Joon-Han Bae

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.

Performance Analysis of a Toroid-Type HTS SMES Adopted for Frequency Stabilization

Superconducting magnetic energy storage (SMES) can overcome fluctuations in frequency because of its fast response time in charging and discharging energy. To stabilize the fluctuations in frequency of wind power generation systems (WPGSs), HTS SMES systems should be connected to the terminal of the WPGSs. Ulleung Islands power network in Korea was modeled with a real-time digital simulator (RTDS) to demonstrate the effectiveness of SMES at stabilizing frequency. A toroid-type HTS SMES cooled by conduction cooling and a DC/DC chopper to charge and discharge current were fabricated for the experiment. The simulation results show the frequency stabilization effected by the HTS SMES system with its operational characteristics such as real time variation in current and temperature.

Conceptual Design of HTS Magnet for a 5 MJ Class SMES

Superconducting magnetic energy storage (SMES) systems with High Temperature Superconducting (HTS) wires have been actively developed world-wide. A 600 kJ class SMES with Bi-2223 HTS wire has been in development as a national project since 2004 and is currently approaching the final testing stage of the first of three phases. In the second phase of the project, several MJ class HTS SMES will be developed. In this paper, designs of magnets for 5 MJ class SMES with DI-BSSCO and YBCO coated conductor are presented and compared.

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

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

Fabrication and test of a 3MJ SMES magnet

For quite a long time many research and developments of superconducting magnetic energy storage (SMES) system have been doing for the enhancement of power quality control of a sensitive electric load. Korea Electrotechnology Research Institute (KERI) has developed a 3MJ, 750 kVA SMES system to improve power quality in sensitive electric loads. This paper describes the design, fabrication and experimental results for the 3MJ SMES magnet made by using the design code of a SMES device that we developed. A computer code was developed to find the parameters of the SMES magnet, which has a minimum amount of superconductor for the same stored energy. And the 3MJ SMES magnet was designed based upon those. In addition, the 3MJ SMES magnet that was ramp up to 1kA without quench.

Design of HTS Transmission Cable With Cu Stabilizer

More than three HTS cable development and installation projects are proceeded over the world. A 22.9 kV/50 MVA class HTS cable system has been developed in Korea during last 3 years. And the HTS cable system for commercialization will be developed and installed on the real or test power grid within 2 years. Every HTS cable system has to satisfy the fault-current specifications of the power grid in order to protect the cable itself from the fault current. HTS cable composed of HTS tapes has some capacity of enduring the fault current by bypassing the fault-current through its Ag-sheath. But it may not be enough. So, some Cu stabilizer is generally introduced inside the conductor layers and outside the shield layers of HTS cable core for some higher fault current grade. In this paper, the design method of HTS cable with Cu stabilizer will be introduced. And the fault current capacity of HTS cable and its eddy current loss generated from the stabilizer will be calculated. And the impedance change of HTS cable in the fault current state will be calculated

Analysis of Eddy Current Losses and Magnetization Losses in Toroidal Magnets for a 2.5 MJ HTS SMES

A SMES magnet can be operating in three different modes: charging, storing, and discharging. The eddy current losses and magnetization losses are generated during charging and discharging in the SMES system. The eddy current losses per cycle are generated mainly during discharging period because the discharging period is generally shorter that for charging. Magnetization losses per cycle are generated mainly during the charging. In this paper, we investigated a decrease in eddy current losses according to the shapes of conduction cooling plates. The cooling plate having small eddy current losses was designed by dividing and slitting. Also, the magnetization losses in the toroidal coil constructed with many pancake coils were analyzed using 3-D finite element method during the initial charging period and some discharging periods in an operating scenario for the 2.5 MJ SMES.

Fabrication and Characteristics of 2G HTS Current Leads

2nd generation high temperature superconducting (2G-HTS) tape consists of multi-layers such substrate, buffer layer, superconducting layer and reinforced lamination tapes. 2G HTS tape is a candidate of good materials for current lead of superconducting magnet system owing to its low thermal conductivity. However, joint resistance between 2G HTS tapes and terminal block can be a major problem because of high electrical resistivity of substrate, buffer layer and reinforced lamination tapes of 2G HTS. So specially considering joint resistance between 2G tapes and terminal block, 2G HTS current lead for 400 A was designed and fabricated. This current lead was consisting of two terminal blocks, a support bar or tube, protection tube and six 2G HTS tapes. Its total length was 300 mm and body diameter 18.3 mm. At liquid nitrogen temperature (77 K) critical current (Ic) of this HTS current lead was 600 A, about 1.5 times the operating current 400 A. Conductive heat loss of 2G HTS current lead between 60 K and 7 K was 50 mW.