Design of Lightning Protection Scheme of a Grid Substation Using Rolling Sphere Method

This paper represents the design of lightning protection system of a grid substation. For justifying the suitability of the design, a calculation has done based on the IEEE Std 998-2012 Guide for Direct Shielding of Substations. Mainly the busbar and the transformer area has focused in this paper. Shield wires have used instead of lighting mast which is cheaper. This design has done in such a way that can ensure the minimization of cost as well as the protection of the aforesaid area of the substation from side and direct lightning stroke. In the calculation firstly, the striking distance has calculated for busbar area and transformer area. The radius of the imaginary rolling sphere around the shield wire has considered equal to the striking distance. Secondly, need to ensure that either the rolling sphere can protect or not. If the condition is fulfilled according to the calculation, the proposed design is acceptable. Some figures have been shown to visualize that as per the calculation how the protection is acting upon the equipment.