Mitigation of Touch Voltages in Fences and Water Pipes, Caused by Itaipu HVDC Ground Return Current

Monopolar operation of HVDC systems induces touch voltages in metallic fences and pipes located near their grounding electrodes. In order to guarantee that such voltages are within safe limits, in an area of influence as small as possible, an original and detailed calculation method was developed and checked during the commissioning of the Itaipu HVDC system. The Thevenin equivalent for fences and pipes is adopted and thoroughly discussed. Practical application of the method for the mitigation of touch potentials in the area of influence of the Itaipu grounding electrodes, is presented.