| The strong,reliable,clean,green,and cost-effective smart grid is an inevitable trend for China and even the world's power grid.The smart grid presents significant diversity in all aspects of power supply composition,load type,and information transmission.In addition to building a flexible,stable,and secure energy network,the real-time measurement feedback and dynamic adjustment is crucial to realize intellisense of information and intelligent self-healing of faults for power generation,transmission,distribution,and power generation.At present,the current/magnetic field sensing technology is relatively mature,and the voltage/electric-field sensing technology is relatively infant.It is urgent to expand the voltage/electric-field sensing technology scheme,and develop sensors with a large dynamic measurement range,a wide frequency band range,and the high precision.Voltage/electric-field sensors could achieve wide-area distributed measurement and transmission for critical node status,which provides information support for grid control decisions.In view of the sensing technology demand of intense electric field,wide frequency band and high stability,an interferometric electric-field sensor based on the electro-optic effect of the Lithium Niobate is proposed that appears suitable for intense electric-field measurement this paper.Aiming at the miniaturization demand of the electric-field sensor,a common-path electric-field sensing scheme is demonstrated.The characteristics test of the designed sensor is carried out to calibrate the time domain response and frequency domain response.For the long-term usage demand of the electric-field sensor in wide temperature and humidity zones,the influence mechanism of temperature factors on sensor's accuracy is theoretically analyzed.And two kinds of intense electric-field sensors are proposed that is suitable for a broad temperature range.Temperature characteristics of two improved sensors are carried out,meanwhile,their humidity characteristics are tested.Finally,an intense electric-field sensor with good temperature and humidity stability is applied to various field tests to verify the sensor's performance.The main research contents and results of this thesis are as follows:(1)Based on Pockels effect of the electro-optic crystal,the basic electro-optic conversion principle and structure model of the intense electric-field sensor are proposed by using the detection method of bulk-crystal polarization.An intense optical electric-field sensing unit is invented by choosing appropriate electro-optical materials,optical functional components,and the optimal coupling method.The characteristic test platform for the electric-field sensor is built to obtain the input and output characteristics and the typical waveform response.The experiment results show that the electric-field sensor could measure an electric field of amplitude 5 kV/m-500 kV/m,and accurately respond to power frequency,intermediate frequency and high frequency transient electric-field signals.(2)Aiming at demand of the minimizing sensor's structure and reducing interference to the original electric field,the miniaturization principle and optimization scheme of the common-path electric-field sensor are proposed.The designed scheme reduces the number of internal components and the overall size.After the characteristic test,the electric-field sensor is capable of measuring an electric field with an amplitude of 0.35 kV/m-280 kV/m.It could accurately respond to electric-field signals of the power frequency,ms level and ?s level.And its frequency response remains stable in the range of 10 Hz to 500 kHz.(3)For the long-term usage demand of the electric-field sensor in the wide temperature zone,the temperature characteristics of the lithium niobate crystal parameters are analysed,and the influence of temperature on the half-wave electric field and the intrinsic phase is investigate.The mechanism of the sensor's measurement error induced by the temperature is obtained.Then,an electro-optic sensing unit with the conjugate compensation structure of a dual crystal and an electric-field sensing unit with the Z-axis propagation are proposed to eliminate the influence of the temperature characteristics.According to the design,two kinds of electric-field sensors are optimized and packaged.(4)Based on the test platform with a board temperature and humidity range,the temperature characteristics of two kinds of improved electric-field sensors are tested.The experiment results show that two kinds of sensors are stable in the wide temperature range of-10 °C to 50 °C.The dual-crystal electric-field sensor with a piecewise transfer function corresponding to ambient temperatures is demonstrated to measure the input/output of the sensor enabling a the maximum measurement error less than 5% over the ambient temperature range of-10 °C to 50 °C for the electric-field amplitude from 1.2 kV/m to 155 kV/m.The linear fitting goodness of the sensor reaches 0.999 that shows the good temperature stability.The electric-field sensor with the Z-axis propagation is suitable for a range of electric-field amplitudes from 5 kV to 600 kV/m in a temperature range of-10 °C to 50 °C.And its maximum measurement error is less than 7.9%.The linear fitting goodness of the sensor reaches 0.998 that shows the good temperature stability.The humidity characteristics of dual-crystal electric-field sensor are carried out.Though coating the hydrophobic glue on the outer casing to improve the humidity adaptability of the sensor,the transfer function parameters remain stable and the maximum measurement error induced by humidity characteristics is less than 1.62% over the wide humidity range of 30% RH-90% RH.(5)Aiming at the time domain and frequency domain measurement requirements of intense electric-field sensors,the designed sensors is calibration.The electric-field sensor response is able to track well electric-field signals of the power frequency,ms level and ?s level,and it has a frequency response fluctuation of less than 3 dB in the frequency range of 10 Hz-1 MHz.The results showed that the electric-field sensor performs well in response speed and accuracy which appears suitable for electric-field signal measurement in high voltage engineering.Thus,an intense electric-field sensor with good temperature and humidity stability is applied to various field tests.It is verified that the designed electric-field sensor is able to effectively perform intense electric-field experiments in complex atmospheric conditions and electromagnetic environment. |
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