Study On Thermal Stability And Influence Under Certain Conditions On Convertor Station Neutral-Bus Of Grounding Electrode In HVDC

With the advantages of large capacity and long transmission distance, HVDC plays an irreplaceable role in China's energy flows, and grounding electrode is a very important part in HVDC system, its reliable operation concerns the stability of the entire DC system. Therefore, study related to grounding electrode has an important practical significance to DC development in China.First, this thesis briefly describes the role and composition of the DC grounding electrode system, then based on post-innovation control and protection strategies for±500 kV DC power transmission project from Tianshengqiao to Guangdong, the effects on the convertor station cased by grounding electrode line breaking when system operates as monopolar earth return mode are studied, after that, control and protection suggestions in reducing the fault impact on the neutral-bus of the converter station are made.Second, different from the usual formula method, this thesis adopts numerical algorithm to analyze the thermal stability of grounding electrode. After comparing the advantages and disadvantages of the existing varieties of PDE numerical algorithms, the 'Unit Energy-Balance Algorithm' base on finite difference is chosen as core algorithm, by which computing formula of grounding electrode temperature field is derived and computer program is wroten, then an example is used to check with the existing results to verify the accuracy of the algorithm.Finally, taking the West-Zhejiang grounding electrode of UHVDC bipolar power transmission project from Xiluodu to West-Zhejiang for example, this thesis check the thermal stability of it and then makes reasonable suggestions in the design of UHVDC grounding electrode and its thermal stability analyzing.