【摘要】 某电厂主变压器(三相变压器组)拟对C相进行单独更换，由于新C相与旧A/B相的阻抗及对地电容值存在差异，需要对主变压器新C相与旧A/B相联合运行下的电气特征量变化进行理论推导和仿真分析，校核与过电流保护相关的三相电流不平衡度，以及与定子接地保护相关的位移电压的变化等，以确定相关继电保护配置及定值整定的应对措施，为后续主变压器C相更换的实施提供决策依据。上述做法将为后续电站类似技改工作提供借鉴。更多还原

【Abstract】 A power plant plans to separately replace phase C of the main transformer (three-phase transformer bank).Due to the difference between the impedance and ground capacitance of the new phase C and the original phase A and B，it is necessary to calculate and analyze the change of electrical characteristics under the combined operation of the new phase C and the original phase A and B of the main transformer，check the three-phase current imbalance related to overcurrent protection and the change of displacement voltage related to stator grounding protection，so as to determine the countermeasures for relevant relay protection configuration and setting calculation.In addition，it can provide reference for similar technical improvement work of subsequent power stations.更多还原