基于高频振荡横向磁场的直流真空电弧模式演变及开断机理研究

Recently, DC electric system is in rapidly development, such as in the wind power generation, solar micro grid and the electric vehicle. The DC switchgears, as the key equipments for the safety and protection of the DC power systems, are expected to meet the rapid growth and the various demands of the DC systems applications. The application of vacuum switch in the DC power grid will greatly meet for the demands of DC switch, including the high electrical life, the airtight arc environment, the small volume and the low cost. The vacuum switches once were considered as the AC switch in essence, with the typical value of the vacuum arc voltage of 20 to 200 V. However, the previous experimental results of the applicant indicate that the DC current can be interrupted successfully by vacuum arcs under high-frequency oscillating transverse magnetic field, with the value of the vacuum arc voltage over than several kV, which should be the great opportunity for the DC vacuum contactors. Thus, it is greatly significant to realize the interrupting mechanism of the DC interruption in vacuum. The objective of this project is to determine the interrupting mechanism of the DC vacuum arcs under the high-frequency oscillating transverse magnetic fields. Firstly, the DC vacuum arcs characteristics will be investigated experimentally, which should be helpful to understand the evolutionary pattern of the vacuum arcs in the DC interrupting process. Secondly, the influence factors of the DC interruption in vacuum will be researched. Finally, based on the experimental researches, the mechanism of DC interruption in vacuum should be provided. This experimental investigation will increase the capacity of the DC successful interruption in vacuum and promote the application of vacuum breaker in DC circuit.

直流系统在通信、微电网和交通运输等行业的广泛应用和快速发展，对直流开关设备提出了更高要求。真空开关具有高电气寿命、密闭燃弧环境、小体积、低成本等优点，但其较低的电弧电压(20-200V)限制了真空开断在直流系统的应用。申请人前期研究结果表明，高频振荡横向磁场作用下直流真空电弧电压将大幅提升至数kV级，使得真空直流开断成为可能，但是，尚不清楚直流真空电弧的开断机理。本项目的研究目标是揭示高频振荡横向磁场作用下直流真空电弧的开断机理。本课题拟研究高频振荡横向磁场作用下直流真空电弧的燃弧特性，建立直流真空电弧模式的演变规律；研究不同横向磁场和触头结构参数对电弧电压的影响规律，明确直流真空电弧电压的提升机制；研究真空直流开断中电弧模式演变和电压的临界条件，建立基于高频振荡横向磁场作用的真空电弧直流开断物理模型，揭示直流真空电弧的开断机理。通过以上关键问题的突破，将推动新型直流真空开断技术的发展。

随着新能源规模的扩大和微电网的发展，直流系统在配电侧的占比逐渐提高。直流开断技术是多端直流电网结网的技术基础和前提，也是维系低压配网运行的重要保障。真空开关具有免维护、高参数、长寿命、高可靠性的优势，但由于真空电弧电压水平低，限制了真空开关在直流开断的应用。外施横向磁场对真空电弧的控制，可使真空电弧失稳并产生高的电弧电压，但其失稳机理尚不清晰，且关键参数如磁场强度、开距对真空直流开断的影响仍然停留在定性阶段。本项目深入研究了高频振荡横向磁场作用下直流真空电弧的燃弧特性，以此进一步揭示高频振荡横向磁场作用下直流真空电弧的开断机理。本项目建立了外施横向磁场直流真空电弧实验平台，研究了外施横向磁场作用下的直流真空电弧特性，对比研究了恒稳横向磁场、振荡横向磁场、旋转横向磁场对于直流真空电弧的作用规律。获得了横向磁场磁感应强度、触头直径、振荡频率对直流真空电弧燃弧和开断特性的影响规律，包括直流真空电弧在不同燃弧阶段的电弧特性、横向磁场施加后电弧由稳态向非稳态转变过程中的阴极斑点集聚、逆安培力方向运动、弧柱拉伸、电弧电压振荡、开断过程直流真空电弧发展物理模型等。对直流开断中真空电弧的影响因素的研究表明，随着横向磁场强度的增加，将提高阴极斑点团簇的运动速度，降低开断时间，有利于提高真空直流开断容量；随着磁场频率的增加，直流真空电弧的特性越来越有利于成功开断；分闸速度的增加降低了脉振横向磁场作用下直流真空电弧的开断时间，提高了阴极斑点移动速度；触头直径将降低阴极斑点的速度，增加阴极斑点的运动时间，对直流真空电弧的开断不利。项目设计并建立了快速斥力机构实验平台，研究了真空直流开断中电弧模式演变，获得了直流真空开断的临界燃弧开距；建立了基于高频振荡横向磁场作用下的直流开断真空电弧物理模型，提出了非稳态真空电弧是横磁作用下真空直流开断的必要非充分条件。本项目的研究对于揭示直流真空电弧的开断机理，推动新型直流真空开断技术的发展,具有重要的意义。