Understanding the effects of condensation on electrical discharge phenomena in next generation more-electric and hybrid aircraft

交通部门的脱碳是国家和全球的一个主要优先事项。据估计，国内和国际航空部门占人类活动产生的全球二氧化碳排放量的2%。联合国国际民用航空组织成员国承诺抵消2020年后排放的任何增加，再加上提高燃油效率的努力，将刺激飞机重量的减轻，超过已经通过采用复合机身材料实现的重量减轻。电动飞机概念允许通过传统的机械和液压飞机子系统的电气化来实现更高的系统效率。它也可以被认为是实现商用混合动力和全电动飞机的垫脚石。这两种类型的飞机将配备更多样化和安全关键的子系统，基于高密度电力电子转换器和超过1000伏的系统额定值。电缆绝缘体、连接器和其它设备所经受的增加的应力，与飞行中所经受的极端和动态环境条件相结合，提出了许多技术挑战。电力系统的提升要求飞行器设计工程师控制在飞行器的正常操作状态内将出现的静电现象，在评估这种系统的性能时，必须考虑到许多因素：-开关直流的使用增加及其对绝缘应力的影响。系统电压的增加及其对暂时性过电压事件的频率和严重程度的影响。海拔和大气条件（温度、压力和湿度）的变化以及其他影响，例如电缆绝缘上的冷凝和冰晶的形成。- 雷击引起的间接效应。迄今为止，很少有关于上升和下降过程中动态大气效应或短期系统和大气引起的过电压的影响的出版物。对中压直流系统中这些参数的基本理解对于机载配电的电气化至关重要，并重新强调绝缘协调和局部放电的缓解。以下未知数已被确定为机载电气系统升级的科学理解的局限性：-规定最小导体隔离的Paschen的有效性。稳态大气校正因子的有效性。冷凝对静电放电现象的影响。局部放电起始对外加电压波形的依赖性。本研究项目提出量化大气条件对多电和全电飞机局部放电阈值的影响。将建立一个专门的试验设施，以复制飞机系统在使用中所经受的动态大气条件。将进行模拟以确定适当的测试条件，然后将其应用于标准测试样品，以研究局部放电活动的机制和阈值，特别关注冷凝和结冰的影响。研究结果将被用来通知一组校正因子，系统设计人员可能会使用在未来的机载电气系统的鲁棒设计。

Decarbonisation of the transport sector is a major priority, both nationally and globally. It is estimated that the domestic and international aviation sectors constitute 2% of the global CO2 emissions arising from human activity. The member states of the UN International Civil Aviation Organisation are committed to offset any increases in emissions beyond 2020 which, combined with the drive for increasing fuel efficiency, will stimulate aircraft weight reduction beyond that already achieved through the adoption of composite airframe materials.The more-electric aircraft concept permits higher system efficiencies to be realised through electrification of traditional mechanical and hydraulic aircraft subsystems. It can also be considered a stepping stone to realising a commercial hybrid and all-electric aircraft. Both types of aircraft will be equipped with more diverse and safety-critical subsystems, based on high density power electronic converters and system ratings in excess of 1000 Volts. The increased stress experienced by cable insulation, connectors and other equipment, combined with extreme and dynamic environmental conditions experienced in flight, presents a number of technical challenges.The uprating of electrical power systems requires the aircraft design engineer to control for electrostatic phenomena which will arise within the normal operating regime of the aircraft, and there are a number of factors that must be taken into account when assessing the performance of such systems:- The increased use of switched dc and its influence on insulation stress.- The increase in the system voltage, and its effect on the frequency and severity of temporary over-voltage events.- Changes in altitude and atmospheric conditions (temperature, pressure and humidity) and other effects such as the formation of condensation and ice crystals on cable insulation. - Indirect effects induced by lightning strikes.There is to date very little published work concerned with dynamic atmospheric effects during ascent and descent, or the implications of short term system- and atmospherically-induced over voltages. A fundamental understanding of these parameters in medium-voltage dc systems is critical to the increasing electrification of airborne power distribution, and places renewed emphasis on insulation coordination and the mitigation of partial discharges. The following unknowns have been identified as limitations of the scientific understanding in the up-rating of airborne electrical systems:- Validity of the Paschen for specifying minimum conductor segregation.- Validity of steady-state atmospheric correction factors.- Influence of condensation on electrostatic discharge phenomena.- Dependence of partial discharge inception on the applied voltage wave shape.This research project proposes to quantify the effect of atmospheric conditions on the partial discharge thresholds on the more- and all-electric aircraft. A purpose-built test facility will be established to replicate the dynamic atmospheric conditions to which aircraft systems are subjected in service. Simulations will be performed to determine the appropriate test conditions, which will then be applied to standard test samples to study the mechanisms and thresholds of partial discharge activity, with particular focus on the influence of condensation and icing. The findings will be used to inform a set of correction factors that system designers may use in the robust design of future airborne electrical systems.