Mechanism analysis of the impact of DC system on power-frequency variation protections [送出直流对工频变化量元件的影响机理分析]

作者：Cai D.; Li H.^*; Zhu X.; Wang G.

来源：Power System Protection and Control, 2019, 47(9): 1-9.

DOI：10.7667/PSPC180583

• Directional element
• Distance element
• Fault characteristics of DC system
• Mechanism analysis
• Power-frequency variation

In order to analyze the operating characteristics of power-frequency variation protections of the sending-end AC system theoretically, the mathematical model of DC system at the rectifier side which is represented by a power-frequency variation impedance in fault superimposed network is deduced in the case that fault occurs in the sending-end AC system. Based on the mathematical model and the response characteristics of HVDC control system, the characteristics of the equivalent power-frequency variation impedance of DC system are analyzed under different fault conditions. Then the impact of DC system on power-frequency variation protections is analyzed based on the fault characteristics of DC system. According to the analysis, when fault occurs in the sending-end AC system, the equivalent power-frequency variation impedance of DC system is capacitive under most fault conditions, which reduces the zone of distance protection based on power-frequency variation and results in misjudgment of directional protection based on power-frequency variation. In the end, the result is verified by simulations on PSCAD/EMTDC.

• 单位
  华南理工大学