高温超导电缆实时监测系统及试验

介绍了用于10米长10．5kV／1．5kA三相交流高温超导电缆的实时监测系统。该系统采用NI分布式测量模块和数字电压表,通过计算机采集数据,能够在高温超导电缆的预冷和长时间通电运行时实时监测超导电缆中超导体的温度和循环冷却液氮的压力,能够监测超导电缆的通电电流和超导体上的电压,可以完成交流损耗试验。测量结果为研究高温超导电缆性能与相关参数变化的关系、研究高温超导电缆运行的最优条件奠定了一定的基础。     

最佳过冷量控制算法在深冷处理设备中的应用

提出了深冷处理过程中的"过冷量"概念,介绍了最佳过冷量的获取方法,为某型号深冷箱建立了冷量控制模型,并设计了基于最佳过冷量控制算法的深冷处理控制系统.该系统的控制输出环节更加合理且能有效提高低温氮气与被处理材料之间的换热效率,大大降低了液氮消耗量,节约了深冷处理工艺成本.     

使用吸附式制冷机实现大型低温系统氦压缩机节能的研究

采用喷油氦螺杆压缩机高压级润滑油废热驱动硅胶一水吸附式制冷机制取冷量.同时利用液氮槽排出的低温氮气冷却高压级压缩机吸、排气的方法可以显著降低压缩机的功耗.以EAST超导托卡马克可控核聚变装置低温系统为例,理论计算证明润滑油的废热完全可以驱动吸附式制冷机正常工作;采用吸附式制冷机+低温氮气冷却吸、排气后氦压缩机能耗可以减少9.7%.     

10米10.5 kV/1.5 kA三相交流高温超导电缆液氮冷却系统的设计

液氮冷却系统是10米10.5kV/1.5kA三相交流高温超导电缆实验装置中的一个主要分系统.介绍了液氮冷却系统设计方案的选择,提供了液氮冷却系统的主要设计计算内容,并通过与高温超导电缆联机试验,表明了该液氮冷却系统的设计是成功的,为75米三相交流高温超导电缆研制提供稳定可靠冷源奠定了基础.     

基于减压降温原理的过冷液氮冷却系统研制

随着超导技术的迅速发展,为超导材料提供低温环境的制冷系统得到了越来越多的关注。本文详细介绍了一种基于减压降温原理的高温超导电机过冷氮冷却系统,包括技术指标及相关要求、总体结构、关键技术、热负荷分析与计算等。系统采用减压降温获得过冷液氮,冷却电机中超导线圈。液氮进口温度68K,出口温度72K。主要由供液杜瓦、过冷箱、抽空泵、超导线圈杜瓦、返液杜瓦、低温管路及温度仪表组成。试验证明,该冷却系统设计合理、操作方便,成功实现了超导电机的加载运行。     

高温超导电缆低温系统数据实时监控

介绍自行研制的高温超导电缆低温系统的实时监控系统.该系统包括温度测量、压力测量、流量测量、液位测量4部分.该系统基于计算机和MCGS组态软件,具有操作简便、运行可靠、采集高效精确等优点,并通过与高温超导电缆的通电实验.结果表明,这套数据实时监控系统能满足高温超导电缆低温系统的各项参数的测量要求.该监控系统的成功研制,为类似的超导低温工程项目中数据的采集和控制提供了参考.     

ITER 10kA高温超导电流引线测试装置低温系统的研究

为ITER CC 10 kA高温超导电流引线服务的低温性能测试装置已研制完成,并成功运行。其低温系统主要由500W/4.5 K氦制冷机,真空杜瓦,低温组件(低温阀门,过冷槽,管道加热器,热防护层),汽化器及低温传输管线等部分组成。本文对真空杜瓦和过冷槽进行设计,并讨论该低温系统的冷却流程方案,最后通过电流引线10 kA稳态实验结果对低温系统的运行效果进行分析,结果表明该低温系统运行稳定,能满足ITER CC电流引线的测试需要。     

用于HEPS-TF低温波荡器的过冷液氮循环系统

在高能同步辐射光源验证装置(HEPS-TF)的插入件系统中,将要研制一台基于镨铁硼永磁铁的低温波荡器(CPMU)。低温波荡器要求磁铁磁极阵列工作温度要在85 K以下,同时整个大梁轴向的温度梯度不超过1.5 K/m。经过理论计算,低温波荡器在有束流情况下的热负荷约660 W@80 K。为冷却低温波荡器大梁磁结构,设计了一套过冷液氮闭循环迫流冷却系统。为了确保磁铁有更好的低温效果和温度均匀性,低温波荡器内大梁采用了双通道冷却设计。最后,根据低温流程设计了可行的机械结构,称其为液氮过冷器冷箱。     

稳态强磁场实验装置低温系统360 W/4.5 K制冷循环热力学分析和优化计算

稳态强磁场实验装置的超导线圈采用4.5 K超临界氦进行冷却,制冷模式下,制冷机的设计容量为360 W/4.5 K.首先对氦制冷循环进行了热力学分析,然后以压缩机氦流量为优化对象,结合低温系统的工程要求,选取合适的参数,对制冷循环进行了优化计算.计算结果显示:液氮消耗量为28.50 L/h,压机消耗功率约102 kW,系统的制冷系数为0.003 5.     

自然冷却/蒸气压缩复合制冷系统研究

本文研发了一种由蒸气压缩制冷和分离式热管集成的自然冷却/蒸气压缩复合制冷空调系统,分别采用第一工质和由液泵驱动的第二工质进行循环。该系统具有蒸汽压缩制冷、复合制冷和自然冷却3种运行模式,高温季节压缩制冷提供全部冷量,过渡季节压缩制冷补充自然冷却不足的制冷量,低温季节自然冷却提供全部冷量。同时,研制了复合制冷系统样机HKF-200FH,其压缩制冷回路由3个独立的制冷单元并联,并与热管环路通过壳管式蒸发冷凝器相连。蒸发冷凝器的管程作为压缩制冷回路的蒸发器,在压缩制冷模式和复合制冷模式下为通过壳程的第二工质提供冷量。对样机性能进行了实验测试,结果显示：随着室外温度降低,复合系统的制冷量变化较小,能效比EER逐渐升高;压缩制冷模式（环境温度35 ℃）和自然冷却模式（环境温度10 ℃）下机组的制冷量分别为197.38 kW和196.89 kW,EER分别为3.5和15.3。2台系统样机自2014年5月在北京某“EB级云存储实验室”空调示范工程安全可靠的运行至今,监测结果显示,相比传统压缩制冷系统年节能率约为45%,节能优势显著。     

The application of the cryogenic system on the HTS power cable circuit in actual grid

The 22.9 kV/50 MVA AC HTS power cable system consisted of power cable with 410 m length and cryogenic system has been manufactured by LS Cable & System and installed in Icheon substation of KEPCO grid in the end of 2010. High temperature superconductor only appears the superconductivity at the constant temperate range. So in order to maintain the superconductivity, the cryogenic system is needed. The cryogenic system, the open-loop type, is consisted of the Pressure Control System (PCS), Gas/liquid separator, Circulation Pump, Decompression unit, Filter and so on. Decompression unit is a device that keeps the sub-cooled nitrogen by way of the latent heat of evaporation and includes the heat exchanger. The effectiveness-NTU method is used for the design of the heat exchanger. After installation of the cryogenic system on the site, the test of the cooling capacity of the cryogenic system and commissioning tests were performed. During the grid operation of the HTS power cable system, no major problems have been encountered to this point. The cryogenic system has been operated sufficiently to maintain a stable of the HTS power cable system. This paper will summarize the design of the cryogenic system and the results of the grid operation.     

Cryogenic system with the sub-cooled liquid nitrogen for cooling HTS power cable

A 10 m long, three-phase AC high-temperature superconducting (HTS) power cable had been fabricated and tested in China August 2003. The sub-cooled liquid nitrogen (LN₂) was used to cool the HTS cable. The sub-cooled LN₂ circulation was built by means of a centrifugal pump through a heat exchanger in the sub-cooler, the three-phase HTS cable cryostats and a LN₂ gas-liquid separator. The LN₂ was cooled down to 65 K by means of decompressing, and the maximum cooling capacity was about 3.3 kW and the amount of consumed LN₂ was about 72 L/h at 1500 A. Cryogenic system design, test and some experimental results would be presented in this paper.     

A novel cooling scheme for superconducting power cables

Long distance transmission of electrical power with superconducting cables is likely necessary for energy conservation and effective utilization of renewable energy sources. The performance and cost of such superconducting lines is as significantly influenced by cryogenic issues as by superconductor performance. One significant cryogenic issue is that in the usual method of cooling using sub-cooled cryogen flow there is a limited cable length before the cryogen needs to be re-cooled. This adds complexity and cost to the cable system. Here we address this problem by utilizing the latent heat of the cryogen without the complication of multi-phase flow. The cryogen is distributed to the superconducting components by spraying it through small holes in a pressurized line. The pressurized liquid exiting the holes turns into mixed liquid and vapor with a temperature near the boiling point of the cryogen at the pressure of the space surrounding the superconducting components. The pressure in the space surrounding the superconducting components is then kept near atmospheric by maintaining short distances to a vent. The sprayed liquid accumulates but rapidly vaporizes in response to the heat load, providing even cooling power at a fixed temperature for the entire length of the line. Our work indicates that it may be possible to implement a cooling system with much simplified cryogenic stations at the cable ends and allowing cable lengths of up to 100 km with no intermediate cooling stations.     

Design of high efficiency mixed refrigerant Joule–Thomson refrigerator for cooling HTS cable

The substitution of high temperature superconducting (HTS) cables for existing subterranean electric transmission lines is arising as a solution to continuously increasing electricity demand in urban areas. A cryogenic refrigeration system having the characteristics of high reliability, high efficiency, large cooling capacity, and low capital cost is essential to enable such a substitution. These requirements can be satisfied with a mixed refrigerant Joule–Thomson (MR JT) refrigerator. Unfortunately, usual MR JT refrigerators exhibit good performance at refrigeration temperatures above 80 K. A precooled neon–nitrogen MR JT refrigerator is proposed in this paper that can cool HTS cables at 70 K. The coefficient of performance (COP) of the proposed MR JT refrigerator is predicted to be 0.058 at 70 K (19.2% for exergy efficiency) with the optimized design variables. The COP can be improved further to 0.064 by enhancing the efficiency of the precooling cycle. The maximum achievable COP demonstrates the feasibility of MR JT refrigerator for cooling HTS cable.     

Cold storage characteristics of mobile HTS magnet

A cold storage system specialized in mobile high-temperature superconducting (HTS) magnets (e.g. for magnetically levitated (maglev) vehicles) has been proposed. In this system, a cooling source is detachable and a HTS coil is capable of maintaining superconducting state with its heat capacity. This system allows a considerably lightweight HTS magnet.An apparatus was constructed to evaluate the possibility of using cold storage systems in maglev vehicles. The thermal characteristic of this apparatus was based on a magnet for previous maglev test vehicles [1]. The operational temperature range of the magnet was assumed from 20 K to 50 K. Some experiments indicated that heat conduction by residual gas was not negligible. Especially over 30 K, gas conduction took a large part of heat input. This phenomenon is attributable to reduction of cryopumping effect. However, activated carbon in the apparatus compensates cryopumping effect. A unique heat capacitor was also used to enhance the cold storage effect. Water ice was chosen as a heat capacitor because water ice has a higher heat capacity than metallic materials at cryogenic temperatures. A small amount of water ice also prolonged cryogenic temperature condition. These results indicate 1 day of cold storage is probable in a magnet for maglev vehicles.     

Investigation of helium injection cooling to liquid oxygen under pressurized condition

Sub-cooling of cryogenic propellant by helium injection is one of the most effective methods for suppressing bulk boiling and keeping sub-cooled liquid oxygen before rocket launch. Compared with the helium injection cooling under atmospheric condition, helium injection cooling under pressurized condition has advantage that it can greatly reduce re-warming time of the sub-cooled liquid oxygen. Helium injection cooling under pressurized condition is characterized by cooling of initially sub-cooled cryogenic liquid, which is significantly different from that of the atmospheric condition where liquid oxygen usually exists at saturated condition. In this paper, we discuss the characteristics of helium injection cooling under pressurized condition, with the associated physical understanding of the process. Experimental results are presented along the simulations of variously combined system parameters based on the finite heat transfer and instantaneous diffusion mass transfer model. A non-dimensional parameter for identifying the cooling regime is conceived. The critical values of the non-dimensional parameters and injected helium temperatures are also estimated.     

An evaluation method for small-scale conduction cooled SMES cryogenic cooling system based on thermal analysis

The current flowing through a SMES is subjected to variations at a rate ranging from 0.1 A/s to 300 A/s under the influence of the power grid. The duration of power exchange varies from milliseconds to minutes, even to hours. When operating, the impact of AC losses in HTS tapes on the cryogenic cooling system should be considered. If the cryogenic cooling system fails to take away the generated heat effectively, this may lead to the temperature rise of the magnet and its possible damage. Therefore, it is essential to evaluate the technical and economical characteristic of cryogenic cooling system. Thus, a 5 MJ SMES model is built to calculate the temperature characteristic. A new factor δ is defined to assess the technological and economical validity of the chosen cryogenic scheme. The suitable capacity of the cryogenic cooling system is evaluated for different applications. The effect of the operating temperature on the technical and economical factor is also discussed.     

Thermal anchoring of conduction-cooled current leads for superconductivity applications near liquid nitrogen temperature

As the YBa₂Cu₃O_7-δ, or YBCO, superconductor is commercially developed and utilized for various HTS (high temperature superconductor) applications such as motor, generator, and fault current limiter, the cryocooling for 50 or 60 K range is more demanded than ever. In this case, non-superconducting current leads instead of HTS ones need to be used for energization from room temperature all the way to the cryogenic operating temperature. This technical note describes a simple method of reducing cooling load requirement for those HTS applications. Non-superconducting current leads are to be thermally anchored at an appropriate intermediate cryogenic temperature before they are connected to the application target temperature. The optimum thermal-anchoring temperature and its configuration have been obtained to minimize the required cryocooler’s cooling capacity for practical as well as ideal cases.