关键词: 高压直流输电, 入地极, 地电场, 多台定位, 极低频

Abstract: The earthing current of HVDC (High Voltage Direct Current) converter station causes the most significant interference in the observation of geoelectric field, which usually causes a step change with 0.5-102 mV/km within a range of hundreds of kilometers near the ground electrode. However, it is difficult to determine which converter station's earthing current causes the step change. Generally, it is necessary to use the data of the influence of the HVDC line on the geomagnetic field to identify it. Firstly, taking Hainanzhou-Zhumadian line, Zhalute-Qingzhou line and Baoji-Deyang line as examples, we obtain the response data of three typical disturbances, and use the data of 58 geoelectric field stations around these three lines to calculate step change. To compare the interference situation, the extremely low frequency data of Dashan station is obtained for comparation. The results show that the stations at different locations have different responses to the earthing currents, that is, in the three cases that the stations are located near one of the grounding poles, between the two grounding poles, and between the two grounding poles near the grounding pole on one side, the corresponding three types of responses are step-like step change, impulse-like response, impulse and half-step-like response, respectively. Then, we use daily variation amplitude to correct the order variable of HVDC interference, and locate the position of ground electrode by the principle that the potential difference of multiple stations has directivity, then determine the source of earthing current and the approximate location of converter station. The locating results have a good direction to the ground electrodes’ positions of the Hainanzhou-Zhumadian line, Zhalute-Qingzhou line and Baoji-Deyang line, Combining the step-change synthesis vector of multiple units can simultaneously determine the approximate location of the converter station; In addition, the step change amplitude after daily variation correction can show the site of the ground electrode, which can supplement the locating results. Furthermore, we build the quantitative diffusion current model of the earthing current to show the law of potential distribution of large input current, and determine the interference range and order variable. Bases on the observation data of 58 geoelectrical field stations and another station of extremely low frequency , the response feature of the earthing current to the surrounding stations are identified, which may serve for the data correction of HVDC interference in future.

Key words: HVDC (high voltage direct current), Ground electrode, Geoelectrical field, Multiple stations location, Extremely low frequency