Research & Application Of All Fiber-Optical High-Voltage Electric Parameter Monitoring System Based On DSP

All Fiber-Optical Current Transformer (OCT) is one of three kinds of new-style electronic current transformers. It has potential benefits over conventional current transformers (CTs) such as inherent high-voltage isolation, immunity to electromagnetic interference, enhancement in signal bandwidth and dynamic range, ease of integration into future digital control and protection systems and will be widely used in power electrical system.Firstly, the paper describes the work principles of Faraday effect and Jones matrix analyzing method of polarization system.Then the paper establishes the theory model of reflective Sagnac interometer based fiber–optical current transformer using Jones matrix analyzing method.Secondly, the paper analyzes the requirement of reflective Sagnac interometer based fiber–optical current transformer, presents the structure of secondary signal processing system and describes the hardware model of each part in detail. Among these, the thesis emphasizes the AD conversion model based on hardware-synchronized sampling method and core model of DSP .Then the paper introduces the software model of the system in brief.Thirdly, the paper studys the harmonic waveform montoring method using FFT, analyzes two factors of errors in harmonic waveform analysis using FFT—asynchronization sampling and picket fence effect of none time-limit signal. Synchronization sampling and windowing to reduce the leakage effect are discussed. Based of that, hanning window and hardware-synchronized sampling method are choosed to apply on the system,and then uses interpolating algorithm to further adjust the analyzing result of signal which is windowed. After that, a new method using wavelet tansform to analyze harmonic waveform is discussed, and base of that, a new method which named Fourier and Wavelet comprehensive detecting algorithm using Fast Fourier Transform combining with Wavelet Transform is discussed. Using the special effect on detecting singularity point and high resolving degree in time domain of wavelet, combined with the exact frequency resolving ability of Fast Fourier Transform, all kinds of harmonic waveform can be analyzed.Finally, all types of harmonic signal models are created and emulate FFT and Wavelet transform to these same signal models.A conclusion about how to use different methods can be got by contrast.And then Fourier and Wavelet comprehensive detecting algorithm is emulated by a well-formated compositive harmonic signal and it is compared with rational method by emulate as well. The emulating results are much better than tradiotional harmonic analysis method's.