| State overhaul based on the online monitoring of electrical apparatus is of great significance for the build-up of strong and smart power grid.However,online monitoring suffers from such barricades as difficult data transferring and power supply due to high voltage and strong magnetic field existing in the medium voltage apparatus.With the help of wireless power supply,monitoring devices could be powered stably with insulating requirements meted.Wireless sensor consisted of MCU,sensors and wireless communication module(for example ZigBee)is one of the important ways of on-line monitoring,whereas the high frequency signal emitted from the wireless communication module(such as signals of 2.4GHz,915MHz and 868 MHz emitted from ZigBee)have potential interference on relay protection control part of the medium and high voltage electrical apparatus.The wireless power and signal synchronous transmission technology is adopted in this paper to replace the existing wireless sensor data transmission mode,build new wireless sensors,and better reflect the advantage of the wireless power supply technology.Firstly,based on the analysis of the existing technical scheme,a system scheme including a class E power amplifier acting as the excitation source on transmitting side,a power transferring structure using resonance between coil inductance and compensated capacitance,where power transfer from low voltage side to high voltage side,a power and signal synchronous transferring structure enabling signals be transferred from high voltage side to low voltage side by load modulation and a communicating network sending data from low voltage side to monitoring center through power line carrier is proposed.Then,the model of the class E power amplifier loaded with the coupling structure is established under circuit theory.Analyses about influences of varying load modulating methods on circuit performances are made and verified through simulations and experiments.And then,the key indicators of prototype is determined according to the internal structure of the switch cabinet,the insulation distance of high and low voltage,the power consumption of the sensor,the amount of data transmission frequency.And online monitoring system using wireless sensors powered by magnetic resonant wireless power transfer system is designed on the basis of the above theoretical analyses and simulations.Considering the compact internal structure and limited space in switchgear,the coupling structure is optimized through orthogonal experiments,where line width,line spacing and number of turns are treated as factors,for a maximum transfer efficiency.Finally,constructed prototype is tested and analyzed,thereby illustrating the stability and reliability of the proposed system.The new type of on-line monitoring wireless sensor,based on wireless power technology via magnetic resonance,is easy to install and is stable and reliable,thus having a great value in research and application. |
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