Temperature characteristics and influence of water-saturated soil resistivity on the HVDC grounding electrode temperature rise. (June 2020) - Wen, Xishan
Highlights: Water-saturated soil resistivity decreases exponentially with rising temperature. An electro-thermal coupled FEM model is established using the obtained function. The experiment proved that model can reach high accuracy for water-saturated soil. Abstract: The temperature rise process has always been the main factor for the safe operation of high-voltage direct current (HVDC) grounding electrodes, and the soil resistivity is the key parameter affecting the temperature rise of the grounding electrode. In some region where rainfall is high or groundwater is abundant, the soil moisture content at the electrode site may be very high or saturated. Therefore, studying the temperature characteristics of soils with saturated water content (water-saturated soil) for grounding electrode heating is particularly important. In this study, the resistivity measurement of temperature rise was conducted on different types of water-saturated soil. On the basis of this measurement result, an electro-thermal coupling finite element model of grounding electrode in water-saturated soil was established. Then the reliability of the coupled model is verified through an experiment of the vertical electrode in water-saturated soil. The comparison of experimental and simulation results shows that the maximum temperature error is 3.5%. Finally, the influence of water-saturated soil resistivity on practical engineering application was analyzed. Under the condition of water-saturated soil, the saturation of electrode temperature rise curve gets more pronounced as the current injection time increases. Thus, the temperature rise rate of the actual grounding electrode is lower than the calculation result without considering the water-saturated soil resistivity. Therefore, using the temperature characteristics of water-saturated soil resistivity to simulate the temperature rise of the grounding electrode can provide a theoretical basis for the grounding electrode to work under water-saturated soil conditions.