According to the specific wiring form of the converter transformer winding of FCC-HVDC, the action equations of three-phase protection and differential current expressions are deduced from its mathematical model. The transformer's three-phase protection model is established using Matlab/Simulink, and simulation results prove that the second order harmonic restraint principle may lead to delayed operation as internal fault of converter transformer occurs. Consequently, the simulation studies based on identification method of magnetic flux characteristics are carried out from the aspect of the action equations. The effectiveness of the proposed protection scheme in distinguishing the internal faults from the energizations of the converter transformer is validated.%根据FCC-HVDC系统中换流变压器绕组的具体接线形式,利用其数学模型推导三相保护的动作方程及差动电流表达式.用Matlab/Simulink建立变压器的三相保护模型,仿真结果验证了二次谐波制动原理在换流变压器内部故障时存在延时动作的可能.据此根据磁通特性原理鉴别法,从动作方程出发进行仿真分析,验证了该方法可以有效地区分换流变压器励磁涌流和故障电流.
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