S.D. Hwang

EXPERIMENTAL STUDIES ON CRYOGENIC SYSTEM FOR 22.9 KV HTS CABLE SYTEM

In terms of high transmission capacity with lower voltage, a high temperature superconducting (HTS) cable system is a very attractive challenge for utilities. However, the concomitant cryogenic system for the HTS cable system is one of the tantalizing problems in the operation. The reliability and maintainability of cryogenic system are the key issues to apply it to the real electric power grid. Korea Electric Power Corporation (KEPCO) is making an attempt to verify the applicability of the HTS cable system to improve the efficiency of electric power industry. Since May 2006, a 22.9-kV, 50-MVA, 3-phase, 100-m class HTS cable system with an open cooling system has been operated at the KEPCO Gochang test yard. Concurrently, another HTS cable verification test with the same electrical specification and an hybrid cooling system has been carried out by LS Cable (LSC) Ltd in close proximity to the KEPCOs HTS cable system within Gochang test yard. KEPCO conducts the operation of the open cooling system, and is ...

THE RESULTS OF COOLING TEST ON HTS POWER CABLE OF KEPCO

Due to the inherent characteristics of the superconductivity that allows large power transmission capability, much research on high-temperature superconducting (HTS) power cables has been carried out world-wide. KEPCO (Korea Electric Power Corporation) had installed a three-phase, 100-m class, HTS cable system at Gochang power test center of KEPCO that handles 22.9 kV, 1250 A, 50 MVA. The HTS cable system of KEPCO consists of two terminations, the HTS power cable, and cooling system. Sub-cooled liquid nitrogen is used for the HTS power cable coolant, providing an inlet temperature to the cable during operations from 66 K to 77 K. Circulation cooling tests at different temperatures were performed to investigate operating conditions, and heat losses under alternating-current (AC) load conditions were measured. The results of performance correlated with cooling test will be presented in this paper.

PERFORMANCE TEST OF COOLING SYSTEM FOR KEPCO HTS POWER CABLE

A cooling system for a 3-phase 100-m HTS power cable with 22.9kV/1.25kA was installed and tested at the KEPCOs Gochang power testing center in Korea. The system consists of a liquid nitrogen decompression cooing system with a cooling capacity of 3kW at 66K and a closed circulation system of subcooled liquid nitrogen. Several cooling performance tests of the cable system such as cooling capacity, heat load, AC loss and temperature stability, were performed at operating temperature of 66.4K. Thermal cycle test which is cool-down to liquid nitrogen temperature and warm-up to room temperature, was also performed to investigate thermal cycle influences. This paper describes the installed cooling system, temperature stability and heat load test results.

Experimental Investigation of Multilayer Insulation by Using Boil‐off Calorimetry

Thermal characteristics of multilayer insulation (MLI) were experimentally investigated by using boil‐off calorimetry. For cryogenic instrument applications such as a HTS power cable system, it is essential to design efficient thermal insulation system. It is well known that the thermal characteristics and heat transfer of MLI are greatly affected by various MLI parameters such as the number of layers and layer density. However, it is difficult to know the thermal characteristics of MLI correctly. The heat leak through MLI between room temperature and liquid nitrogen temperature was measured at various conditions using a cylindrical cryostat. The cryostat consists of two guard vessels located at both ends and a test vessel between them. The guard vessels are also filled with liquid nitrogen to prevent radiation heat leak through the ends of the cylindrical test vessel to measure the heat leak only through the MLI. In this paper, in order to investigate the effect of the wrapping method on the heat leak, w...

LONG TERM OPERATION OF COOLING SYSTEM FOR THE KEPCO HTS POWER CABLE

HTS power cable systems of to several hundred meters in length are presently being developed and evaluated for practical use in real power grids. Since 2006, a cooling system for the 3‐phase, 100‐m HTS power cable with 22.9 kV/1.25 kA has been installed and tested at the KEPCO’s Gochang power‐testing center. Performance reliability through several demonstration tests of over 9,000 hours was demonstrated. This paper mainly describes the cooling performance test results of the HTS power cable system obtained during the long‐term performance tests.

Field Test of 3 phase, 22.9kV, 100m HTS Cable System in KEPCO

Starting from investigation of feasibility and basic studies, KEPCO/KEPRI has carried an enterprising project for HTS cable system since 2002. The objectives of this project are to demonstrate HTS cable system and evaluate the feasibility in electricity utilitys view. The installation of 100m/3phase/22.9kV/50MVA HTS cable system is undergoing in KEPCOs test yard, located in Gochang, Korea. The HTS cable system consists of 100m long cable, two terminations and a cooling system. To simulate the actual cable installation, the 55m section of the 100m long cable was installed into an underground tunnel. Commissioning test is scheduled at the end of September, 2005 and followed by long term operation test. In this paper, the installation of HTS cable system and initial results of system operation will be summarized

Investigation of thermal insulation for HTS cable systems

Publisher Summary This chapter covers an investigation of thermal insulation for HTS cable systems. Heat leaks into LN2 vessel are measured using boil-off calorimetry and performances of MLI related to the number of layers, patterns, and layer density are studied. It is well known that the capability of HTS cable system in electric power transmission is increased as the temperature of the cable conductor is decreased. LN2 is used to cool down the cable conductor. Vacuum and MLI (Multi-Layer Insulation) is employed to minimize heat leak and keep low temperature. In all the experiment, surfaces of LN2 and vacuum vessel are cold and warm boundary, respectively. In the case without MLI, it takes about 7 hours until LN2 vessel becomes empty. The evaporating times for the cases with MLI are twice or more than without MLI. The flow rates are stabilized after 1–5 hours after filling LN2 vessel. In the case without MLI, difference in temperatures between Ptl and Pt3 exists.