中文摘要：

牵引负荷具有功率瞬时阶跃冲击的特性,会在接入电网中激发邻近发电机组参与的小幅振荡。利用牵引负荷地理分布广、扰动时间固定的特点,可以实现电网易激发模式阻尼的在线监测。文中首先基于数据采集与监控（SCADA）实测数据分析了牵引负荷阶跃扰动的特点,然后基于单机无穷大系统和多机系统分析了牵引负荷阶跃冲击引发机组自由振荡的机理和主要影响因素,并给出了利用该自由振荡响应进行系统模式阻尼在线监测的实施步骤。最后以实际河南电网为例,进行监测机组选择,通过牵引负荷扰动SCADA实测量和观测机组振荡的相量测量单元（PMU）实测量间的对应和辨识,实现了基于牵引负荷冲击响应在线监测系统模式阻尼。

英文摘要：

Traction load has a characteristic of transient step impact and will set off weak oscillations in which the generators nearby participate in the accessed grid.Based on the characteristics of wide geographical distribution and fixed disturbance time of traction load,the online monitoring of the system damping corresponding to the particular easily stimulated mode is realized.The characteristic of the disturbing traction load is first analyzed based on the data measured from the supervisory control and data acquisition（SCADA）system.Then the mechanism of oscillations caused by step impact of traction load and the main influences are analyzed on a single-machine infinite-bus system and multi-machine power system,and the online monitoring steps are introduced.Finally,the monitoring units are selected and the correspondence between SCADA measured data of traction load and phasor measurement unit（PMU）measured data of observation units is analyzed in Henan power grid.The online damping monitoring of the system is realized based on the response to the traction load impact.