• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.8
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• pp.650-657
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• 1989

The conversion efficiency of an ozone generator can be significantly improved by modifying the discharge electrode of a helical strip line rod-to-cylinder type ozone generator to a pyramid-project-embossed rod, and by using a pulse corona discharge. Parametric studies have been carried out to obtain optimum values of peak pulse voltage, pulse forming capacitance, feeder cable and ozone generator capacitance, interelectrode spacing and corona tip density of ozone generator, and feed air flow rate and temperature. The generated ozone concentration was very dependent upon the value of pulse forming capacitance, feeder cable and ozone generator capacitance, and corona tip density. Maximum conversion efficiency was obtained with a pulse forming capacitance of about 500pF, 75pF matched feeder cable and ozone generator, and a corona tip density of 16mm. When operated at optimum values, ozone yield of 79, 99, 80 g/KWh for the different interelectrode type ozone generators tested were obtained, which are approximately 30% higher than that of an industrial ozone generator.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.260-262
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• 2002

This study presents a AC electric railway system model using PSCAD/EMTDC. Ver.3.08 for circuit analysis and fault studies. This system model made by PSCAD/EMTDC is composed of feeder, contact line, rails, Scott-transformer, Auto-transformer. This model is based on four-port network which is an extension of two-port network theory. In order to verify the proposed model, each voltage of feeder-rail, contact line-rail and feeder-contact line is measured and fault studies are also simulated.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1305-1309
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• 2013

The application of the superconducting fault current limiter (SFCL) in a power distribution system is expected to contribute the voltage-sag suppression of the bus line as well as the fault-current reduction of the fault line. However, the application effects of the SFCL on the voltage sag of the bus line including the fault current are dependent on its application location in a power distribution system. In this paper, we investigated the fault current limiting and the voltage sag suppressing characteristics of the SFCL due to its application location such as the outgoing point of the feeder, the bus line, the neutral line and the 2nd side of the main transformer in a power distribution system, and analyzed the trace variations of the bus-voltage and fault-feeder current. The simulated power distribution system, which was composed of the universal power source, two transformers with the parallel connection and the impedance load banks connected with the 2nd side of the transformer through the power transmission lines, was constructed and the short-circuit tests for the constructed system were carried out. Through the analysis on the short-circuit tests for the simulated power distribution system with the SFCLs applied into its representative locations, the effects from the SFCL's application on the power distribution system were discussed from the viewpoints of both the suppression of the bus-voltage sag and the reduction of the fault current.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.368-370
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• 2005

Due to the tendency towards large capacity and complexity of power system, an enhancement of power system equipment make a system impedance to be low in power system. Generally if an equivalent impedance of system becomes lower, a system stability will be better. But the fault current becomes very larger. The 345kV ultra-high voltage system will use current limit reactors(CLR) in a transmission line or a bus in substation to limit the magnitude of fault current. The CLR makes a significant contribution to the severity of the transient recovery voltage(TRV) experienced by feeder and bus circuit breakers on clearing feeder faults. Based on the conclusions of an investigation of actual circuit breaker failures while performing this duty, the mitigation of the transient recovery voltage associated with the reactors is described. Therefore in this article we simulated the TRV by EMTP at Bus Terminal Fault.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2206-2214
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• 2011

LDC(Line Drop Compensation) is widely used in controlling ULTC(Under Load Tap Changer) output voltage at distribution substation. However, LDC may experience some difficulties in voltage control due to renewable energy resources and distributed generations. Therefore, more advanced voltage control algorithm is necessary to deal with these problems. In this paper, a modified voltage control algorithm for ULTC and DG is suggested. ULTC is operated with the voltages measured at various points in distribution system and prevents overvoltage and undervoltage in the distribution feeders. Reactive power controller in DG compensates the voltage drop in each distribution feeders. By these algorithms, the voltage unbalance between feeders and voltage limit violation will be reduced and the voltage profile in each feeder will become more flat.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.3
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• pp.325-329
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• 2010

Capacitor has been used principally for the power factor compensation long ago. However now it does as passive filter to reduce harmonics of nonlinear load with reactor. Most of the customer's low-voltage feeder has been designed with approximately balanced and connected at the 3 phase four wire system. But voltage and current unbalance is appeared by the mixing operation of single or three phase load etc. The addition of reactor at the condenser may rise its terminal voltage. Voltage and current values above rating can act on electrical stress on the condenser. In this paper, we calculated and measured that voltage, current and capacity of condenser are changed under the voltage balance. We conclude that magnitude and deviation of phase voltage act on major point of electrical stress.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1658-1671
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• 2017

To address the inaccurate load demand sharing problems among parallel inverter-interfaced voltage-controlled distributed generation (DG) units in islanded microgrids (MGs) with different DG power ratings and mismatched feeder impedances, an enhanced voltage control scheme based on the active compensation of circulating voltage drops is proposed in this paper. Using the proposed strategy, reactive power and harmonic currents are shared accurately and proportionally without knowledge of the feeder impedances. Since the proposed local controller consists of two well-separated fundamental and harmonic voltage control branches, the reactive power and harmonic currents can be independently shared without having a remarkable effect on the amplitude or quality of the DGs voltage, even if nonlinear (harmonic) loads are directly connected at the output terminals of the units. In addition, accurate load sharing can also be attained when the plug-and-play performance of DGs and various loading conditions are applied to MGs. The effects of communication failures and latency on the performance of the proposed strategy are also explored. The design process of the proposed control system is presented in detail and comprehensive simulation studies on a three-phase MG are provided to validate the effectiveness of the proposed control method.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.171-177
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• 2014

PWM converter trains exhibit excellent load characteristics in comparison with conventional phase-controlled trains with low power factors, as they can be operated at power factors which are close to unity by means of a voltage vector control method. However, in the case of a high track density or extended feeding, significant line losses and voltage drops can occur. Instead of operating these trains at a fixed unity power factor, this paper suggests a continuous optimal power factor control scheme for each train in an effort to minimize line losses and improve voltage drops according to varying load conditions. The proposed method utilizes the steepest descent algorithm targeting each car in the same feeding section to establish the optimized reactive power compensation levels that can minimize the reactive power loss of the feeder. The results from a simulation of a sample system show that voltage drops can be improved and line losses decreased.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.9
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• pp.903-911
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• 1990

When load areas on a feeder are deenergized due to faults and scheduled outage, operators need to identify neighboring feeders, try to restore customers and minimize out-of-service areas. These cases include knowledge of system states and various constraints such as voltage drop. This paper concerns the load transfer in fault restoration and scheduled outage. Also, the operating constraints such as line current capacity, relay trip current, transformer capacity, voltage drop and line loss are considered. This expert system can propose the optimal load transfer method by analyzing the system state and considering the constraints.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.207-209
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• 2004

저압간선의 굵기산정시 일반적으로 간이 계산식이 사용되고 있으나 이는 교류 임피던스를 적용한 정식과는 허용 전압강하를 기준으로한 포설거리에서 차이가 있으므로 저압간선의 설계시 보다 정확한 계산을 위해 교류 임피던스를 기준으로한 정식을 사용하여 계산이 이루어져야 한다. 따라서, 본 논문에서는 정식과 간이식에 따른 계산결과와 실측을 통한 전압강하를 비교하여 정확한 전압강하 계산법을 검토하여 보았다.