变压器空投匝间故障特征及机制

Features and mechanism of interturn short circuit fault by energizing no-load transformer

变压器空投于单相匝间故障时,由于闭锁判据直接闭锁三相,导致单相匝间故障无法快速切除,威胁变压器安全运行。通过建立变压器匝间故障等效模型,推导出了空投于匝间故障时励磁绕组磁通的解析表达式,并对系统阻抗及故障匝数对故障特征的影响进行了分析,得出系统阻抗越大空投匝间时越不易发生励磁涌流,以及匝间故障匝数越多空投匝间时越不易励磁涌流的结论。利用PSCAD软件进行仿真,验证了结论的正确性,为差动保护闭锁判据及闭锁方案的选择提供了理论依据。

When interturn short circuit fault by energizing noload transformer occurs,the three-phase current differential protection is blocked by blocking criteria,and it causes the singlephase interturn short circuit fault could not be rapidly removed,which threats the safe operation of transformer.Through establishing the equivalent model of interturn short circuit fault,this paper deduced the analytical expression of magnetic flux of exciting windings and analyzed the influences of system impedance and number of faulted turns on fault features.It concluded that the larger system impedance and number of faulted turns,the more difficult the inrush current occurs.Using the PSCAD software,the correctness of the conclusion was verified,and it provided a theoretical basis for the selection of blocking criteria and blocking schemes of differential protection.