ITAIPU HVDC ground electrodes: interference considerations and potential curve measurements during Bipole II commissioning

A simplified method is presented to measure the grounding resistance of adjacent electrodes which can be of use in other situations, when ground electrodes are composed of many elements or when an existing electrode is extended. The opportunity of remeasuring electrode potential curves showed that local gradients can change, but in a relatively small range, ±10%. For applications like the design of mitigation procedures or the prediction of corrosion currents, this range is deemed to be insignificant, not only because the verified range is small, but also because of the tendency of the changes to compensate. The tests in the irrigation system changed somewhat the formula previously used for evaluating touch potentials in irrigation pipes. The adopted mitigation criteria concerning electric shocks to immersed persons are explained together with suggestions for further work on evaluating body currents in the case of large DC gradients in water near energized metal parts