Research And Design Of An Online Energizing Device For Transmission Lines

With the development of smart grid,it is particularly important to monitor the operation status of transmission lines in real time and detect faults in time so as to ensure their safe operation.However,the problem of energy supply of monitoring equipment has always been the difficulty of on-line monitoring of transmission lines,in which the magnetic coring of transmission line has good practical application value.Low permeability due to air gap in magnetic core.The air gap in magnetic core leads to low permeability of traditional magnetic core energy extraction methods.Moreover,the shunt of the excitation inductance of the core itself to the line current leads to the low output power when the line current is small.In this thesis,firstly aiming at improving traditional energy extraction methods,a parallel resonant energy extraction method is proposed.Parallel capacitance on the secondary side of the core makes it resonate with the excitation inductance of the core in parallel,which weakens the shunt of the excitation inductance.However,due to the resonance,it is quite easy for the magnetic core to saturate when the line current is very high.Hence,an impedance matching magnetic core energy extraction method is proposed.The current on the transmission line is diverted to the load,and the power can be output normally under the wide range bus current.Then,through quantitative analysis and calculation of output power and core parameters of impedance matching energy acquisition method,the optimum design of core is carried out.In order to achieve high power output when the load is fixed,PWM rectifier circuit based on input impedance control is adopted.It can adjust the input impedance of load branch and match the equivalent impedance of core branch.Moreover,the bus current is shunt to the load branch current,and the hardware circuit of the power supply is designed.Finally,the PWM rectifier circuit based on input impedance control is simulated by Simulink.The results verify the correctness of the theoretical analysis.Furthermore,the output power experiments of traditional on-line energy acquisition,parallel resonance energy acquisition and impedance matching energy acquisition methods are earried out.The results show that the power supply designed in this thesis can obtain more power supply for monitored equipment,and can output power normally in a wide range of bus currents.