Korea Electrotechnology Research Institute Research Articles

Status of KERI's Pulsed Power Research and Development

This paper reviews the research and development results achieved in the Korea Electrotechnology Research Institute (KERI) in a decade. KERI develops pulsed power technology and its applications are mostly based on power electronics. KERI's research and development activity covers components, military systems, and industry applications. High-voltage switching means developed in KERI are a rotary arc gap (RAG) switch (11 kV and 400 kAp), a vacuum RAG (20 kV and 150 kAp), an inverse pinch switch (20 kV and 150 kAp), and 10-kV semiconductor switch stacks made of thyristors and Insulated Gate Bipolar Transistors (IGBTs). The IGBT and thyristor stacks consist of 10 or 12 1.2-kV discrete devices and are operated by only one active drive circuit installed in the groundside. Some ferromagnetic opening switch schemes are also researched on trial bases. Some of KERI's research and development works from devices to application systems will be described.

AC transport current loss analysis for a face-to-face stack of superconducting tapes

AC Losses for face to face stacks of four identical coated conductors (CCs) were numerically calculated using the H-formulation combined with the E-J power law and the Kim model. The motive sample was the face to face stack of four 2 mm-wide CC tapes with 2 thick superconducting layer of which the critical current density, , was on IBAD-MgO template, which was suggested for the mitigation of ac loss as a round shaped wire by Korea Electrotechnology Research Institute. For the calculation the cross section of the stack was simply modeled as vertically aligned 4 rectangles of superconducting (SC) layers with $E

배전용 S2급 차단기의 차단 성능평가 시험법에 관한 연구

Technical requirements for medium voltage class circuit breaker were harmonized by IEC and IEEE, and IEC newly adopted the requirements for class S2 circuit-breaker for overhead-line with the ratings of high-frequency TRV(Transient Recovery Voltage), which IEEE already adopted. Under these circumstances, KERI(Korea Electrotechnology Research Institute) studied testing technologies and facilities, which enable to perform interrupting capacity tests for class S2 circuit-breaker. As results, KERI could carry out interrupting capacity tests for medium voltage class circuit breaker rated up to 3-phase 52[kV] 40[kA], which satisfies the IEC standard.

직류전원을 이용한 배전급 차단기의 등가 3상 합성투입시험법

The study about three-phase synthetic making test using DC power has been performed in order to increase the making test capacity on Vacuum Circuit Breaker. And, it made possible to solve the limitations that short-circuit testing facilities can not fulfill the testing requirements of VCB exceeding three-phase 36[㎸] 31.5[㎄]. By using DC power and high speed spark-gap switch, this method made the equivalence with the pre-arc that occurred during the making process under the fault condition of power system. As results, KERI(Korea Electrotechnology Research Institute) could have capacity to carry out type test for VCB under three-phase 52[㎸] 40[㎸], which satisfies the IEC Standard.

배전용 변압기의 단락시험 불량원인 및 그 대책에 관한 연구

This study aims to research and analyze the cause and countermeasures of the short-circuit test failures of the distribution transformer, which captures failure share at the highest level when carrying out its performance test. For this purpose, the research was done on the basis of 77 failure cases out of 998 tests in total performed by the Korea Electrotechnology Research Institute(KERI) from 2004 to 2010. Based on the research, the paper also includes analysis of the causes of the short-circuit test failures in its early stage of transformer development and proposes its countermeasures accordingly.

SU‐E‐T‐423: Feasibility and Parameter Study on the Radiation Therapy with Laser‐Accelerated Electrons Using a Sharp Density Transition Scheme

Purpose: In the cancer therapy using laser‐accelerated VHEE (very high energy electron) beams, stability of the beam generation is a very important issue. Generation of stable mono‐energetic electron beam is affected by the conditions of electron injection. We used the sharp density transition scheme for the stable generation of the VHEE beams and investigate the characteristics of the mono‐energetic electron beams with a laser focal spot size. Methods: To generate sharp density transition structure experimentally, a study on the generation of plasma shock structure was performed at Korea Electrotechnology Research Institute. The characteristics of VHEE beams generated from laser‐plasma interaction via linearly polarized intense laser pulses are investigated using two‐dimensional particle‐in‐cell simulations. To investigate the feasibility of the cancer therapy with VHEE beams with a sharp density transition scheme, Monte‐Carlo simulations are performed for calculating the dosimetric properties. Results: The sharp density transition structure can be generated using a pre‐pulse propagating orthogonal to the main laser pulse. 200 ps and 400 mJ pre‐pulse can generate the plasma shock structure with a sharp density transition under 10㎛. The charge of the electron bunch is related to the area of the phase‐mixing region. The electron bunch with the maximum charge was produced in the maximum area of the mixing region for the specific laser focal size. Energy spread of electron bunch increases with the increasing focal spot size and transverse bunch size decrease with increasing focal spot size. Dose distributions have also been calculated with the GEANT4 code and we present the feasibility of the particle therapy with sharp density transition scheme based VHEE beams for the deep seated tumor. Conclusions: In this paper, we present the superior feasibility of the cancer therapy using laser‐accelerated VHEE beams with a sharp density transition scheme.

Modeling of a 22.9 kV 50 MVA superconducting power cable based on PSCAD/EMTDC for application to the Icheon substation in Korea

Two projects for high temperature superconducting (HTS) power cable have been carried out in Korea since 2001. One of them is a HTS cable project in DAPAS (Development of Advanced Power system by Applied Superconductivity technologies) program funded by the Ministry of Education, Science and Technology. In this project, LS Cable Ltd. (LSC) and Korea Electrotechnology Research Institute (KERI) jointly developed a 22.9kV, 50MVA, 3phase, 100m HTS cable using first generation (1G) HTS wire in 2006. The HTS cable system has been tested in a power test center of Korea Electric Power Corporation (KEPCO). LSC and KEPCO have been developing a 22.9kV, 50MVA, 3phase, 500m HTS cable system using second generation (2G) HTS wire since 2008, based on the technology of the DAPAS project. This project is called as GENI (Green Superconducting Electric Power Network at the Icheon Substation) project. The target of GENI project is to install and operate the HTS cable system in the Icheon substation located in near Seoul. In order to analyze the Icheon substation power system employing the HTS cable, an analysis model of the HTS cable is necessary. This paper describes the development of an analysis model for the 22.9kV, 50MVA HTS cable that will be applied to the Icheon substation in Korea.

Performance test of a 1 MW class HTS synchronous motor for industrial application

This paper deals with development activities of high temperature superconducting (HTS) synchronous motor at DOOSAN heavy industry and Korea Electrotechnology Research Institute (KERI) in Korea, and is sponsored by DAPAS program which is supported by Korean government. The final aim of the project is realization of HTS motor in the field of industry such as large driving pumps, fans and compressors for utility and industrial environments. At present time, 1 MW HTS motor is developed for the purpose to fully represent the design and manufacturing issues for the larger capacity machine. The number of pole and rotating speed of machine are 2 pole and 3600 rpm. The HTS field coil of the developed motor is cooled by way of neon thermosyphon mechanism and the stator coil is cooled by water through hollow copper conductor. This paper describes status of 1 MW HTS motor development, such as design, fabrication and performance test results, which was conducted at steady state in generator mode and motor mode.

Development of a 13.2 kV/630 A (8.3 MVA) High Temperature Superconducting Fault Current Limiter

This paper deals with fabrication and development of a high temperature superconducting (HTS) fault current limiter (FCL) based on YBCO coated conductor (CC) wire for distribution systems. The capacity of the developed HTS FCL is 8.3 MVA and its rated voltage is 13.2 kV which corresponds to a three-phase power equipment voltage class of 22.9 kV. Tests of the developed prototype HTS FCL were conducted at Korea Electrotechnology Research Institute (KERI) accredited as a testing laboratory by the Korea Laboratory Accreditation Scheme (KOLAS). A short-circuit test and an AC dielectric withstand voltage test for the HTS FCL were conducted under sub-cooled liquid nitrogen (LN2 ) conditions of 3 bar and 65 K. The magnitude of an asymmetric short- circuit current without FCL reached 30 kApeak in a short-circuit test. The superconducting coil quenched instantaneously after the fault, and the magnitude of the fault current was limited to 3.6 kApeak within quarter cycle by the developed resistance of the superconducting coil. An AC dielectric withstand voltage test was performed, and the HTS FCL successfully withstood 143 kV for 1 minute. Also, it was found that there was no electrical or mechanical damage on the superconducting coil after the tests.

Characteristics of the joint mini-model high temperature superconducting cable

To obtain realistic data on the high temperature superconducting (HTS) power cable, 3-phase 100 m long, 22.9 kV class HTS power transmission cable system have been developed by Korea Electrotechnology Research Institute (KERI) and LS cable Ltd. that is one of 21st Century Frontier Project in Korea. This cable was installed at Go-chang testing site of Korea Electric Power Corporation (KEPCO). For the application of the HTS power cable joint is very important to ensure the performance. Therefore, this paper gives some investigation of AC loss, critical current and joint resistance in jointed HTS tape. We experimentally showed that the influence of joint resistance on AC loss by using several joint methods. Finally, we are measured critical current, AC loss and jointed resistance for the manufactured mini-model cable.

Status of HTS Motor Development for Industrial Applications at KERI & DOOSAN

This work is development of HTS motor at DOOSAN heavy industry and Korea Electrotechnology Research Institute in Korea, and is sponsored by DAPAS program which is supported by Korean government. The final aim of the project is realization of HTS motor in the field of industry such as large driving pumps, fans and compressors for utility and industrial environments. In the first phase (2001-2004), 100 hp HTS motor was developed in order to implement the preliminary technology for the large applicable HTS motor. All of the performance characteristics are well met to the designed ones. In second phase (2004-2007), 1 MW HTS motor is developed for the purpose to fully represent the design and manufacturing issues for the larger capacity machine. The machine is 2 pole and 3600 rpm, and all of the components are completely manufactured. This machine is now under assembly. This paper summarizes the status of 1 MW HTS motor development, such as design, construction, and experimental test results.

Analysis of magnetic field distribution and AC losses of a 600 kJ SMES

Development of a 600 kJ superconducting magnetic energy storage (SMES) system is being in progress by Korea Electrotechnology Research Institute (KERI). 3-ply BSCCO-2223 wire was considered as a conductor for the winding of the SMES system and auto-tuning niching genetic algorithm was adopted for an optimization method of the HTS magnets in the 600 kJ SMES system. Several constraint conditions were considered for optimal design of HTS magnet of SMES system such as operating current, length of HTS wire in piece, gap between double pancake coils, stored magnetic energy, etc. As a result, output parameters for 6 case designs of 600 kJ SEMS were obtained as optimal design results according to the operating currents. In this research, one of the 6 cases was chosen to analyze magnetic field distribution of the 600 kJ SMES system. AC loss for each double pancake module of SMES during discharge period was also calculated. These HTS windings will be applied to the SMES system whose purpose is stabilization of the power grid.

PI 3D apparatus and technology at KERI

The paper outlooks development of plasma immersion ion implantation and deposition (PI 3D) hardware and process at Korea Electrotechnology Research Institute (KERI), and discuss some issues of the technology. Taking into account implications of modeling and measurements of PI 3, we developed a series of large volume dense plasma sources and high-voltage pulsed power supplies (HV PPS). Three built PI 3D facilities have been served as stand benches for research on control of PI 3D process, and improvement of the entire system specifications toward commercialization. Surface modification of various metals and polymers with PI 3D were carried out to find out the prospective market niche for the technology. Eventually, closed cooperation of the plasma physics and pulsed power staff allowed creating state-of-the-art PI 3D tools capable to fulfill industry demand.

Comparisons between impulse voltage calibrators and digitizers

AbstractImpulse voltage calibrators are important instruments for the calibration of impulse voltage digitizers and other measurement devices. The impulse digitizers, on the other hand, are often sufficiently accurate for checking the performance of impulse voltage calibrators. Comparisons between impulse calibrators and digitizers are useful in determining the uncertainties of the instruments, especially when multiple devices are being cross compared.In this paper, comparisons among calibrators and digitizers from Nippon Institute of Technology (NIT), Japan, National Measurement Institute (NMI), Australia, and Korea Electrotechnology Research Institute (KERI), Korea, are reported. Comparisons of full lightning impulse and switching impulse waveforms were performed. The results of the comparisons are reported with an analysis of the sources of the uncertainties. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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.

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 of a single-phase 30 m HTS power cable

HTS power transmission cables appear to be the replacement and retrofitting of underground cables in urban areas and HTS power transmission cable offers a number of technical and economic merits compared to the normal conductor cable system. A 30 m long, single-phase 22.9 kV class HTS power transmission cable system has been developed by Korea Electrotechnology Research Institute (KERI), LS Cable Ltd., and Korea Institute of Machinery and Materials (KIMM), which is one of the 21st century frontier project in Korea since 2001. The HTS power cable has been developed, cooled down and tested to obtain realistic thermal and electrical data on HTS power cable system. The evaluation results clarified such good performance of HTS cable that DC critical current of the HTS cable was 3.6 kA and AC loss was 0.98 W/m at 1260 Arms and shield current was 1000 Arms. These results proved the basic properties for 22.9 kV HTS power cable. As a next step, we have been developing a 30 m, three-phase 22.9 kV, 50 MV A HTS power cable system and long term evaluation is in progress now.

Development of a 3 MJ/750 kVA SMES system

Research and development on superconducting magnetic energy storage (SMES) system have been carried out to realize efficient electric power management for several decades. 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. A computer code was developed to find the parameters of the SMES magnet which used minimum amount of superconductors for the same energy storage capability, and the 3 MJ SMES magnet was designed based upon that. This paper describes the fabrication and experimental results of the 3 MJ/750 kVA SMES system.

Transport Alternating Current Losses of BSCCO and YBCO Tapes

After the discovery of HTS (High Temperature Superconductor), many types of HTS conductors have been developed. Several BSCCO tapes fabricated by PIT (Powder In Tube) method became commercially available, and the transport current loss characteristics of BSCCO tapes have been investigated by many research groups. The transport current loss characteristics of YBCO tapes, however, are not well studied. This is because measuring transport current requires tape samples over a certain length (15 cm for our own system). Many groups are currently focusing their effort on manufacturing long YBCO tape conductors, and new world records of length and current carrying capability are replacing the old ones in an increasingly fast rate. This paper deals with transport current losses of commercially available BSCCO tapes and YBCO tapes made at Korea Electrotechnology Research Institute (KERI) of Korea. YBCO tapes show relatively high transport current losses. This can be explained by the fact that the YBCO tape does not consist of filaments. Measurement results of the tapes are presented with analyses and discussions.

Development of a 100 hp Synchronous Motor With HTS Field Coils

A 3-phase, 100 hp, 4 pole, 1800 rpm superconducting synchronous motor built and tested in Korea Electrotechnology Research Institute(KERI). This machine consists of HTS rotor and air-core stator. The HTS field windings are composed of the double-pancake coils wound with AMSC's stainless steel-reinforced Bi-2223 tape conductor. These were assembled on the support structure and fixed by a bandage of glass-fiber composite. The cooling system is based on the heat transfer mechanism of the thermosyphon by using GM cryocooler as cooling source. The cold head is in contact with the condenser of a Ne-filled thermosyphon. The rotor assembly was tested independently at the stationary state and combined with stator. The open circuit, no-load, and short circuit characteristic were obtained. Also, load tests in motor mode driven by inverter and generator mode connected to resister load bank were conducted. This paper will present design, construction, and experimental test results of the 100 hp HTS machine.