The Study of Mechanism and Limit Measures for 500kV Single Phase Short Circuit Current Exceeding Limit in UHVDC Converter Station

Abstract

With the rapid development of UHVDC(Ultra High Voltage Direct Current) project, the problem that 500kV single phase short circuit current exceeding limit in UHVDC converter station become more and more serious. In this paper, the influence of UHVDC converter transformer winding connection on 500kV single phase short circuit current is derived, then the measures by adding small reactance to the neutral point of Y N d connection converter transformer to limit the short circuit current is proposed for the first time, and the selection method of small reactance is given at the same time. Finally, the proposed strategy is validated in a real UHVDC case, results show that the proposed adding small reactance to the Y N d connection converter transformer can effectively limit the 500kV single phase short circuit current, and the proposed small reactance selection method has good adaptability in limiting the power frequency over-voltage of the converter transformer neutral point.