The Study Of Transformer Winding Temperature On Line Monitoring Using Distributed Fiber Bragg Grating Based On FPGA

With the rapid development of Chinese economic, the level of our country's power grid operation is ever increasing. Power transformer is one of the most expensive and important equipments in the power system. And its reliability is directly related to the safety, efficiency and economy of the power grid operation. Most of the transformers end of life because of the loss of its insulation capability. The most important factor which affects the insulation capability is the winding temperature of transformer in operation. If the temperature in the hottest district is too low in operation, the capacity of transformer will not be in full use so that to reduce the economic efficiency. If the temperature in the hottest district is too high in operation, it will not only affect the life of transformer but also pose a threat to the safe operation of the transformer. The inside of power transformer is in the environment of high voltage and strong electromagnetic field. Compared to traditional electrical signal sensing technology, the fiber Bragg grating sensing technology has unmatched advantages for the monitoring of transformer winding temperature, especially suitable for the complex electromagnetic environment inside power transformer.Firstly, this paper studies the theory of the fiber Bragg grating sensor. By making use of coupled-mode theory, it analyses the transmission characteristics of uniform-period fiber Bragg grating and construes the fiber Bragg grating temperature and strain sensing principle.Secondly, this article compares the more commonly used distributed fiber Bragg grating demodulation techniques. To be adapt to multi-point monitoring of transformer winding temperature, this article designs a dual-channel distributed fiber Bragg grating temperature on-line monitoring system by improving the intensity of wavelength division multiplexing demodulation. Finally, the paper designs FPGA signal processing system on the platform of XC3S500E chip in Spartan3E series. The system includes optical detection circuit module, sawtooth generated modules, low-pass digital filter, data computing module and the temperature display module. The FPGA processing system design methods are explained in detail, and the corresponding simulation graphics are given. In this paper, the optical experiments and FPGA experiments are done. The experiments show that the design of the system is correct, and it can be able to achieve temperature monitoring function.