【作者】 任丽；

【导师】 唐跃进；

【作者基本信息】 华中科技大学 ， 电工理论与新技术， 2008， 博士

【摘要】 超导电力技术可望为未来的电力系统带来革命性的技术突破,但超导电力技术要真正进入市场还存在诸多问题,其中,运行成本的降低和入网考核就是两个亟待解决的主要问题。在超导电力装置中,通过电流引线侵入低温环境的热损耗占整个低温系统损耗的绝大部分,为提高超导电力装置的效率,抑制电流引线的热侵入是一个非常重要的技术课题。同时,由于电力系统的重要性,超导电力装置入网前必须通过严格的性能测试,但目前国内外尚未建立一套完善的试验检测规程和方法,无法对超导电力装置是否具备入网条件进行科学的判断。因此,本文以超导电力装置电流引线的设计及装置的试验检测方法为中心展开了研究。在电流引线的设计方面,根据传热学理论,构建了一元引线和二元引线的热流模型,应用迭代法对模型低温端的热流进行了分析和仿真。在考虑电流引线的冷却方式、工作温区、工艺制作、经济成本及其所属超导装置的运行状态的前提下,提出了运动型小电流等级超导电力装置宜采用的引线形式和结构。结合引线的运行环境、绝缘水平和工艺特点,对300kVA高温超导变压器的电流引线进行了结构优化。针对电动车组超导变压器的空间限制,提出了延长引线路径的方法,有效解决了引线长度的延长与空间高度的限制之间的矛盾。分析了引线温升、热流与引线横截面积的关系,提出了超导装置电流引线的工程设计应先确定引线横截面积,再进行优化设计的原则。设计并制作了简易的引线漏热测量装置,对仿真结果进行了试验验证,试验结果与仿真计算基本吻合。通过引线预冷试验,探讨了引线绝缘层的覆盖方式和浇铸工艺,较好地完成了从引线优化,到实验验证,再到工艺实现的过渡。建立了制冷机直接冷却的高温超导磁储能系统二元引线的热流模型。为便于引线设计、制作和分开检测,提出了模块式引线构造,并分模块对引线进行了优化设计:对三种不同金属材料的最小漏热、价格和机械性能进行了分析和比较,确定了金属模块的材料,优化后的单根铜引线的漏热与Hull所计算的传导冷却形式的电流引线的漏热相当,比Wilson于1983年所得到漏热值略低;设计了引线的绝缘与导热结构,计算了中间连接部分的焦耳热和界面热阻引起的漏热;将理论计算与成本分析相结合,确定了高温超导模块的长度。分析了与引线共用一台制冷机的辐射屏的辐射漏热,在此基础上,得到了所需制冷机的冷量。通过磁体冷却、通额定电流、过载电流、不同升流速率通流和动模实验验证了引线的性能,并对实验结果进行了分析,讨论了改善引线室温端热流分布的措施。探讨了引线通流水平对其密封性能的影响。为验证激光切割后氮化铝垫片的适用性,对氮化铝垫片进行了激光打孔试验。将激光打孔后的垫片制成试样,在金相显微镜和电子扫描电镜下进行了形貌观察和成分分析。根据氮化铝的传热机理和激光打孔后孔周区域化学变化的分析,提出了激光打孔后,自孔向外延伸,将激光打孔对氮化铝热导率的影响分为三个区域的观点;阐述了激光打孔后孔周表面Al和Al2O3的析出及其分布状态与孔周绝缘水平的关系。在此基础上,给出了氮化铝激光打孔的适宜切割条件。在超导电力装置试验检测方法的研究方面,针对目前国内在超导电力装置性能检测方法研究方面的空白,从超导电力装置的电磁特性出发,对其试验内容和检测方法进行了研究,初步建立了超导电缆、超导限流器、超导变压器和超导磁储能系统的基本试验大纲和检测方法。更多还原

【Abstract】 The study of service test procedures and design of current leads for superconducting power devices are two important aspects in superconducting power technology. The standardization of service test procedures can help to promote the technical advantage and reliability of the superconducting power devices, and it is necessary to accelerate superconducting power manufactures to go on the market. Current leads are often the major heat link to the low-temperature level of cryogenic systems and cause the main part of the boil-off of the cryogenic liquids or the power consumption of the cryocoolers. Therefore, the standardization of the service test procedures and the design of the current leads are centered about in this paper.In the aspect of design of current leads, firstly, the conceptual models of heat load for all-metal current leads and hybrid current leads are conceived, respectively. Secondly, based on the finite element method and heat transfer theory, their low-temperature heat load is analyzed and simulated. Furthermore, considering the dynamic case motion and cooling system of the superconducting power devices, the suitable type of the current leads are brought forward. Thirdly, after the operating condition, insulation level and technics characteristics have been investigated, the current leads for 300kVA high temperature superconducting transformer are optimized. According to the room limitation of the electrical colomotive, a method of prolonging of the path for heat transfer is put forward. Then, a simple test set for heat leakage to liquid nitrogen is desiged and fabricated, and a series of experiments are carried out on measuring the gas flux respectively. The experimental results show a good accordance with the simulation, which show that the unitary helical current lead meets the requirements of design. In order to choose tectorial mode and moulding technics for insulating materials covered on the current leads, a cooling experiment is done in advance and a feasible scheme is determined. Lastly, the current leads are carried to completion.A heat transfoer model of the hybrid current lead for cryocooler conduction-cooled high temperature magnetic energe storage system (H-Tc SMES) is schemed to calculate the low-temperature heat load. The current lead consists of three modules. This kind of structure is used to facilitate its design, fabrication and test in division form. According to the requirements for different modules, the current lead is optilized. At first, the minimam heat leakage values for three different metal matirals are calculated and judged. After that, copper is choosed for the metal module. The optimum heat leakage value of a copper current lead is 41.7W/kA which is almost equal to that of 42W/kA of the conduction-cooled case calculated by Hull, but, it is slightly lower than that of 47W/kA obtained by Wilson in 1983. At second, a structure for electrical insulation and thermal conduction is designed, and, the thermal contact resistance and heat leakage of AlN undertaking the work for electrical insulation and thermal conduction. Furthermore, the radiant heat of H-Tc SMES is figured. Based on these above, the electric power consumption of the cryocooler for this case is obtained. Finally, the temperature profiles, such as lead temperature during cooling down, temperature variation of the lead during DC excitation, temperature variation of the lead during different current slopes, temperature of dynamic experiments, are shown and analysed.In order to know the serviceability of AlN after laser drilling, its insulating strength and thermal conductivity are studied. According to the infuences of laser drilling on the hole-surface of AlN in the thermal conductivity, a concept of three areas is put forward. The relationship among the contents of Al and Al2O3 on the surface of hole, their distributions and insulation level is illustrated. Then, the suitable laser cutting velocity is represented.In the aspect of design of the service test procedures for superconducting power devieds, based on the electromagnetic characteristic, the test items of superconducting magnetic energy storage systems, superconducting fault current limiters, superconducting cables and superconducting transformers are studied and generalized. This work fills a blank in power application on superconductivity in China.更多还原