城市轨道交通牵引供电系统直流快速断路器开断及灭弧分析

Analysis of DC Fast Circuit Breaker Opening and Arc Extinction in Urban Rail Transit Traction Power Supply System

[目的]直流灭弧技术是城市轨道交通牵引供电系统的设计难点之一,因此有必要对主要直流快速断路器的直流开断及灭弧原理进行分析。[方法]介绍了直流电流开断及电弧熄灭原理;介绍了直流电流的稳定燃烧点及熄灭条件;分析了直流电弧的开断参数,介绍了直流快速断路器的灭弧设计原理;分析了地铁供电系统直流快速断路器易烧损的原因。[结果及结论]要开断直流电弧,需产生一个高于电源电压的电弧电压,即加大电弧电压能够熄灭直流电弧;直流快速断路器的开断过程要综合考虑燃弧时间和系统过电压因素;在直流断路器设计研发时,需重点关注非稳定弧电压和小电流开断弧电压;在电弧熄灭时,设置一个额外的RC(电阻电容电路)吹弧线圈,同时结合灭弧室金属格栅设计,可以稳定燃弧电压。

[Objective]Arc extinction technology for DC(direct current)is one of the design challenges in urban rail transit traction power supply systems.Therefore,it is necessary to analyze the principles of DC opening and arc extinction for main DC fast circuit breakers.[Method]The principles of DC current interruption and arc extinction are introduced.The stable burning point and extinction conditions of DC current are discussed.Parameters for DC arc interruption are analyzed with an introduction to the arc extinction design principles of DC fast circuit breakers.Causes for the easy burning damage of DC fast circuit breakers in metro power supply systems are examined.[Result&Conclusion]To interrupt a DC arc,higher arc voltage than the power supply voltage is required,because increasing the arc voltage can extinguish the DC arc.The opening process of DC fast circuit breakers needs to consider both the arc burning time and system overvoltage factors.During the design and development of DC circuit breakers,attention should be paid to non-stable arc voltage and arc voltage for small current interruptions.During arc extinction,setting an additional RC(resistor-capacitor circuit)blowout coil during arc extinction,with the design of metal grids in the arc extinction chamber,can stabilize the arc voltage.