Title: Transformer partial discharge online monitoring research ABSTRACT Power transformer on-line monitoring technology to improve the stability of power system is of great significance. This paper focuses on the on-line transformer oil chromatography monitoring method for a comprehensive study, developed a kind of oil chromatographic on-line monitoring system. The research of oil chromatographic on-line monitoring system to overcome the other on-line monitoring method is less certain, timely and accurate monitoring of dissolved H2, CO, CH4, C2H6, C2H4 and C2H six characteristic gases. In this paper, the conventional polytetrafluoroethylene membrane and hollow fiber structure of PTFE membrane gas separation properties are tested and compared. Experiments show that, for the characteristic gases dissolved in oil, the hollow structure of PTFE membrane can be reached within 24 hours of saturated permeability, permeability rate is obviously superior to the conventional film. The study of system utilizes a single chromatographic column and by HAYESEP D and Porapak T composite stationary phase, under certain conditions, high efficient packed chromatography column can be rapid simultaneous separation of6 kinds of gas. This paper introduces the design of the utility of the online monitoring and control system, the system includes a host and a plurality of terminals, a high degree of automation, strong capacity of resisting disturbance.