Sub-Cooled Nitrogen Cryostat for 66 kV/750A Superconducting Fault Current Limiter Magnet

One of the items included in the Super-conductive AC Equipment (Super-ACE) project, being performed from 2000 to 2004, is a development of a 66 kV/750 A high-T c superconducting (HTS) fault current limiter (FCL) magnet. This research focuses on fundamental technical items essential for a 66 kV class fault current limiter, that is, high current capacity, high voltage insulation and sub-cooled nitrogen cooling. This paper describes the design of the magnet and the test results obtained so far. The magnet mainly consists of a vacuum vessel, a nitrogen bath, a pair of current leads, cryocoolers, and six sets of unit-coils wound with Bi2223 tapes. The rated current of each coil is about 125 A at 70 K, and so the total current capacity of the magnet is 750 A. The insulation voltage of the magnet is of the 66 kV class. By the end of FY2002, three sets of the unit coils were set connected in the cryostat and some evaluation tests were implemented as a milestone of the program. In the cooling down test, sub-cooled nitrogen of 65 K was obtained with homogenous temperature distribution in the cryogen. In the overvoltage test, no breakdowns were observed in the case of applying both ac voltage of 140 kV for one minute and lightning impulse voltage of 350 kV. Voltage-current characteristics of the coils were measured in sub-cooled nitrogen. The rated current of 375 A was successfully obtained for both direct and alternate current tests. All the targets constituting the milestone of the 66 kV/750 A magnet development were achieved. Index Terms-Bi2223, fault current limiter, high voltage, subcooled nitrogen.

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“…The design of the cryostat was described in detail in another paper [7]. This paper describes the essence of the design.…”

Section: Cryostat Designmentioning

confidence: 99%

Development of 66 kV/750 A High-<tex>$rm T_rm c$</tex>Superconducting Fault Current Limiter Magnet

Yazawa

Ootani

Shimizu

et al. 2004

IEEE Trans. Appl. Supercond.

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“…Equation (1) can be directly solved for the circumferential temperature distribution (4) from which the temperature difference between the warmest and coldest parts of the band is calculated as (5) Total heat removed to the cryocooler is calculated in terms of the temperature gradient at .…”

Section: Thermal Design Of Cooling Systemmentioning

confidence: 99%

“…Another significant benefit of using subcooled liquid nitrogen as a cooling medium is to suppress bubbles that may be generated from an internal or external heat load [7]. Since bubbles play a critical role in deteriorating the breaking voltage of liquid nitrogen, the subcooled state is essential for electrical insulation in high-voltage applications such as HTS transformers [2], [3], HTS fault current limiters [4], [5], or HTS cables [6]. The typical subcooled-liquid region for these HTS magnets is indicated on phase diagram of nitrogen in Fig.…”

Section: Introductionmentioning

confidence: 99%

A Compact Cryocooling System With Subcooled Liquid Nitrogen for Small HTS Magnets

Chang

Kim

Sim

et al. 2008

IEEE Trans. Appl. Supercond.

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A compact cryogenic cooling system is developed for small HTS magnets to be continuously refrigerated in subcooled liquid nitrogen at temperatures below 77 K by a cryocooler. This thermal design is particularly useful when electrical insulation and compactness are significant at the same time. HTS elements are immersed in a cylindrical liquid-nitrogen vessel, and a copper band is brazed around the exterior sidewall of the cylinder at vertical location just under the liquid level in order to achieve peripherally uniform cooling with a GM cryocooler. The vapor space above liquid nitrogen in the vessel provides a fully open room for current leads and mechanical supports to the magnets. Heat is removed from the HTS magnets by natural convection of subcooled liquid nitrogen to the cold sidewall. The key components are designed based on heat transfer analysis. A prototype is fabricated, and it is successfully demonstrated that the thermal load is effectively removed and temperature is spatially uniform.

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“…Since the heat leak through current leads is a major source of cooling load, an optimal design to minimize the cryogenic load [1]- [7] is important in the commercialization of HTS FCL. This study is part of our ongoing efforts in Korea toward a practical scale of the prototypes to be continuously refrigerated in subcooled liquid nitrogen by a cryocooler [8]- [10]. Fig.…”

Section: Introductionmentioning

confidence: 99%

Current-Lead Design for Cryocooled HTS Fault Current Limiters

Chang

Kim

et al. 2007

IEEE Trans. Appl. Supercond.

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A comprehensive design procedure is presented for the current leads in HTS fault current limiters continuously refrigerated by a cryocooler. Two specific aspects are focused here in addition to the standard lead-design. The first is an optimization with taking into account the heat conduction through electrical insulator needed for high-voltage applications. Through a rigorous analysis, it is verified that the standard design should be modified in order to minimize the overall heat leak. The second is the transient thermal behavior that may be caused by excessive current. A numerical analysis is performed to estimate the peak temperature after a short current-limiting period, including the effect of fins as enhanced local heat capacity. Some of the design details are demonstrated for the specifications of FCL's under development in Korean R&D Programs.

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Sub-Cooled Nitrogen Cryostat for 66 kV/750A Superconducting Fault Current Limiter Magnet

Cited by 12 publications

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Development of 66 kV/750 A High-<tex>$rm T_rm c$</tex>Superconducting Fault Current Limiter Magnet

Development of 66 kV/750 A High-<tex>$rm T_rm c$</tex>Superconducting Fault Current Limiter Magnet

A Compact Cryocooling System With Subcooled Liquid Nitrogen for Small HTS Magnets

Current-Lead Design for Cryocooled HTS Fault Current Limiters

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Sub-Cooled Nitrogen Cryostat for 66 kV/750A Superconducting Fault Current Limiter Magnet

Cited by 12 publications

References 0 publications

Development of 66 kV/750 A High-&lt;tex&gt;$rm T_rm c$&lt;/tex&gt;Superconducting Fault Current Limiter Magnet

Development of 66 kV/750 A High-&lt;tex&gt;$rm T_rm c$&lt;/tex&gt;Superconducting Fault Current Limiter Magnet

A Compact Cryocooling System With Subcooled Liquid Nitrogen for Small HTS Magnets

Current-Lead Design for Cryocooled HTS Fault Current Limiters

Contact Info

Product

Resources

About

Development of 66 kV/750 A High-<tex>$rm T_rm c$</tex>Superconducting Fault Current Limiter Magnet

Development of 66 kV/750 A High-<tex>$rm T_rm c$</tex>Superconducting Fault Current Limiter Magnet