| In the extra-high voltage and above voltage level grid,aiming at the problem that the amplitudes of power frequency over-voltage and secondary arc current are too large,when the system is in normal operating or aroused by the fault,the relevant researches,such as electromagnetic performance of the magnetically controlled saturated reactor(MCSR),the coordinated suppression method of system power frequency overvoltage and secondary arc current,are carried out.The mathematical model of MCSR for electromagnetic analysis is established.The nonlinear problem of the magnetic circuit and the circuit is fully considered,which is under the combined action of AC winding and DC winding,the distribution law of MCSR magnetic field is given.The variation laws of magnetic saturation degree and reactance parameter with current of control winding are revealed.The operating characteristics,control characteristics and harmonic characteristics of MCSR are given based on magnetic field analysis.On the basis of magnetic field analysis,an accurate calculation method of leakage inductance parameters for MCSR is proposed based on energy method,the voltage equation and flux linkage equation of MCSR are deduced.A magnetic and current-circuit coupling simulation model of MCSR segmented magnetic circuit is established.The calculation result and measured value are compared and analyzed by two different ways of field and circuit,and the correctness of mathematical model for MCSR is verified.A compensation method of collaboratively suppressing power frequency overvoltage and secondary arc current for MCSR and inter-phase shunt reactor is proposed.Power frequency overvoltage aroused by no-load capacitance effect and load shedding is studied,the compensation method of MCSR is given,and the variation laws of line voltage varying with physical quantities as inductance parameter,transmission power of lines and compensation degree are gained.In order to calculate secondary arc current,the three phase full-order equivalent circuit of long line is built up.The theoretical results of inductance component and capacitance component for secondary arc current are shown.Taking the 500kV network system as an example,the model of system simulation is established,and the results of the theoretical analysis are verified.The distribution laws and influencing factors of system secondary arc current and recovery voltage are studied.The influence laws of line arrangement,transposition mode,position of the fault point,transmission power,compensation way and compensation degree on secondary arc current are analyzed,the control law of 500kV MCSR is obtained.The low voltage experimental platform of 500kV secondary arc current is established.According to experiment-simulation consistency principle,the secondary arc current of high voltage lines is simulated at low voltage status,and the experiment of proposed suppression scheme is carried out.Under the same parameter conditions,by comparing live experiment data with simulation results,the theoretical analyses and simulated calculation results are verified. |
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