Asymmetry Of Small Current Grounding System For High Resistance Grounding Research On The Influence And Solution Of Fault Line Selection

The fault characteristics of the fault feeder are not as obvious as that of the gold fault when the low current grounding system has a high resistance grounding fault,and the imbalance of the ground parameters of the three-phase feed in the distribution network is common.Because the existence of misalignment has changed the fault characteristics of fault feeder and non-fault feeder to a certain extent,it has a certain influence on the correct line selection of distribution network.Therefore,it is particularly important to study the influence of the asymmetry of small-current grounding system on the fault line selection of high-resistance grounding.Firstly,this paper aims at the domestic and international research on the method of line selection in case of single-phase grounding failure of small-current grounding system and the unsymmetry of distribution network.It is important to get the commonly used method of wire selection and to study the influence of asymmetry on the fault line selection of the distribution network.Secondly,the fault characteristics of the fault feeder of the low current grounding system under different asymmetry and different grounding resistors are analyzed.The effects of the asymmetry of the neutral point UnGrounded system on the zero-order current of each feeder and the asymmetry of the neutral point of the distribution network on the five harmonic and zero-order transient components of the zero-order current of each feeder are obtained.Then,in view of the influence of asymmetry on the fault line selection of high resistance grounding,a solution to add resistive current to the neutral point is proposed.The resistive current method is to ground the neutral point through the resistor and generate a resistive current at the neutral point.When the distribution network fails,The resistive current can only flow through the earth to the fault feeder,and the zero-order current of the fault feeder will increase,highlighting the fault characteristics,and then the effect of the resistive current method on the high-impedance grounding fault line selection of the low-current grounding system is obtained through simulation.law,Finally,the influence of asymmetry on the fault line selection of high impedance grounding system and the feasibility of resistive current method are verified by laboratory experiments.Through the analysis of the paper,the change law of zero-order current of UnGrounded system in distribution network is revealed.The influence of the asymmetry of the grounding system via the arc cancellation coil on the five harmonics of the zero-sequence current is analyzed.The influence of asymmetry on the transient component of zero-sequence current in the distribution network via arc cancellation coil is studied.The solution of neutral point injection resistive current is proposed,and the feasibility of this method is verified by software simulation and laboratory experiment.