换流变压器有载分接开关级间短路故障差动保护动作特性  

Differential Protection Performance for Converter Transformer Intertap Short-Circuit Faults in On-Load Tap Changers

作　　者：闫晨光[1] 张芃 徐雅 武炬臻 李凌南 Yan Chenguang;Zhang Peng;Xu Ya;Wu Juzhen;Li Lingnan(State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University,Xi’an 710049 China;State Grid Economic and Technological Research Institute Co.Ltd,Beijing 102209 China)

机构地区：[1]电力设备电气绝缘国家重点实验室(西安交通大学),西安710049 [2]国网经济技术研究院有限公司,北京102209

出　　处：《电工技术学报》2023年第21期5878-5888,5912,共12页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金项目(52277125,51807151);国家电网总部科技项目“换流变新型有载调压开关关键技术的研究及应用”(52090020002Q)资助。

摘　　要：近年来,换流变压器有载分接开关级间短路故障引起的爆炸起火事故时有发生。由于缺少有效的计算手段,故障过程难以复现,保护性能难以进行深入研究。鉴于此,该文提出基于直接场-路耦合的换流变压器有载分接开关级间短路故障模型及求解算法,通过场-路双向耦合实现绕组漏磁和短路电流的瞬态同步计算,并利用改进电弧黑盒模型模拟油中电弧的时变电导特性。针对典型单相两心柱式换流变压器级间短路故障开展建模仿真,以实际工程配置的保护装置为研究对象,定量分析不同分接位置短路故障下不同差动保护方案的动作特性。结果表明,严重级间短路故障条件下,换流变压器内部感应出的横向漏磁峰值达到3.77T,短路环流峰值达到92.87kA。当故障发生在调压绕组端部时,差动电流的有效值为0.23(pu),比率差动保护和零序差动保护因灵敏性不足而存在拒动风险。In recent years,explosions and fire accidents caused by converter transformer intertap short-circuit faults inside on-load tap changers(OLTCs)have occurred in succession,seriously threatening the safe operation of the power grid.As the main protection for converter transformers,the insufficient sensitivity and rapidity of differential protection under such faults have attracted widespread attention.However,due to the lack of effective theoretical models and calculation methods for intertap short-circuit faults in OLTCs,the fault process is difficult to reproduce,and the existing protection performance remains to be further studied.Given this background,this paper proposed a direct field-circuit coupling model and calculation method for converter transformer intertap faults in OLTCs.The bidirectional field-circuit coupling enabled the transient calculations of the winding leakage flux and the short-circuit current,and the improved black box model was adopted to simulate the time-varying arc-in-oil conductance characteristics.With this method,intertap fault simulations were carried out on a typical single-phase two-core-limb converter transformer,and the differential protection performance under short-circuit faults at different tap positions was quantitatively analyzed.First,the converter transformer intertap short-circuit fault process was analyzed based on a typical vacuum-type OLTC circuit topology and intertap short-circuit loop.Second,the governing equation of the internal electromagnetic field and the constraint equation of the external electric circuit were successively established and unified as coupled equations in matrix form. With an improved black-box arc model directly integrated into the short-circuit loop, the direct field-circuit coupling relations and a corresponding calculation method for converter transformer intertap short-circuit faults were developed to capture the transient interactions among the electromagnetic field, the electric circuit and the electric arc in the insulating oil. Third, w

关 键 词：换流变压器 有载分接开关 级间短路故障 直接场-路耦合 差动保护 

分 类 号：TM772[电气工程—电力系统及自动化]