自耦变压器零序电流方向纵联保护

Study on zero-sequence current directional comparison protection of autotransformer

高压大容量自耦变压器在高、中压侧常配有零序电流差动保护,以提高对接地故障的灵敏性,但其受电流互感器饱和影响较大,不易整定.据此提出一种自耦变压器零序电流方向纵联保护原理,通过比较自耦变高、中压侧零序电流和中性点零序电流相位实现保护判别,该原理能够灵敏地反应变压器的匝地和匝间故障,受电流互感器饱和影响小.仿真和动模试验数据验证了该方法的可行性.

In order to enhance the sensitivity of ground fault protection, zero-sequence current differential protection is often applied to large capacity autotransformers. With the influence of current transformer saturation, it＇s difficult to choose a proper setting threshold. To solve this problem, a new type zero-sequence current directional comparison protection is proposed in this paper. The new method compares the phase angle of high-voltage side zero-sequence current, middle-voltage side zero-sequence current and the neutral current to decide the fault region. It can sensitively detect the coil-ground, coil-coil fault in transformer, and can basically avoid the infection of current transformer saturation. Computer and dynamic simulation results verify the above characteristics of the proposed protection method.