Study On On-line Temperature Measurement Technology Of Oil-immersed Transformer

With the rapid development of our society, It would make a higher demand for thecorresponding device security. the reliability of the power system needs to be assured. Themain reason that most transformers’ life ended is insulating ability. The most main factorthat affected the ability of the transformer insulation is the temperature of transformerwinding. So the monitoring technology of transformer winding is the focus of the relatedresearch on the transformer. Now there are two detection methods of oil-immersedtransformer winding temperature. They are direct measurement and indirect measurementmethod. The indirect measurement method is a estimating simulation method. Thesimulation results are a little different from the real situation. The direct measuring methodcan make the sensors are in the interior of the transformer, real-time measurement, themeasurement results are accurate. The method can achieve real-time measurement and themeasurement results are accurate. So the direct measurement method which is used tomonitor the performance of the transformer is the important trend in the future.In the paper the temperature measuring system of the fluorescence optical fibertemperature sensor is designed by using the fluorescence lifetime temperaturemeasurement principle. The sensing probe is designed which includes fluorescent materials,optical fiber and optical fiber coat. The breakthrough tank is designed to connect opticalfiber inside and outside. According to the temperature properties of fluorescent material,the red material was selected as fluorescent material. The system hardware circuit isdesigned. According to the bandwidth of measured signal and magnification, three-stageamplifier circuit is designed. PCI2000data acquisition card is used as A/D converter tocollect data in real time. The least-square method, integral area ratio method and programProny algorithm is written by using Matlab and C++.The Least-square fitting aresusceptible to the influence of the dc component. When the dc location is different, thefluorescence afterglow life τ values vary widely. Integral area ratio method is notinfluenced by dc component, but it has low sensitivity. Prony algorithm is not affected bydc, it has high sensitivity. So the Prony algorithm is seclected as a way to obtain fluorescence afterglow lifetimeτvalue. The construction of the whole system is completed.In20℃~70℃(once every5℃) of transformer oil is measured. The correspondingtemperature fluorescence afterglow lifetime τ value is calculated by using the Pronyalgorithm. The relationship between temperature and τvalue is calibrated. τvalue is alinear relationship with temperature.