| Monitoring,controlling and judging the information of key nodes in power grid plays an important role in the safe operation of power system.Based on the sensor devices,the state information at the key nodes of the power network is measured,collected and transmitted.When laying out a wide-band and reliable sensor network,the establishment of a large-capacity and reliable interconnected sensor network is the physical basis for monitoring and collecting the information signals of each node in the "ubiquitous power Internet of things".Voltage is one of the most important key parameters to determine and affect the operation state of power grid,which is directly related to equipment safety and operation state.Realizing real-time voltage monitoring of key nodes in power grid is of practical significance to the control of power grid operation state,the feedback of power grid fault state and the formulation of power grid operation strategy.It is also an effective aid to the process of intellectualization and digitization of power grid.The existing power grid voltage monitoring devices are generally large in size,weak in anti-electromagnetic interference ability,small data transmission volume and low reliability of non-station voltage measurement nodes,which are not conducive to the development requirements of the new era of large data interconnection and real-time data updating of the whole power grid.Using optical fiber devices to monitor voltage signals can directly couple optical fibers for information transmission,which has the advantages of large data transmission,high reliability,strong anti-electromagnetic interference ability,small size and light weight.Therefore,the research of voltage sensors and related sensing systems based on optical fiber devices is of great significance for accelerating the process of intellectualization and digitization of power grid.Based on the energy coupling mechanism of electro-deformation-photophysical quantities,a voltage sensing model based on inverse piezoelectric materials and fiber Bragg gratings is established.In order to reduce the limitation of measurement range caused by additional demodulator and environmental temperature change,the dual grating demodulation method is used to realize the function of self-demodulation and temperature compensation of the sensor.The calibration test platform of optical voltage sensor is built.The basic sensing characteristics of the sensor,such as frequency response,power frequency amplitude response,transient signal sensing characteristics and temperature characteristics,are studied,and the optimal working range and conditions of the sensor are determined.Based on coupled mode theory,the reflection spectrum of grating is calculated and simulated,and the influence of grating parameters on the output characteristics of the sensor is further studied.Two decisive parameters(grating length,refractive index modulation depth)and a commonly used post-processing method(apodization processing)are selected to study the influence of parameter changes and apodization processing functions on the sensing characteristics of sensors,and a grating parameter recommendation scheme for fiber Bragg piezoelectric ceramic voltage sensors is proposed.The proposed scheme is used to re-customize the Fiber Bragg Grating(FBG),complete the preparation of the new sensor,verify and test the sensing characteristics of the new sensor and compare with the original sensor,verify the effectiveness of the proposed scheme of grating parameters.Based on the finite element method,the influence of the structure and parameters of the piezoelectric ceramic tube on the output of the sensor is studied.Comparing and calculating the polarization direction deformation of rectangular,cylindrical and tubular piezoelectric ceramics under the same applied voltage;Comparing and calculating the change of shape variable of the outer diameter edge of piezoelectric ceramic tubes under the same applied voltage and different piezoelectric ceramic tube structures;Comparing and calculating the influence of different piezoelectric ceramic tube structure parameters on the lowest kHz resonance frequency under the same applied voltage The deformation and frequency characteristics of piezoelectric ceramics under different structures and parameters were studied.Three kinds of piezoelectric ceramic tubes with different thicknesses are used to compose the fiber grating-piezoelectric ceramic voltage sensor,and the sensing characteristics are compared and tested.The parameter selection scheme of the piezoelectric ceramic tube for the fiber grating-piezoelectric ceramic voltage sensor is given.The influence of different coupling modes between piezoelectric ceramic and voltage signal on the sensing characteristics of the sensor is checked and tested,and the favorable points for the sensor are obtained.Resolution of piezoelectric ceramic-voltage coupling mode.Based on the principle of demultiplexing,the structure design of the multi-point voltage sensing system based on a single sensor is studied by using the optical splitter and the optical circulator.The basic characteristics of the multi-point voltage sensing system,such as frequency response and power frequency amplitude response,are verified and tested.In addition,the temperature characteristics of the sensing system are verified and tested by using the temperature control box.The power frequency three-phase voltage response of the sensing system is verified and tested.The characteristics,single-phase ground fault response characteristics and other application characteristics are tested and analyzed,and the effective measurement range of the sensor system is verified by signal analysis methods such as Fourier analysis.The research results of this paper strive to expand the direction of voltage sensing,enrich the ways and systems of voltage sensing,promote the distributed application of voltage sensors in power plants and transmission lines to build intelligent sensing system,and accelerate the progress of intelligent and digital power grid. |
PDF Full Text Request