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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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Journal DOI :
The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 61, Issue 12 - Dec 2012
Volume 61, Issue 11 - Nov 2012
Volume 61, Issue 10 - Oct 2012
Volume 61, Issue 9 - Sep 2012
Volume 61, Issue 8 - Aug 2012
Volume 61, Issue 7 - Jul 2012
Volume 61, Issue 6 - Jun 2012
Volume 61, Issue 5 - May 2012
Volume 61, Issue 4 - Apr 2012
Volume 61, Issue 3 - Mar 2012
Volume 61, Issue 2 - Feb 2012
Volume 61, Issue 1 - Jan 2012
Selecting the target year
Jeju area's Voltage Stability Analysis which use the Real Time Voltage Stability Analysis Program
Lee, Sung-Woo ; Ahn, Kyo-Sang ; Seo, Dong-Wan ; Jang, Moon-Jong ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1387~1392
DOI : 10.5370/KIEE.2012.61.10.1387
These days people use a lot of electric power, because industry advancement and a standard of living is elevated. So voltage stability analysis and control problems are very important in these days. U.S.A has already developed voltage stability analysis program, and use it on power transmission scheme such as generator overhaul, transmission line off and so on. So voltage stability analysis is more and more interested in Korea, too. In this paper, we introduce a standard theory of voltage stability analysis and real time voltage stability analysis program that use sPMU(Satellite Phasor Measurement Unit). And we also introduce the calculation result about voltage stability in Jeju power transmission system.
Determining Optimal Installed Capacity and the Interconnected Bus of Renewable Energy Sources Considering the Cost of Energy Not Supplied
Kim, Sung-Yul ; Lee, Sung-Hun ; Kim, Jin-O ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1393~1398
DOI : 10.5370/KIEE.2012.61.10.1393
Due to environmental regulation and technical improvements, renewable energy sources (RES) are increasingly penetrated and operated in power systems. Clean energy technologies have become cost-competitive with conventional power systems, and in the near future, the generation cost of RES is expected to approach grid parity. In this situation, it should be considered an extraordinarily important issue to be maximized resulting in utilization of RES as well as to develop technologies for efficiency improvement of RES. Therefore, in this paper, the method for determining an optimal installed capacity and interconnected location of RES is proposed in order to minimize the cost of energy not supplied, which can contribute to improve distribution reliability.
A study on the Turbine-Generator Governor Dynamic Characteristic Testing System
Choi, Hyung-Joo ; Lee, Heung-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1399~1411
DOI : 10.5370/KIEE.2012.61.10.1399
The grid frequency is controlled cooperatively by the governor of the Turbine-Generator and the automatic generation controller(AGC) of the KPX(Korea Power Exchange). It is a basic requirement that the reliability of the governor is verified to enhance the power system stability but it is not easy to confirm the response characteristics of the governor because all generators are operated in the grid system that has the constant voltage and frequency. Therefore, it is necessary to study a new test method in order to examine the governor dynamic characteristic in the similar fault conditions. A study has shown that it is verified to simulate the turbine-generator power control system, the governor response characteristic under limited conditions and contribution of AGC with the gas turbine generator simulation model as well as demonstrate the dynamic response of the governor with the developed governor dynamic characteristic tester based on digital controller while the turbine-generator is connected to the grid system. This tester is constructed by the built-in functions of the turbine-generator main controller. In this treatise, the theoretical background, development method and the results of both simulations and demonstrations are described as another way to verify the turbine-generator governor dynamic characteristics.
Development of Protection Coordination Algorithm for Smart Distribution Management System using Communication Method based on IEC61850
Chu, Cheol-Min ; Yun, Sang-Yun ; Kwan, Seung-Chul ; Chu, Kyung-Yong ; Jin, Young-Kyu ; Choi, Myeon-Song ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1412~1419
DOI : 10.5370/KIEE.2012.61.10.1412
In this paper, we propose the protection coordination algorithm using communication methode based on IEC 61850. The communication protocol in power distribution management system has been issued by IEC standard, IEC61850 of them, which was made for substation automation system, has researched to apply into power distribution system, even though the standard is not a suitable for the system. In smart distribution management system' launched in 2009, the communication network based on the ethernet network for IEC 61850 has been designed to apply the self-healing concept, which is to perform the system protection through the communication between remote terminal units(RTU) according to the standard. However, it is first time to apply the scheme in the real. Thus, this paper proposed the protection algorithm and consideration for applying communication method and introduced the result of demonstration.
Thermal Analysis of IPMSM According to Current Vector Control Method
Kye, Seung-Hyun ; Jeong, Tae-Seok ; Cho, Gyu-Won ; Jang, Ki-Bong ; Kim, Gyu-Tak ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1420~1425
DOI : 10.5370/KIEE.2012.61.10.1420
Nowadays, Interior permanent magnet synchronous motor(IPMSM) which having high power density is much used for the vehicles. However, IPMSM causes a lot of losses because of high-speed driving and high current density, and temperature rising by iron loss and copper loss could reduce torque characteristics and durability of IPMSM. Therefore, analysis about thermal characteristics of IPMSM is required at design stage. In this paper, temperature characteristics according to current vector control method were analyzed through calculate thermal equivalent circuit. And calculated results were verified through comparing with the experiments.
Performance Analysis for Optimizing Degaussing Coil Currents in Ships with a Breakdown in Parts of Degaussing Devices
Choi, Nak-Sun ; Jeung, Gi-Woo ; Kim, Dong-Wook ; Yang, Chang-Seop ; Jun, Hyun-Ju ; Kim, Dong-Hun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1426~1431
DOI : 10.5370/KIEE.2012.61.10.1426
This paper analyzes re-degaussing performances of various breakdown conditions of degaussing coils in a ship to reduce underwater magnetic field anomaly due to the hull magnetization induced under the Earth's magnetic field. To achieve this, first, it is implemented to optimize degaussing coil currents by a magnetomotive force sensitivity formula combined with the coil effects. The re-degaussing processes are then executed when a breakdown occurs in degaussing coils, one by one. Finally, the re-degaussing performances are examined with the results of normal degaussing and coil breakdown conditions.
Improved LCCT Z-Source DC-AC Inverter for Ripple Reduction of Input Current and Capacitor Voltage
Shin, Yeon-Soo ; Jung, Young-Gook ; Lim, Young-Cheol ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1432~1441
DOI : 10.5370/KIEE.2012.61.10.1432
In this study, an improved LCCT(Inductor-Capacitor-Capacitor-Trans) Z-source inverter(Improved LCCT ZSI) with characteristics of Quasi Z-source inverter(QZSI) and LCCT Z-source inverter(LCCT ZSI) is proposed. The proposed inverter can also reduce the voltage stress and input current/capacitor voltage ripples compared with conventional LCCT ZSI and Quasi ZSI. A two winding trans in Z-impedance network of the conventional LCCT ZSI is replaced by a three winding trans in the proposed inverter. To verify the validity of the proposed inverter, a DSP controlled hardware was made and PSIM simulation was executed for each method. Comparing the current and voltage ripples of each method under the condition of input DC voltage 70[V] and output AC voltage 76[Vrms], the input current and capacitor voltage ripple factors of the proposed inverter were low as 11[%] and 1.4[%] respectively. And, for generation of the same output AC voltage of each method, voltage stress of the proposed inverter was low as 175[V] under the condition of duty ratio D=0.15. As mentioned above, we could know that the proposed inverter have the characteristics of low voltage stress, low ripple factor and low operation duty ratio compared with the conventional methods. Finally, the efficiency according to load change/duty ratio and the transient state characteristics were discussed.
Direct Power Sensorless Control of Three-Phase AC/DC PFC PWM Converter using Virtual Flux Observer
Kim, Young-Sam ; Kwon, Young-Ahn ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1442~1447
DOI : 10.5370/KIEE.2012.61.10.1442
In this paper, direct power control system for three-phase PWM AC/DC converter without the source voltage sensors is proposed. The sinusoidal input current and unity effective power factor are realised based on the estimated flux in the observer. Both active and reactive power calculated using estimated flux. The estimation of flux is performed based on the Reduced-order flux observer using the actual currents and the command control voltage. The source voltage sensors are replaced by a flux estimator. The active and reactive powers estimation are performed based on the estimated flux and Phase anble. The proposed algorithm is verified through simulation and experiment.
The Study of Transient Radiation Effects on Commercial Electronic Devices
Oh, Seugn-Chan ; Lee, Nam-Ho ; Lee, Heung-Ho ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1448~1453
DOI : 10.5370/KIEE.2012.61.10.1448
In this study, we carried out transient radiation test for identify failure situation by a transient radiation effect on operational amplifier devices. This experiments were carried out using a 60 MeV electron beam pulse of the LINAC(Linear Accelerator) facility in the Pohang Accelerator Laboratory. In this test, we has found that a serious failure as a burn-out effect due to overcurrent on the partial electronic devices.
Properties of EMNC and EMNSC for Insulation New Material as Apply to High Voltage Heavy Electric Machine
Park, Jae-Jun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1454~1460
DOI : 10.5370/KIEE.2012.61.10.1454
In order to develop an new electric insulation material for heavy electric equipments, epoxy/micro/nano composite (EMNC) was prepared by mixing micro-silica with nano layered silicate, where the nano layered silicate was synthesized by our electric field dispersion method, EMNSC was prepared by treating the EMNC with a silane coupling agent. Thermal properties such as glass transition temperature (Tg) and thermal expansion coefficient, and DMA characteristics were studied, and mechanicla properties such as tensile and flexural tests were performed. AC electrical insulation strength was also tested. All properties of EMNSC were modified by treating EMNC with silane coupling agent and it was confirmed that our new developed composites could be used in the heavy electric equipments.
Analysis of Leakage Current Waveforms for Transmission Line Porcelain Insulators due to ESDD Contamination
Park, Jae-Jun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1461~1470
DOI : 10.5370/KIEE.2012.61.10.1461
This paper reports the contamination performance of transmission line porcelain insulators tested under five different contaminant conditions - clean and ESDD (equivalent salt deposit density) level (A, B, C, and D) through measurement of their leakage current under drop of potential method. To estimate the contamination for transmission line porcelain insulators, leakage current waveform and its maximum value were measured under step-up power test. In the clean insulators test, % distortion factors decreased with increasing step-up power, and as the ESDD level increased, some characteristics such as frequency analysis, harmonics and % distortion facotor could be used for contamination diagnosis of the transmission line porcelain insulators.
A Study on the Dielectric Characteristics of GFRP in LN
under Lightning Impulse Voltage According to Pressure
Hong, Jong-Gi ; Heo, Jeong-Il ; Nam, Seok-Ho ; Kang, Hyoung-Kul ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1471~1476
DOI : 10.5370/KIEE.2012.61.10.1471
A study on the dielectric characteristics of the Glass Fiber Reinforced Plastic (GFRP) is important for designing a reliable high voltage superconducting machines such as transmission superconducting fault current limiters, superconducting cables, and superconducting transformers. In this paper, dielectric experiments of the GFRP under lightning impulse voltage are conducted in liquid nitrogen(
) according to various experimental conditions such as the thicknesses of the GFRP, the diameters of electrode systems and the pressures. The dielectric characteristics of the GFRP are analyzed by using a Finite Elements Method(FEM) according to various field utilization factors. It has been reported that the electrical insulation design of the GFRP would be conducted by considering the mean electric field intensity(
) distributed inside the GFRP. In this study, it is found that the dielectric performance of the GFRP could be explained by not only
but also the maximum electric field intensity (
). Finally, the empirical formulae of the GFRP to estimate an electrical breakdown voltage at sparkover under the lightning impulse condition are deduced. It is expected that the presented experimental results in this paper are helpful to design electrically reliable high voltage superconducting machines using the GFRP as an insulation material.
Design of Variable Power Distributor and Waveguide Connecting Structure for Wireless Microwave Power Transmission in a Building
Choi, Young-Kyu ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1477~1482
DOI : 10.5370/KIEE.2012.61.10.1477
This paper deals with a new variable microwave power distributor and a connector between a deck plate and a input power waveguide for indoor microwave wireless power transmission. We design a new type connector built in the 3-stage coaxial line structure, and calculate the return loss of the connector at 2.45GHz. Newly designed connector shows the excellent return loss performance less than -30dB at the operating frequency of 2.45GHz. And we show a power distributor in which the dividing ratio of the power is controlled mechanically by three rotary fins. The distributor can control the dividing power from 4.5% to 58% with the variance of 5% output power. The experimentally tested results of the distributor are good agreement with the simulation within the return loss of 1%.
The Effect of Altitude Errors in Altitude-aided Global Navigation Satellite System(GNSS)
Cho, Sung-Lyong ; Han, Young-Hoon ; Kim, Sang-Sik ; Moon, Jei-Hyeong ; Lee, Sang-Jeong ; Park, Chan-Sik ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1483~1488
DOI : 10.5370/KIEE.2012.61.10.1483
This paper analyzed the precision and accuracy of the altitude-aided GNSS using the altitude information from digital map. The precision of altitude-aided GNSS is analysed using the theoretically derived DOP. It is confirmed that the precision of altitude-aided GNSS is superior to the general 3D positioning method. It is also shown that the DOP of altitude-aided GNSS is independent of altitude bias error while the accuracy was influenced by the altitude bias error. Furthermore, it is shown that, since the altitude bias error influenced differently to each pseudorange measurement, the effect of the altitude bias error is more serious than clock bias error which does not influence position error at all. The results are evaluated by the simulation using the commercial RF simulator and GPS receiver. It confirmed that altitude-aided GNSS could improve not only precision but also accuracy if the altitude bias error are small. These results are expected to be easily applied for the performance improvement to the land and maritime applications.
Active Noise Control of Induction Motor using Co-FXLMS Algorithm
Kim, Young-Min ; Nam, Hyun-Do ; Lee, Young-Jin ; Lee, Kwon-Soon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1489~1495
DOI : 10.5370/KIEE.2012.61.10.1489
In this study, the active noise control experiment has been performed using induction motor noises. While the noises were measured, a induction motor was operated in different speed. For the simulation of ANC(Active Noise Control), test-bed is composed a multi-channel ANC system was constructed. In order to compare the control performance, we performed noise reduction simulations of ANC by Co-FXLMS algorithm and FXLMS algorithm. Through the simulation results, we confirmed that convergence performance and noise decrease effect of the proposed Co-FXLMS algorithm have been improved from existing FXLMS algorithm.
A Study on Efficiency Improvement by Fine Tuning of Power Plant Control
Kim, Ho-Yol ; Kim, Byoung-Chul ; Byun, Seung-Hyun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1496~1501
DOI : 10.5370/KIEE.2012.61.10.1496
A fine tuning on a control system is essential not only for stable operation but also for efficient operation of the power plant. There has been a very few studies on efficiency change by control system tuning. So, it was not clear that if it could be improved or not when the control is stable by fine tuning and how much it could be improved if it works. An accurate algorithm for measurement of the plant efficiency was newly introduced and implemented to measure integrated fuel flow and electricity MW output and to calculate the mean efficiency for given time. As a result, stable operation after fine tuning of control parameters for major controlled variables brought higher efficiency than un-stable operations like a cycling or an oscillation. The plant efficiency has been monitored during various tests and tunings to confirm how much it changes by tuning of the control system on power plant. Now, we can say that the efficiency can be improved in stable operation by fine tuning of the control system.
A Performance Study of Multi-core Out-of-Order Superscalar Processor Architecture
Lee, Jong-Bok ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1502~1507
DOI : 10.5370/KIEE.2012.61.10.1502
In order to overcome the hardware complexity and power consumption problems, recently the multi-core architecture has been prevalent. For hardware simplicity, usually RISC processor is adopted as the unit core processor. However, if the performance of unit core processor is enhanced, the overall performance of the multi-core processor architecture can be further increased. In this paper, out-of-order superscalar processor is utilized for the multi-core processor architecture. Using SPEC 2000 benchmarks as input, the trace-driven simulation has been performed for the out-of-order superscalar cores between 2 and 16 extensively. As a result, the 16-core out-of-order superscalar processor for the window size of 16 resulted in 17.4 times speed up over the single-core out-of-order superscalar processor, and 50 times speed up over the single core RISC processor. When compared for the same number of cores on the average, the multi-core out-of-order superscalar processor performance achieved 3.2 times speed up over the multi-core RISC processor and 1.6 times speed up over the multi-core in-order superscalar processor.
Relaxed Stability Condition for Affine Fuzzy System Using Fuzzy Lyapunov Function
Kim, Dae-Young ; Park, Jin-Bae ; Joo, Young-Hoon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1508~1512
DOI : 10.5370/KIEE.2012.61.10.1508
This paper presents a relaxed stability condition for continuous-time affine fuzzy system using fuzzy Lyapunov function. In the previous studies, stability conditions for the affine fuzzy system based on quadratic Lyapunov function have a conservativeness. The stability condition is considered by using the fuzzy Lyapunov function, which has membership functions in the traditional Lyapunov function. Based on Lyapunov-stability theory, the stability condition for affine fuzzy system is derived and represented to linear matrix inequalities(LMIs). And slack matrix is added to stability condition for the relaxed stability condition. Finally, simulation example is given to illustrate the merits of the proposed method.
Driver Design with Linear Feedback Function for the Optimum Power Consumption of LED BLU
Lee, Seung-Woo ; Yu, Nam-Hee ; Cho, Seong-Ik ; Shin, Hong-Gyu ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1513~1517
DOI : 10.5370/KIEE.2012.61.10.1513
As demands for green industry increase, this paper proposes a power control technique that can substitute pre -existing CCFL(Cold Cathode Fluorescent Lamp) and optimize power consumption of LED BLU. This technique is designing LED driver circuit that make a DC-DC output voltage(VLED) to have a linear control function for a supply voltage of LED string. The proposed LED driver have an advantage that can increase or decrease a DC-DC output voltage compared with conventional LED driver. The designed LED driver circuit was designed using 0.35um CMOS technology. And its operation was verified through simulation.
Suppression of Noisy Characteristics of Biosignals by Implementing Digital Filters with an Android Smartphone Platform
Kim, Jeong-Hwan ; Kim, Kyeong-Seop ; Shin, Seung-Won ; Kim, Hyun-Tae ; Lee, Jeong-Whan ; Kim, Dong-Jun ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1518~1523
DOI : 10.5370/KIEE.2012.61.10.1518
In this study, the novel digital filtering algorithms are implemented to suppress the noisy characteristics embedded in ambulatory electrocardiogram signals by an android smartphone platform. With this aim, Graphical User Interface (GUI) is designed and implemented by utilizing multithread-Java programming to realize Finite Impulse Response and Infinite Impulse Response filter. With simulating our implemented digital filters built in an android smartphone, we can find the fact that we can efficiently suppresses the noisy characteristics due to baseline wandering and 60 Hz powerline source fluctuations especially in electrocardiograms.
Consideration for Confirmity Assessment of Eco-friendly Public Transportation System based on the Wireless Power Transfer Technology
Shin, Jung-Jin ; Kim, Gi-Hyun ; Lee, Kang-Hee ; Kim, Han-Su ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1524~1528
DOI : 10.5370/KIEE.2012.61.10.1524
According to the Article 4(Confirmity Assessment)of the Electrotechnical Regulation, Confirmity Assessment for the Electrotechnical Regulation decides confirmity of Electrotechnical Regulation; whether to satisfy performances and requirements(determined from Electrotechnical Regulation). It evaluates technical requirements, new technology and standards. However, it does not evaluate technical content stated from Electrotechnical Regulation & Conformity Criteria. From Confirmity Assessment, the technology will be decided whether to fulfill performances and technical requirements. Which is predetermined by contents related to Electrotechnical Regulation. Test standards and test conditions will be overlooked to determine its performances and technical requirements for safety. This paper will show that, studies have been done to determine the guideline for Confirmity Assessment, which is evaluated from performances and technical requirements associated with Confirmity Assessment of electrical installation for new technology of wireless power transfer.
Design of Fuzzy PI Controller for Variable Speed Drive of Switched Reluctance Motor
Yoon, Yong-Ho ; Park, Jun-Suk ; Song, Sang-Hoon ; Won, Chung-Yuen ; Kim, Jae-Moon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1529~1535
DOI : 10.5370/KIEE.2012.61.10.1529
This paper presents the application algorithm for speed control of Switched Reluctance Motor. The conventional PI controller has been widely used in industrial applications. But it is very difficult to find the optimal PI control gain. Fuzzy control does not need any model of plant. It is based on plant operator experience and heuristics. The proposed fuzzy logic modifier increases the control performance of conventional PI controller. Simulation and experimental results show that the proposed fuzzy control method was superior to the conventional PI controller in the respect of system performance. The experiments are performed to verify the capability of proposed control method on 6/4 salient type SRM.
Problem Analysis by Iron Core Structure of the Transformer on Asymmetric three Phase lines and Prevention Measures
Shin, Dong-Yeol ; Yun, Dong-Hyun ; Cha, Han-Ju ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1536~1541
DOI : 10.5370/KIEE.2012.61.10.1536
The study analyzed problems by iron core structure of the three phased transformer on asymmetric three phase lines, which included line disconnections, ground faults, COS OFF, and unbalanced loads on the power distribution system. In particular, by analyzing PT combustion cases within the MOF, the study was able to analyze the combustion cause of the core-type transformer and its effect on the system, conduct simulations and practice demonstrations on the characteristics for each iron core structure of the three phase transformer using PSCAD/EMTDC, and suggest measures to prevent the combustion of the core-type transformer.
Development of Asynchronous Blocking Algorithm through Asynchronous Case Study of Steam Turbine Generator
Lee, Jong-Hweon ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1542~1547
DOI : 10.5370/KIEE.2012.61.10.1542
Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. When calculation method of protection settings and logic for protection of generator asynchronization will be recommended, a distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection, this paper describes an improved backup protection coordination scheme using a new logic that will be suggested.
Optimal Microgrid Operation Considering Combined Heat and Power Generation with Variable Heat and Electric Ratio
Lee, Ji-Hye ; Park, Je-Se ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1548~1553
DOI : 10.5370/KIEE.2012.61.10.1548
The important requirement for microgrid operation is to meet the balance between supply and demand. To meet, Combined Heat and Power (CHP) generation should be considered in microgrid scheduling. CHP generation is economical on the side of a consumer because it products heat and power. Therefore, it is high efficient. This paper presents a mathematical model for optimal microgrid operation including CHP generation using the optimal ratio of heat and power due to demand. The objective function and constraints are modeled by linear program (LP). Through the case study, the validation of the proposed model is shown.
Even Harmonic Analysis of Series Arc-fault Current Using BPF of GIC Application in Computer
Ko, Won-Sik ; Moon, Won-Sik ; Bang, Sun-Bae ; Kim, Jae-Chul ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1554~1560
DOI : 10.5370/KIEE.2012.61.10.1554
In this paper, the even harmonic current(2nd, 4th, 6th, 8th) of the arc fault current and normal current were measured in computer load and analyzed. The BPF with GIC was developed to detection of harmonic, the exact center frequency and a high degree of sharpness could be easily obtained. The total even harmonic distortion due to series arc fault in computer load was 31.2%, this value was increased 3.9 times better than the total even harmonic distortion of normal current. The results of analysis of arc fault current RMS variation rate and Peak variation rate per half-cycle, The RMS average variation rate are as follows ; the 2nd harmonic was 0.24, the 4th harmonic was 0.15, the 6th harmonic was 0.19, the 8th harmonic was 0.25, respectively. The Peak average variation rate are as follows ; the 2nd harmonic was 0.19, the 4th harmonic was 0.12, the 6th harmonic was 0.13, the 8th harmonic was 0.15, respectively. The results of this analysis utilize data to detect of series arc fault on wiring of computer load.
Physical and Electrical Properties of Nanocrystalline Carbon Films Prepared with Ti Concentration for Contact Strip Application of Electric Railway
Park, Yong-Seob ; Jung, Ho-Sung ; Park, Chul-Min ;
The Transactions of The Korean Institute of Electrical Engineers, volume 61, issue 10, 2012, Pages 1561~1564
DOI : 10.5370/KIEE.2012.61.10.1561
In this work, we have fabricated the nanocrystalline carbon films by using unbalanced magnetron sputtering method with graphite and Ti targets for contact strip application of electrical railway. The power density of graphite target was fixed and the power density was increased for the increase of Ti concentration in TiC films. We investigated the hardness, surface roughness, contact angle, resistivity, HRTEM and XPS of TiC films with Ti concentration. The hardness and resistivity were improved with increasing Ti concentration. These results indicate that the improvement of hardness and resistivity is related to the increase of sp2 clusters in TiC films.