Abstract: Based on tendency analysis of time series data, the author proposed a method of insulation abnormality detection  based on tendency analysis for power equipment  to solve the problem of real-time detection of abnormal capacitive power equipment in the substation. Firstly, the data of dielectric loss factor obtained from on-line monitoring was used to divide the monitoring data stream reasonably, and the method of least square was used to fit it into a straight line. Secondly, based on the characteristic value of fitting line, the abnormal tendency was detected and analyzed. Finally, the insulation abnormality detection results of capacitive equipment were obtained. According to the analysis and judgement of the measured data of capacitive equipement in the substation, the effectiveness and practicability of the method were verified.

Key words: substation equipment, abnormality detection, tendency analysis, dielectric loss factor