Research On Fault Phase Selection Criterion Of Active-Intervention-Type Arc Suppression Device And Its Influence On Fault Diagnosis

With the acceleration of the construction of distribution network and the continuous increase of cable applications,the level of system capacitance current is constantly rising,and a single bus of urban distribution network often exceeds 200A.The increase of residual current in single-phase-to-ground fault will make arc current difficult to self-extinguish,and arc overvoltage will damage the insulation ability of equipment.During the duration of single-phase-to-ground fault,it may develop into two-phase-to-ground fault or even three-phase-to-ground fault,threatening the safety of human life and equipment.Therefore,rapid arc extinguishing under fault has become the first priority of single-phase-to-ground fault handling,and it is also a necessary means to avoid the expansion of fire and power outage loss.Active-intervention-type arc suppression device integrates the advantages of voltage-type arc suppression technology and current-type arc suppression technology which can effectively extinguish the arc at the fault point and has been popularized and applied in the distribution network of many provinces in China.Fault phase selection is the key link of the active-intervention-type arc suppression device.If the faulty phase is selected incorrectly,the device will cause two phase fault and may lead to the fault in substation;For permanent ground fault,the fault diagnosis algorithm needs to be activated as soon as possible to provide specific fault line and fault section information;The action process of the active-intervention-type arc suppression device will disturb the distribution network system and affect the single-phase-to-ground fault feature.Therefore,this paper makes an in-depth analysis of the above problems,and the specific research content is as follows:(1)The difference between the sudden change of healthy phase current and the fault phase current waveform is analyzed,and a fault phase selection method based on the extraction of the phase current of the selected frequency band is proposed.Wavelet packet decomposition is used to determine the selected frequency band of high-frequency components,which eliminates the interference of load current variation on phase current sudden change.The similarity coefficient of three-phase current sudden change in selected frequency band is quantified by improvd-grey-correlation degree,so as to realize the identification of single-phase-to-ground fault phase.(2)The characteristics of the zero-sequence current before and after the action of the active-intervention-type arc suppression device are analyzed,and the fault line selection and fault section location methods considering the influence of the active intervention type arc suppression device are proposed.By improvd-grey correlation-degree,the waveform difference of zero-sequence current between fault section and healthy section is quantified mathematically,so as to realize fault line selection and fault section location.(3)Considering the two typical working conditions of device phase selection error and device reset process,the relevant mathematical model is established to analyze the influence of active-intervention-type arc suppression device on single-phase-to-ground fault feature and corresponding solutions or suppression methods are proposed in a targeted manner.