Analysis Of The Effectiveness Of Voltage Arc Extinguishing In Medium Voltage Distribution Network

Medium voltage distribution network mostly adopts the neutral point non-effective grounding,which relies on the traditional arc suppression coil when single-phase arc-ground fault occurs.In recent years,The arc-extinguishing technology of transfer fault point fast is a supplement and replacement for the arc-suppression coil.The technology is also called the“Arc extinguishing cabinet,and it has been widely used because of its high cost performance.The idea is to identify the fault phase and use a circuit breaker to quickly ground the faulty phase bus to clamp the fault phase voltage and achieve ground fault transfer to extinguish the original grounding point arc.In response to the shortcomings of this technology,this paper has done the following three aspects:1.The prerequisite of Fault Point Transfer Technology is to identify fault phase correctly in one cycle.However,the traditional fault phase identification method based on steady process is prone to failure in the case of grounding fault via intermittent arc.This paper analyzes the defects of the conventional methods,establishes the equivalent model of distribution network,and derives the transient time domain expression of the three phase voltages after the arc extinguishing.The multiscale wavelet transformation is used to extract the transient high-frequency components of three phase voltages.A novel method is proposed to identify the fault phase by calculating the amplitude and phase characteristics of the high-frequency components and the conventional methods are combined with this novel method.2.The arc-extinguishing technology of transfer fault point fast has been widely used.Aiming at the single-phase arc-ground fault in the neutral point non-effective grounding system,the principle is to ground the faulty phase bus directly to extinguish the grounding arc.However,the onsite operation found that the technology could not completely guarantee the arc on the original fault point extinguished reliably.The effects of arc characteristics,bus grounding time,length of lines,load and other factors on the effectiveness of arc extinguishing are analyzed in depth.Among these factors,the grounding time is the only controllable factor.The improvement measures of grounding the faulty phase bus at the zero point of the arc current are proposed.Based on the actual project,this paper designs and develops a complete set of application equipment for transfer fault point fast technology,including monitoring terminal,action module,control module and background station.And based on the CUBA platform to build software construction,to achieve data collection,physical information transmission,fault phase identification,grounding time determination,background alarm and other functions.