SELECTION OF GROUND ELECTRODE SITES USING GEOPHYSICAL TECHNIQUES FOR RESISTIVITY MEASUREMENTS FOR FIRST ±800 kV HVDC SYSTEM IN INDIA

摘要

It is important to ensure that the site selected for the ground electrode should have low surface electrical resistivity to keep the step and touch potential within safe limits. It is also necessary to ensure that the ground current penetrates deep into the structure of the earth so that the grounding resistance/potential rises in the vicinity of the electrode are within acceptable limits. This shall ensure that the ground current does not cause corrosion of buried pipelines and does not enter the neutrals of transformers installed in the close vicinity of the Electrode station. For this purpose it is important to know the electrical resistivity of the earth up to the depth of 5 to 10 km. High-resolution multi-electrode DC resistivity imaging techniques were used for shallow resistivity measurements and Magnetotelluric (MT) techniques were used to determine deep resistivities upto depths of 5 to 10 kms. Based on these results, suitable earth electrode sites were identified.