Post-arc Current Measurement And Correlation Analysis In Forced DC Interruption

Transmission of high-voltage direct current has the advantages of low-cost and low active power loss on the line,which makes it capable of exerting advantages in long-distance large-capacity power transmission and multi-terminal flexible DC power transmission systems.DC circuit breaker,as the key switching element and protective equipment of DC system,has become a research hotspot in the field of power switching in recent years.The post-arc zero-zone process determines whether the circuit breaker can withstand the recovery voltage that rises rapidly after the current crosses zero.The post-arc current is one of the important research contents of zero-zone characteristics.The research of post-arc current on DC,especially in vacuum is rarely seen.In this paper,the post-arc current in vacuum DC interruption under multiple parameters is completed,and the correlation analysis is carried out from multiple angles.Identifying the dynamic factors that may affect the post-arc current is the core issue of experimental research.In this paper,the overall theoretical analysis of the DC interruption process is carried out,using the zero-zone parameters,including current change rate before current zero di/dt and recovery voltage change rate du/dt,and initial plasma density during the recovery of the post-arc medium to guide the change of the post-arc current,and the influences of the system parameters?load current,I_L and high-frequency reverse current,I_H?and switching parameters(opening speed,V_O and arcing time,T_ARC)on the post-arc current are analyzed.The post-arc current has a short duration and small amplitude,which is difficult to measure.In this paper,PSCAD is used to simulate the system parameters,and based on this,a post-arc current measurement system based on DC forced zero-crossing is designed.Constantan wire is selected as the transfer resistance of the post-arc current measurement device.Based on the hardware control system designed by the laboratory team,this paper carries out the relevant logic and timing control.Combined with the high-power synthetic loop test platform of DC forced zero-crossing,the measurement of post-arc current in this paper is completed.Based on the post-arc current measurement system,the 2-5KA DC interruption was completed and the post-arc current was measured for different system parameters?I_L,I_H?and different switching parameters(V_O,T_ARC).Through the simulation of zero-zone parameters affected by current source and commutation source parameters,the corresponding equivalence relation is established for the comparison of experimental data in this paper.On the basis of processing and analyzing experimental data,this paper takes post-arc current as the main object of analysis,analyzes the changing rules of post-arc current under different I_L,I_H,V_O and T_ARCRC respectively from the horizontal study.The influencing degree of the zero-zone parameters,including di/dt and du/dt,and charging residual current of commutation source,V_O and I_H on the post-arc current were analyzed respectively from the vertical comparison.The analysis results show that the post-arc current is in the range of 0-30A,I_L and I_H have opposite effects on the post-arc current,while V_O and T_ARC make the change trend of the post-arc current consistent,and the post-arc current is more affected by I_H than V_O.In addition,when du/dt reaches a certain value,the post-arc current increases for a second time,the analysis shows that di/dt mainly determines the first peak,while the second peak is mainly affected by du/dt.Finally,based on the experimental results and practical experience,some suggestions are put forward for the application of DC interruption.The conclusions drawn in this paper can provide a good scientific basis for the selection of reasonable breaking parameters for DC circuit breakers.