• 조명전기설비학회논문지
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• 제30권2호
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• pp.43-48
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• 2016

Operational applications such as service restoration, voltage control and protection coordination are calculated based on the active and reactive power loading of the sections in the distribution networks. Loadings of the sections are estimated using the voltage and current measured from the automatic switches deployed along the primary feeders. But, due to the characteristics of the potential transformer attached to the switches, accuracy of the voltage magnitude is not acceptable to be used for section loading calculation. This paper proposes a new accurate section loading estimation method through voltage measurement error compensation by calculating voltage drop of the distribution line. In order to establish feasibility of the proposed method, various case studies based on Matlab simulation have been performed.

• 전기의세계
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• 제18권2호
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• pp.7-14
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• 1969

From the first customer located right at the substation to the last customer at the end of the line, voltage must be held within close limits, so the voltage regulation is more important than the thermal limit. On a typical distribution system during the peak load period, the voltage drop may be serious enough to cause unsatisfactory operation of home appliances in the residential area, and present many problems to manufacturing industries, where the voltage must be maintained within close limits to insure smooth operation. Among all the factors contributing to voltage drop in the distribution system, the voltage drop in the distribution transformer may account for 30% of this figure. If we can eliminate this factor, the power companies can provide better quality electricity to more customers with the existing distribution facilities, thus saving on initial investment costs. Taking all these problems into consideration, the author undertook the design of a capacitive transformer which would give zero voltage drop at rated load and at 80% lagging power factor while incorporating overload features to withstand 400% overload for at least 100 seconds. The following are the results obtained through design, manufacture and test of an initial experimental transformer built with these specific purposes.

• Journal of Power Electronics
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• 제17권2호
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• pp.522-532
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• 2017

This paper presents a novel integrated structure for a cascaded distribution static compensator (D-STATCOM) and distribution transformer for medium-voltage reactive power compensation. The cascaded multilevel converter is connected to a system via a group of special designed taps on the primary windings of the Dyn11 connection distribution transformer. The three-phase winding taps are symmetrically arranged and the connection point voltage can be decreased to half of the line-to-line voltage at most. Thus, the voltage stress for the D-STATCOM is reduced and a compromise between the voltage rating and the current rating can be achieved. The spare capacity of the distribution transformer can also be fully used. The working mechanism is explained in detail and a modified control strategy is proposed for reactive power compensation. Finally, both simulation and scaled-down prototype experimental results are provided to verify the feasibility and effectiveness of the proposed connection structure and control strategy.

• 전기학회논문지P
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• 제63권4호
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• pp.266-270
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• 2014

In this paper, the effects of superconducting fault current limiter (SFCL) installed in power distribution system on reliability are evaluated and analyzed. The fault current will be decreased in power distribution system with SFCL because of the increased impedance of SFCL. The decreased fault current will improve the voltage drop of the bus of substation. The voltage drop is an important factor of power distribution system reliability. In this paper, improvement of reliability worth is analyzed when SFCLs are installed at the starting point in power distribution system. First, resistor-type SFCL model is used in PSCAD/EMTDC. Next, typical power distribution system is modeled. Finally, when the SFCLs with impedance 0.5 [${\Omega}$] are installed in feeder, power distribution system reliability is evaluated. Also, the improvement effect of reliability worth including the effect of voltage sag is analyzed using customer interruption cost according to whether or not SFCL is installed.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.200-204
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• 2012

This study has presented the analysis of breakdown voltage for a double-gate metal-oxide semiconductor field-effect transistor (MOSFET) based on the doping distribution of the Gaussian function. The double-gate MOSFET is a next generation transistor that shrinks the short channel effects of the nano-scaled CMOSFET. The degradation of breakdown voltage is a highly important short channel effect with threshold voltage roll-off and an increase in subthreshold swings. The analytical potential distribution derived from Poisson's equation and the Fulop's avalanche breakdown condition have been used to calculate the breakdown voltage of a double-gate MOSFET for the shape of the Gaussian doping distribution. This analytical potential model is in good agreement with the numerical model. Using this model, the breakdown voltage has been analyzed for channel length and doping concentration with parameters such as projected range and standard projected deviation of Gaussian function. As a result, since the breakdown voltage is greatly changed for the shape of the Gaussian function, the channel doping distribution of a double-gate MOSFET has to be carefully designed.

• 대한전기학회논문지:전력기술부문A
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• 제48권6호
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• pp.699-703
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• 1999

It is known that the LDC(Line-Drop Compensator) becomes to lose the function of proper voltage regulation for its load currents due to the real and reactive power generated by DGS(Dispersed Generation System), when DGS is introduced into the power distribution system of which the voltage is controlled by LDC. Therefore, in that case, it is very difficult to regulate the distribution line voltage properly by using LDC. One possible solution for this problem is the real-time voltage regulation method which is to optimally regulate the sending-end voltage in real-time by collecting the real-time load data of each load data of each load section between measuring points and by calculating the optimal seding-end voltage value from them. For this, we must know the real-time load data of each load section. In this paper, a modeling method of representing a load section on high voltage line with DGSs as an equivalent lumped load is proposed for gaining the real-time load data. In addition a method of locating the measuring points is proposed. Then, these proposed methods are evaluated through computer simulations.

• 대한전기학회논문지:전력기술부문A
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• 제51권2호
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• pp.93-101
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• 2002

This paper describes a new method for determining the permissible operating range of DG(Distributed Generation) when DG is introduced into power distribution systems of which the voltage is controlled by LDC(Line Drop Compensator). Much of the DG installed during the next millennium will be accomplished through the reconstruction of the electric power industry. But in that case, it is difficult to properly maintain the terminal voltage of low voltage customers by using only LDC. This paper presents a method for determining the permissible operating range of DG for proper voltage regulation of power distribution systems with LDC. Proposed method has been applied to a 22.9 kV model and practical distribution systems, and its result is almost identical with the simulation result.

• 전기학회논문지
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• 제65권1호
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• pp.9-15
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• 2016

Distribution networks are operated in radial fashion during the normal state. Loop configuration is also required temporally in case of live load transfer among the adjacent feeders. Voltage angles of each substation buses are very important data in order to calculate power flow of the loop structured distribution feeders. This paper proposes substation bus voltage angle calculation method using voltage angle difference measured at the normally open tie switches. Simulation case studies using Matlab simulink have been performed to establish feasibility of proposed method.

• 조명전기설비학회논문지
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• 제24권9호
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• pp.108-117
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• 2010

The main contents of this paper are the PQM system construction case and distribution system harmonic voltage analysis. The PQM system has constructed by KEPCO in order to investigate power quality of distribution power system for new power quality standard of KEPCO. In result, we have confirmed that voltage harmonic measurement value of the high voltage contract customer 8 households is suitable the KEPCO harmonic standard tentative plan. And the voltage harmonic value of distribution line end side is not always more high than source side by harmonic current offset effect. In the future, acquired data by season, region, load from the PQMS will be used on the resonable harmonic standard enactment in KEPCO.

• 전기학회논문지P
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• 제62권4호
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• pp.159-163
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• 2013

In this paper, voltage quality improvement is analyzed in case of Superconducting Fault Current Limiter (SFCL) installed in grounding line of main transformer in power distribution system. First, a resistive-type SFCL model is used. Next, Korean power distribution system is modeled. Finally, when SFCL is installed in the starting point of feeder and grounding line of main transformer, voltage qualities are evaluated according to various fault locations and resistance values of SFCL using PSCAD/EMTDC. The voltage quality results in case of grounding line are compared with the voltage in case of feeder.