New grounding systems for enhancing OHL performances and reducing environmental impact

The effects of climate change include an expected increase of the keraunic level and longer draught events. At the same time, the renewable energy penetration on the electric power system exacerbates the effects of the ground faults caused by back-flashover, in terms of power quality (voltage dips). Terna, the Italian Transmission System Operator, developed an innovative (patent-pending) grounding system design for HV and EHV overhead lines, allowing for better performances and reducing environmental impact. Terna also developed a novel procedure for selecting the optimal design for each tower, considering construction costs, voltage dips cost, site (keraunic level, soil resistivity) and pylon (height, number of shield wires) characteristics. The novel modular grounding system design allows for significantly lower failure rates and land consumption. The paper introduces the new standard design for Terna's overhead lines grounding systems and deals with the development of the optimization procedure for selecting the most cost-efficient topology for each tower.