10kV Distribution Cable Arc Fault Detection Technology

With the development of the city,the proportion of cable lines in the distribution network continues to increase,and the capacitive current in the distribution network system continues to increase,due to the existence of insulation layer in the cable,so that when the cable line fails,it is usually first manifested as a single-phase arc ground fault.In the arc grounding state,the arc fault causes the three-phase current to change,but it does not reach the fixed value of overcurrent speed off protection,and the tripping measures cannot be taken immediately.Due to the timely identification of the arc ground fault,the grounding arc will occur many times to extinguish-re-ignite in this process,the temperature of the cable will rise instantly,and the free electrical body generated in the arc arc column can reach 5000～15000℃,resulting in the expansion of the fault.It poses serious harm to the safe,stable and reliable operation of the distribution network system.However,the type of ground fault is always assumed to be metallic or resistive ground,and the real situation of the arc fault of the cable line cannot accurately reflect the action characteristics of the existing arc model using the existing arc model.Therefore,it is very important to establish an arc model according to the structural characteristics of the cable to identify the arc fault of the cable circuit.Firstly,the characteristics of single-phase ground faults and the development status of arc-flash ground fault detection are analyzed,the essence and physical characteristics of arc are expounded,the structure of cables is analyzed according to the complexity of classical arc model modeling and the different application ranges,and a new fault arc model is established according to the characteristics of cable routes by ATP-EMTP software.According to the actual situation of the arc at the time of failure,the parameter values of the arc model are adjusted to make the simulation model closer to the engineering reality.Then,a distribution network simulation model is established to comprehensively simulate the effects of different grounding modes,fault initial angles,grounding resistance,etc.on the steady-state and transient currents of single-phase metallic or resistive grounding and single-phase arc-flash grounding.A new method is proposed to decompose the zero-sequence current signal at fault time by wavelet packet transformation,and then analyze the relative energy of the frequency band of the waveform,and distinguish the metallic ground or resistive ground fault and arc-flash ground fault according to the quantified zero-sequence current signal as the criterion.At the same time,combined with the arc phenomenon generated when arc ground occurs in the cable line as a criterion,the arc ground fault is further verified.Through a large number of simulation data analysis and experimental verification,this method can effectively distinguish metal grounding or resistive grounding and arc-flash ground ground faults,and can accurately and timely take measures when arc-flash grounding occurs.It improves the reliability of power supply in the distribution network and avoids the further expansion of faults,which provides an important reference for further research on the selection,location and post-processing of single-phase ground faults.