Application Analysis Of Active Transfer Type Arc Extinguishing Device Under Long Feeder Line And Heavy Load

China's distribution network generally adopts a neutral point non-effective grounding method.When a single-phase ground fault occurs,the current flowing through the grounding point is small.With the continuous expansion of the urban distribution network and the general increase in the cable rate,the single-phase ground fault point current increases sharply.When the grounding current i,s large,the grounding arc is difficult to extinguish naturally,and it is easy to generate an arc grounding overvoltage,which can cause the equipment to burn and cause an interphase short circuit accident and threaten the safe operation of the power grid.An active transfer type arc-extinguishing device has been introduced in recent years in order to solve the problem of difficulty in arc-extinguishing single-phase grounding fault in neutral point non-effective earthing system.By grounding the faulty phase busbar metal ground in the substation,the single-phase grounding point is made.The current is transferred to the metal grounding point of the busbar,thereby reducing the fault grounding point current,while clamping the faulty phase voltage to achieve a "dual" arc extinction of the fault grounding point voltage and current.However,some scholars believe that the active-transfer arc-extinguishing device will operate in the long-feeder and heavy-duty operation.When the faulty phase bus is grounded,the line voltage drop from the single-phase grounding point to the busbar grounding point will form a circulating current between the two grounding points.When the grounding resistance is small,the fault grounding point current will increase,the arc energy of the fault point will be enhanced and it will be more difficult to extinguish,causing the zero sequence protection action on the line to trip,resulting in the interruption of the load that could be continued due to the transient fault.Therefore,the arc-extinguishing performance of the active transfer type arc-extinguishing device under the condition of heavy feeder heavy load is questioned,but the arc-extinguishing performance of the active transfer type arc-extinguishing device is not analyzed in depth.In order to clarify whether there is an arc-extinguishing obstacle in the active transfer type arc-extinguishing device during long-load heavy-duty operation,a single-phase ground fault arc-extinguishing equivalent circuit is established.The theoretical derivation of the fault-phase busbar grounding after flowing through the fault grounding point is theoretically derived.Expression;based on the ATP-EMTP simulation software,simulate the verification of the change law of the fault grounding point current after the faulty phase bus is grounded.For the heavy load operation of the long feeder of the distribution network,when the single-phase grounding occurs at the end of the feeder,the grounding transition The relationship between the resistance and the fault grounding point current is simulated and analyzed.The relationship between the single-phase grounding transition resistance and the fault grounding point current is obtained.By measuring the grounding resistance value of the feeder single-phase grounding in different grounding scenarios,combined with foreign measurement The results and related measurement standards show the range of grounding transition resistance when the feeder line is single-phase grounded.Under the most unfavorable arc-extinguishing conditions,the active-shifting arc-extinguishing device is extinguished by setting up the arc-extinguishing capability test platform.The arc capability is tested and tested.The test results show that when the arc length of the single-phase ground fault point exceeds 1.5 mm The arc will be completely extinguished.Therefore,the active transfer type arc extinguishing device can reliably extinguish the arc in the case of heavy feeder heavy load,and there is no arc extinguishing obstacle.