励磁涌流对变压器差动保护影响的分析及防范措施

Analysis and Preventive Measures of the Impact of Excitation Inrush Current on Transformer Differential Protection

由于变压器励磁涌流的多变性和不确定性,其值可达额定电流的6~8倍,通常在保护装置切除区外故障或空投变压器时在电压恢复时出现,可能引起差动保护不正确动作,特别是基于二次谐波制动原理的变压器差动保护,由于定值设定、制动模式选择的差异都有可能造成保护误动。文章针对兰州铝业有限公司自备电厂升压站联络变投运时差动保护误动的问题,结合现场故障录波图和相关数据,分析保护装置误动的原因,且通过对变压器励磁涌流波形特点进行分析,说明励磁涌流对变压器差动保护的影响并提出防范措施,以期为今后解决励磁涌流的相关问题提供参考依据。

Due to the variability and uncertainty of transformer excitation inrush current,its value can reach 6-8 times the rated current.It usually occurs during voltage recovery when there is a fault outside the protection device cut-off area or when the transformer is airdropped,which may cause incorrect operation of differential protection,especially for transformer differential protection based on the second harmonic braking principle.Due to differences in setting values and braking mode selection,protection misoperation may occur.This article focuses on the problem of differential protection misoperation during the operation of the contact transformer in the booster station of Lanzhou Aluminum Industry Co.,Ltd.'s self owned power plant.Based on the on-site fault recording waveform and relevant data,the reasons for the misoperation of the protection device are analyzed.By analyzing the waveform characteristics of the transformer excitation inrush current,the impact of excitation inrush current on transformer differential protection is explained and preventive measures are proposed,in order to provide reference for solving related problems of excitation inrush current in the future.