| The distribution network plays a role in distributing electric energy to users.With the progress of society,its safe and reliable operation is becoming more and more important.Ground faults are prone to occur in the distribution network,and more than 80% of the faults are single phase grounding faults.If the faults are not suppressed in a timely and effective manner,i t is easy to cause accidents such as wildfires and personal electric shocks,and may develop into inter-phase short circuits expanding the fault area.Aiming at the problems existing in the traditional singlephase grounding fault phase selection and arc su ppression methods in the distribution network,this paper proposes an improved phase selection scheme and an arc suppression scheme respectively,which can reduce the cost of arc suppression devices on the basis of effective arc suppression.The specific w ork is carried out as follows:In view of the fact that the phase selection method based on transient characteristics,the accuracy of phase selection is easily affected by fault conditions,and the phase selection method based on steady-state characteristics has the problem of misjudgment due to the failure to capture steady-state information when intermittent arc ground fault occurs,a phase selection method based on the combination of signal skewness and phase difference is proposed.Calculating the skewness value of fault component of three-phase phase current,if the skewness value of one phase is different from the other two,it is judged as a fault phase.Considering that in the neutral point grounding system through the arc suppression coil,when the transition resistance is large,it may cause the same sign of the skewness value of the three phases.For this reason,the phase information of the three-phase power frequency phase voltage is introduced.The phase with the smallest absolute value of the phase difference between the power frequency phase voltage and the corresponding phase power frequency phase current fault component is the faulty phase.Matlab/Simulink is used to build a single phase grounding fault simulation model of 10 k V distribution network.The simulation results verify that the phase selection method proposed in this paper can accurately select phases under different fault conditionsAiming at the problems of residual current in the passive arc suppression method and large equipment capacity,high cost and complicated control in the active arc suppression method of single phase grounding fault in distribution network,a hybrid compensation method is proposed,which uses a line-phase converter in series with an active compensation device.The hybrid compensation method use the line-phase converter to connect the electromotive force of the faulty phase power supply to the neutral point in reverse..Considering that a deviation between the voltage of the primary side and the secondary side of the line-phase converter due to the existence of the internal impedance,the active compensation device is used to compensate for this deviation,so that the sum of the voltage of the secondary side of the line-phase converter and the output voltage of the active device is always equal to the inverse number of the electromotive force of the faulty phase power supply.Matlab/Simulink is used to build a simulation model of hybrid compensation for single phase grounding fault in 10 k V distribution network.The simulation results verify that the arc suppression scheme proposed in this paper can achieve effective arc suppression of single phase grounding fault.Compared with traditional methods,the advantages of the method proposed in this paper are proved.To sum up,this paper first studies the method of improving the phase selection accuracy of single-phase grounding fault in distribution network,and then studies the arc suppression method to reduce the cost of arc suppression device on the basis of ensuring reliable arc suppression.Therefore,a complete and effective arc suppressi on scheme is formed. |
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