Research On A Battery-less And Contact-less Optic Overvoltage Sensor And Measurement System Based On Pockels Effect

The smart grid(SG)is regarded as the next generation power grid and is intended to improve the operational efficiency and reliability of power systems,is an important direction for the development of electric power system in the 21 st Century.The intelligent sensor is an important unit of the smart grid,and the real-time perception of the power grid over-voltage is helpful to obtain the overall operation status of the power system.The current devices for voltage and overvoltage monitoring are the traditional contact system,they have advantages including high operating reliability,but they also have disadvantages in narrow measuring band,weak anti electromagnetic interference ability,inconvenient installation and maintenance deficiencies.Therefore,the research for non-contact overvoltage sensor with good response characteristics of the broadband can effectively expand the information depth of measured power grid voltage waveform,and provide data support for further research on overvoltage behaviors.In this paper,based on the Pockels effect and the principle of air coupling stray capacitance,the circuit and the optical model of the non-contact measurement method of passive overvoltage of power system are established.The physical properties of different crystal materials are analyzed,according to the measurement requirements and measurement principle,electro-optic crystal material is selected reasonable,and the research on the Linear working range and optimal allocation scheme of this kind of electro-optic crystal are studied.The layout method of each unit and the whole sensor package scheme are studied.The measurement platform is built in the laboratory to measure the frequency response characteristics,amplitude frequency characteristics and impulse voltage response characteristics of the sensor.Based on the basic optical path model of sensor,the main factors affecting the stability of the sensor are analyzed,and the temperature compensation method of dual crystal structure is studied to improve the temperature stability of the sensor.Based on the improved optical path model,the electro-optic sensing unit based on the dual lithium niobate crystal structure is designed,the temperature stability and long-term stability of the electro-optic sensor unit with single crystal structure and double crystal structure are compared in the laboratory.After the packaging of the improved sensor is completed,measurement platform in the laboratory is built to verify the input and output characteristics of the sensor.Combining with the data acquisition system,a overvoltage measurement system for the power system is constructed,and the application of the overvoltage measurement system in power system is achieved.Based on the principle of non-contact measurement of sensor,the coupling mechanism of voltage signal in multi conductor system is studied.The three-phase voltage measurement platform is set up,and the main factors affecting the phase coupling of the sensor in the three-phase voltage measurement are analyzed,and the corresponding suppression methods are proposed.The equivalent circuit model of the sensor in the three-phase voltage measurement is established,and the decoupling method of output waveforms is studied.The voltage measurement platform is set up in the laboratory and the field,compared with the output signal of the contact voltage divider to verify the validity of the proposed decoupling method.Based on the principle of wavelength division multiplexing,a data transmission optimization method in multi point simultaneous monitoring is studied,and the multi point voltage measurement system is established in laboratory.The input-output characteristics and high frequency response characteristics of the measurement system are tested.On the other hand,the input and output characteristics of electro-optical sensor unit in different input laser wavelength is analyzed,the method of extending the effective measurement range of voltage is proposed.The optical path model of the electro-optic sensor unit with dual wavelength input is established,the input-output characteristics of the electro-optic sensor unit with dual wavelength input are obtained by experiments.The work of this paper can provide a new idea for the research of the power system voltage and over-voltage monitoring sensors,which is of great significance in academic research and engineering guidance.