摘要
针对复杂和应涌流导致差动保护误动问题,建立了复杂和应涌流研究模型,利用拉普拉斯变换求出解析解,揭示了变压器的磁链变化过程和复杂和应涌流的机制特征。结合变压器饱和与电流互感器(current transformer,CT)暂态饱和的特点,从变压器自身和CT饱和两方面分析了差动保护的误动原因。仿真研究了发变组产生复杂和应涌流的实例,验证了理论研究结果的正确性。以时间、差流、制动电流和二次谐波含量为不同的坐标轴绘制了保护工作点的二维和三维轨迹曲线,完整地展现了保护误动过程和差流、二次谐波含量变化特征。提出了变比率制动差动保护,通过实时改变比率制动系数值来提高保护性能。测试结果表明,该保护性能可靠,能有效解决常规差动保护误动的问题。
In order to solve the problem of differential protection mal-operation caused by the complex sympathetic inrush,the complex sympathetic inrush model is constructed.The flux linkage and current of transformer are expressed by analytic solution,which explain the variation course of flux linkage and the characteristic of the sympathetic inrush.The reasons of the differential protection mal-operation are explained with both sides of transformer and current transformer saturation.The theory analysis results are validated through simulating an application case of a transformer and generator unit.The trace of protection working point is plotted in two dimension and three dimension space,which coordinates consist of time,differential current,restraint current and the second order harmonic,and it presents the course of protection mal-operation clearly and the variation characteristics of the differential current and the second harmonic.The variation ratio restraint differential protection,which takes the advantage of characteristic both the differential current and the second harmonic percentage during the course of the complex sympathetic inrush,is presented.Meanwhile the new protection also can act reliably when a fault takes place in transformer.The testing results prove the new protection＇s reliability and correctness.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2011年第1期86-93,共8页
Proceedings of the CSEE
基金
国家自然科学基金项目(50877031
50837002)~~
关键词
电力系统
复杂和应涌流
差动保护
拉普拉斯变换
二次谐波制动
轨迹特征
power system
complex sympathetic inrush
differential protection
Laplace transformer
second harmonic restraint
locus characteristic
