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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Electrical Engineering and Technology
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The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 7, Issue 6 - Nov 2012
Volume 7, Issue 5 - Sep 2012
Volume 7, Issue 4 - Jul 2012
Volume 7, Issue 3 - May 2012
Volume 7, Issue 2 - Mar 2012
Volume 7, Issue 1 - Jan 2012
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Short-term Electric Load Forecasting Using Data Mining Technique
Kim, Cheol-Hong ; Koo, Bon-Gil ; Park, June-Ho ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 807~813
DOI : 10.5370/JEET.2012.7.6.807
In this paper, we introduce data mining techniques for short-term load forecasting (STLF). First, we use the K-mean algorithm to classify historical load data by season into four patterns. Second, we use the k-NN algorithm to divide the classified data into four patterns for Mondays, other weekdays, Saturdays, and Sundays. The classified data are used to develop a time series forecasting model. We then forecast the hourly load on weekdays and weekends, excluding special holidays. The historical load data are used as inputs for load forecasting. We compare our results with the KEPCO hourly record for 2008 and conclude that our approach is effective.
Application of Particle Swarm Optimization to the Reliability Centered Maintenance Method for Transmission Systems
Heo, Jae-Haeng ; Lyu, Jae-Kun ; Kim, Mun-Kyeom ; Park, Jong-Keun ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 814~823
DOI : 10.5370/JEET.2012.7.6.814
Electric power transmission utilities make an effort to maximize profit by reducing their electricity supply and operation costs while maintaining their reliability. The development of maintenance strategies for aged components is one of the more effective ways to achieve this goal. The reliability centered approach is a key method in providing optimal maintenance strategies. It considers the tradeoffs between the upfront maintenance costs and the potential costs incurred by reliability losses. This paper discusses the application of the Particle Swarm Optimization (PSO) technique used to find the optimal maintenance strategy for a transmission component in order to achieve the minimum total expected cost composed of Generation Cost (GC), Maintenance Cost (MC), Repair Cost (RC) and Outage Cost (OC). Three components of a transmission system are considered: overhead lines, underground cables and insulators are considered. In regards to aged and aging component, a component state model that uses a modified Markov chain is proposed. A simulation has been performed on an IEEE 9-bus system. The results from this simulation are quite encouraging, and then the proposed approach will be useful in practical maintenance scheduling.
Coordinated State-of-Charge Control Strategy for Microgrid during Islanded Operation
Kim, Jong-Yul ; Jeon, Jin-Hong ; Kim, Seul-Ki ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 824~833
DOI : 10.5370/JEET.2012.7.6.824
In this paper, a coordinated state-of-charge (SOC) control strategy for the energy storage system (ESS) operating under microgrid islanded mode to stabilize the frequency and voltage was proposed. The proposed SOC control loop is made up of PI controller, which uses a SOC state of the energy storage system as an input and an auxiliary reference value of secondary control as an output. The SOC controller changes the auxiliary reference value of secondary control to charge or discharge the ESS. To verify the proposed control strategy, PSCAD/EMTDC simulation study was performed. The simulation results show that the SOC of the ESS can be regulated at the desired operating range without degrading the stabilizing control performance by proposed coordinated SOC control method.
Intelligent Coordination Method of Multiple Distributed Resources for Harmonic Current Compensation in a Microgrid
Kang, Hyun-Koo ; Yoo, Choel-Hee ; Chung, Il-Yop ; Won, Dong-Jun ; Moon, Seung-Il ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 834~844
DOI : 10.5370/JEET.2012.7.6.834
Nonlinear electronic loads draw harmonic currents from the power grids that can cause energy loss, miss-operation of power equipment, and other serious problems in the power grids. This paper proposes a harmonic compensation method using multiple distributed resources (DRs) such as small distributed generators (DGs) and battery energy storage systems (BESSs) that are integrated to the power grids through power inverters. For harmonic compensation, DRs should inject additional apparent power to the grids so that certain DRs, especially operated in proximity to their rated power, may possibly reach their maximum current limits. Therefore, intelligent coordination methods of multiple DRs are required for efficient harmonic current compensation considering the power margins of DRs, energy cost, and the battery state-of-charge. The proposed method is based on fuzzy multi-objective optimization so that DRs can cooperate with other DRs to eliminate harmonic currents with optimizing mutually conflicting multi-objectives.
Measurement-based Estimation of the Composite Load Model Parameters
Kim, Byoung-Ho ; Kim, Hong-Rae ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 845~851
DOI : 10.5370/JEET.2012.7.6.845
Power system loads have a significant impact on a system. Although it is difficult to precisely describe loads in a mathematical model, accurately modeling them is important for a system analysis. The traditional load modeling method is based on the load components of a bus. Recently, the load modeling method based on measurements from a system has been introduced and developed by researchers. The two major components of a load modeling problem are determining the mathematical model for the target system and estimating the parameters of the determined model. We use the composite load model, which has both static and dynamic load characteristics. The ZIP model and the induction motor model are used for the static and dynamic load models, respectively. In this work, we propose the measurement-based parameter estimation method for the composite load model. The test system and related measurements are obtained using transient security assessment tool(TSAT) simulation program and PSS/E. The parameter estimation is then verified using these measurements. Cases are tested and verified using the sample system and its related measurements.
Evaluation of the Wind Power Penetration Limit and Wind Energy Penetration in the Mongolian Central Power System
Ulam-Orgil, Ch. ; Lee, Hye-Won ; Kang, Yong-Cheol ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 852~858
DOI : 10.5370/JEET.2012.7.6.852
This paper describes evaluation results of the wind power penetration limit (WPPL) and the wind energy penetration (WEP) in the Mongolian central power system (MCPS). A wind power plant (WPP) in a power system possesses an output power limit because the power system must maintain a balance between the generation and consumption of electricity at all times in order to achieve an adequate level of quality. The instantaneous penetration limit (IPL) of wind generation at a load is determined as the minimum of the three technical constraints: the minimum output, the ramp rate capability, and the spinning reserve of the conventional generating units. In this paper, a WPPL is defined as the maximum IPL divided by the peak load. A maximal variation rate (VR) of wind power is a major factor in determining the IPL, WPPL, and WEP. This paper analyzes the effects of the maximal VR of wind power on the WPPL, WEP, and capacity factor (CF) in the MCPS. The results indicate that a small VR can facilitate a large amount of wind energy while maintaining a high CF with increased wind power penetration.
Development of Fault Location Algorithm and Its Verification Experiments for HVDC Submarine Cables
Jung, Chae-Kyun ; Park, Hung-Sok ; Kang, Ji-Won ; Wang, Xinheng ; Kim, Yong-Kab ; Lee, Jong-Beom ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 859~868
DOI : 10.5370/JEET.2012.7.6.859
A new fault location algorithm based on stationary wavelet transform and its verification experiment results are described for HVDC submarine cables in this paper. For wavelet based fault location algorithm, firstly, 4th level approximation coefficients decomposed by wavelet transform function are superimposed by correlation, then the distance to the fault point is calculated by time delay between the first incident signal and the second reflected signal. For the verification of this algorithm, the real experiments based on various fault conditions and return types of fault current are performed at HVDC submarine cable test yard located in KEPCO(Korea Electric Power Corporation) Power Testing Center of South Korea. It proves that the fault location method proposed in this paper is very simple but very quick and accurate for HVDC submarine cable fault location.
Operation Scheme for a Wind Farm to Mitigate Output Power Variation
Lee, Sung-Eun ; Won, Dong-Jun ; Chung, Il-Yop ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 869~875
DOI : 10.5370/JEET.2012.7.6.869
Because of the nature of wind, the output power of wind turbines fluctuates according to wind speed variation. Therefore, many countries have set up wind-turbine interconnection standards usually named as Grid-Code to regulate the output power of wind farms to improve power system reliability and power quality. This paper proposes three operation modes of wind farms such as maximum power point tracking (MPPT) mode, single wind turbine control mode and wind farm control mode to control the output power of wind turbines as well as overall wind farms. This paper also proposes an operation scheme of wind farm to alleviate power fluctuation of wind farm by choosing the appropriate control mode and coordinating multiple wind turbines in consideration of grid conditions. The performance of the proposed scheme is verified via simulation studies in PSCAD/EMTDC with doubly-fed induction generator (DFIG) based wind turbine models.
Study on the Transfer Functions for Detecting Windings Displacement of Power Transformers with Impulse Method
Shon, Chae-Hwa ; Yi, Sang-Hwa ; Lee, Heun-Jin ; Kang, Dong-Sik ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 876~883
DOI : 10.5370/JEET.2012.7.6.876
The paper investigates three types of transfer function methods for detecting displacements of winding in a model transformer. To acquire these transfer functions, the measuring method of input voltage, current and its response is used in impulse method. The applied impulse voltages had three rising times, which were short rising time (less than 0.6
), medium rising time (about 0.8
) and long rising time (about 1
) in front waves. Every 10 measurements of voltage and current waves were averaged from 50 measurements of voltage and current waves. These transfer functions were tested in normal, 24mm elevated and 48mm elevated windings conditions and were analyzed with correlation coefficients and spectrum deviations. In the analysis, the results depend on the types of transfer functions and the rising times of input voltages.
Dynamic Hysteresis Model Based on Fuzzy Clustering Approach
Mourad, Mordjaoui ; Bouzid, Boudjema ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 884~890
DOI : 10.5370/JEET.2012.7.6.884
Hysteretic behavior model of soft magnetic material usually used in electrical machines and electronic devices is necessary for numerical solution of Maxwell equation. In this study, a new dynamic hysteresis model is presented, based on the nonlinear dynamic system identification from measured data capabilities of fuzzy clustering algorithm. The developed model is based on a Gustafson-Kessel (GK) fuzzy approach used on a normalized gathered data from measured dynamic cycles on a C core transformer made of 0.33mm laminations of cold rolled SiFe. The number of fuzzy rules is optimized by some cluster validity measures like `partition coefficient` and `classification entropy`. The clustering results from the GK approach show that it is not only very accurate but also provides its effectiveness and potential for dynamic magnetic hysteresis modeling.
Observer Based Nonlinear State Feedback Control of PEM Fuel Cell Systems
Kim, Eung-Seok ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 891~897
DOI : 10.5370/JEET.2012.7.6.891
In this paper, the observer based nonlinear state feedback controller has been developed to control the pressures of the oxygen and the hydrogen in the PEM(Proton Exchange Membrane) fuel cell system. Nonlinear model of the PEM fuel cell system was introduced to study the design problems of the state observer and model based controller. A cascade observer using the filtering technique was used to estimate the pressure derivatives of the cathode and the anode in the system. In order to estimate the pressures of the cathode and the anode, the sliding mode observer was designed by using these pressure derivatives. To estimate the oxygen pressure and the hydrogen pressure in the system, the nonlinear state observer was designed by using the cathode pressure estimates and the anode it. These results will be very useful to design the state feedback controller. The validity of the proposed observers and the controller has been investigated by using the Lyapunov`s stability analysis strategy.
Ride-through of PMSG Wind Power System Under the Distorted and Unbalanced Grid Voltage Dips
Sim, Jun-Bo ; Kim, Ki-Cheol ; Son, Rak-Won ; Oh, Joong-Ki ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 898~904
DOI : 10.5370/JEET.2012.7.6.898
This paper presents a ride-through skill of PMSG wind turbine system under the distorted and unbalanced grid voltage dips. When voltage dips occur in the grid, pitch control and generator speed control as well as a parallel resistor of DC-link help to keep the turbine`s safety. Modern grid code requires a wind turbine to supply reactive currents to help voltage recovery after grid faults clearance. In order to supply reactive currents to the grid in case of the distortedly unbalanced grid voltage dips, a special PLL is needed to control the grid side converter and to regulate the grid voltages symmetrically. The proposed method is applied to 2MW multi-pole PMSG wind turbine system, and verified by simulation.
Thermal Analysis of Interior Permanent-Magnet Synchronous Motor by Electromagnetic Field-Thermal Linked Analysis
Lee, Sang-Taek ; Kim, Hee-Jun ; Cho, Ju-Hee ; Joo, Dae-Suk ; Kim, Dae-Kyong ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 905~910
DOI : 10.5370/JEET.2012.7.6.905
This paper reports an investigation of pulse width modulation (PWM) techniques for twophase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electricaldegree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.
Digital Speed Regulator System Design for a Permanent Magnet Synchronous Motor
Choi, Han-Ho ; Jung, Jin-Woo ; Kim, Tae-Heoung ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 911~917
DOI : 10.5370/JEET.2012.7.6.911
In this paper, a digital speed regulator system design method is developed for a permanent magnet synchronous motor (PMSM). Firstly, an accurate approximate discrete-time model is proposed for a PMSM considering its inherent nonlinearities. Based on the discrete-time model, a digital acceleration observer as well as a digital speed regulator is designed. The exponential stability of the augmented control system is analyzed. The proposed digital speed regulator system is implemented by using a TMS320F28335 floating point DSP. Simulation and experimental results are given to verify the effectiveness of the proposed method.
Performance Improvement of Grid-Connected Inverter Systems under Unbalanced and Distorted Grid Voltage by Using a PR Controller
Lee, Jong-Hyun ; Jeong, Hae-Gwang ; Lee, Kyo-Beum ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 918~925
DOI : 10.5370/JEET.2012.7.6.918
This paper proposes a control method for grid-connected inverter systems under unbalanced and distorted grid voltage. The proposed method can reduce the power ripple caused by the unbalanced condition and compensate for the low-order harmonics of the output currents caused by the distortion of grid voltage. To reduce the power ripple, our method replaces the two conventional PI controllers with one PR controllers in the stationary frame. PR controllers can implement selective harmonic compensation without excessive computational requirements; the use of these controllers simplifies the method. Both the simulated and experimental results agree well with the theoretical analysis.
A Study of Advanced Spherical Motor for Improvement of Multi-DOF Motion
Park, Hyun-Jong ; Cho, Su-Yeon ; Ahn, Han-Woong ; Lee, Ho-Jun ; Won, Sung-Hong ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 926~931
DOI : 10.5370/JEET.2012.7.6.926
Since robot industry growing, the machine that could move with multi-DOF has been studied in many industrial fields. Spherical motor is one of the multi-DOF machine that doesn`t need gear for multi-DOF motion. Unlike conventional motor, spherical motor can not only rotate on the shaft axis (rotating motion), but tilt the shaft with 2-DOF motion (positioning motion). In the typical type of spherical motor, one coil took part in positioning motion and rotating motion at the same time. As the result, the control algorithm was complex. To solve this problem, this study proposed a novel type of coil on the stator. The coils were separated for positioning motion and rotating motion. Thus the linkage flux of rotating coil didn`t be affected the positioning angle. In this paper, comparing the back-EMF of typical and novel type was conducted and the driving experiment was carried out as the positioning angle. From the experiment result, the performance of proposed spherical motor could be verified.
Electric Model of Li-Ion Polymer Battery for Motor Driving Circuit in Hybrid Electric Vehicle
Lee, June-Sang ; Lee, Jae-Joong ; Kim, Mi-Ro ; Park, In-Jun ; Kim, Jung-Gu ; Lee, Ki-Sik ; Nah, Wan-Soo ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 932~939
DOI : 10.5370/JEET.2012.7.6.932
This paper presents an equivalent circuit model of a LIPB (Li-Ion Polymer battery) for Hybrid Electric Vehicles (HEVs). The proposed equivalent circuit can be used to predict the charging/discharging characteristics in time domain as well as the impedance characteristic analysis in frequency domain. Based on these features, a one-cell model is established as a function of Depth of Discharge (DoD), and a 48-cell model for a battery pack was also established. It was confirmed by experiment that the proposed model predict the discharging and impedance (AC) characteristics quite accurately at different constant current levels. To check the usefulness of the proposed circuit, the model was used to simulate a motor driving circuit with an Insulated Gate Bipolar Transistor (IGBT) inverter and Brushless DC (BLDC) motor, and it is confirmed that the model can calculate the battery voltage fluctuation in time domain at different DoDs.
Maximum Power Control of IPMSM Considering Nonlinear Cross-Magnetization Effects
Kim, Youn-Hyun ; Kim, Won-Kyu ; Kim, Sol ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 940~947
DOI : 10.5370/JEET.2012.7.6.940
Interior permanent magnet synchronous motor is widening its application compared to other AC machines because of magnetic and reluctance torque. Despite of the advantages, improving control performance with parameter nonlinearity consideration is crucial during the field weakening control. This paper shows a maximum power control method at the field weakening region that considers d, q inductance`s nonlinearity due to magnetic saturation and d, q mutual inductance. To verify the feasibility of control scheme, FEM simulations and experiments about comparison between linear and nonlinear maximum power control are carried out.
Optimizing Design Variables for High Efficiency Induction Motor Considering Cost Effect by Using Genetic Algorithm
Han, Pil-Wan ; Seo, Un-Jae ; Choi, Jae-Hak ; Chun, Yon-Do ; Koo, Dae-Hyun ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 948~953
DOI : 10.5370/JEET.2012.7.6.948
The characteristics of an induction motor vary with the number of parameters and the performance relationship between the parameters also is implicit. In case of the induction motor design, we generally should estimate many objective physical quantities in the optimization procedure. In this article, the multi objective design optimization based on genetic algorithm is applied for the three phase induction motor. The efficiency, starting torque, and material cost are selected for the objectives. The validity of the design results is also clarified by comparison between calculated results and measured ones.
Flexible Patch Rectennas for Wireless Actuation of Cellulose Electro-active Paper Actuator
Yang, Sang-Yeol ; Kim, Jae-Hwan ; Song, Kyo-D. ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 954~958
DOI : 10.5370/JEET.2012.7.6.954
This paper reports a flexible patch rectenna for wireless actuation of cellulose electro-active paper actuator (EAPap). The patch rectenna consists of rectifying circuit layer and ground layer, which converts microwave to dc power so as to wirelessly supply the power to the actuator. Patch rectennas are designed with different slot length at the ground layer. The fabricated devices are characterized depending on different substrates and polarization angles. The EAPap integrated with the patch rectenna is actuated by the microwave power. Detailed fabrication, characterization and demonstration of the integrated rectenna-EAPap actuator are explained.
A Method to Monitor Vacuum Degree Using Capacitive Partial Discharge Coupler
Sun, Jong-Ho ; Youn, Young-Woo ; Hwang, Don-Ha ; Yi, Sang-Hwa ; Kang, Dong-Sik ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 959~964
DOI : 10.5370/JEET.2012.7.6.959
Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from
torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen`s law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.
Enhanced Photocurrent from CdS Sensitized ZnO Nanorods
Nayak, Jhasaketan ; Son, Min-Kyu ; Kim, Jin-Kyoung ; Kim, Soo-Kyoung ; Lee, Jeong-Hoon ; Kim, Hee-Je ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 965~970
DOI : 10.5370/JEET.2012.7.6.965
Structure and optical properties of cadmium sulphide-zinc oxide composite nanorods have been evaluated by suitable characterization techniques. The X-ray diffraction spectrum contains a series of peaks corresponding to reflections from various sets of lattice planes of hexagonal ZnO as well as CdS. The above observation is supported by the Micro-Raman spectroscopy result. The optical reflectance spectra of CdS-ZnO is compared with that of ZnO where we observe an enhanced absorption and hence diminished reflection from CdS-ZnO compared to that from only ZnO. A very small intensity of the visible photoluminescence peak observed at 550 nm proves that the ZnO nanorods have very low concentrations of point defects such as oxygen vacancies and zinc interstitials. The photocurrent in the visible region has been significantly enhanced due to deposition of CdS on the surface of the ZnO nanorods. CdS acts as a visible sensitizer because of its lower band gap compared to ZnO.
150 kJ Compact Capacitive Pulsed Power System for an Electrothermal Chemical Gun
Lee, Byung-Ha ; Kim, Jin-Sung ; Kim, Seong-Ho ; Lee, Young-Hyun ; Yang, Kyung-Seung ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 971~976
DOI : 10.5370/JEET.2012.7.6.971
A 150 kJ compact capacitive pulsed power system (CCPPS) capable of delivering electrical energy into an electrothermal chemical (ETC) gun on a vehicle has been studied. The CCPPS provides pulsed electrical energy into a capillary plasma injector which generates plasma of tens of thousands
in temperature and has a nonlinear resistance depending on the current. The design requirements of the CCPPS are as follows: the maximum power of 250 MW, the pulse width of about 0.6 ms, the volume of no more than 0.5 cubic meter, the efficiency of energy transfer over 80 % and the repetition rate of 4~5 times per minute. The constructed CCPPS is composed of four 37.5 kJ capacitor bank modules in parallel to make a trapezoid pulse shape and to satisfy the design requirements. Each module is designed to achieve high reliability, safety, efficiency and energy density to endure severe operating conditions. The results of the performance test on the CCPPS using a 120 mm ETC gun are described.
Analysis of Partial Discharge Inception Voltages for the Wrong Positioning Defects in the Joint of Distribution Power Cables
Kim, Jeong-Tae ; Kim, Dong-Uk ; Lee, Young-Jo ; Koo, Ja-Yoon ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 977~982
DOI : 10.5370/JEET.2012.7.6.977
In order to find out partial discharge (PD) phenomena in the cable joint due to the poor workmanship during the installation, the relationship between PD inception voltages and joint defects was investigated. For the purpose, in the joint of 22.9kV CNCV cables, electric fields were calculated for various semiconductive layer wrong positioning (WP) defects. And, PDIV were investigated through the experiments and compared with the results of electric field analysis. In all WP defect cases, the PD inception field calculated using measured PDIVs was similarly shown to be the average value of 1.84kV/mm. In addition, the calculated PDIV and the measured PDIV were almost equal, from the PDIV calculation using maximum electric fields and the measured PDIV for the normal case. Throughout this study, it is possible to analyze WP defects due to the poor workmanship and to establish better joint design for the distribution grade extruded cable system.
Effect of Oxygen for Diamond Film Synthesis with C-Hexane in Microwave Plasma Enhanced CVD Process
Han, Sang-Bo ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 983~989
DOI : 10.5370/JEET.2012.7.6.983
The purpose of this paper is to decide the optimum synthesis conditions of polycrystalline diamond films according to the ratio of gas mixture. Diamond films were deposited with cyclo-hexane as a carbon precursor by the microwave plasma enhanced chemical vapor deposition process. The optimum oxygen ratio to cyclo-hexane was reached about 125 % under the fixed 0.3% c-hexane in hydrogen. Oxygen plays a role in etching the graphitic components of carbon sp2 bond effectively. By OES measurement, the best synthesis conditions found out about 12.5 % and 15.75 %, which is the emission intensity ratios of CH(B-X) and
, respectively. Also, the electron temperature was similar about 5,000 to 5,200 K in this work.
3D Conversion of 2D Video Encoded by H.264
Hong, Ho-Ki ; Ko, Min-Soo ; Seo, Young-Ho ; Kim, Dong-Wook ; Yoo, Ji-Sang ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 990~1000
DOI : 10.5370/JEET.2012.7.6.990
In this paper, we propose an algorithm that creates three-dimensional (3D) stereoscopic video from two-dimensional (2D) video encoded by H.264 instead of using two cameras conventionally. Very accurate motion vectors are available in H.264 bit streams because of the availability of a variety of block sizes. 2D/3D conversion algorithm proposed in this paper can create left and right images by using extracted motion information. Image type of a given image is first determined from the extracted motion information and each image type gives a different conversion algorithm. The cut detection has also been performed in order to prevent overlapping of two totally different scenes for left and right images. We show an improved performance of the proposed algorithm through experimental results.
Segmentation of Welding Defects using Level Set Methods
Mohammed, Halimi ; Naim, Ramou ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 1001~1008
DOI : 10.5370/JEET.2012.7.6.1001
Non-destructive testing (NDT) is a technique used in science and industry to evaluate the properties of a material without causing damage. In this paper we propose a method for segmenting radiographic images of welding in order to extract the welding defects which may occur during the welding process. We study different methods of level set and choose the model adapted to our application. The methods presented here take the property of local segmentation geodesic active contours and have the ability to change the topology automatically. The computation time is considerably reduced after taking into account a new level set function which eliminates the re-initialization procedure. Satisfactory results are obtained after applying this algorithm both on synthetic and real images.
Position DOP Analysis for Sensor Placement in the TDOA-based Localization System
Lim, Deok-Won ; Kang, Hee-Won ; Lee, Sang-Jeong ; Hwang, Dong-Hwan ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 1009~1013
DOI : 10.5370/JEET.2012.7.6.1009
A relationship between the sensor placement and the PDOP (Position Dilution of Precision) is derived in the TDOA-based localization system. And the geometric condition of the sensor placement is analyzed in order to get a minimum PDOP based on the derived relationship. Through computer simulations, effect of the sensor placement on the PDOP is observed.
Finite Wordlength Recursive Sliding-DFT for Phase Measurement
Kim, Byoung-Il ; Cho, Min-Kyu ; Chang, Tae-Gyu ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 1014~1022
DOI : 10.5370/JEET.2012.7.6.1014
This paper proposes a modified recursive sliding DFT to measure the phase of a single-tone. The modification is to provide a self error-cancelling mechanism so that it can significantly reduce the numerical error, which is generally introduced and accumulated when a recursive algorithm is implemented in finite wordlength arithmetic. The phase measurement error is analytically derived to suggest optimized distributions of quantization bits. The analytic derivation and the robustness of the algorithm are also verified by computer simulations. It shows that the maximum phase error of less than
radian is obtained even when the algorithm is coarsely implemented with 4-bit wordlength twiddle factors.
Optimal Underwater Coverage of a Cellular Region by Autonomous Underwater Vehicle Using Line Sweep Motion
Choi, Myoung-Hwan ;
Journal of Electrical Engineering and Technology, volume 7, issue 6, 2012, Pages 1023~1033
DOI : 10.5370/JEET.2012.7.6.1023
An underwater planar covering problem is studied where the coverage region consists of polygonal cells, and line sweep motion is used for coverage. In many subsea applications, sidescan sonar has become a common tool, and the sidescan sonar data is meaningful only when the sonar is moving in a straight line. This work studies the optimal line sweep coverage where the sweep paths of the cells consist of straight lines and no turn is allowed inside the cell. An optimal line sweep coverage solution is presented when the line sweep path is parallel to an edge of the cell boundary. The total time to complete the coverage task is minimized. A unique contribution of this work is that the optimal sequence of cell visits is computed in addition to the optimal line sweep paths and the optimal cell decomposition.