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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Transactions of The Korean Institute of Electrical Engineers
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The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 60, Issue 12 - Dec 2011
Volume 60, Issue 11 - Nov 2011
Volume 60, Issue 10 - Oct 2011
Volume 60, Issue 9 - Sep 2011
Volume 60, Issue 8 - Aug 2011
Volume 60, Issue 7 - Jul 2011
Volume 60, Issue 6 - Jun 2011
Volume 60, Issue 5 - May 2011
Volume 60, Issue 4 - Apr 2011
Volume 60, Issue 3 - Mar 2011
Volume 60, Issue 2 - Feb 2011
Volume 60, Issue 1 - Jan 2011
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Estimation of Harmonic Sources in a Power System using Recursive Least-Squares Technique
Han, Jong-Hoon ; Lee, Key-Byung ; Park, Chang-Hyun ; Jang, Gil-Soo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1639~1645
DOI : 10.5370/KIEE.2011.60.9.1639
A technique to allocate responsibilities among the interested parties in electric power system with harmonic voltage distortion at the point of common coupling (PCC) has been presented. The recursive least-squares technique has been used to estimate the parameters of the Thevenin equivalent load model. The validity of the technique has been verified using a simulation which considered the voltage waveform distortion at the PCC between the utility and two industrial consumers. With the estimated data from the measured voltage and current waveform at the PCC, the individual contributions to the distortion of voltage waveform at an interested harmonic frequency have been calculated and could provide a flexible solution to identify the source of harmonic pollution in distribution systems.
A Study on the Reliability Index and Customer Density of Distribution System
Bae, In-Su ; Kim, Jin-O ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1646~1650
DOI : 10.5370/KIEE.2011.60.9.1646
SAIDI(System Average Interruption Duration Index) is the index that signifies the power quality of customers. SAIDI is also used to know how well utilities operate their systems. The annual interruption time in the areas that consists of widely distributed customers, is generally longer than that in the areas that consists of heavily concentrated customers. The Reliability index of huge system is not necessarily better or worse than that of small system, because SAIDI is irrelevant to the total amount of power sold or the total number of customers. This paper proposes a customer density very relevant to SAIDI. The proposed customer density is used to modify the existing SAIDI to more clearly express the service level of power supply. A modified WSAIDI(weighted SAIDI) can be a useful indicator helping utilities improve the reliability of their systems and customers evaluate the service level of receiving power.
A Study on the Calculation of Reference Impedances in Domestic Low-Voltage Power System
Kang, Moon-Ho ; Song, Yang-Hoe ; Lee, Heung-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1651~1655
DOI : 10.5370/KIEE.2011.60.9.1651
The reference impedances which is about 95% supply impedance value of residential consumers' supply impedances was published by IEC in 1980. The reference impedances are the standard values for use in determining the voltage disturbance characteristics of electrical equipment like the flicker. In IEC 60725, the reference impedances for premises having service current capacities less than 100A per phase and for service current capacities more than 100A per phase are recommended. And these reference impedances are targeted for the countries using 50Hz power frequency. Because of the frequency difference, the reactance values of the reference impedances will be increased in 60Hz power system like Korea, And also the reference impedances are different significantly each other according to declared voltage variation, power consumption and service wire length etc. Therefore It is needed to calculate the reference impedances suitable for domestic low-voltage power system. In this paper, the reference impedances for service current capacities less than 100A in 220/380V, 60Hz single-phase two wire and three-phase four wire low-voltage system are calculated, And the equations for service current capacities more than 100A to calculate the modulus value of maximum supply impedances are suggested base on IEC 60725 and the reference impedances for those are calculated on service current of 100A per phase.
Improvement of Detailed Fault Point Decision Using EMTP Analysis of Search Coil Method for HVDC Cables
Jung, Chae-Kyun ; Park, Jin-Woo ; Yang, Byeong-Mo ; Kang, Ji-Won ; Lee, Jong-Beom ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1656~1662
DOI : 10.5370/KIEE.2011.60.9.1656
In a previous paper, the EMTP modeling technique using search coil test is established through various transient analysis including system grounding condition and grounding resistance for HVDC submarine cables. It was also proved by comparison with real test results. Based on this EMTP modeling technique, in this paper, it will be applied for modeling of
real HVDC submarine system(Jeju~Haenam). This paper variously analyses the effects of fault resistance including the resistance between core and sheath, the resistance between sheath and amore and the resistance between amore and sea water through EMTP modeling of search coil method. The results can contribute to the accuracy of detailed fault point prediction of search coil test for HVDC submarine cables.
A Study on Flicker Management Standard for Distribution Power System in Korea based on IEC 61000-3-7
Kang, Moon-Ho ; Lee, Heung-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1663~1667
DOI : 10.5370/KIEE.2011.60.9.1663
Voltage variation caused by large loads such as arc furnace and large motors, which use the large and instantaneous currents, can cause the voltage flicker. The flicker irritates the human's eyes and also has an adverse effect on protection device, rotating machine and electronic device etc, therefore the flicker needs to be managed effectively. Recently, the Korea power quality standard has been established on the IEC standards. This paper presents the flicker management standard for distribution power system and suggests the flicker transfer coefficients for Korea power system based on the IEC 61000-3-7.
A Study on the Integrated Model Design and Circulation of the Customer Information for Electricity Market Competition
Ko, Jong-Min ; Park, Sang-Hoo ; Noh, Jae-Koo ; Kim, Young-Il ; Choi, Seong-Hwan ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1668~1673
DOI : 10.5370/KIEE.2011.60.9.1668
Recent power industries are to be progressed as moving into horizontal markets and expanding of competitive systems through promoting SmartGrid. In these environments, the information on power consumers leads to establish a part of power markets through active and real-time participations instead of participating it as a passive manner presented by a vertical integration. Also, such information should be established as a way that effectively reflects changes and market behaviors occurred in power market participants. Therefore, in this study, a method that develops consumer information models, performs integrated managements, implements registration and distribution, and forms integrated management centers is presented to commonly use the consumer information according to the change in the environment of power industries.
A Feasibility Study on DC Microgrids Considering Energy Efficiency
Yu, Cheol-Hee ; Chung, Il-Yop ; Hong, Sung-Soo ; Chae, Woo-Kyu ; Kim, Ju-Yong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1674~1683
DOI : 10.5370/KIEE.2011.60.9.1674
More than 80% of electric loads need DC electricity rather than AC at the moment. If DC power could be supplied directly to the terminal loads, power conversion stages including rectifiers, converters, and power adapters can be reduced or simplified. Therefore, DC microgrids may be able to improve energy efficiency of power distribution systems. In addition, DC microgrids can increase the penetration level of renewable energy resources because many renewable energy resources such as solar photovoltaic(PV) generators, fuel cells, and batteries generate electric power in the form of DC power. The integration of the DC generators to AC electric power systems requires the power conversion circuits that may cause additional energy loss. This paper discusses the capability and feasibility of DC microgrids with regard to energy efficiency analysis through detailed dynamic simulation of DC and AC microgrids. The dynamic simulation models of DC and AC microgrids based on the Microgrid Test System in KEPCO Research Institute are described in detail. Through simulation studies on various conditions, this paper compares the energy efficiency and advantages of DC and AC microgrids.
Improved E&S Vector Hysteresis Model for the Precise Modeling of Vector Magnetic Properties of Electrical Steel Sheet
Song, Min-Ho ; Yoon, Hee-Sung ; Koh, Chang-Seop ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1684~1692
DOI : 10.5370/KIEE.2011.60.9.1684
Recently, several vector hysteresis models such as vector Preisach, vector Jiles-Atherton and dynamic E&S model have been proposed to describe vector magnetic properties of electrical steel sheets. However, it is still difficult to find an adequate vector hysteresis model in finite element application for both the Non-oriented and Grain-oriented electrical steel sheets under alternating and rotating field conditions. In this paper, an improved E&S vector hysteresis model is suggested to describe the vector magnetic properties of both Non-oriented and Grain-oriented electrical steel sheets under various magnetic field conditions including alternating and rotating magnetic field conditions. The validity of the proposed model is tested through comparisons with the experimental results under various magnetic field conditions.
Analysis of Deperming Performance According to Deperming Protocol Transform of Vessel Model
Kim, Jong-Wang ; Kim, Ji-Ho ; Park, Hyun-Soo ; Jung, Hyun-Ju ; Lee, Hyang-Beom ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1693~1699
DOI : 10.5370/KIEE.2011.60.9.1693
In this paper, for magnetic silence technology of naval vessel, is to make lab deperm system and to evaluate the deperm capacity of naval vessel regarding deperm protocol. Initial permanent magnetic field of naval vessel is magnetized before deperm, having the magnetic field of the same size, to evaluate the deperm capacity regarding a variety of deperm protocol for experimental reliability growth. Current dead time effect of deperm protocol is measured at the different initial current, which are 8A, 6A and 4A respectively. Furthermore, the experiment under the same condition except changing duty cycle into 50% is carried out. As a result, it is possible to compare the six different experiment outcomes. The result shows that the experiment with dead time improve the deperm capacity more than 48.51 percent comparing to the case without dead time.
High Performance Speed Control of IPMSM Drive using Recurrent FNN Controller
Ko, Jae-Sub ; Chung, Dong-Hwa ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1700~1707
DOI : 10.5370/KIEE.2011.60.9.1700
Interior permanent magnet synchronous motor(IPMSM) adjustable speed drives offer significant advantages over induction motor drives in a wide variety of industrial applications such as high power density, high efficiency, improved dynamic performance and reliability. Since the fuzzy neural network(FNN) is recognized general approximate method to control non-linearities and uncertainties, the development of FNN control systems have also grown rapidly. The FNN controller is compounded of fuzzy and neural network. It has an advantage that is the robustness of fuzzy control and the ability to adapt of neural network. However, the FNN has static problem due to their feed-forward network structure. This paper proposes high performance speed control of IPMSM drive using the recurrent FNN(RFNN) which improved conventional FNN controller. The RFNN has excellent dynamic response characteristics because of it has internally feed-back structure. Also, this paper proposes speed estimation of IPMSM drive using ANN. The proposed method is analyzed and compared to conventional FNN controller in various operating condition such as parameter variation, steady and transient states etc.
A Study on the Voltage Drop and Earth Leakage Current according to Interval of AT in the AT Feeding Method
Kim, Min-Seok ; Choe, Seung-Hyuk ; Lee, Jong-Woo ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1708~1714
DOI : 10.5370/KIEE.2011.60.9.1708
AT feeding system of the electric railway system is installed every about 10km at between the feeder and catenary in parallel and the mid-point of the transformer is connected to the rail The supply voltage of this system is doubled than rolling stock voltage. So the voltage drop is smaller than usual. And the other merit of this system is the decreasing inductive disturbance to the communication line because of the reduced current in rail which runs reversed in a point of view of rolling stock. Also, ATP(Auto Transformer Post) is installed to reduce the voltage drop and to mitigate the inductive disturbance, but still now the proper distance between the ATP and AT feeding system is not established which ranges from 2 to 10[km]. The stable result of simulation(which is set that the end of the line AT is installed) to the voltage drop and inductive disturbance can not analyzes the effect to the supply system due to the ATP. This paper analyzes the effect to the system depending on the location of ATP by forecasting the voltage drop and inductive disturbance.
A Study on Establishment of Signaling Systems to Speed up Conventional Railway
Jeong, Rag-Kyo ; Yoon, Young-Ki ; Kim, Baek-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1715~1720
DOI : 10.5370/KIEE.2011.60.9.1715
Studies suggested an increase in the competitiveness and roles of mainline railways like speed and accessibility improvement, as a fundamental direction of the National Transport Network Plan. At this point, topics presented especially for strengthening the role of human and environment centered transportation: as to the greatly improved speed competitiveness, there are an operational speed above 180km/h ~ 200km/h and traveling within 2 ~ 3 hours among big cities. As to accessibility improvement, there are accessibility to main railway stations within 30 minutes, and the improvement of accessibility, safety, eco-friendliness, amenity etc. As a part of these suggestions, field specific plans were proposed for the establishment of expressed mainline railway network in Korea such as train's, civil structures, trolley lines etc. In this paper we analyzed the conventional lines and systems to figure out whether to change details in terms of H/W of signaling system. Additionally, we reviewed the compatibility or difference of signalling system depending on train's speed. With this result, we deduced the number of virtual blocks specific to the speed of 180km/h, 200km/h and 230km/h, which were showed for the speed improvement considering each variable like blocks, braking distance etc. In this way, we suggested the railway signal system establishment plan considering safety operation.
Development of High Efficiency Solar Power Generation with Two-axis Tracking Control
Ko, Jae-Sub ; Chung, Dong-Hwa ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1721~1726
DOI : 10.5370/KIEE.2011.60.9.1721
Recently, interest in renewable energy is increased due to exhaustion of fossil fuel and environmental pollution all over the world, therefore the solar power generation using solar energy is many researched. The solar power generation is required solar tracking control and high concentration solar thermal collector because generation performance is depended on concentrator efficiency. This paper proposes high efficiency solar power generation with two-axis tracking control using dish-type solar thermal collector that has excellent thermal collector performance and tracking algorithm that can be accurately tracked solar position. This paper proves validity through analysis with accuracy of tracking algorithm and generating efficiency.
On the Optimization of the Coaxial-Conical-Radial Type Power Divider/Combiner and the Improvement of Isolation Characteristics
Choi, Young-Kyu ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1727~1732
DOI : 10.5370/KIEE.2011.60.9.1727
In order to realize a high performance(low loss, high isolation) microwave power divider/combiner, we have designed the power combiner/divider precisely in accordance with the different hight of central part. In the case of the high central part of the hight of
=10.2, a compensating part of the conical line is inserted in the conical conversion transmission line, and in the case of low central part of the hight of
=5.0, the conical conversion transmission line is remodeled into the 2-stage bend structure. In both case, the reflection characteristics are improved to 30dB over the operating frequency range of 5GHz bandwidth. A resistance is inserted between the peripheral ports so as to try to improve the isolation characteristics of the device. For the 16-divider/combiner, the isolation characteristics are improved to 10dB over the operating frequency range of 5GHz bandwidth.
Improvement of Sense Mode Bandwidth of Vibratory Silicon-On-Glass Gyroscope Using Dual-Mass System
Hwang, Yong-Suk ; Kim, Yong-Kweon ; Ji, Chang-Hyeon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1733~1740
DOI : 10.5370/KIEE.2011.60.9.1733
In this research, a MEMS vibratory gyroscope with dual-mass system in the sensing mode has been proposed to increase the stability of the device using wide bandwidth. A wide flat region between the two resonance peaks of the dual-mass system removes the need for a frequency matching typically required for single mass vibratory gyroscopes. Bandwidth, mass ratio, spring constant, and frequency response of the dual-mass system have been analyzed with MATLAB and ANSYS simulation. Designed first and second peaks of sensing mode are 5,917 and 8,210Hz, respectively. Driving mode resonance frequency of 7,180Hz was located in the flat region between the two resonance peaks of the sensing mode. The device is fabricated with anodically bonded silicon-on-glass substrate. The chip size is 6mm x 6mm and the thickness of the silicon device layer is
. Despite the driving mode resonance frequency decrease of 2.8kHz and frequency shift of 176Hz from the sensing mode due to fabrication imperfections, measured driving frequency was located within the bandwidth of sensing part, which validates the utilized dual-mass concept. Measured bandwidth was 768Hz. Sensitivity calculated with measured displacement of driving and sensing parts was 22.4aF/deg/sec. Measured slope of the sensing point was 0.008dB/Hz.
Performance Improvement for PID Controllers by using Dual-Input Describing Function (DIDF) Method
Choe, Yeon-Wook ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1741~1747
DOI : 10.5370/KIEE.2011.60.9.1741
Though various techniques have been studied as a way of adjusting parameters of PID controllers, no perfect method of determining parameters is available to date. This paper proposes a new method for enhancing performance of PID controllers by using the characteristics of dual-input describing function (DIDF). In other words, if nonlinear elements with two inputs (DIDF) are connected in series to the plant, the critical point (-1+j0) for Nyquist stability theory can be moved to a position arbitrarily selected on the complex plane by determining necessary coefficients of the DIDF appropriately. This makes the application of the existing conventional PID parameter tuning methods a lot easier, and stability and robustness of the system are improved simultaneously due to the DIDF inserted.
Stability of Linear Systems with Interval Time-varying Delay via New Interval Decomposition
Kim, Jin-Hoon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1748~1753
DOI : 10.5370/KIEE.2011.60.9.1748
In this paper, we consider the stability of linear systems with an interval time-varying delay. It is known that the adoption of decomposition of delay improves the stability result. For the interval time-delay case, they applied it to the interval of time-delay and got less conservative results. Our basic idea is to apply the general decomposition to the low limit of delay as well as interval of time-delay. Based on this idea, by using the modified Lyapunov-Krasovskii functional and newly derived Lemma, we present a less conservative stability criterion expressed as in the form of linear matrix inequality(LMI). Finally, we show, by well-known two examples, that our result is less conservative than the recent results.
A Robust Global Exponential Stabilization of Uncertain Affine MIMO Nonlinear Systems with Mismatched Uncertainties by Multivariable Sliding Mode Control
Lee, Jung-Hoon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1754~1760
DOI : 10.5370/KIEE.2011.60.9.1754
In this paper, a systematic design of a robust nonlinear multivariable variable structure controller based on state dependent nonlinear form is presented for the control of MIMO uncertain affine nonlinear systems with mismatched uncertainties and matched disturbance. After a MIMO uncertain affine nonlinear system is represented in the form of state dependent nonlinear system, a systematic design of a robust nonlinear variable structure controller is presented. To be linear in the closed loop resultant dynamics, the linear sliding surface is applied. A corresponding diagonalized control input is proposed to satisfy the closed loop global exponential stability and the existence condition of the sliding mode on the linear sliding surface, which will be investigated in Theorem 1. Through a design example and simulation study, the usefulness of the proposed controller is verified.
Obstacle Avoidance of Leader-Follower Formation
Oh, Young-Suk ; Park, Jong-Hun ; Kim, Jin-Hwan ; Huh, Uk-Youl ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1761~1766
DOI : 10.5370/KIEE.2011.60.9.1761
This paper presents obstacle avoidance of Leader-Follower formation. The follower robot maintain the formation with leader robot and avoid the detected obstacle. When obstacle is detected, follower robot avoid it considering leader robot and follower robot position and follower robot and obstacle position. In addition, follower robot avoid obstacle irrespective of obstacle size. Controller of follower robot is designed to satisfy Lyapunov stability by backstepping method. Simulation results shows that the designed controller has a stable performance.
Channel Selection Scheme using Statistical Properties in the Cognitive Radio Networks
Park, Hyung-Kun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1767~1769
DOI : 10.5370/KIEE.2011.60.9.1767
In a CR (cognitive radio) network, channel selection is one of the important issues for the efficient channel utilization. When the CR user exploits the spectrum of primary network, the interference to the primary network should be minimized. In this paper, we propose a spectrum hole prediction based channel selection scheme to minimize the interference to the primary network. To predict spectrum hole, statistic properties of primary user's traffic is used. By using the predicted spectrum hole, channel is selected and it can reduce the possibility of interference to the primary user and increase the efficiency of spectrum utilization. The performance of proposed channel selection scheme is evaluated by the computer simulation.
Optimization of Measuring Cardiac Output by Both Hands Electrode Impedance Method
Jung, Sang-O ; Sim, Myeong-Heon ; Jung, Woon-Mo ; Kim, Min-Yong ; Yoon, Chan-Sol ; Yoon, Hyung-Ro ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1770~1776
DOI : 10.5370/KIEE.2011.60.9.1770
In this study, a new method that can estimate ICG data from a subject's both hands to measure Cardiac Output under convenient sensor environment. With this aim, a grip-type electrode was implemented to measure ICG. To improve the accuracy of measurement, the regression equation was extracted using multiple bio-parameters and our result was compared with the thoracic ICG equipment(Physio Flow
, PF104D, Manatec Biomedical, France), which is being used in clinics. The subjects consist of 26 men and 4 women(age in
). They are no cardiac disease. Parameters available for regression model were used gender, BMI, MBP, LVET, dZ/dt(max), distance between the measured electrodes, body impedance, and PTT. As a result of analyzing the ICG measurement value on thorax and both hands, the correlation with stroke volume, heart rate, and cardiac output was
The PSO-PID Speed Controller Design for the BLDC Motor
Kim, Seung-Ki ; Han, Byung-Jo ; Yang, Hai-Won ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1777~1782
DOI : 10.5370/KIEE.2011.60.9.1777
Brushless DC motors applied in many control systems because of the good respose characteristic and the easy control characteristic. The speed control of the BLDC motors is important in the systems. This paper has designed PSO-PID speed controller for the speed control of BLDC motors. The PSO algorithm optimized the parameters of the PID controller in the PSO-PID speed controller. The several methods obtained the optimal inertia weight of the PSO algorithm by comparison. The optimal inertia weight of the PSO algorithm optimized the PSO-PID speed controller for BLDC motors. This paper confirmed the performance of proposed PSO-PID speed controller through simulation results.
Speed Estimation of Induction Motor in Steady State Using the RSH
Yang, Chul-Oh ; Park, Kyu-Nam ; Song, Myung-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1783~1787
DOI : 10.5370/KIEE.2011.60.9.1783
The slip frequency is included in feature frequency for fault diagnosis of rotor bar, so rotating rotor speed is needed. In this study, rotor slot harmonic(RSH) method is suggested for speed estimation of induction motor. When the rotor is rotating, motor current signal include the harmonic signal of back-emf voltage related with number of rotor slot. So from the power spectrum of current signal, the rotor speed can be founded. This method of rotor speed estimation gives the slip frequency, and the feature frequency of rotor bar fault can be calculated. Comparing with stroboscope speed meter, the error rate of suggested method is less than 0.1[%].
Implementation of a Condition Monitoring System for Mold Transformers in DC Substations
Park, Young ; Jung, Ho-Sung ; Park, Chul-Min ; Jang, Soon-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 60, issue 9, 2011, Pages 1788~1794
DOI : 10.5370/KIEE.2011.60.9.1788
The mold transformer is a complex and critical component of DC substations in Metro system. In this paper, a cost effective and intelligent condition monitoring system for mold transformers in DC substations was developed. This paper also provides an overview of the management program using PD (partial discharge) data on mold transformers. Prior to application of the proposed system to Metro DC substations, experiments were performed at the metro line substation located in Seoul and presented case studies for the use of the intelligent condition monitoring system for mold transformer in DC substations. The experiment results indicated that the developing system can be need in helping mange the risk of unexpected failure of mold type transformers.