零序电流差动保护选相元件

Phase Selection Elements for Zero Sequence Current Differential Protection

针对零序电流差动保护选相元件受负荷电流影响,在高阻接地故障中灵敏度较低的情况,文中提出了一种基于序分量的零序电流差动保护选相元件。选相元件包括三部分:利用负序与零序差动电流大小相近区分单相接地两相高阻接地故障;利用正序差动电流与负序差动电流的相位关系区分单相接地与两相金属性接地故障;利用低制动系数差动判据防止区外三相短路不平衡零序电流。RTDS仿真结果表明:提出的选相元件不受过负荷影响,无需补偿,可以准确选出单相接地故障相,灵敏度高于零序电流差动保护,保证零序电流差动保护准确分相跳闸。

For zero sequence current differential protection phase selection element influenced by load current leading to low sensitivity in high impedance ground fault conditions,this paper puts forward a zero sequence differential protection phase selection element based on the sequence component.The phase selection element consists of three parts：to distinguish between single-phase grounding fault and two-phase high impedance ground fault using the similarity in strength of negative sequence to zero sequence differential;using phase relationship between positive sequence and negative sequence differential current to distinguish between single-phase grounding fault and two-phase grounding fault;using differential criterion of low restraint coefficient to prevent unbalanced zero sequence current by outside three-phase short circuit.A simulation model is developed and verified in RTDS,the results showing that：the phase selection element proposed is not affected by overload,can accurately select single-phase grounding fault without compensation,and ensure the higher sensitivity than zero sequence differential protection to trip out the faulty phase of zero differential protection.