Soil resistivity modeling for temperature rise calculating of HVDC deep-well earth electrode

Abstract

Deep-well DC earthing electrode occupied much smaller area than the traditional one, which greatly reduce the difficulty of site selection. However, due to the extremely high current density at the end of linear earthing electrode, temperature rise has become an important factor restricting the development of deep-well earthing technology. In order to evaluate the heating situation of deep-well earthing electrode in an accurate way, this paper carried out the field temperature rise test of deep-well earthing electrode, and the error between the temperature rise result calculated by the wide-area soil resistivity model obtained by conventional measurement methods are analyzed. It was found that the local soil resistivity near the deep-well earthing electrode determines the temperature rise characteristic. Based on the fitting results of the apparent resistivity logging, a local soil resistivity modeling method suitable for deep-well earthing electrode temperature rise calculation is proposed, and the deep-well earthing electrode temperature rise calculation model considering temperature characteristics of water-saturated underground medium and local soil model is established. The calculation result of this model is used to compare with the field measured data of the temperature rise in actual projects, and the maximum temperature error is found to be 5.5 °C. The trend of electrode temperature rise is in good agreement with the test results, which explains the special phenomenon of high temperature rise in low resistance layer. Project cases prove the effectiveness and accuracy of the soil modeling and temperature rise simulation method proposed in this paper.