J.W. Cho

3 MJ/750 kVA SMES System for Improving Power Quality

The purpose of this study is to develop a superconducting magnet energy storage system (SMES), which protects sensitive loads on the power system, when an interruption or voltage sag occurs. Industries have many sensitive machines, and keeping the power in a good condition is very important for nonmilitary machines also. Korea Electrotechnology Research Institute (KERI) has developed a 3 MJ/750 kVA SMES system to improve power quality in sensitive electric loads. It consists of an IGBT based power converter, NbTi mixed matrix Rutherford cable superconducting magnet, and a cryostat with HTS current leads. The operating current of the 3 MJ SMES magnet was 1000 A. The SMES system is tested under short time power interrupt to verify the feasibility of the SMES system as a 750 kVA power converter

Development and testing of 30 m HTS power transmission cable

To obtain realistic data on HTS power cable, single-phase 30 m long, 22.9 kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LG cable Ltd. that is one of 21st century frontier project in Korea. The HTS cable consists of Ag/Bi-2223 tapes, high voltage insulation paper which is impregnated by LN/sub 2/. The cable is rated at 22.9 kV, 50 MVA, 60 Hz and is cooled with pressured liquid nitrogen at temperature from 70 to 80 K. This paper describes the results of design, fabrication and evaluation of the single-phase, 30 m HTS power cable system.

The Electrical Insulation Characteristics for a HTS Cable Termination

A research on several characteristics such as volume breakdown and surface discharge of insulators for a termination of power transmission class high temperature superconducting (HTS) cable was performed. In this paper, we investigated the surface discharge of glass fiber reinforced plastic (GFRP) in the air, nitrogen gas (GN2) and cryogenic nitrogen gas (CGN2) media. The breakdown characteristics of these media were also studied. Experimental results revealed that flashover voltage greatly depends on pressure, temperature, the kinds of insulating media and voltages. However, it is shallowly affected by shape and material of electrode. The breakdown voltage of liquid nitrogen (LN2), GN2 and CGN2 deeply depends on the shape and dimension of electrode, kinds of voltages and pressure. Moreover, the breakdown voltage of CGN 2 and flashover voltage of GFRP in the CGN2 is also influenced by temperature and vapor-mist density of the gas

Development of the 22.9-kV class HTS power cable in LG cable

Since 2001, LG Cable has been developing the HTS cable system as a member of national DAPAS project. In 2003, 30 m long cold dielectric HTS cable with 22.9 kV, 1260 A/sub rms/ with single core was fabricated to validate the design concept and long-term performance for 4 months. In this year, 30 m long cable with 3 cores in 1 cryostat has been fabricated and installed to conduct long-term reliability test. At this time, the evaluation of basic properties has been completed and long-term test is in progress. Also, a termination to connect with other conventional power equipment and a cryogenic refrigeration system has been developed concurrently. This paper describes the design, fabrication, and evaluation processes of these two cable systems and gives a chance to take the interim examination of this project through the analysis of test results. In next stage, LG cable plant to develop a splice for a long length cable, a cooling system with high efficiency and capacity, and 154 kV HTS cable system.

Research on the Insulation Design of a 154 kV Class HTS Power Cable and Termination

A 154 kV class high-temperature superconducting (HTS) power cable system Is developing in Korea. For insulation design of this cable, the grading method of insulating paper is proposed. The electrical insulation material has been used two kind of laminated polypropylene paper (LPP) that has different thickness. The use of graded insulation gives improved mechanical bending properties of the cable. Also, within a HTS cable technology the terminations are important components. A HTS cable termination is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors, in the axial direction there is a temperature difference from ambient to about 77 K. For insulation design of this termination, the insulation material of the termination body used glass fiber reinforced plastic (GFRP) and the capacitance-graded method is proposed. Therefore, in order to insulating design of a 154 kV class HTS power cable and termination, this paper will report on the experimental investigations in impulse breakdown and surface flashover characteristics of the insulation materials. Based on these experimental data, the electrical insulation design of a 154 kV class HTS power cable and termination were calculated.

Design and Experimental Results of a 3 Phase 30 m HTS Power Cable

HTS power cables appear to be the replacement and retrofitting of underground cable in urban areas and HTS power cable offers a number of technical and economic merits compared to normal conductor cable system. A 3 phase 22.9 kV, 50 MVA class HTS power cable system have been developed by Korea Electrotechnology Research Institute (KERI), LS Cable Ltd. and Korea Institute of Machinery and Materials (KIMM) that is one of 21st century frontier project in Korea. The 30 m long cable with 3 cores in 1 cryostat has been manufactured and installed to conduct long-term reliability test. The HTS power cable consists of two layers of phase conductor and two layers of shield used Ag/Bi-2223 tapes and polypropylene laminated paper is used in LN2 as electrical insulation. A HTS power cable has been tested with DC and rated current and voltage in pressurized liquid nitrogen. The evaluation results clarify good performance of HTS cable and these results prove that the HTS power cable has the basic electrical properties for 22.9 kV HTS power cable. This paper describes the results of developmental the 30 m, 3 phase, 22.9 kV, 50 MVA HTS power cable in Korea

A design and tests of HTS power cables and feasibility study of HTS power transmission system in Korea

In this paper we present the results of tests for high-T/sub c/ superconducting (HTS) power cables and the analysis of an HTS power transmission system in Korea. Prototype HTS cables have been constructed using Bi-2223 based Ag-sheathed HTS tapes. The prototype cable has been tested at 77 K with DC currents. Results shows that the cable carried up to 730 A DC and the authors analyzed the feasibility of a HTS power transmission system in the Seoul area in Korea. According to the analysis results, the HTS power system can be reduced by 5.2%/spl sim/9.7% of the underground transmission lines compared to the conventional cable system in Seoul, Korea and the HTS power cable is feasible in future power systems.

Critical Current, Critical Temperature and Magnetic Field Based EMTDC Model Component for HTS Power Cable

Before applying the high temperature superconducting (HTS) power cable to real utility network, system analysis should be performed using simulation tools. For the practical use of HTS devices in electrical power system, prior simulation analysis is very important. PSCAD/EMTDC simulation is one of the most popular and useful analysis tools for electrical power system. Unfortunately the model component for HTS power cable is not provided in the PSCAD/EMTDC simulation tool. In this paper, EMTDC model component for HTS power cable has been developed considering critical current, critical temperature, magnetic field, and recovery time constant which depend on the sorts of HTS wire. The numerical model of HTS power cable in the PSCAD/EMTDC was designed by using the real experimental data obtained from a real HTS 1G wire test. The utility application analysis of HTS power cable was also performed using the model component developed. The component for HTS power cable could be variously used when the power system includes HTS power cable, especially it will be readily analyzed by the PSCAD/EMTDC in order to obtain the data for the level of fault current, power flow, and power losses, and so on.

Investigation on the Thermal Behavior of HTS Power Cable Under Fault Current

During the operation of HTS power cable, large fault current can be introduced to a HTS power cable due to several accidents. In this case, a circuit breaker limits the fault current to protect the HTS power cable just as conventional power cables. However, heat is necessarily generated until the circuit breaker operates and severe performance degradation or even burn-out can occur at HTS tapes. To ensure the safety against the fault current, thermal characteristic of the HTS power cable should be verified under the fault current. Several experiments with a simple cable are performed using an AC pulse power supply. During the experiment, the increase of temperature and current redistribution are measured for the various fault current conditions. Through the experiments, safety margin of Korean HTS power cable is verified and the allowable peak current is suggested

Electrical Insulation Design and Experimental Results of a High-Temperature Superconducting Cable

A 22.9 kV/50 MVA class high-temperature superconducting (HTS) power cable system was developed in Korea. For the optimization of electrical insulation design for HTS cable, it is necessary to investigate the ac and impulse breakdown and partial discharge inception stress of the liquid nitrogen (LN2)/ laminated polypropylene paper (LPP) composite insulation system. These results were used to insulation design of the model cable for a 22.9 kV class HTS power cable and the model cable was manufactured. The insulation test of the manufactured model cable was evaluated in various conditions and was satisfied standard technical specification in Korea. Based on these experimental data, the single-phase and three-phase HTS cable of a prototype were manufactured and verified.