中文摘要：

针对无功补偿用的并联电容以及超高压长输电线分布电容的存在，容易引起二次谐波判据制动的变压器差动保护误动，提出了一种基于平方根滤波法参数辨识的保护方法。参数辨识法依据变压器在内部故障时其结构及某些参数会改变，而励磁涌流及外部故障时不变的原理．利用变压器绕组的漏感值是否发生变化作为区分变压器内、外部故障与涌流的判据。和应涌流与励磁涌流的本质相同．只是变压器铁心发生了饱和，其内部结构及漏感等参数并不改变。大量仿真实验验证该方法的可行性和有效性．当励磁涌流、和应涌流与区外故障时能够可靠闭锁差动保护，而区内故障时保护能够准确动作。该方法计算量小、数值稳定性好．避免了最小二乘、卡尔曼滤波等算法可能发散的问题。

英文摘要：

Because the shunt compensation capacitor or the distributed capacitance of long UHV （Ultra- High- Voltage） transmission line may cause the maloperation of transformer differential protection restrained by second harmonic criterion,the parameter identification method based on the square-root algorithm is put forward for transformer protection. Transformer structure and some of its parameters are changing during internal fault while keeping invariable during excitation and external fault. The leakage inductance of transformer winding is thus used to distinguish the internal fault from external fault and excitation inrush. The sympathetic inrush has the same characteristics as magnetizing inrush except the transformer core is saturated,its internal structure,leakage inductance and other parameters are unchanged. Simulation results validate the feasibility and reliability of the proposed method,which blocks the differential protection properly during external fault and current inrush and operates precisely during internal fault. It has lower calculation load and better numerical stability,without the possible divergence problem as RLS and Kalman filtering algorithms.