发电机定子绕组单相接地保护自适应判据研究

Research on Adaptive Criterion of Single-Phase Earth Fault Protection of Generator Stator Winding

分析了发电机机端和中性点的零序基波及3次谐波电压故障暂态分量的特点,在此基础上提出了发电机定子绕组单相接地保护的自适应判据。该判据考虑了零序基波电压及3次谐波电压故障分量的综合效应,并以制动信号谱能量和动作信号谱能量的比值作为制动系数,该值在发电机正常运行时接近为1,在发电机定子绕组单相接地时远小于1。因此,自适应判据有效提高了保护在定子绕组经过渡电阻单相接地情况下的灵敏度。文章还建立了发电机的多回路暂态数学模型,采用半隐格式求解法对定子单相接地故障进行了仿真,结果证明了所提判据的有效性和良好的抗噪性。

The features of transient components of zero-sequence voltage and the third harmonic voltages at generator terminal and at neutral are analyzed. On this basis an adaptive criterion for single-phase earth fault occurred in generator stator winding is proposed. In this criterion the comprehensive effect of transient components of zero-sequence voltage and the third harmonic voltage is considered, and the ratio of spectral energy of restraint signal to that of operation signal is taken as restraint coefficient. The value of the ratio approximates to 1 under normal operation of generator and is far less than 1 under single-phase earth fault occurred in generator stator winding. Thus, the proposed adaptive criterion can effectively improve the sensitivity of generator protection is improved while the single-phase of stator winding is grounded via transition resistance. In this paper, a multi-circuit transient mathematical model of generator is built, and by use of semi-implicit format solution method the single-phase earth fault occurred in generator stator winding is simulated. Simulation results show that the proposed criterion is effective and possesses good anti-noise performance.