EVALUATION OF GROUNDING GRIDS IN SUBSTATIONS CONSTRUCTED OVER A STEPLIKE TERRAIN USING CLASSICAL CHARGE SIMULATION METHOD

With urbanisation, the availability of levelled land is becoming quite difficult and hence Electric Power Transmission utilities are forced to construct the substation in available landscape. As levelling of the land is not technically and economically viable option, substation bays are constructed in different land levels. Consequently, the grounding grids of the different bays will be at different relative depths. Moreover, the current will have to face a step-like jumps in the soil-air interface. As such a situation is not dealt much in the literature and in standards, more studies on the performance of such a construction was believed essential. The present work proposes a Charge Simulation based Methodology (CSM) for the analysis of the performance of such grounding grids. The classical Galarkins approach is used for modelling of the buried conductor, while CSM is employed for modelling of the interfaces. The proposed approach, as compared to the surface current simulation based method (SCSM) proposed in the literature, is much simpler and requires lesser computational efforts. Suitable validation is provided for demonstrating its accuracy and time saving. In spite of deploying discrete simulation sources using CSM method, it can be observed that the computed spatial potential and electric field profiles are accurate and smooth.