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A grounding grid of a substation is essential for reducing the ground potential rises inside and outside the substation during a short-circuit event. The performance of a grounding grid is affected by a number of factors, such as the soil conductivity and grounding rod corrosion. Industry always has a strong desire for a reliable and cost-effective method to monitor the condition of a grounding grid to ensure personnel safety and prevent equipments damage. In view of the increased adoption of telecom and sensor technologies in power industry through the smart grid initiative, this paper proposes an online condition monitoring scheme for grounding grids. The scheme monitors touch and step voltages in a substation through a sensor network. The voltages are created by a continuously-injected, controllable test current. The results are transmitted to a database through wireless telecommunication. The database evaluates the grid performance continuously by comparing the newly measured results with the historical data. Many of the limitations of the offline measurement techniques are overcome. Computer simulation studies have shown that the proposed scheme is highly feasible and technically attractive.