulgurites : their formation, chemical composition and impacts on network failures in Swaziland

M.Ing. (Electrical Engineering)Abstract: Swaziland experiences significant loss of overhead transformers due to lightning during the rainy seasons. Most of the Swaziland power network is overhead and is, therefore, exposed to lightning. To avoid damages to the equipment, earthing systems such as deep driven rods are normally used to divert excessive current during lightning strikes. It is thus important to design an effective earthing system that will be able to protect the equipment during fault conditions. Fulgurites are highly resistive and are normally formed when lightning and fault currents flow through the soil. They may modify the ground impedance of the earthing systems. In this research, the soil around the affected feeder was taken and create fulgurites in that by applying laboratory current impulse. Chemical composition of the soil sample and the fulgurites were analysed to determine the elementary atoms. The resistivity of the soil sample and the resistivity of fulgurites were also tested to determine the effects of fulgurites on the earthing system. It was found from the tests that indeed fulgurites has high resistivity compared to the original soil