Study Of Chromatography On-Line Monitoring System Of Power Transformer

Techniques for chromatography on-line monitoring and fault diagnosis of oil-immersed power tarnsformer play an important role in keeping the reliability of electricity supply. Recently there have been many developments in this area,however some universal defects exist in the running products, for instance, only a few kinds of gases are detected, the detecting cycle is long, the accuracy is not high enough, and the structure is too complicated.This paper is concerned with the chromatography on-line monitoring and fault diagnosis system, which overcomes the shortcomings of other on-line monitoring methods. It can detect the key gases of H2, CO, CH4, C2H6, C2H4, and C2H2 dissolved in oil timely and accurately, then make diagnoses on the equipment. The creative studies in the developing of the system is summarized as follows:(1) To decrease the detecting cycle, permeability of polyamide membrane, PFA membrane, polytetrafluoroethylene membrane and Microporous polytetrafluoroethylene membrane are compared in experiments. The microporous polytetrafluoroethylene membrane is better than other membranes; it only needs 24 hours to separate all the key gases dissolved in oil. In addition, the affection of microhole diameter on permeability and mechanical strength is studied, and the optimal diameter is found out.(2) To make the system simple and easy maintainable, a new chromatography column is developed, and it can separate 6 key gases with single column at atmospheric temperature. Based on theory analysis and experiments, the stationary phase and operating conditions, including column internal diameter, column length, column pressure, sample quantity and separating time are determined.(3) The sensor used in on-line monitoring should have a good output performance on 6 key gases. Hot wire semiconductor gas sensor is compared with normal semiconductor gas sensor in experiments, and the former is better than the latter in linearity and sensitivity. Besides, since the hot wire semiconductor sensor has a little volume, it can be fixed with the column properly and achieve a better output peak than other sensors.(4) A principal-subordinate control system for on-line monitoring, which consists of one main unit and several terminal units is designed, the automation performance is good and the ability of anti-interference is high.(5) Research has been made on the system integration. The reliability and the accuracy of the chromatography on-line monitoring system are all good during the running time; therefore it is proved to have practical value.