自并励发电机后备保护改进方案  

Improved Scheme of Backup Protection for Generators with Self-shunt Excitation

作　　者：刘振武 魏建忠[2] 高仕斌[2] 

机构地区：[1]华电集团白音华金山发电有限公司,西乌珠穆沁旗026200 [2]西南交通大学电气工程学院,成都610031

出　　处：《电力系统及其自动化学报》2013年第2期53-57,共5页Proceedings of the CSU-EPSA

基　　金：国家自然科学基金重点项目(U1134205)

摘　　要：随着电网规模的扩大,大型发电机组普遍采用自并励励磁系统,但由于短路电流衰减易造成后备保护拒动,基于理论分析,通过推导短路电流方程并计算,总结外部短路电流与外接电抗的关系即自并励发电机在不同位置发生三相和两相短路故障下的短路电流变化趋势,得出三相短路及近端两相短路时短路电流均衰减,但三相短路电流衰减会使后备保护拒动的结论,结合工程实际在现有保护基础上给出了两种分别加设低压保持元件和出口解锁的低压记忆回路的改进后备保护方案。With the expansion in size of power grid, the self-shunt excitation system is prevalently applied in turbine generator, however, the decay of short-circuit current may probably generate failure of relay tip. Based on the theoreti- cal analysis, via the deduced equation of short-circuit current and relevant calculation, this paper summerizes the re- lationship between external short current and external impedance （i.e. the short current trendency caused by three- phase or two-phase short circuit of generators with self-shunt excitation in different locations）. It can be concluded from above work that short-circuit currents decay in the circumstance of three-phase short-circuit fault and two-phase short-circuit fault near generator＇s terminal, but the decay of short-circuit current may probably generate failure of re- lay tip. On the basis of existing protection and the integration of engineering practice, two kinds of improved backup protection schemes have been put forward, and they are respectively plused low-voltage maintained component or low- voltage memorized circuit with unlocked trip.

关 键 词：大型发电机 自并励励磁 短路故障 故障电流特性 后备保护 

分 类 号：TM772[电气工程—电力系统及自动化]