Study On Signal Processing System Of Optical Voltage Transformer

The optical voltage transformer,OVT,can realize voltage measurements by using principle of electro-optical modulation for upply network.Compared with the traditional electromagnetic Voltage Transformer,OVT has the following advantages:small volume,light quality,good insulation,large dynamic range,high measurement precision,etc.Although OVT’s research has a history of decades,but there are still serious problems with stability and long-term reliability,can not pass the relevant standards of measurement,failed to obtain the recognition of the state grid to obtain a network license.The signal processing system is one important part of the OVT.It can correct the measuring error caused by the polarization instability factors.and visual display voltage waveform and the related technical parameters(RMS and harmonic),and realize the remote communication.It plays an important role in the optical fiber electric transformer.For the OVT signal processing system,this paper adopts the overall structure of the microcomputer digital centralization control.and completes the hardware design and software programming of the signal processing system.The hardware part,we design and make the laser driver circuit,temperature control circuit,back light detection circuit and a detector circuit.Using the data acquisition card to realize the communication between the circuit and the microcomputer,and the digital control of the laser and the acquisition of detector electrical signal are completed.Software part,through Labview write a kV voltage acquisition processing program to realize the instrument control and data processing functions.The control functions includes the feedback control,alarm,and switch control of the laser,such as data processing includes signal collection,correction and the wavelet analysis,FFT transform,voltage RMS calculation,waveform display,storage,etc.The experimental results show that the signal processing system can effectively correct the measurement errors caused by polarization instability.Finally in order to analyze the concrete influencing factors of the unstable of OVT polarization,we put forward a new extinction ratio measurement method for elliptically polarized light.And measured the extinction ratio of the optical fiber and connectors used in the OVT degradation extinction ratio measurement.