电极分断速度对电感分断放电特性的影响分析与建模

Arc equivalent resistance modeling of inductor-disconnected-discharged arc considering electrode breaking speed

工作于爆炸性环境的电气电子设备在发生断路故障时,电感元件产生的电弧可能引燃易燃易爆气体,严重危及煤矿井下等危险性工作环境的人身及设备安全。电极分断速度v作为非电气参数,与电感L、分断初始电流I0等电气参数一样会对电弧放电特性产生影响。在IEC安全火花试验规程中规定电极以恒定速度(25 cm/s)分离,而实际工况下故障点分断速度是随机的,因此即使符合IEC安全火花试验规程的本质安全电路在特定分断速度下也有可能引燃爆炸性气体。通过IEC安全火花试验装置对电感电路分断放电进行试验研究,发现电弧放电时间T L随电极分断速度v的增加近似呈指数规律减小,最终趋于稳定值,并随电感L和分断初始电流I0增加而增长;初始电弧电阻Rarc0随分断初始电流I 0增大而减小;电极分断速度v主要影响电弧电阻Rarc的增长速度,而电感L对电弧电阻Rarc的变化趋势没有明显影响。根据电弧功率的变化趋势,将其分为上升、稳定、衰减3个阶段。在上升阶段中,最大电弧功率Parcmax随分断初始电流I0增大而增大;稳定阶段中,电感L越大,电弧功率Parc的减小速度越慢;电极分断速度v的增大加快电弧功率从稳定阶段向衰减阶段的转化。基于函数回归分析和线性叠加定理建立电极分断速度v与电弧放电时间TL的关系表达式。考虑电极分断速度,提出了一种电弧等效电阻模型,通过莱文贝格-马夸特优化算法确定模型特征参数,推导出电弧电压、电流、功率及能量的关系表达式,仿真分析及试验结果证明了理论分析及所提出的电弧等效电阻模型的可行性及准确性;理论计算和试验表明电弧功率Parc和电弧能量Warc均随电极分断速度v的增大而减小,即电极分断速度v的增大有助于减小电路故障时的电弧能量。

When an open circuit fault occurs in electrical and electronic equipment working in an explosive environment,the arc generated by the inductor may ignite flammable and explosive gases,which seriously endangers the safety of personal and equipment in hazardous environments such as underground coal mines.As a non-electrical parameter,the electrode breaking velocity v has the same effect on the arc discharge characteristics as the electrical parameters such as the inductance L and the initial breaking current I 0.The IEC safety spark test procedure requires that electrodes should be separated at a constant speed of 25 cm/s,while the actual breaking speed of the fault point is random.Therefore,even the intrinsically safe circuit conforming to the IEC safety spark test procedure may ignite explosive gas at specific breaking speed.Based on IEC safety spark test apparatus(SSTA),the inductor-disconnected-discharged(IDD)arc was studied.It was found that the arc discharge time T decreases exponentially with the increase of the electrode breaking speed v and tends to be stable.However,T increases with the increase of inductance L and the initial breaking current I0.The initial arc resistance Rarc0 decreases as the breaking initial current I0 increases;the electrode breaking speed v mainly affects the growth rate of the arc resistance R arc;the inductance L has no significant influence on the variation trend of the arc resistance R arc.According to the tendency of arc power,it was divided into three stages:arcing,stable and declining stage.In the arcing stage,the maximum arc power Parcmax increases with the increase of the breaking initial current I0;in the stable stage,the larger the inductance L is,the slower the decreasing trend of arc power P arc will be;the increase of the electrode breaking speed v accelerates the conversion of Parc from the stable stage to the declining stage.Based on the function regression analysis and the linear superposition theorem,the relationship between the electrode breaking speed v and the arc discharge time T was established.Considering the electrode breaking speed v,an arc equivalent resistance model was proposed.The model parameters were determined by the Levinberg-Marquart optimization algorithm,and the expressions of arc voltage,current,power,and energy were derived respectively.Simulation and experimental results show that the theoretical analysis and the proposed arc equivalent resistance model are valid and feasible.Theoretical calculations and experiments show that the arc power Parc and the arc energy Warc both decrease with the increase of the electrode breaking speed v.That is,an increase in the electrode breaking speed v is helpful to reduce the arc energy during circuit fault.