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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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KEPCO Journal on Electric Power and Energy
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Korea Electric Power Corporation
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Volume & Issues
Volume 1, Issue 1 - Sep 2015
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Study on EMTP Simulation Applying Dual Reactor for Prevention of the Ferro-resonance and VT Burnout in Substation System
Kim, Seok-kon ; An, Yong-ho ; Jang, Byung-tae ; Choi, Jong-kee ; Lee, Nam-ho ; Han, Jung-yeol ; Lee, You-jin ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 1~8
DOI : 10.18770/KEPCO.2015.01.01.001
When the line and switchgear of the substation system are disconnected, ferro-resonance can occur. This happens even if the capacitive reactance and inductive reactance are not equal, which are not common resonance conditions. Resonance conditions vary depending on the busbar configuration environment. Although the damping resistance method applying the existing saturable reactor to cope with ferro-resonance has been successfully applied on site, there can be loss of normal function during long-term operation. The reason is because the rise in the operating frequency of saturable reactors means the saturation number is increased. Therefore, it can no longer function as saturable reactor since the resistor having inadequate capacity is burned out. To address this problem, in this paper, an EMTP-based simulation test was performed by designing and applying a dual reactor method, which adds an extended divergence reactor to the 1st side of the VT. The test result confirms that when the divergence reactor is inserted, the voltage and current values obtained at the 1st side and 2nd side of the VT as well as current values of divergence reactor part were stabilized from the transient phenomena and return to normal values. When compared with existing measures, although this method is similar in adding having a reactor added to a system regarding ferro-resonance, it has the advantage of being able to prevent ferro-resonance in advance since the reactor is added before the system is saturated. In addition, because it does not use damping resistance, it can extend the equipment life and stabilize its operation. Therefore, there are a lot of differences in terms of its operating characteristics and achivement of goal between the conventional method and new divergence reactor method.
Development of the Control System for Fast-Responding Frequency Regulation in Power Systems using Large-Scale Energy Storage Systems
Lim, Geon-Pyo ; Park, Chan-Wook ; Labios, Remund ; Yoon, Yong-Beom ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 9~13
DOI : 10.18770/KEPCO.2015.01.01.009
Energy storage systems (ESS) can be used to provide frequency regulation services in a power system to replace traditional frequency regulation power plants. Battery ESS, in particular, can provide "fast-responding frequency regulation," wherein the facility can respond immediately and accurately to the frequency regulation signal sent by the system operator. This paper presents the development and the trial run results of a frequency regulation control system that uses large-scale ESS for use in a large power system. The control system was developed initially for the 4 MW ESS demonstration facility in Jocheon Jeju Island, and was further developed for use in the 28 MW ESS facility at the Seo-Anseong substation and the 24 MW ESS facility at the Shin-Yongin substation to provide frequency regulation services within mainland Korea. The ESS facility in Seo-Anseong substation responds to a sudden drop in frequency via governor-free control, while the ESS facility in Shin-Yongin responds via automatic generator control (AGC).
Study on the Magnetic Shield Effect of Carbon-based Materials at Extremely Low Frequency
Oh, Seong Moon ; Kang, Dong Su ; Lee, Sang Min ; Baek, Un Gyeong ; Roh, Jae Seung ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 15~20
DOI : 10.18770/KEPCO.2015.01.01.015
To examine the magnetic shielding effect for carbon-based materials at extremely low frequencies (60 Hz), two types of carbon black (Super-P and Denka Black) and a natural graphite (HC-198) were mixed into organic binder at 10 wt.% to produce a coating solution, and a powder coating with varying thickness was applied on an aluminum disk measuring 88 mm in radius. A device was developed to measure the sheielding effect at extremely low frequencies. A closed circuit was achieved by connecting a transformer and a resistor. The applied voltage was fixed at 65 V, and the magnetic field was measured to being the range of 4.95~5.10 mG. Depending on the thickness of the coating layer, the magnetic field showed a decreasing trend. The maximum decrease in the magnetic field of 38.3% was measured when natural graphite was coated with specimens averaging
. This study confirmed that carbon-based materials enable magnetic shielding at extremely low frequencies, and that the magnetic shielding effect can be enhanced by varying the coating thickness.
Study on the Distribution of Electromagnetic Force for 154 kV Power Transmission Cable on Dual Underground Lines by Normal and Earth Fault Current
Kim, Hui Min ; Kim, So Young ; Im, Sang Hyeon ; Park, Gwan Soo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 21~27
DOI : 10.18770/KEPCO.2015.01.01.021
The goal of this study is the size and distribution of the electromagnetic force generated by the current flowing through the second underground line of 154kV power transmission cables by using electromagnetic finite element analysis. So we interpret how mutually electromagnetic force has an effect on the comparable judgement of Trefoil, Duct and Flat, which shows in a numerical arrangement. 154kV OF 1200SQ Cable 1.281km not only is applicable to modeling for underground transmission cable but also examine the effect of line to line, phase to phase and size and direction of the electromagnetic force preparing for the occurrence of normal state and single-phase earth fault, which are arranged in trefoil, duct and flat formation between sections. As showing how the trajectory, and size distribution of the electromagnetic force translate as the arrangement of the cables when a steady-state current and a fault current flows on the underground cables, I hope that when Underground transmission is designed, this data will be useful information.
Study on Calculation of Dynamic Penetration Limit of WTG and Applications of BESS in Power Systems
Gwon, Han Na ; Choi, Woo Yeong ; Kook, Kyugn Soo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 29~32
DOI : 10.18770/KEPCO.2015.01.01.029
Since the characteristics of Renewable Energy Sources like wind turbine generators are very different from those of existing thermal power generators and their response to the sudden change of the frequency are not as good as that from thermal power generators. Especially when the penetration level of the wind power generation is substantially high, the output from the WTG would be possibly limited to keep the stability of power systems. For this, this paper implements the process for calculating the dynamic penetration limit of WTG and analyze the potential application of BESS for increasing the dynamic penetration limit of WTG.
Computational Simulation on Power Prediction of Lithium Secondary Batteries by using Pulse-based Measurement Methods
Park, Joonam ; Byun, Seoungwoo ; Appiah, Williams Agyei ; Han, Sekyung ; Choi, Jin Hyeok ; Ryou, Myung-Hyun ; Lee, Yong Min ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 33~38
DOI : 10.18770/KEPCO.2015.01.01.033
Energy storage systems (ESSs) have been utilized widely in the world to optimize the power operation system and to improve the power quality. As lithium secondary batteries are the main power supplier for ESSs, it is very important to predict its cycle and power degradation behavior. In particular, the power, one of the hardest electrochemical properties to measure, needs lots of resources such as time and facilities. Due to these difficulties, computer modelling of lithium secondary batteries is applied to predict the DC-IR and power value during charging and discharging as a function of state of charge (SOC) by using pulse-based measurement methods. Moreover, based on the hybrid pulse power characteristics (HPPC) and J-Pulse (JEVS D 713, Japan Electric Vehicle Association Standards) methods, their electrochemical properties are also compared and discussed.
DC Electric Field Characteristics considering Thermal Effect for HVDC Slip-on Type Outdoor Termination
Kwon, Ik-Soo ; Hwang, Jae-Sang ; Koo, Jae-Hong ; Sakamoto, Kuniaki ; Lee, Bang-Wook ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 39~46
DOI : 10.18770/KEPCO.2015.01.01.039
A outdoor termination installed at the outdoor substation is required to connect undergroud cables and overhead transmission lines. The joint box for AC transmission system is already developed and widely used to interconnect overhead and undergroud systems. But the development of the joint box for DC transmission system was only introduced from China and Japan, but theire developemnt staus and core technologies were not fully reported. In order to implement HVDC systems connecting ovehead transmission lines and undergroud cables, a outdoor termination should be developed, but the detailed specifications and information of this device were not reported. It is estimated that the development of the joint box for DC environment has some technical obstacles including insulating materials, electric field mitigation, thermal temperature rise, and space charge accumuations. Among this, the most important one is the DC elctrical insualtion design. Therefore, in order to investigate the DC elctrical insualton design of outdoor termination, the design of AC slip-on type outdoor termination is reffered, and DC electric field analysis performed to verify the possiblity of application of AC joint box into DC joint box. Especially for DC electric field analysis, temperature rise of insualting materials of a joint box was considered, because the conductivity of materials could be changed due to temperature rise. Furthermore, DC electric field analysis considering transinet state, and polarity reversal state were also investigated to verify which state is the most severe condition for the DC joint box. From the simualtion resulsts, it was shown that the value and the position of maximum electric field was obtained comparing AC state, DC state without temperaure rise, and DC state with temperaure rise. And it was confimred that severe DC electric field was observed considing temperaure rise. Finally, in order to reduce DC eletric field intensifation, different configuration of the joint box was applied and it was not possible to obtain satisfactory results. It means that the slight change of configuration of AC joint box was not the suitable soluton for DC joint box. It is essential to establish novel DC insulaton design skills and method for DC joint box to commercialze this product in the near future.
An Improved Service Restoration Algorithm under Consideration of Abnormal Conditions in Distribution Automation Systems
Cho, Namhun ; Kim, Insung ; Lee, Sungwoo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 47~54
DOI : 10.18770/KEPCO.2015.01.01.047
The most important function in distribution automation system (DAS) is the service restoration. KEPCO's current service restoration provides a very effective restoration service. However, it has been developed without the consideration of unexpected abnormal conditions that may occur while processing the sequence of switching operations. The objective of this paper is to provide practical service restoration schemes under consideration of abnormal conditions. The proposed service restoration schemes have been integrated to a branch office (B/O) in KEPCO. The proposed method strongly supports the conventional service restoration and adds to its value.
A Survey on Defense Mechanism against Distributed Denial of Service (DDoS) Attacks in Control System
Kwon, YooJin ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 55~59
DOI : 10.18770/KEPCO.2015.01.01.055
Denial of Service (DoS) attack is to interfere the normal user from using the information technology services. With a rapid technology improvements in computer and internet environment, small sized DoS attacks targeted to server or network infrastructure have been disabled. Thus, Distributed Denial of Service (DDoS) attacks that utilizes from tens to several thousands of distributed computers as zombie PC appear to have as one of the most challenging threat. In this paper, we categorize the DDoS attacks and classify existing countermeasures based on where and when they prevent, detect, and respond to the DDoS attacks. Then we propose a comprehensive defense mechanism against DDoS attacks in Control System to detect attacks efficiently.
Study on DAS-Based Time Synchronization for Improving Reliability of Section Load Estimation
Lee, In-tae ; Lee, Ji-Hoon ; Jung, Nam-Joon ; Jung, Young-Beom ; Lee, Byung-sung ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 61~65
DOI : 10.18770/KEPCO.2015.01.01.061
For effective distribution planning and operation, we need a reliable estimation of operation capacity. But it is difficult to ensure reliability due to the low accuracy of section load data, which is used as a basis in estimating the operation capacity. This paper discusses how to improve the accuracy of section load data by analyzing the existing method of estimating the section load, using statistical techniques to adjust the acquired data, and using the section load estimation algorithm to estimate the section load based on the adjusted data.
Study on Operating Guidelines of Electric Vehicles considering Negawatt Market
Yang, Ken-Mo ; KIM, DONG-MIN ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 67~71
DOI : 10.18770/KEPCO.2015.01.01.067
The concept known as Vehicle-to-Grid (V2G) is to provide power to help balance loads by charging at night when demand is low and sending power to the grid when demand is high. Therefore, it is important to model the cost-benefit characteristics of Electric vehicle(EV)'s operation considering the negawatt market in real time. This paper proposes a methodology to formulate the various costs and economic benefits for sending the EV's power back to the grid, including a concept of inconvenience costs caused by operating the EV as a battery. This paper also introduces the general decision-making process based on the cost-benefit analysis in order to simulate the reasonable participation of V2G service. In the case study, it is confirmed by two-case simulations that the proposed approach is useful to help EV owners' decision-making. In the future, it is expected that the proposed methodology can be used as a decision-making guideline to help prepare the EV' power transmission.
Economic Assessments of LFAC and HVDC Transmissions for Large Offshore Wind Farms
Park, Taesik ; Kwak, Nohong ; Moon, Chaeju ; Cha, Seungtae ; Kwon, Seongchul ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 73~77
DOI : 10.18770/KEPCO.2015.01.01.073
Offshore wind farms extend a distance from an onshore grid to increase their generating power, but long distance and high power transmissions raise a lot of cost challenges. LFAC (Low Frequency AC) transmission is a new promising technology in high power and low cost power transmission fields against HVDC (High Voltage DC) and HVAC (High Voltage AC) transmissions. This paper presents an economic comparison of LFAC and HVDC transmissions for large offshore wind farms. The economic assessments of two different transmission technologies are analyzed and compared in terms of wind farm capacities (600 MW and 900 MW) and distances (from 25 km to 100 km) from the onshore grid. Based on this comparison, the economic feasibility of LFAC is verified as a most economical solution for remote offshore wind farms.
The Response to Impulse Signal on Three Phase Transformer using Vector Network Analyzer
Kim, Kwangho ; Jung, Jongman ; Nah, Wansoo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 79~84
DOI : 10.18770/KEPCO.2015.01.01.079
Transformer is widely used element on power system and industrial area. Especially the transformers installed at power system are exposed to an environment of arbitrary changed. Thus the prediction of degradation and the analysis of response to impulse are important. To conduct those works, the electrical characteristics of system should be analyzed, effectively. But the analysis of electrical characteristic in electric machine level such as pole and pad-mounted transformer is almost no, thus commercial VNA (Vector Network Analyzer) is used to getting the response in wide frequency range. However, the output power of VNA is usually under 10mW, so verification for effectiveness of measuring electrically large component should be conducted, firstly. Next, after getting total S-parameter of transformer, predicting impulse response can be performed in time-domain with circuit simulator. In this paper, it is introduced that verification effectiveness of VNA using transfer function from SFRA (Sweep Frequency Response Analyzer), firstly. Next, total S-parameter, six by six matix form, was built using measured 2 port S-parameter from vector network analyzer. To get the response to impulse which is defined by IEC 60060-1, time-domain simulation is conducted to ADS (Advenced Design System) circuit simulator.
Analysis of RF Inductive Couplers for Power Line Communication
Noh, Young Seok ; Lee, Gunbok ; Park, Wee Sang ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 85~91
DOI : 10.18770/KEPCO.2015.01.01.085
We investigated the structure of inductive coupler and its magnetic coupling to increase the transmission coefficient for power line communication. A Rogowski coil, which is an air-cored inductive coupler, and a magnetic cored coupler were fabricated to analyze the transmission coefficient for different coupler parameters. This paper proposes the impedance matching method using lumped elements and an impedance transformer to increase the transmission coefficient. In the experiment, the transmission coefficient of the proposed system was increased in both narrowband and broadband cases, and a trade-off between the transmission coefficient and the bandwidth was shown. This method will be useful for the further study of impedance matching with the load variation.
Co-combustion of Bituminous Coal with Anthracite in a Down-firing, 200 MW Boiler
Park, Ho Young ; Baek, Se Hyun ; Kim, Young Joo ; Kim, Tae Hyung ; Kim, Hyun Hee ; Lim, Hyun Soo ; Park, Yoon Hwa ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 93~97
DOI : 10.18770/KEPCO.2015.01.01.093
The combustion tests for Korean anthracite-bituminous coal blend were carried out in the 200 MW utility boiler. The burning characteristics of the blend were studied with a thermogravimetric analyzer (TGA). From the observation of TGA burning profiles, it was found that the presence of bituminous coal in the blend appeared to enhance the reactivity of anthracite in the higher temperature region, indicating certain interactions between the two coals. The plant test showed the boiler operation was reasonably stable with somewhat poor combustion efficiency, and some modification of the combustion environment in the furnace is necessitate for the further stable plant operation.
Development of Noise Source Detection System using Array Microphone in Power Plant Equipment
Sohn, Seok-Man ; Kim, Dong-Hwan ; Lee, Wook-Ryun ; Koo, Jae-Raeyang ; Hong, Jin-Pyo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 99~104
DOI : 10.18770/KEPCO.2015.01.01.099
In this study, it has been initiated to investigate the specific abnormal vibration signal that has been captured in the power equipment. Array Microphone can be used in order to detect the direction and the position of the noise source. It is possible to track the abnormal mechanical noise in the power plant by utilizing the program and the microphone array system developed from this research. Array microphone system can be operated as a constant monitoring system.
Development of a Hydro Turbine Governor and Validation Test
Kim, Jong-An ; Woo, Joo-Hee ; Choi, In-Kyu ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 105~108
DOI : 10.18770/KEPCO.2015.01.01.105
A digital Governor (GOV) has been developed for being used for a Francis hydro turbine, and the validity of the GOV has been tested. As for the hardware system for the GOV, we purchased a basic digital control system that already had proven its reliability in the power industry. We developed a set of new GOV software and integrated it with the hardware system, and finally verified the performance of the whole GOV system. For the human-machine interface (HMI), we configured and implemented appropriate graphic interfaces for the turbine operations. This paper describes the major GOV control functions, approaches we took in developing the GOV control logics, and the validity tests and the results.
Evaluation of Corrosion Resistance of Materials for Supercritical Carbon Dioxide Power Plant
Chae, Hobyung ; Seo, Sukho ; Jung, Yong Chan ; Lee, Soo Yeol ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 109~113
DOI : 10.18770/KEPCO.2015.01.01.109
Screening of Spray-Dried K
-Based Solid Sorbents using Various Support Materials for CO
Eom, Tae Hyoung ; Lee, Joong Beom ; Baek, Jeom In ; Ryub, Chong Kul ; Rhee, Young Woo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 115~120
DOI : 10.18770/KEPCO.2015.01.01.115
-based dry regenerable sorbents were prepared by spray-drying techniques to improve mass produced
sorbents (KEP-CO2P, hereafter), and then tested for their
sorption capacity by a
capture pilot plant built for Unit 3 of the Hadong thermal power station in 2010. Each of the sample sorbents contained 35 wt.%
as the active materials with various support materials such as
, MgO, Zeolite 13X,
and hydrotalcite (HTC). Their physical properties and reactivity were tested to evaluate their applicability to a fluidized-bed or fast transport-bed
capture process. The
sorption capacity and percentage utilization of
-MgO based sorbent, Sorb-KM2, was
-sorbents and 90%, respectively, along with good mechanical strength for fluidized-bed application. Sorbs-KM2 and KT were almost completely regenerated at
. No degradation of Sorb-KM by
added as a pollutant in flue gas was observed during a cycle test.
Review on Evaluation of Rare Earth Metals and Rare Valuable Metals Contained in Coal Ash of Coal-fired Power Plants in Korea
Park, Seok-Un ; Kim, Jae-Kwan ; Seo, Yeon-Seok ; Hong, Jun-Seok ; Lee, Hyoung-Beom ; Lee, Hyun-Dong ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 121~125
DOI : 10.18770/KEPCO.2015.01.01.121
Distribution of rare earth metals (REMs) and rare valuable metals (RVMs) contents in coal ashes (fly ash, bottom ash, and pond ash) and leachate from 11 coal-fired power plants in Korea were investigated. Coal ashes and leachates were found to contain important REMs and RVMs such as Yttrium (Y) and Neodymium (Nd), which was in the range of 23~75 mg/kg. However, it still requires developing effective recovery and separation methods in order to utilize REMs and RVMs in ash and leachate. Recovery of valuable elements (Y and Nd) from various and extensive ash sources (8.21 million tons/year in 2013) can provide the existing power plants with additional profit; therefore, it can significantly improve economics of the power plants.
Experimental Study on Interfacial Behavior of CFRP-bonded Concrete
Chu, In-Yeop ; Woo, Sang-Kyun ; Lee, Yun ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 127~134
DOI : 10.18770/KEPCO.2015.01.01.127
Recently, the external bonding of carbon fiber reinforced polymer (CFRP) sheets has come to be regarded as a very effective method for strengthening of reinforced concrete structures. The behavior of CFRP-strengthened RC structure is mainly governed by the interfacial behavior, which represents the stress transfer and relative slip between concrete and the CFRP sheet. In this study, the effects of bonded length, width and concrete strength on the interfacial behavior are verified and a bond-slip model is proposed. The proposed bond-slip model has nonlinear ascending regions and exponential descending regions, facilitated by modifying the conventional bilinear bond-slip model. Finite element analysis results of interface element implemented with bond-slip model have shown good agreement with the experimental results performed in this study. It is found that the failure load and strain distribution predicted by finite element analysis with the proposed bond-slip are in good agreement with results of experiments.
Study on CO
Decomposition using Ar/CO
Inductively Coupled Plasma
Kim, Kyung-Hyun ; Kim, Kwan-Yong ; Lee, Hyo-Chang ; Chung, Chin-Wook ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 135~140
DOI : 10.18770/KEPCO.2015.01.01.135
Decomposition of carbon dioxide is studied using
mixture inductively coupled plasmas (ICP). Argon gas was added to generate plasma which has high electron density. To measure decomposition rate of
, optical emission actinometry is used. Changing input power, pressure and mixture ratio, the plasma parameters and the spectrum intensity were measured using single Langmuir probe and spectroscope. The source characteristic of Carbon dioxide ICP observed from the obtained plasma parameters. The decomposition rate is evolved depending on the reaction and discharge mode. This result is analyzed with both the measurement of the plasma parameters and the dissociation mechanism of
Development and Test of a Cooling System for a 154 kV Superconducting Fault Current Limiter
Kim, Heesun ; Han, Young Hee ; Yang, Seong-Eun ; Yu, Seung-Duck ; Park, Byung Jun ; Park, Kijun ; Yoo, Jaeun ; Kim, Hye-Rim ; In, Sehwan ; Hong, Yong Joo ; Yeom, Hankil ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 141~144
DOI : 10.18770/KEPCO.2015.01.01.141
The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen (
), which cools the superconductor modules of the SFCL. The
is circulated between the cooler and the cryostat that contains superconductor modules. The
also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in
, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.
Medium Voltage HTS Cable Thermal Simulation using PSCAD/EMTDC
Jung, Chaekyun ; Kang, Yeonwoog ; Kang, Jiwon ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 145~150
DOI : 10.18770/KEPCO.2015.01.01.145
This paper described the medium voltage high temperature superconducting cable thermal simulation and its application. New simulation method for HTS cable modeling using PSCAD/EMTDC is introduced in this paper. The developed simulation method consists of electrical model part and thermal model part. In electrical model part, power loss and thermal capacitance can be calculated in each layer, then the temperature of each layer can be calculated by power loss and thermal capacitance in thermal model part. This paper also analyzes the electrical and thermal characteristic in the case of normal operating condition and transient including single line to ground fault and line to line ground fault using new simulation method.
Development and Characterization of High Temperature Superconducting Wire for Superconducting Cable System
Mean, Byoungjean ; Lee, Jae-Hun ; Kim, Young-Soon ; Lee, Hunju ; Moon, Seung-Hyun ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 151~156
DOI : 10.18770/KEPCO.2015.01.01.151
In order to improve the properties of high-temperature superconducting wire for superconducting cable system, we optimized the electro-polishing (EP), ion-beam assisted deposition (IBAD), superconducting (SC) layer, and baking (heat) treatment. The buffer layer was deposited on electro-polished substrate with RMS roughness (
) less than 5 nm. The IBAD process was carried out at
: 1100 V and
: 850 V that resulted in highly crystalline film of
. Chemical composition of SC layer is key to higher critical current, and we found that composition can be determined by surface color of SC layer. We adopt a proprietary contorl system based on RGB analysis of the surface and achieved critical current of 150 A/4 mm-width. The proposed baking treatment resulted in decreasing of about 10% of fraction defects.
Study on the 2G High Temperature Superconducting Coil for Large Scale Superconducting Magnetic Energy Storage Systems
Lee, Ji-Young ; Lee, Seyeon ; Kim, Yungil ; Park, Sang Ho ; Choi, Kyeongdal ; Lee, Ji-Kwang ; Kim, Woo-Seok ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 157~162
DOI : 10.18770/KEPCO.2015.01.01.157
Large scale superconducting magnetic energy storage (SMES) system requires very high magnetic energy density in its superconducting coils to enhance the energy capacity and efficiency of the system. The recent high temperature superconducting (HTS) conductors, so called 2G conductors, show very good performance under very high magnetic field so that they seem to be perfect materials for the large scale SMES coils. A general shape of the coil system with the 2G HTS conductor has been a tor oid, because the magnetic field applied perpendicularly to the surface of the 2G HTS conductor could be minimized in this shape of coil. However, a toroid coil requires a 3-dimensional computation to acquire the characteristics of its critical current density - magnetic field relations which needs very complicated numerical calculation, very high computer specification, and long calculation time. In this paper, we suggested an analytic and statistical calculation method to acquire the maximum magnetic flux density applied perpendicularly to the surface of the 2G HTS conductor and the stored energy in the toroid coil system. Although the result with this method includes some errors but we could reduce these errors within 5 percent to get a reasonable estimation of the important parameters for design process of the HTS toroid coil system. As a result, the calculation time by the suggested method could be reduced to 0.1 percent of that by the 3-dimensional numerical calculation.
Study on Wind Power Prediction model based on Spatial Modeling
Jung, Solyoung ; Hur, Jin ; Choy, Young-do ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 163~168
DOI : 10.18770/KEPCO.2015.01.01.163
In order to integrate high wind generation resources into power grid, it is an essential to predict power outputs of wind generating resources. As wind farm outputs depend on natural wind resources that vary over space and time, spatial modeling based on geographic information such as latitude and longitude is needed to estimate power outputs of wind generation resources. In this paper, we introduce the basic concept of spatial modeling and present the spatial prediction model based on Kriging techniques. The empirical data, wind farm power output in Texas, is considered to verify the proposed prediction model.
Controlling the Properties of Graphene using CVD Method: Pristine and N-doped Graphene
Park, Sang Jun ; Lee, Imbok ; Bae, Dong Jae ; Nam, Jungtae ; Park, Byung Jun ; Han, Young Hee ; Kim, Keun Soo ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 169~174
DOI : 10.18770/KEPCO.2015.01.01.169
In this research, pristine graphene was synthesized using methane (
) gas, and N-doped graphene was synthesized using pyridine (
) liquid source by chemical vapor deposition (CVD) method. Basic optical properties of both pristine and N-doped graphene were investigated by Raman spectroscopy and XPS (X-ray photoemission spectroscopy), and electrical transport characteristics were estimated by current-voltage response of graphene channel as a function of gate voltages. Results for CVD grown pristine graphene from methane gas show that G-peak, 2D-peak and C1s-peak in Raman spectra and XPS. Charge neutral point (CNP; Dirac-point) appeared at about +4 V gate bias in electrical characterization. In the case of pyridine based CVD grown N-doped graphene, D-peak, G-peak, weak 2D-peak were observed in Raman spectra and C1s-peak and slight N1s-peak in XPS. CNP appeared at -96 V gate bias in electrical characterization. These result show successful control of the property of graphene artificially synthesized by CVD method.
Facile Chemical Growth of Cu(OH)
Thin Film Electrodes for High Performance Supercapacitors
Patil, U.M. ; Nam, Min Sik ; Shinde, N.M. ; Jun, Seong Chan ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 175~180
DOI : 10.18770/KEPCO.2015.01.01.175
A facile soft chemical synthesis route is used to grow nano-buds of copper hydroxide [
] thin films on stainless steel substrate[SS]. Besides different chemical methods for synthesis of
nanostructure, the chemical bath deposition (CBD) is attractive for its simplicity and environment friendly condition. The structural, morphological, and electro-chemical properties of
thin films are studied by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurement techniques. The results showed that, facile chemical synthesis route allows to form the polycrystalline, granular nano-buds of
thin films. The electrochemical properties of
thin films are studied in an aqueous 1 M KOH electrolyte using cyclic voltammetry. The sample exhibited supercapacitive behavior with
specific capacitance. Moreover, electrochemical capacitive measurements of
electrode exhibit a high specific energy and power density about
, respectively, at
current density. The superior electrochemical properties of copper hydroxide (
) electrode with nano-buds like structure mutually improves pseudocapacitive performance. This work evokes scalable chemical synthesis with the enhanced supercapacitive performance of
electrode in energy storage devices.
Study on Analysis of Transfer Torque and Improvement of Transfer Torque in Non-Contact Permanent Magnet Gear
Park, Gyu-Sang ; Kim, Chan-Ho ; Kim, Yong-Jae ;
KEPCO Journal on Electric Power and Energy, volume 1, issue 1, 2015, Pages 181~188
DOI : 10.18770/KEPCO.2015.01.01.181
The non-contact permanent magnet gear has advantages of high efficiency and improved reliability. It has other advantages of no mechanical friction loss, very little noise and vibration, and no need for lubricant. With these advantages, the non-contact permanent magnet gear that solves the physical contact problem of the mechanical gear has drawn attention. Due to this unique non-contact characteristic, the non-contact permanent magnet gear which is capable of non-contact torque transmission has replaced mechanical gear. The mechanical gears which is in many fields of the modern industry, is used mostly for power transmitting mechanical devices. However, it also has the problem of a low torque density, which requires improvement. In this paper, a novel pole piece shape is proposed in order to improve the problem of low torque density of the non-contact permanent magnet gear. The experiment data required for predicting the relationships among them are obtained using finiteelement Operating method based on two-dimensional (2-D) numerical analysis. Therefore, this paper derived an optimal model for thenon-contact permanent magnet gear with the novel pole piece using the Box-Behnken design, and the validity of the optimal design of the proposed pole piece shape through variance analysis and regression analysis demonstrated. In this paper, we performed the thransfer torque analysis in order to improve the torque density and power density, we have performed on optimal design of proposed pole piece shape using box-behnken.