• Journal of Electrical Engineering and Technology
• /
• v.9 no.4
• /
• pp.1188-1195
• /
• 2014

This paper presents an analytical technique for reliability evaluation of electrical distribution network (EDN) containing distributed generation (DG). Based on hierarchical levels of circuit breaker controlling zones and feeder sections, a directed-relation-graph (DRG) for an END is formed to describe the hierarchical structure of the EDN. The reliability indices of EDN and load points can be evaluated directly using the formed DRG, and the reliability evaluation of an EDN containing DGs can also be done without re-forming the DRG. The proposed technique incorporates multi-state models of photovoltaic and diesel generations, as well as weather factors. The IEEE-RBTS Bus 6 EDN is used to validate the proposed technique; and a practical campus EDN containing DG was also analyzed using the proposed technique.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.1
• /
• pp.86-93
• /
• 1999

It is necessary to calculate the system's factor for reasonable operation and security enhancerrent of large scale distribution system This paper presents an effective three phase load flow calculation for distribution system unbalance evaluation. It takes into account an untranspoed transmission line, the core loss as a functioo of voltage on the serondary side of the transformer, and a generator unbalance mxle1 which is also suitable for a salient pole machine. The load flow algorithm is used Newton-RaiDson method of load flow equations in bus phase voltage.oltage.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1482-1488
• /
• 2014

The reliability evaluation of the electrical distribution networks (EDN) requires sufficient consideration of the effects of planned outages. The planned outages of the EDN can be divided, by outage models and their effects on the reliability into two major categories: by equipment and by feeder. After studying the characteristics of different categories of planned outages, this paper expands the classification of load points by outage time from 4 types to 7 types and defines corresponding reliability parameters for the different types. By using the section algorithm, this paper proposes a reliability evaluation technique of EDN considering equipment random failures and two categories of planned outages. The proposed technique has been applied to the RBTS-BUS6 test system and some practical EDNs in China. The study results demonstrate that the proposed technique is of higher practical value and can be used for evaluating the reliability performance of EDN more efficiently considering the planned outages.

• Journal of Information Processing Systems
• /
• v.13 no.6
• /
• pp.1516-1526
• /
• 2017

Many organizations today use patch management systems to uniformly manage software vulnerabilities. However, the patch management system does not guarantee the integrity of the patch in the process of providing the patch to the client. In this paper, we propose a method to guarantee patch integrity through dual electronic signatures. The dual electronic signatures are performed by the primary distribution server with the first digital signature and the secondary distribution server with the second digital signature. The dual electronic signature ensures ensure that there is no forgery or falsification in the patch transmission process, so that the client can verify that the patch provided is a normal patch. The dual electronic signatures can enhance the security of the patch management system, providing a secure environment for clients.

• Current Optics and Photonics
• /
• v.2 no.2
• /
• pp.185-194
• /
• 2018

Ultra-small optical anisotropy of a rubbed polyimide (PI) alignment layer is quantitatively characterized using the improved reflection ellipsometer. Twisted nematic (TN) cells are fabricated using the rubbed PIs of known surface anisotropy as alignment layers. Distribution of liquid crystal (LC) molecules in the TN cell is characterized using transmission ellipsometry. The retardation of the rubbed PI surface increases as rubbing strength increases. The tilt angle of the optic axis of the rubbed PI surface decreases as rubbing strength especially as the angular speed of the rubbing roller increases. Pretilt angle of LC molecules in the TN cell shows strong correlation with tilt angle of the optic axis of the rubbed PI surface. Both the apparent order parameter and the effective twist angle of the LC molecules in the TN cell decrease as the pretilt angle of LC molecules increases.

• Journal of Electrical Engineering and Technology
• /
• v.3 no.3
• /
• pp.314-319
• /
• 2008

Power quality simulation plays an important role in many practical cases, for example, when deciding the capacity of the related mitigation devices, assessing the influence of installing a nonlinear load in the distribution part, dissolving the quality issues between utilities and customers, and so on. For these purposes, many dedicated tools have been used in order to assess the level of quality distortions by various kinds of PQ indices. However, there are few modules that can accurately simulate the flicker phenomenon, that is, $P_{st}$ and the nonlinear and chaotic behavior of the electrical arc furnace, which is one of the representative nonlinear loads. This paper deals with the useful and simple modules for the voltage flicker simulation in the distribution and transmission level under the environment of Matlab/Simulink. With these modules, the various conditions of distribution systems and the capacities of arc furnaces with the chaotic characteristic can be easily taken into account.

• Proceedings of the KIEE Conference
• /
• 2002.07a
• /
• pp.108-110
• /
• 2002

In this paper, a fault location algorithm is suggested for line to line faults in distribution networks. Conventional fault location algorithms use the symmetrical component transformation, a very useful tool for transmission network analysis. However, its application is restricted to balanced network only. Distribution networks are, in general, operated in unbalanced manners, therefore, conventional methods cannot be applied directly, which is the reason why there are few research results on fault location in distribution networks. Especially, the line to line fault is considered as a more difficult subject. The proposed algorithm uses direct 3-phase circuit analysis, which means it can be applied not only to balanced networks but also to unbalanced networks like distribution a network. The comparisons of simulation results between one of conventional methods and the suggested method are presented to show its effectiveness and accuracy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.704-707
• /
• 1999

Partial discharge(PD) in air insulated electric power systems is responsible for considerable power lossesfrom high voltage transmission lines. PD in air often leads to deterioration of insulation by the combined action of the discharge ions bombarding the surface and the action of chemical compounds that are formed by the discharge and may give rise to interference in ommunication systems. PD can indicate incipient failure. Thus understanding and classification of PD in air is very important to discern source of PD. In this paper, we investigated PD in air by using statical method. We classified air discharge with corona, surface discharge and cavity discharge by source of discharge. we used the mean pulse-height phase distribution $H_{qmean}(\psi)$, the max pulse-height phase distribution $H_{qmax}(\psi)$ , the pulse count phase distribution $H_n(\psi)$ and the max pulse height vs. repetition rate $H_{q}(n)$ for analysis PD pattern. We used statistical operators, such as skewness(S+. S-1, kurtosis(K+, K-), mean phase(AP+. AP-), cross-correlation factor(CC) and asymmetry from the distribution.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1489-1494
• /
• 2014

A hardware-in-the-loop simulation (HILS) method for a wind farm controller using a real time digital simulator (RTDS) is presented, and performance of the wind farm controller is analyzed. A 100 MW wind farm which includes 5 MW wind power generation systems (WPGS) is modeled and analyzed in RSCAD/RTDS. The wind farm controller is implemented by using a computer, which is connected to the RTDS through transmission control protocol/internet protocol (TCP/IP). The HILS results show the active power and power factor of the wind farm, which are controlled by the wind farm controller. The proposed HILS method in this paper can be effectively utilized to validate and test a wind farm controller under the environment in practice without a real wind farm.

• Journal of Information Technology Applications and Management
• /
• v.28 no.1
• /
• pp.33-41
• /
• 2021

In this study, we estimated the number of secondary COVID-19 infections caused by students with potential transmission potential home. When the existing Monte Carlo method was applied to Korean data, the average number of household members of the second COVID-19 infected was predicted. The summary of this study is as follows. First, in general, the number of secondary infections by students returning home from school is greatly influenced by the virus infection rate of each student group they contact while returning home from school. Korea-based empirical research on this is needed. Second, the number of secondary infections by Korean students was relatively lower than that of previous studies. This can be interpreted as being due to the domestic furniture structure. Third, unlike previous studies that assumed the distribution of secondary infected individuals as normal distribution, assuming a negative binomial distribution, the number of secondary infected individuals was sensitively changed according to the estimated parameters. Interpretation of this result shows that the number of secondary infections may vary depending on the time of decision making, the target region, and the target student group. Finally, according to the results of this analysis, a proposal was made to support education policy decisions.