基于等效电路的变压器保护原理性能分析与判据改进

Performance Analysis and Criterion Improvement for Transformer Protection Theory Based on Transformer Equivalent Circuit

以单相双绕组变压器匝间故障为例,对基于变压器等效电路平衡方程的保护原理的故障识别、励磁涌流鉴别能力进行了分析。在此基础上,考虑到在保护实用化中必须考虑电流互感器测量精度对保护计算的影响问题,结合变压器各种运行状态下保护特征量反映故障的灵敏度差异,对保护判据的选择进行研究。分析表明,外部电流将降低保护特征量反映故障的灵敏度,并可能导致较大的计算误差。在上述分析的基础上,提出了带有比例制动逻辑的保护判据,并给出了其整定方法,以提高保护的可靠性。试验数据验证表明,改进后的判据具有较好的灵敏性和可靠性。

By applying the equivalent circuit based transformer protection theory to single-phase two-winding transformer models,the theory＇s capability of distinguishing inrush currents from internal faults is analyzed. Considering that the computation of protection characteristic quantities is affected by measurement errors of current transformers and that the sensitivity of protection characteristic quantities to faults is influenced by transformers＇ operating status,the selection of protection criterion is studied. Analysis shows that external currents can decrease the sensitivity of characteristic quantities to internal faults,which leads to significant computational errors. As a result,an improved criterion with restraint logic is proposed to improve the reliability of protection operations,and the setting method is also provided. The tests with experimental data show that the improved criterion has good performance on sensitivity and security.