Abstract:Short circuit current calculation and grounding design both are the important parts of engineering design, which is of great significance to the safe and stable operation of the converter station. In this paper, based on ±1100kV Guquan UHVDC converter station with hierarchical connection, different levels of short-circuit current have been calculated. After considering the shunting effect of short-circuit current via lightning shield wires and the transformer neutral point, the grounding fault current of converter station is calculated. According to the grounding fault current, design scheme of grounding grid for the UHVDC converter station and safety evaluation have been proposed. For converter stations with hierarchical access, the asymmetric short-circuit current should be calculated for different AC buses based on variant operating situations, and the maximum value of short-circuit current should be used to verify the ground grid design indicators.