Study Of Online Monitoring And Influencing Factors Of Fiber Grating On Temperature Distribution In Transformer Windings

As one of the most important equipments in power system, the normal operation ofpower transformer is concerned to the power supply reliability, its life and internalwinding temperature are closely linked. Transformer winding temperature is one of thekey factors to influence transformer internal insulation, and is one of the factors to limittransformer load. It has important significance for life assessment and overloadregulation to monitor winding temperature of transformer.First of all, the dissertation combined with temperature characteristics what isshowed by oil-immersed power transformer internal heat generation and divergent,analyzed the produce mechanism of transformer internal loss, as well as the influence ofno-load loss and load loss on the winding temperature of transformer. The heating andcooling characteristic equations of winding, iron core and oil as the major componentsof the transformer are given, and gives the heating and cooling characteristic curve ofthese parts are given.Second, according to the present research situation of on-line monitoring oftransformer winding temperature, optical fiber temperature sensor and the specificrequirements of the measurement of transformer internal temperature, chose the fiberBragg grating temperature sensor to measure the transformer winding temperaturedistribution. Analyzed the sensing principle of optical fiber Bragg grating temperaturesensor, designed the detection and treatment process of signal of FBG, studied principleand method of transformer winding temperature distribution on-line monitoring basedon optical fiber grating sensor, built the fiber grating on-line monitoring platform ofwinding temperature distribution based on the temperature rise test of oil-immersedtransformer in laboratory.Third, based on the FBG on-line monitoring platform of temperature, through theconstant load test，change load test and force oil cycle test to simulate the heating oftransformer windings, and used the FBG temperature sensor and thermocouple to doreal-time measurement of the temperature of different disks of transformer winding.From the test results, it can be seen: the results of FBG on-line monitoring and thereal-time monitoring of thermocouple are basically the same, its stability is better thanthe thermocouple, its reaction to temperature changes is more quickly thanthermocouple. The force oil circulating experiment shows that the force which caused by the flow of oil in transformer internal has no impact on temperature measurement ofFBG.Finally, to the error character of the fiber Bragg grating on-line monitoring oftemperature, determined the main influence factors when monitoring. Using the methodof multi-wavelength reference to overcome the error caused by the nonlinear responseof F-P filter, using polynomial fitting to overcome the inaccuracy of peak detection ofwavelength. In the laboratory, there are electromagnetic interference, the interferencenoise of power supply, noise of grounding loop and so on, the dissertation uses printedcircuit board, copper shields, the isolation transformer and common grounding toeliminate the influence of interference on FBG on-line monitoring.