This paper provides the steady-state UPFC model referred as UPFC injection model for power flow control. The application of UPFC for the line overload alleviation is demonstrated through a numerical example. It is shown that UPFC has the capability of regulating the power flow, therefore alleviating the line overload.

In recent deregulation and competitive power market environment, electric utilities plan and operate their systems for economic benefit with secure system condition. Therefore, implementation of Flexible AC Transmission Systems (FACTS) devices can be planned for the efficient utilization of the present system facility. This paper presents a technique to solve the problem about optimal allocation of FACTS devices far the purpose of enhanced system operation.

This paper presents an $H_{\infty}$ based robust STATCOM supplementary controller design to suppress the SSR in series-compensated line. This controller is designed to have the robust stability against the plant model uncertainty. Time domain simulations using a nonlinear system model show that the proposed STATCOM supplementary controller can suppress the SSR efficiently against the plant model uncertainty

The design of an $H{\infty}$ controller for a TCSC to enhance the damping of an inter-area oscillation in a Power system is presented. The paper describes a comprehensive and systematic way of applying the $H{\infty}$ control design algorithm in power systems. Eigen sensitivity analysis to selction a TCSC location is described. Time simulation and eigenvalue analysis show that the proposed TCSC $H{\infty}$ controller can suppress the inter-area oscillations efficiently with robustness.

To improve the damping of all poorly damped oscillation modes, a control strategy of Static Synchronous Series Compensator (SSSC) based on energy method is presented in this Paper As a synchronous voltage-sourced inverter, SSSC is used to provide controllable series compensation. SSSC can provide controllable compensating voltage over an identical capacitive and inductive range. The damping effect of control strategy based on energy function is robustness with respect to loading condition, fault location and network configuration. Furthermore, the control inputs are based on local signals. In two area system, the effect of damping inter-area mode oscillation is demonstrated by the robust control strategy of SSSC.

Recently Advanced Static Var Compensators(ASVC) or STATic Synchronous COMpesator(STATCOM) has been considered as a next generation reactive power controller. [2] STATCOM is a voltage source inverter(VSI) based static VAr compensator with only small capacitors on the do side. The main function of the STATCOM is to keep the bus voltage magnitude at the desired value. [1] This paper compares the PAM STATCOM with PWM STATCOM. The characteristics and the control method of each model is analyzed. And the simulation of STATCOMs based on the above two methods was presented.

This paper presents a new method for contingency selection of the transient stability. Contingency ranking in transient stability is done by estimating the change in the imaginary part of electro-mechanical oscillation mode, which represents modal synchronizing coefficient. And the change in the imaginary part is obtained by applying eigen-sensitivity theory of augmented matrix to linear system model. The Proposed algorithm was tested for New England System and compared the results with PSS/E dynamic simulation.

This Paper compares two mathematical decomposition coordination methods to implementing the distributed optimal Power flow(OPF) using the regional decomposition: the Auxiliary Problem Principle(APP) and the Alternating Direction Method(ADM), a variant of the conventional Augmented Lagrangian approach. A case study was performed with IEEE 50-bus system.

It is important to measuring and monitoring about state vectors of power system for precise operation control. All state vectors cannot be measured because it is economically disadvantageous, so that some state vectors are determined using state estimator. Determination of observability is a important precondition of power system state estimation because state estimation can be performed when given power system is observable. Recently as time-synchronization technique progress, using the PMU(Phasor Measurement Unit), state vector can be measured directly so that voltage phasor and current phasor measurements can be used for power system estimation. In this paper, observability algorithm is proposed to determinate the observability with real/reactive injection power measurements and real/reactive lineflow power measurements of existing measurement system and with phasor measurements of PMU. The jacobian matrix is newly composed for state estimation with measurements of added PMU, and state estimation is performed with least square estimatior. Comparison between state estimation result of existing measurement system and that of measurement system added PMU is presented.

It is the most important in small signal stability analysis of large scale Power systems to compute only the dominant eigenvalues selectively with numerical stability and efficiency. In this Paper evoluted linear analysis program, transformed state matrix using Inverse transformation with complex shift and then Hessenberg process and iterative scheme are used to accelerate Hessenberg process, can calculate dominant eigenvalues. In this Paper, The accuracy of this Program has been validated against 4-machines 11-bus system and New England 10-machines 39-bus system. Also applied to KEPCO system - about 791-bus 250-machines 2500-branches, got 2568 order state matrix, and calculated two dominant modes. This analysis result equaled to result of EPRI's SSSP program to use commonly, and calculating time is faster.

A procedure to develop dynamic equivalent systems of the KEPCO power system in the year 2010 was proposed, and 3 different equivalent systems in which the number of generators are 39, 30, and 19 were developed in this paper. The static and dynamic property of the reduced systems was verified by the comparison of time-domain simulation for the original system and the reduced systems.

This paper proposes a guideline of choosing the optimum stabilizer input considering the gain margin of power system stabilizer between the optimum stabilizer gain and the allowable maximum stabilizer gain in accordance with the five inputs, such as generator shaft speed, bus frequency, electrical power, accelerating power and bus terminal voltage. The local mode damping and exciter mode damping are considered with increasing the stabilizer gain to determine each gain margin of the inputs.

This paper presents an extended integral control with the PID controller by introducing the delay and decaying factors. The convolution integral control scheme is developed by substituting proportional convolution integral controls for the proportional-integral control. So far, the integral part of the PI controller produces a signal that is proportional to the time integral of the input of the controller. The steady-state operation points are affected forever by the errors in the past due to the input signal containing the information of the errors in the past. These phenomina may cause some disturbances for other control purposes related to the given PI control. Introduction of forgetting factors of the error in the past can resolve the disturbance problems. Various forgetting factors are developed using the delay, the decaying factors, and the combination of the delay and the decaying factors. The proposed various extended integral control schemes can be applicable to corresponding PI control designs in which the error in the past may badly affect to the current steady-state operation points and may cause some disturbances for other control purposes.

This paper presents a network reduction using weak coupling method. Weak coupling method of identifying coherent generator groups are proposed. The partitioning technique used in this paper is based on a property of sparse matrix factorization. When a matrix has been factorized, a system is divided into study area, boundary buses and external area. A reduction process for external system starts with the load bus elimination and coherent generator aggregation. An identification of coherent generator group, network partitioning and network reduction are presented.

Automatic Generation Control(AGC) is a control system whose objectives are to hold system frequency close to a specified nominal value and to maintain each unit's generation at the most economic value. It has been used to control the output of a generator by the control signal of the generator, but it is not appropriate to apply to generators which adopt the distributed control system. In this paper a method for improving the AGC operation is proposed, and the different response of each generator and various types of control systems of generators are considered. The interface among Remote Terminal Detector(RTU) and control systems and the direct delivery of the data between EMS and DCS also are proposed in the paper.

This Paper Presents the process of load management for distribution Pole transformer at KEPCO. The purpose of this process is to establish reasonable peak load forecasting and prevention of Pole transformer damages caused by overload through the investigation of correlation coefficient for recent load characteristics. In this Paper, we newly proposed more reliable correlation coefficient using improved method and verified its reliability in various ways.

In this paper, pseudomeasurements have decided using real-time measurements and forecasting data in order to reduce the difference between accuracy of real-time measurements and pseudomeasurements. A decided pseudomeasurement by means of the presented method can look for estimated solution as compared to conventional pseudomeasurement because there is no difference between accuracy of measurements. The simulations are carried out for test systems and corresponding results are presented.

This paper presents the standard for dividing/tieing the distribution lines and installing optimally the automated distribution switch-gear in multi-line faults. Also this paper recommends the distribution system design in consideration of the live load transfer of the concentrated load in the last load-side. This recommendation will be useful for designing the distribution network, developing the feeder automation software and operating the distribution automation system.

A fault detection of power system must be fast and correctly over input signal without relation to any disturbance. But, it is difficult to detect fault state for digital relay comparison of fault perfectly. In this Paper, we measure each Phase current and infer type of fault using ANFIS(Adaptive Neuro-Fuzzy Inference System).

In this paper, we propose the method for assessing the effect of voltage sag in power distribution system using fuzzy risk assessment model. The proposed method is based on SCBEMA curve that expresses the representative susceptibility curve by voltage sag for each customer type. These corves are made using the CBEMA curves obtained from the experiment for the customers'sensitive equipment. In order to transform SCBEMA curves to the probability damage by voltage sag, the fuzzy risk assessment model is used in this paper. Case studies were performed to analyze the effect of voltage sag by varying parameters. The Monte Carlo simulation method and the historical reliability data in KEPCO are used for case studies.

The radio noise produced by corona discharge in high voltage transmission tines is one of the most important line design considerations. Therefore it is necessary to pre-evaluate radio noise for transmission line designers using Prediction formulas or field test results. In this Paper, more accurate and useful formulas for Predicting radio noise during fair and foul weathers in AC transmission lines were proposed through comparison with the existing formulas. Also it was verified by comparing with the long-term measured data from operating lines that the Proposed formulas are very accurate. The Proposed prediction formulas are developed by the applications of nonlinear least square optimization method to radio noise database collected from lines throughout the world.

This paper discusses the surveying of a power transmission line using Real Time Kinematic(RTK) GPS technology. The use of RTK provides users with an accurate position at the moment in time. Application result of a 765kV transmission line surveying proved to be more accurate and efficient than using a traditional EDM (Electro-magnetic distance measurement) method. More, decrease in numbers of trees cut down which is a major cause of public discontents was achieved. Improvements in doing a surveying of a power transmission line using GPS is expected in the future.

This paper presents a new PID control scheme based on the feedback of averaged derivatives to realize a noise-free differential control. The PID(Proportional, Integral and Differential) control is still one of the control methods in most wide use. In the paper, the conventional PID control adopting filtering technique is analyzed with new interpretation of filtering function. In order to overcome the drawbacks of the conventional PID control, this paper introduces the feedback of averaged derivatives in the noisy environment, and suggests a new PID control scheme using delay components to realize a noise-free differential control. The proposed PID control yields good performance much similar to the original system response in case of no noises. The proposed control scheme has been tested for the load frequency control of power systems.

This paper proposes a method of solving a unit commitment problem using tabu search (TS). The TS is efficient optimization method using meta-heuristic. To improve the diversification properties of TS, path relinking method is introduced. To show the usefulness of the proposed method, we performed an experiment for the system of 10 units. Numerical results show improvements in the generation cost and the computation time compared to previously obtained results.

Deregulation and restructuring of electric industry change the fundamental nature of electric business which will be coordinated by the evolved market structures such as spot market with pool and bilateral transaction structure, forward market and future market. Introduction of competition can significantly change the system operation in near-terms as well as long-run generation expansion planning Previous centralized planning by monopoly utilities which was guided for the public service purpose will be replaced by decentralized investments plan by individual generation companies in response to commercial incentives. This paper reviews WASP model as a centralized planning tool and presents a methodological analysis of generation expansion planning in deregulated power systems. It stresses how affects the process of planning new generation investments by the introduction of competition and how maintains proper fuel mix and continuously sustains system reliability under deregulated environments.

A new technique using search method based on fuzzy multi-criteria function is proposed fur flexible generator maintenance scheduling. Minimization of probabilistic production cost, maximization of system reliability level and air pollution are considered fur fuzzy multi-criteria function. To obtain an optimal solution for generator maintenance scheduling under fuzzy environment fuzzy multi-criteria relaxation method(fuzzy search method) is used. The practicality and effectiveness of the proposed approach are demonstrated by the simulation results of the real size model system of KEPCO-1997 SYSTEM.

본 연구를 통하여 전력계통의 송변전 계획에 필요한 장기 지구별 수요예측 산법을 제안하였다. 소규모 지구의 수요예측을 위한 중회귀 모형 도입시 단순한 다항식 회귀모형만으로는 장기예측을 하는데 한계가 있으므로 다항회귀 과정을 변형하거나, 새로운 기능을 보완하여 예측정확도를 높이려는 시도가 수행 되어왔다. 본 논문에서는 장기 예측시 나타나는 미래의 예측 수요의 과도한 변화를 감소시켜 예측 정확도를 개선할 수 있는 수평년도수요를 도입하였으며, 종래 추세 분석에서 난점으로 지적되어 온 변전소의 신설 및 폐지에 따른 수요이전으로 야기되는 예측의 불안정성을 개선하였다. 제안한 산법을 검증하기 위하여 우리나라 실계통에 적용하였다.

This paper presents a algorism for evaluating contingency case power wheeling effects using Monte-Carlo simulation The effects of wheeling on generating cost, transmission losses, and system security are considered. For a specific operating condition, the effects are quantified by the sensitivity of specific quantities of interest with respect to wheeling level. This model is utilized within a Monte-Carlo simulation to calculate probability distribution functions of the incremental effects of wheeling on operating cost, transmission losses, and system security. The model and solution methods are applied on a IEEE RTS-96 system power system and the results are presented.

This paper presents a new algorithm which evaluates production cost and reliability indices under various constraints of the thermal generation system. In order to consider the operational constraints of thermal units effectively, the proposed algorithm is based on Monte Carlo techniques instead of analytical ones which have difficulty in modelling the units with additional constraints. At that point, generating units are modelled into two types, base load units and peaking units. These generating unit models are used in state duration sampling simulation for which approach can readily consider the peaking unit operating cycles and easily calculates frequency-duration indices. The proposed production simulation algorithm is applied to the IEEE Reliability Test System, and performs the production simulation under the given constraints. The results show that the proposed algorithm is accurate, reliable and useful.

This paper presents a new approach for the optimal routing problem of distribution system planning using the well known Hopfield Neural Network(HNN) method. The optimal routing problem(ORP) in distribution system planning(DSP) is generally formulated as combinational mixed integer problem with various equality and inequality constraints. For the exceeding nonlinear characteristics of the ORP most of the conventional mathematical methods often lead to a local minimum. In this paper, a new approach was made using the HNN method for the ORP to overcome those disadvantages. And for this approach, a appropriately designed energy function suited for the ORP was proposed. The proposed algorithm has been evaluated through the sample distribution planning problem and the simulation results are presented.

This paper introduces a clustering for Central Control System in New Distribution Automation System. There are three primary benefits to use clustering: improved availability, easier manageability and more cost-effective scalability. Availability: Clustering can automatically detect the failure of an application or server and quickly restart it on a surviving server. Clients only experience a momentary pause in service. Manageability: Clustering lets administrators quickly inspect the status of all cluster resources and easily move workload around onto different servers within a cluster. Scalability: Applications can use the Clustering services through the MSCS Application Programming Interface(API) to do dynamic load balancing and scale across multiple servers within a cluster.

This paper proposes an optimization technique using Genetic Algorithm(GA) for service restoration in the distribution system. Restoration planning problem can be treated as a combinatorial optimization problem. So GA is appropriate to solve the service restoration problem in the distribution network. But searching capabilities of the GA can be enhanced by developing relevant repairing operation and modifying GA operations. In this paper, we aimed at finding appropriate open sectionalizing switch position for the restoration of distribution networks after disturbances using enhanced GA with repairing operation and modified mutation. Simulation results show that proposed method found the open sectionalizing switches with less out of service area and minimize transmission line losses and voltage drop.

In this paper theoretical review for the design and the algorithm of Artificial Fault Generator, on the power distribution center is which able to purposely generate and get rid of fault with the view of testing distribution systems including switchgears, was made. For the following paper verification with EMTP will be performed in order to review the function and the algorithm so that the optimized design can be established.

This paper presents the feature extraction of fault current related to the multi-shot reclosing scheme in the power distribution system. Fourier transform is used to extract the feature of the fault current waveform in the case of the temporary fault and the permanent fault. After the waveform is analyzed using Fourier transform, the magnitude spectrum and the relative variation of THD are calculated. These results are that the relative variation of THD is great in the temporary fault and is little in the permanent fault.

In this paper we propose to develop program witch can improve the detecting capability of impedance fault in power transmission system. It is difficult to setting relay because the different type relays have many setting values to coordinate with each other. The proposed program assist a user in setting relay with convenience grapic environment and database.

This paper describes a new method of the modeling of protection system and fault diagnosis in power systems using Petri nets. The Petri net models of protection system are compose of the operating process of protective devices and the fault diagnosis process. Fault diagnosis model which makes use of the nature of Petri net is developed to overcome the drawbacks of methods that depend on operator knowledge. The proposed method can reduce processing time and increase accuracy when compared with the traditional methods. And also this method covers online processing of real-time data from SCADA.

A variable percentage current differential relaying algorithm is widely used for bus protection. However, it may maloperate in case of high-impedance internal faults and external faults with CT saturation and thus additional method to cope with CT saturation is necessary. This paper proposes a percentage current differential relaying algorithm for bus protection using a compensating algorithm of secondary current of CTs. As the proposed method compensates the distorted secondary currents of CTs it can improves the sensitivity of relays in a large current region and does not need any additional method for CT saturation.

본 논문에서는 최근 선진국에서 활발히 연구중인 EMF 차폐 대책의 일환인 수동 루프에 대한 이론적 분석 방법을 기술하고, 송전선로 자계 저감 효과를 실제 우리나라 345kV, 765kV를 대상으로 정량적 효과를 분석하였다. 그 결과 수동 루프를 적용한 경우, 약 30% 정도의 자계 저감 효과를 나타내어 전력설비의 유효한 대책임을 확인하였다.

This paper is introducing a newly developed spark gap switch with dual trigger system, into which the current from the voltage source is injected along wi th the test sequence during the synthetic testing of high voltage circuit-breaker.

현재까지 회로 역률을 정확히 계산할 수 있는 방법은 없다. 그러나, 표준을 목적으로 규격마다 서로 다른 계산 방법을 명시하고 있다. 실제로 실험을 통해, 시험 조건이나 시험 결과에 따라 적합한 계산 방법을 적용함으로써 보다 정확한 역률을 계산할 수 있음을 알 수 있었다. 그러나, 이러한 각종 역률 계산 방법들이 역률 크기나 전류 투입각에 대하여 얼마 만큼의 오차를 가지는지 알려져 있지 않기 때문에 적합한 방법을 결정하기란 쉬운 일이 아니다. 따라서, 본 논문에서는 각종 규격에 명시되어 있는 역률 계산 방법들을 구현하여 전류 투입각과 역률 크기에 대한 상대적 계산 오차를 구하고, 문제점과 보완법을 제시하며, 시험 조건에 따른 계산법을 제시하고 이를 실험을 통해서 입증하고자 한다.

Recently. due to the drastic development of communication method between substations for pilot protective relaying system. The power line carrier(PLC) application is getting obsolete. Consequently, the coupling capacitor voltage transformer (CCVT) loses its necessity for the carrier coupling function, and so wound voltage transformer(VT) can be used to substitute CCVT for voltage signal. However, VT has been reported to give rise to ferro-resonance phenomena, so sufficient consideration on applying the VT to line side is required. This study introduces probable technical problems in using the VT on T/L side, and carries out feasibility study on the basis of modeling results by EMTP(Electro-magnetic transient program)

The UPFC is known to have the ability to control both the real power flow and the reactive power flow. [1],[2] The power flow in the system is heavily related with the system security. [4] This paper deals with the operation of the UPFC to increase the power system security. The concept of the power system security is verified and the index to indicate the power system security level is suggested. And the algorithm to find the optimum operation point of the UPFC improving the system security level is presented.

This paper proposes a SSSC(Static Synchronous Series Compensator) power flow model to be incorporated into power flow calculation for the steady state analysis of the power system. SSSC provides controllable compensating voltage, which is in quadrature with the line current, over an capacitive and an inductive range, independently of the magnitude of the line current. This SSSC model is obtained from the injection model for series connected VSC(Voltage Source Converter) by adding a constraint that the injected voltage should be in quadrature with the line current. In this paper the static model is implemented into the continuation power-flow (CPF) program. It is shown that SSSC has its intrinsic superiority over TCSC in controllable power flow range.

This paper presents the new unified power flow controller(UPFC) steady-state model. This is derived from UPFC bus power equations of UPFC Synchronous voltage source model. This is very simple and exact model. This can easily be incorporated in a load flow Program, which is suited for monitoring the Power system state as well as determining the magnitude and phase angle of UPFC serial voltage source.

This paper presents Static Synchronous Series Compensator(SSSC) model for power flow study using IPLAN. In the proposed model, SSSC is represented by the equivalent load variation. The equivalent load consists of active power load specified by user and reactive power load which is founded for considering characteristic of SSSC. And this is implemented by IPLAN which is a macro-external program for PSS/E. Using this model, SSSC can be solved in load-flow by just calling the model in PSS/E. The proposed model was applied to a realistic power system for validity test.

This paper presents the new unified power flow controller(UPFC) load flow algorithm using UPFC transmission line constant model. The UPFC transmission line constant model represents a function of transmission line constant(G.B) UPFC's effect in power system. It can easily be incorporated in a load flow program. The algorithm is suited for monitoring the power system state as well as determining the magnitude and Phase angle of UPFC serial voltage source.

HALS(Hypermidia Aided Learning System) is very useful computer networking educational system in high information society, and was developed by Kyungwon University. This system has three characteristics; 1) face-to-face learning, 2) ultra-high-speed information networking, 3) web-based hypermedia courseware. So, the purpose of this paper is to introduce the application to university educational program(electrical engineering: electric power system, control system). For this purpose it is described the definition and characteristics of HALS. Next, it is represented the model of electrical engineering educational program applied to HALS and the developed courseware.

전력계통에서 발생하는 저주파 동요에 대해서 가장 효과적인 제동력 향상방안으로 알려진 PSS의 최적 설치지점을 결정하기 위하여 NSE(Normalizing Speed Eigenvectors), SPF(Speed Participation Factors), TFR(Transfer Function Residues) 및 주파수 응답법을 각각 비교분석 하였다. 분석결과 SPF는 제어/입력 행렬을 포함하지 않는 상태행렬만을 고려하기 때문에 PSS의 제어특성을 반영하지 못하는 단점이 있었으며 TFR은 여자기 이득에 민감하여 최적위치 선정에 있어서 문제점을 보였다. 본 연구에서는 SPF법을 이용하여 PSS 설치 후보지를 선정하고 이들 후보지에 대해서 TFR법과 주파수 응답법으로 최적의 발전기를 결정하도록 하였으며 PSS를 설치하여 그 효과를 검증하였다.

This paper presents a design of artificial neural network power system stabilizer(ANNPSS) using adaptive evolutionary algorithm(AEA). We have proposed an adaptive evolutionary algorithm which uses both a genetic algorithm(GA) and an evolution strategy(ES), useing the merits of two different evolutionary computations. ANNPSS shows better control performances than conventional power system stabilizer(CPSS) in three-phase fault with heavy load which is used when tuning ANNPSS. To show the robustness of the proposed ANNPSS, it is applied to damp the low frequency oscillation caused by disturbances such as three-phase fault with normal and light load. the proposed ANNPSS shows better robustness than CPSS.

Modeling for utility interactive photovoltaic power generation system has been studied using PSCAD/EMTDC. The proposed model system consists of a simple utility circuit configuration, 3kW of single phase utility interactive photovoltaic system, single phase PWM voltage source inverter module, and feed forward PID controller as control circuit. In the system, the DC current is assumed constant, and the voltage source inverter provides sinusoidal ac current for the loads of utility system. The simulation results are given in order to verify the effectiveness of the proposed model. The phases of output voltage of utility system and the output current of the inverter module are compared. Especially, the compensation effect of the photovoltaic system for the unbalanced load is analyzed. and the transient phenomena for a phase to ground fault are also simulated.

The basic purpose of economic dispatch problem is that minimize fuel cost with inequality constraint of generator output. To solve this problem it is very important to express power loss equation that have quadratic function of generator output power included B-coefficient. This Paper presents a method in determining B-coefficient by use A-matrix that is calculated by loss re-distribution algorithm (LRDA) considering voltage dependent load model (VDLM)s. The Proposed algorithm is tested with IEEE 6 bus sample system, which shows the result in each cases by the change of load component factor.

When we perform the test related to the power distribution system such as artificial fault test, protective coordination test, distribution automation test in short length test line, Lumped Constant Circuit, a kind of variable impedance, should be attached to the test line in order to make it equivalent to a real line in length electrically. In this paper we designed the positive sequence and zero sequence Lumped Constant Circuit with optimized inductor and resister for the modification of long, 16km, distribution line, when they are attached to the short, 4km, distribution test line.

This paper deals with the real and reactive power control of BESS(Battery Energy H Storage System) interconnected to power system. The real and reactive power control of proposed customer side BESS are performed by controlling the amplitude and the phase of inverter output voltage via power flow equation. Also in order to control the amplitude and phase of output voltage of proposed BESS, single-pulse width control method is used. The BESS and controller is implemented and the active and reactive power control is simulated by using the PSCAD/EMTDC simulation program.

Recently, there has been growing interest in utilizing cogeneration(COGN) system which has high energy efficiency due to the lacking of energy resource, but insertion of cogeneration system into existing power distribution system can cause several problems such as voltage variations, reenergizing of feeder isolated by fault, increasing fault current because of reverse power of COGN. Also these problems increase the complexity of control, protection, and maintenance of power distribution systems. Hence, some problems according to COGN interconnection operation to power distribution system must be taken into account so that operation and security of power distribution system is not disturbed. This paper deals with momentary voltage variations and fault analysis caused by interconnection operation of COGN.

This paper presents optimal placement of minimal set of phasor measurement units(PMU's) and observability of measurement system with PMU. By using the incidence matrix symbolic method which directly assigns measurement and pseudo-measurement to incidence matrix, it is much simpler and easier to analyze observability. The optimal PMU set is found through the simulated-annealing(SA) and the direct combinational method. The cooling schedule parameter which is suitable to the property of problem to solve is specified and optimal placement is proven by presented direct combinational method. Search spaces are limited within reasonable feasible solution region to reduce a unnecessary one in the SA implementation based on global search. The proposed method presents to save CPU time and estimate state vectors based on optimal PMU set.

This paper presents a ventilation method and control of stand-by generating system installed underground building. The regulational problem & current ststus of ventilation system inciuding the architectural construction & building service and facility are also investigated.

This paper proposes a value-based pricing suitable for deregulation situation in electricity market, where the value is measured based on the service quality such as system reliability. The proposed approach makes it possible to maximize social welfare, in that diversified service can produce the optimal combination set of demand and supply. The proposed pricing can also be applied to a direct load control.

All the submarine cable lines have been repaired restored and newly installed since 1970' s they were installed by the foreign technician around the islands off the southern and western coast of Korean peninsula. But April, 10th, 1998, for the first time in Korea, we Korean team of technicains succeeded in repairing and restoring the troubled cable lines from HEUGIL island to MASAG island, WANDO county, CHUN-NAM province. This job was done only by applying our newly researched and developed technology. The troubled cable lines were connected again by this technology.

Design & operation power systems for meeting increase of electric power demand is becoming more difficult and complex. Some of limitations of conventional technology can be broken through by the application of superconductivity technology. This paper presents a new concept & image for the configuration of superconducting power system which has introduced superconducting(SC) generator, cable, transformer, fault current limiter(SFCL), SMES, etc. Engineering evaluation of each power apparatus and its assessment of application to power system were conducted. Futhermore, it is pointed that superconducting power system require a new operating condition. This is, SFCL should play a important part of quenching current level coordination to prevent the other superconducting devices from quenching. Its designing & operating condition including SFCL was discussed in viewpoint of quenching current level and insulation coordination of SC coil.

Power system operating conditions vary with system configuration and loading conditions. Coefficients in nominal system model change in a complex manner with different operating point and so does system dynamic behavior. With the aid of unstructured and structured uncertainty descriptions the worst system variations can be estimated and formulated into two different uncertainty models multiplicative unstructured uncertainty in the form of transfer function and structured uncertainty with the parametric uncertainty description. in frequency domain

Electrical studies are required to assure the proper integration of cogeneration facility into a industrial plant electrical system and the connected utility grid. Details of such study efforts are presented, including boundary limit for the system modeling, short-circuit and load flow studies, stability studies, load shedding studies, and harmonics studies.

In this paper, we developed object-oriented analysis method for electric power system. It was applied to fault diagnosis, power system stability analysis and service restoration system in emergency state. Objectoriented programming(OOP)is a more flexible method than procedural programming. We proposed flexible modeling method for power system analysis.

The safety loads in a nuclear power plant perform a critical function to plant safety. The design of the electrical auxiliary system should ensure the availability and adequacy of the power supply, and therefore, the frequency and voltage relaying schemes should be installed on the system to monitor and protect against the degraded system condition. If unforeseen contingencies degrade the switchyard frequency and voltage to below the minimum values, the safety related bus should properly be transferred to alternate power source. This paper presents guidelines associated with the protection of nuclear power plants during frequency/voltage decay and the steady-state and dynamic analysis of auxiliary power system that should be performed to support the degraded voltage relay(second level undervoltage relay) setting.

When electrical engineers get started with the design of main electrical system of a complex petrochemical plant along with chemical and mechanical engineers, they are usually confronted with lack of power system data. This paper presents a procedure how to perform power system stability analysis for the purpose of design studies within the limited system data given and to verify the given data to get reliable convergence in dynamic simulation as well as to apply the stability analysis result on practical system design. The power system stability analysis on the Cadereyta petrochemical plant in Mexico is provided as a study case.

The ATP Draw is a graphical mouse-driven preprocessor to ATP on the Windows Platform. User can build a graphical picture of the electric circuit by selecting components from menus. In this paper, ATP Draw is used to analyze power transformer transient characteristics and lightning overvoltage phenomenon in underground transmission cables. The results obtained by simulations will be used to identify the response of the digital protection algorithms in power system equipment

In this research, ANN load model was built on results of field test using residential load, and then proposed ANN load model was applied to transient analysis. The results of this research are as follows. The first, component load modeling using ANN was implemented. The second, group load model was proposed by aggregation of component load. The third, proposed load model was applied to power system analysis. Therefore, Importance of load modeling and precise load modeling method was suggested in this paper.

This paper is about to the branch topology error identification in electric power systems. Topology errors may cause the state estimators to converge to a wrong solution or in some cases not to converge at all. The branch error identification is carried out as part of the state estimation procedure. The basic idea is that the estimates of these error variables will be insignificant if the branch is modeled correctly and they will be relatively large otherwise. A two step procedure for the identification of faulted branches is proposed.

This paper presents an effect of cross magnetization to the generator simplified linear model which is used for multi-machine power systems. The formulae of reactances and time constant with saturation effect are presented. The simulation results show that cross magnetization has an effect which can not be ignored, to the reactances, time constant and eigenvalues in one machine infinite bus system of simplified linear model.

In this paper, we propose real time transient stability assessment and energy margin estimation using fuzzy approximate reasoning. The proposed method used rotor angle, kinetic energy and acceleration power of generators at clearing time as fuzzy input. In order to calculate energy margin in transient energy function (TEF), we obtained controlling unstable equilibrium point (UEP) using mode of disturbance procedure (MOD). The proposed algorithm is tested on 4-machine, 6-bus, 7-line power system to prove of effectiveness.

AVR parameter tuning for voltage control of power system generators has generally been done with the open-circuit model of the synchronous generator. When the generator is connected on-line and operating at rated load conditions, the AVR operates in an entirely different environment from the open-circuit conditions. This paper describes a new method for AVR parameter tuning using optimization technique with on-line linearized system model. As this method considers not only the on-line models but also the off-line open-circuit models, AVR parameters tuned by this method can give the sufficiently stable performance at the open-circuit commissioning phase and give the desired performance at the operating conditions. Also this method estimates the optimum parameters for desired performance indices that are chosen for satisfying requirements in some practical applications, the performance of the AVR can satisfy the various requirements.

This paper describes the optimal reconfiguration of distribution network. The optimal routing of distribution network should provide electricity to customers with quality, and this paper shows that optimal routing of distribution network can be obtained by Neural-Tabu algorithm while keeping constraints such as line power capacity, voltage drop and reliability indices. The Neural-Tabu algorithm is a Tabu algorithm combined with Neural network to find neighborhood solutions. This paper shows that not only the loss cost but also the reliability cost should be considered in distribution network reconfiguration to achieve the optimal routing.

To provide electricity power of good quality, it is essential to establish generation of electricity plan in electric power system based on accurate power-demand prediction and cope with changes of power-need fluctuating constantly. The role of hydraulic-power generation of electricity in electric power system is of importance because responding to electric power-demand counts or reservoir-type hydraulic-power generation of electricity which is designed for additional load in electric power system. So hydraulic-power generation of electricity must have fast start reserve. But the amount of water, resources of reservoir-type hydraulic-power generation of electricity is restricted and multi-used, so the scheduling of management by exact forecasting the amount of water is critical. That is why efficient hydraulic-power generation of electricity makes a main role on pumping up the utility of energy and water resource. This thesis introduced the example of optimal generation of electricity plan establishment which is used in managing reservoir-type hydraulic-power generation of electricity.

This paper presents database design and construction for VSECOMs (Voltage Security On-line Monitoring System). The database design has steps of requirements collection and analysis, conceptual design, logical design, and physical design. For interconnection between New EMS and VSECOMs to get the needed data, Snapshots in ORACLE are proposed. It proved the proposal to be compatible through the case study.

Electric industry has been the object of major reforms in many countries. These reforms are aimed at attaining efficiency through competition. Thus network companies do not charge transmission cost for line user the same as method at past. This paper presents a transmission cost allocation through reliability differentiated transmission pricing in competitive electric industry. The proposed method considers only the line capacity affecting the reliability of transmission pricing under normal state and contingency state.

The paper proposes a simple method to calculate the portion of real power losses allocated to individual loads. The method is implemented by loss distribution factors, and analyses the share of loads in transmission line losses. Effectiveness of the algorithm is verified by a computer simulation. The results can be used to compute the cost of ancillary services under deregulated environment in electric power industries.

More precise operation and control is required to ensure the stability and security of modern large power systems that is a complicated and widely dispersed structure. To ensure the precise operation and control of modern power system, most of all, precise monitoring and measurement of the various state values of power system is required. This paper discusses phasor measurement unit using synchronization signals from the GPS satellite system- Synchronized Phasor Measurement Unit. Considering the power system operation state, the transmitting data format over modems is defined. To provide all available information, PMU process the measurements to generate three phase symmetrical component. This paper proposes the transmitted data format and implements the PMU model using EMTP/Models. The validity of proposed model is confirmed through several contingency on the simple power system.

This paper studies on arrangement of load correlation coefficient for advanced load management. To accurate load correlation coefficient, we used two real factors, electrical energy(kWh) and peak load current of pole transformers, acquired by measuring instrument. Out of several correlation equations, we find that the quadratic equation is the most accurate to express peak load current and working electrical energy. If the data is located in the outside of ${\pm}3{\sigma}$ it is discarded. For load management, we rearranged load correlation coefficient considering +2${\sigma}$ at load correlation equation. Comparing conventional load correlation coefficient with rearranged one, we can get the result of error reduced and it is adjacent to the actual data. It will be used peak load forecasting from working electrical energy and we are able to prevent from the damaging of pole transformer due to overload.

The generator cost function is one of the basic data for the generation scheduling. Generally the cost functions are obtained form design calculations or from heat rate tests. The real operating condition may be different from the condition of design or the tests. Some of the conditions may not be tested during the periodical maintenance. In order to improve the calculation of the generator cost function, this paper presents a new calculation method of the generator cost functions using the utilization factors of generators and the mixed fuel burning ratio of the generators.

This paper describes the optimal operation scheduling on cogeneration systems which have thermal loads of different pressure each other. The cogeneration systems has two units and operate connecting with various auxiliary devices as heat storage tanks, independent generators and auxiliary boilers. The optimal modeling and scheduling technique proposed in this paper will be applied to industrial cogeneration systems.

This paper proposed the optimal operational scheduling of cogeneration system for paper mill connected with several auxiliary devices. Auxiliary devices that include auxiliary boiler, waste boiler and sludge incinerator operate with multi-cogeneration system. Especially environment element was considered in objective function to solve environment problem. Electricity can be purchased through power system from utility. The proposed operational strategy on cogeneration system for paper mill to increase energy efficiency can be applied to the similar cogeneration system in industrial field.

The learning automaton is an automaton to update systematically the strategy for enhancing the performance in response to the output results, and several schemes of learning automata have been presented. In this paper, S-model learning automata are applied to achieving a best compromise solution between an optimal solution for economic operation and an optimal solution for stable operation of the power system under the circumstance that the loads vary randomly. It is shown that learning automata are applied satisfactorily to the multiobjective optimization problem for obtaining the best tradeoff among the conflicting economy and stability objectives of power systems.

This paper presents the DQ transfomation and space vector modulation method to develop a control algorithm of distribution STATCON(STATic CONdenser) for line voltage regulation, dc link voltage regulation and harmonics compensation. The Performance analysis of a PI with ramp comparision and synchronous reference frame current controller is carried out. Based on these analysis, the control performances are desirable to compensate the harmonics and to regulate de link and line voltage of Distribution line.

The UPFC(Unified Power Flow Controller) controls the magnitude and phase of the series injected voltage to exchange the real and reactive power with transmission line. The UPFC consists of two inverters connected together through the DC link capacitor. This paper describes the detailed UPFC switching-level model. PWM (Pulse Width Modulation) method is chosen to operate the inverters. Automatic voltage control mode and automatic power flow control mode is selected to control the UPFC. EMTP simulation is offered to obtain the basic operation characteristics of the UPFC and the dynamic characteristics of the UPFC is studied in detail.

In this paper. continuation power flow for Power system including UPFC has been performed. The decoupled model, by which power flow can be performed without any modification of conventional power flow program is used as steady-state model. A numerical example has been given to analyze the influence on the voltage stability by UPFC.

This paper describes a power flow method for the unified power flow controller(UPFC) considering equipment sizes and constraints. The operation of UPFC subject to the practical constraints encounted in an actual high power installation. So the Power flow method for FACTS must be considered its constraints for power system analysis. The proposed UPFC power flow method was implemented by PSS/E and IPLAN.

This paper describes a initial screening methods for weak line selection using sensitivity matrix. The elements of sensitivity matrix for line suceptance have 1 or -1, 0. From this property of sensitivity matrix, the eigen-sensitivity for line suceptance can be computed very simply and selected weak line for small signal stability or transient stability. The proposed algorithm is applied to small signal stability of New England 39-bus system and also applied to voltage stability of New England 30-bus system too.

This Paper Proposes the FACTS site selection method using subtransmission system reduction. A general method which uses the sensitivity of the variation in voltage and reactive Power has been used to determine the location of shunt type FACTS device, but there is a difficulty to find a proper location due to the overestimation of the effect of sub-transmission systems. Therefore, there is a need to reduce sub-transmission system for finding an effective location of shunt type FACTS devices such as SVC(Static Var Compensator), STATCOM(Static Synchronous Compesator), and so on.

dynamic analysis of power systems is required the information for building a transfer function of has the heavy calculation of high order matrices. Since generally the order of the state matrix is over the limit of commercial analysis programs such as MASS(Multi-Area Small Signal Stability) Program, it is necessary to develop dynamic equivalent systems with preserving essential properties of the original system. In this work, a procedurd to find an optimal location of FACTS controllers is presented. The procedure was applied to KEPCO system in the year of 2000. The results on a test system demonstrate the accuracy of dynamic equivalencing and verify the effect of FACTS controllers.

The addition of SVC increases the range of dynamic stability in the power system. The inclusion of SVC is explained in detail and a numerical example is presented. The entire construction of the system A matrix is analyzed, and then the effect of SVC on Hopf bifurcations and the PV curves are illustrated in the cabs study.

This paper presents the selection of suitable locations for PSSs in large power system using Speed Participation Factor(SPF). And practical considerations for optimal locations of PSSs are discussed. In this paper, the simulation results for SPF in KEPCO's power system using SSSP by EPRI are also included.

In this paper, we design an Adaptive Neuro-Fuzzy Inference System(ANFIS) Precompensator for the performance improvement of conventional proportional integral derivative (PID) controller that the governor system of power plant constantly maintains the load frequency of two-area power system. The ANFIS Precompensator is expressed as the membership functions of premise parameters and the linear combination of consequent parameters by Sugeno's fuzzy if-then rules using nonlinear input-output relation for the set point automatic modification maintaining conventional PID controller. The proposed compensation design technique is hoped to be satisfactory method overcome difficulty of exact modelling and arising problems by the complex nonlinearities of power system, and our design shows merit that is easily implemented by adding an ANFIS precompenastor to an existing PID controller without replacement.

Recently, according to the growth of national economy and the improvement of lining conditions, electric power demand is increasing gradually. So it is being examined to construct large thermal power plants or nuclear plants. For the effective use of lands and for the economy of generations sites, the distance between generation and demand locations becomes farther and farther. At the same time, people desire higher quality or electric power. So in this paper, the optimal modulation controller for HVDC transmission system are designed by a recursive algorithm that determines the state weighting matrix Q of a linear quadratic performance. It means that the application of optimal modulation controller in HVDC transmission system can contribute the propriety to the improvement of the stability in HVDC transmission system.

In this paper, a robust $H_{\infty}$ optimal design problem under a structure-specified PSS is investigated for power systems with parameter variation and disturbance uncertainties. Genetic algorithm is employed for optimization method of PSS parameters. It is shown that the proposed $H_{\infty}$ PSS tuned using genetic algorithm is more robust than conventional PSS.

This paper demonstrates the insulation-destruction of high-voltage-motors for intake pump. To analyze the causes of damage in motors, electrical, mechanical and environmental fiery-development were investigated. The insulation-destruction of high-voltage-motors are generally due to the fiery-stress by void where composite materials such as mica/epoxy are used. But this paper shows that electrical and mechanical stresses can be the main reason of the damage, too.

In this paper control hierarchy of Haenam-Cheju HVDC link are analyzed and their functional specifications are summarized related to their level. The control functions for the submarine DC transmission are implemented by software programs on 16-bit parallel processor-based machines which are composed of subunits hierarchically linked each other

In Haenam-Cheju HVDC link several modes of operations and controls are provided, which are constant frequency control, constant power control and constant current control. This paper describes basic control action of converters under three control modes and shows EMTDC simulation results at ground fault and steady state respectively.

전력산업의 구조개편으로 기존의 한국전력 독점체제에서 다수의 전력회사로 나누어 질 것이다. 따라서 손실과 공급의 신뢰도 확보 등의 책임분배와 비용분배의 문제가 새로이 나타날 것으로 예상된다. 손실에 대한 비용의 경우 계산법과 이러한 비용을 분배하는 방법이 중요한 문제가 되고 있다. 본 논문은 전력산업구조개편이 이미 이루어진 선진국들의 손실비용의 처리방법을 비교하였다. 그리고 손실에 대한 비용계산 방법을 모의 시스템에 각각 적용시켜보고 결과를 비교하였다.

This paper presents transmission pricing mechanisms based on postage stamp rule. Two pricing mechanisms with three different calculation methods are suggested, followed by case studies in KEPCO system.

This Paper Presents a new analytic load decrement method for the evaluation of avoided generation costs of independent power producers (IPPs), named as probabilistic load decrement method. Unlike conventional load decrement methods, the proposed method exactly consider the random outage characteristic of a generating unit, economic dispatch order, and the resulting loss of load probability. Therefore, we can Provide the exact generation avoided costs of an IPP by applying the developed method. In the case studies, we have shown the correctness and effectiveness of the method, and compared with conventional load decrement methods.

This paper presents a game theoretic approach for power transactions analysis in a competitive market. The considered competitive power market is regarded as PoolCO model, and the participating players are restricted by only two generating entities for simplicity in this paper. The analysis is performed on the basis of marginal cost based relations of bidding price and bidding generations. That is, we assume that the bidding price of each player is determined by the marginal cost when the bidding generation is pre-determined. This paper models the power transaction as a two player game and analyzes by applying the Nash eauilibrium idea. The generalized game model for power transactions covering constant-sum(especially zero-sum), and nonconstant-sum game is developed in this paper. Also, the analysis for each game model are Performed in the case studies. Here, we have defined the payoff of each player as the weighted sum of both player's profits.

접지는 최근까지 대형 변전소를 제외한 대부분의 분야에서 정확한 현장 분석 없이 단순히 접지저항만을 계산하여 시공하고 있다. 본 논문에서는 접지 설계에 필수적인 시공 현장의 대지저항률을 실측하여 컴퓨터 시뮬레이션을 통해 지질특성을 분석한 후, 3가지 방식의 접지시스템을 현장에 맞게 설계 시공하였다. 각각의 접지 시스템의 시공은 동일한 장소에서 이루어 졌으며, 시공된 각각의 접지시스템들의 결과를 실측하여 접지 설계에 따른 시공 성능을 확인하였으며, 접지시스템들의 성능과 특성을 상호 비교 분석함으로써 현장에 가장 적합한 접지시스템을 제안하였다.

전력계통의 고장용량 억제를 위한 송전망 구조의 방사상화는 경제적이고 적용이 간단하다는 장점을 갖는다. 그러나 선로개방에 따라 선로조류의 편중과 모선전압의 변동이 발생하기 때문에 계통의 안정성 검토가 전제되어야 한다. 본 연구에서는 고장용량의 감소를 목적으로 하면서 선로조류와 모선전압에 대한 제약조건이 반영되는 최적화 문제를 다룬다. 최적성의 향상을 위해서 호필드 신경망이 사용되며 이를 위해서 관련된 가중행렬 식을 유도한다.

토양에 대한 연구는 오래 전부터 시작되었으며, 여러 가지 방법으로 토양의 특성을 조사하고 이를 적용하기 위한 분류법이 제안되어 왔다. 국내에서도 해방 전부터 토양에 대한 연구가 시작되었으나, 농업에 이용하기 위한 연구가 대부분을 차지하고 있으며 각각의 연구결과는 물리, 화학적으로 정량화 되어 있지 않기 때문에 환경에 따른 특성의 변화를 예측할 수 없다. 또한 접지설계 등의 전기관련 분야에 활용하기 위한 연구는 전무한 실정이다. 본 논문에서는 토양의 개념, 생성인자, 분류 및 전기적 특성 등의 개요를 알아보고, 지질학 및 지구물리학적인 방법을 통하여 국내의 암석 및 토양에 대한 비저항의 물리적, 화학적 특성을 측정하기 위한 방법을 조사하였다. 이를 바탕으로 암석과 토양에 대한 개략적인 토양비 저항도를 작성하여 접지설계 및 지하매설 금속물의 방식 설계 등에 활용하기 위한 토대를 마련하고자 한다.

This paper presents fault detection in cables. We developed the device for detecting pinpoint location of faults in power cables using acoustic method. The proposed device consists of hardware and software for the fault detection. Using the device, we explain how to detect the pinpoint of faults and introduce that the other method use the time delay between electro-magnetic and acoustic signals for the pinpoint of the faults.

This paper describes the fault location technique using wavelets in transmisson line. Estimation of fault location is performed using synchronized data sampled at two ends of line and travelling wave. The similar current wave modeled in PSCAD/EMTDC and MATLAB was applied to evaluate the accuracy of theory proposed in this paper. The results of fault location shown in this paper will be evaluated as an effective suggestion for fault location in real transmisson line

This paper Presents an algorithm for the computation of fault location for a transmission line by means of the voltage and current signals. It is impossible to calculate the accurate fault distance, because of the fault resistance and fault current which are unknown. All Currents in the lines are divided by the current distribution factor, so the fault current through the fault resistance can be represented by using data from one terminal of transmission line. This algorithm proposed can calculate the fault distance with only the faulty phase information.

With conventional single pole auto-reclosure (SPAR), unsuccessful reclosure using a fixed dead time in the case of transient fault, or reclosure onto a permanent fault. may aggravate the potential damage to the system and equipment. In this respect, the research is needed to implement SPAR effectively. In this paper, we present a wavelet transform approach to detect and discriminate between transient fault and permanent fault in transmission lines.

We investigated the current limiting characteristics of resistive and inductive SFCLs with 100${\Omega}$ of Quench impedance for a double line-to-ground fault, in the 154 kV transmission system. The fault simulation at the phase angles $0^{\circ}$, $45^{\circ}$, and $90^{\circ}$ showed that the resistive SFCL limited the fault current less than 17 kA without any DC component after one half cycle from the instant of the fault. On the other hand, the inductive SFCL suppressed the current below 12 kA, but with 3$\sim$5 kA of DC component which decreased to zero in 6 cycles. We concluded that the inductive SFCL had higher performance in current limiting but the resistive SFCL was better from the view point of DC components.

High impedance fault (HIF) is defined as fault the general overcurrent relay can not detect or interrupt. Especially when HIF occur in residential areas, energized high voltage conductor results in fire hazard, equiment damage or personal threat. This paper proposes the model of HIF in transmission line using the ZnO arrester and resistance to be implemented within EMTP. Wavelet transform is efficient and useful for the detection of HIF in power system, because it uses variable windows according to frequency. HIF detection method using wavelet transform can distinguish HIF from similar phenomena like arcfurance load, capacitor bank switching and line switching.

Most conventional protection relays are based on processing information in the spectrum that is close to or at power frequency. It is, however, widely known that faults on transmission lines produce frequency components of a wide range In this respect, this paper describes the basis of a Protection technique for transmission lines which utilises high-frequency components. Fault-generated signals caused by post-fault and the signal derived from stack tuner is connected to the coupling capacitor of CVT. Digital signal processing is then applied to the captured information to determine whether the fault is inside or outside the Protected zone, and to discriminate the fault type on transmission line.

The unbalance current on the bundled conductors of the UHV overhead transmission line is one of the factors affected on power transmission system. It is varied by distance between of bundled conductors and of phase to phase, phase arrangement. In this paper, we calculated unbalance current on the bundled conductors by a variety of line arrangements and also calculated magnetic field at the circumference of the line fed with this unbalance current.

Traditional magnetic field computation techniques assume that the current carrying power line conductors are straight horizontal wires. This assumption result in much errors. So this paper considerd catenary curve for the dip of real transmission line. We have data from various position at transmission line, on the earth. And as far from transmission condutor a eddy current affect of the position are con siderd.

Electric power consumption is highly increasing as the social trend requiring comfortable life, the population concentration in a big city and the industrial development. Therefore it has become to be very important to supply the stable high-quality power. As these trends, the underground power transmission facilities are unavoidable in the center of a city and are going to increase more and more. As the proportion to increase facilities, the efficient management and maintenance become more important and are going to play an important role in the high-quality of power supply.

Environments of electric power industries are fastly changing due to the WTO, opening of the capital market and free trade. Accordingly, it is very important to invest in technical developments for securing international competitive power. But our construction techniques in T/L are insufficient in comparing with the advanced countries. This paper suggests the status and prospect of construction techniques of domestic and foreign countries in T/L, including developing prospects of T/L constriction.

This paper have analyzed sheath induced voltage in underground transmission cable system which will be operated with cable cover protection unit(CCPU). Simulation was carried out to analyze sheath induced voltage using on real cable system in the case with and without CCPU. Sheath induced voltage was also analyzed according to grounding method, fault resistance and fault angle. Simulation was performed using EMTP and ATP Draw, the simulation results represent whether the arrester is necessary or not in cable system.

It is important the protective relay should have high selectivity and sensitivity performance and it is achieved by correct setting of the relay parametes. The verification of accurate setting for the protective relay is very difficult before a actual fault occurs. This paper reports a diagnosis expert system to verify the correctness of the relay setting by using the operation results in the power system fault simulation.

The function of newly developed equipments must be verified in real power system before they put into operation. However, it is hard to test them in real power system due to the possibility of abnormal operation. In this paper, test method for new relays is developed in order to simulate their function in real power system using RTDS (Real Time Digital Simulator) and the simulation results show the capability of method.

This paper presents a distance relaying algorithm for transmission line compensated with Static Synchronous Series Compensator (SSSC). The compensation voltage driven by SSSC is calculated from the line current measured at a relaying point Then the compensation voltage is subtracted from the voltage measured by the relay. We can apply conventional distance relaying algorithm with this subtracted voltage to locate a fault. The results of case studies using EMTP (Electro-Magnetic Transient Program) show the proposed algorithm has higher precision.

전력계통에서 전류를 측정하는 변류기는 주요 전력 설비와 연계되어 보호 및 감시에 있어 중요한 역할을 수행한다. 그러나 기존방식의 전류 변성기는 자기포화에 의한 파형 왜곡과 써지나 잡음 등의 전기적 장치가 갖는 구조적 문제점을 가지고 있다. 이러한 문제점을 개선하기 위한 방법으로 전류에 의해 형성된 자계에 의해 광신호의 편광(polarization) 회전을 발생시키는 Faraday 효과를 가지는 광센서를 이용하여 보호계전 분야에 적용 가능한 전류계측기술을 개발하였다. 본 논문에서는 기존 전류변성기의 계통 보호에서 발생하는 문제점을 PSCAD/EMTDC 시스템을 이용하여 시뮬레이션 하였으며, 아울러 동일 조건에서 광 CT의 동작 특성을 산출하여 기존 전류변성기와 비교 분석하였다. 분석 결과들로부터 광 CT는 기존 전류변성기가 자기포화되는 상황에서도 정확한 1차 전류의 측정이 가능함을 보였다.

Distance relay is being used for transmission line protection. Recently, current differential relay is used with high reliability in power system. This kind of relay is reported that it has a reliable detection ability, even so high impedance faults take place in transmission line. Therefore it is expected to use and expand widely in many utilities. Tripping of the relay is decided according to the difference between differential and restraint current. However the tripping criterion can be changed by the manufacturers. This paper presents an operational scheme of current differential relay for transmission line protection with graphical model. It is developed for educational purpose for students interesting in power system and protection engineer in utility. MATLAB is used to establish the models.

Protective relay for transformer operates in general by comparing with the differential current and the restraint current. These kinds of currents are changed on magnitude and phasor during the fault according to winding type and vector group. This paper presents the differential and restraint currents and operational principle of differential protective relay for two-winding and three-winding transformer with graphical model. It is developed using MATLAB for an educational purpose on engineer related in power system and protection in university and power utility including large factory.

배전선로상에서는 상 불평, 고저항 지락사고나 선로탈락이 발생할 수 있다. 또한, 고장 감지기 정보의 불확실성 등으로 배전 SCADA 정보로부터 정확한 사고유형과 사고위치를 확인하는 작업은 매우 어렵다. 따라서 본 연구에서는 배전선로상에서 발생할 수 있는 다양한 사고들에 대해 사고유형과 사고발생 위치를 신속하고 정확하게 추론할 수 있는 전문가 시스템을 제안한다. 전문가 시스템은 배전 SCADA기능과 수집된 데이터를 종합적으로 활용하게 되는데, 특히, 정확한 사고유형 확인을 위해 절분점 감시 메카니즘이 새롭게 채택되며, 또한, 선로사고시 시스템 운영자들의 오류로부터 발생할 수 있는 파급효과를 최소화하기 위해 고장구간의 자동진단 전략이 개발된다.

This paper presents a restoration method by using Dijkstra algorithm for outage restoration problems in distribution system that considering load capacity constraints and operation constraints. Restoration problem in distribution system is difficult to solve problem in a short times, because of a distribution system that supplies power for customers combined with many tie-line switches and sectionalizing switches and have to satisfy plenty of operation conditions. Therefore, this paper applied Dijkstra algorithm which is satisfy radial operation conditions in distribution system. This proposed method used Kruskal algorithm include to Dijkstra algorithm Therefore, proposed method is restored to a outage sections in a short times and just then to satisfied with a operation conditions in distribution system. A 26-bus, 31-branch model system is used to demonstrate the effectiveness of the proposed method.

CADPAD program has been used as a distribution planning tool in KEPCO since 1989. In recent we've been upgraded the I/O modules. Now we analyze the key algorithm of FEEDERSITE module. The objective function is represented by the sum of the multiples of Power flow and cost. To minimize the objective function, it is used to Linear Programming algorithm. We will show this algorithm in this paper.

This Paper Presents a efficient algorithm for loss reduction of distribution system by automatic sectionalizing switch operation in distribution systems of radial type. To apply tabu search to reconfiguration of distribution system, in this Paper we Propose the several move methods and efficient reconfiguration procedure. We also discuss the tabu search techniques of diversifying the search of solution space as well as the simple tabu search. The experimental results show that the proposed tabu search techniques have the ability to search a good solution.

This paper represents improved service restoration algorithm to deal with concurrent multiple outage areas. Restoration sequence is the most important to use backup feeders effectively. In order to decide restoration sequence, the algorithm calculates restorability of each outage area based on fuzzy evaluation of outage load and total backup feeder margin.

The New Distribution Automation System(NDAS) was composed of several equipments, computer system, communication system, feeder remote unit, switches and so on. In this paper, we introduce the conception of hardware and software design about Central Control System, the communication method and protocol in Feeder Remote Unit, the Automatic Switch, the operating software, consideration factors in the feeder automation(FA) and the system configuration of NDAS in power distribution test center.

In this paper, we present diagnosis system for pole and pad transformers using wireless data communication. This system used radio frequency modem for communication between transformer and mobile car. We studied communication's protocol and data frames for operating diagnosis system of distribution transformers

In this Paper, we present the method to determine the insulate deterioration of transformers sticking the temperature sensor to the distribution transformers and analyzing the trend of temperature. And we present the method to make economical on-line system using the PCS and RF modem instead of the conventional method of measuring the data by manager. Also we deal with the method to make database for the distribution transformers.

This paper describes test method though low voltage power system implementation for high impedance fault relay test before its operation in real power system. Through this test, relay tested its function and algorithm. In this paper, we will provides test method using low voltage power system and its results.

This paper proposes fault detection method using a neural network & fuzzy logic on distribution lines. Fault on distribution lines is simulated using EMTP. The pattern of high impedance fault on pebbles, ground and short-circuit fault were take as the learning model. In this paper proposed fault detection method is evaluated on various conditions. The average values after analyzing fault current by FFT of even odd harmonics and fundamental rms were used for the neural network input. Test results were verified the validity of the proposed method

In the calculation of lightning-induced voltage, it is used the various parameters obtained by LPATS being operated in KEPCO from 1995. Based on the lightning-induced voltage and the exact lightning position acquired by the developed program, we can predict the extent of damages in distribution systems. The result in this paper is very useful in finding fault location by lightning and performing rapid outage recovery and maintenance of distribution line equipments.

The KEPCO is developing the load forecasting system using land-use simulation method and distribution planning system. A distribution planning needs the data of present loads, forecasted loads and substations. distribution lines information. By the distribution planning system, the distribution line designer determines the substations and feeder lines plan. This paper presents the method of formulation process for the long term load forecasting and optimal distribution planning, and describes the case study of long term distribution planning of Suwon-city according to the newly applied method.

This paper presents the method of determination for optimal underground power distribution system in our country. To get optimal system, it is necessary to evaluate reasonably important factors such as installation cost, reliability index, customer interruption cost, convenience of installation and system flexibility. This study also described the new method which was applied to UI-San industrial park as a case study.

This paper presents an economical generation planning for operating power systems with dispersed generation. As dispersed generation introduced into an electric power distribution system, the power system will be complicated and have much variable aspects. So there is need for developing new generation scheduling. In this paper, the proposed method is tested for distribution system with two battery storage resources. Optimal generation planning of 15 thermal units in 24-hours is achieved by improved genetic algorithm. Also, to show its effectiveness, the results are compared with those of not including battery storage resources.

As the system reliability of power supply is highly increased, we need distribution maintenance techniques without any power interruption. To meet such an increasing demand, a groat deal of hot line work on the high voltage overhead distribution lines has been carried out. In this regard, Hot line work techniques has being applied widely. However, hot line work techniques can not cover all kinds of work without interruption. To cope with those problems, the temporary power supply work technique such as bypass cable truck technique, temporary switch technique and mobile transformer technique was developed and applied. This paper presents the most optimal method according to distribution work contents through the comparison and analysis the characteristis and problems of the existing various work techniques. Also this paper suggested the countermeasers of the prsent problems.

Distribution systems is consist of network in physical aspect, and radial in electrical aspect. Therefore, radial operation is realized by changing the status of sectionalizing switches, and is usually done for loss reduction in the system. In this paper, we propose a optimal method for distribution systems reconfiguration. Specifically, we use K-optimal algorithm and tabu search method to solve distribution systems reconfiguration for loss minimization problem.

This paper describes the principle and the implementation of a heuristic methodology to restore service to the isolated portions of distribution system. With an aim to increase the ease of the maintenance and expansion. Object-oriented technique was adopted to implement the package. UML was officially adopted OMG standard. It simplifies the complex process of software design, making a "blueprint" for construction. Therefore This package can be easily reused.

An Algorithm is devised to discriminate power distribution faults from other activites utilizing the arc activity and changes in the loading. This scheme intends to determine the cause of the transients and identify them. the discrimination algorithm was tested using recorded event data.

This paper presents a method of the regional long-term distribution planning considering economic indicator with the assumption that energy demands proportionally increases with the economic indicators. For the practical distribution planning, it is necessary to regional load forecasting, distribution substation planning, distribution feeder planning. Accordingly, in this paper, after performing regional load forecasting considering economic indicator, it is performed distribution substation planning and distribution feeder planning in order by using this result. For accurate distribution planning, it is very important to scrutinize the correlation among the regional electric power demands, economic indicator and other characteristics because distribution planning results may vary depending on many different factors such as electric power demands, gross products, social trend and so on. In this paper, various steps microscopically and macro scopically are used for the regional long-term distribution planning in order to increase the accuracy and practical use of the results

This paper proposes the estimation method about how much reactive power can be increased or decreased under prescribed bus voltage limits in non-linear reactive power and power flow equations. The static nonlinear reactive power voltage problem can be formulated using a linear resistive(I-V) network with voltage dependent current sources. Linear programming model is derived for finding bounds on reactive power. This method was applied to future Korean power system and proved its effectiveness.

The setting of protective relays, which is critical to the system security, requires a huge volume of data and a lot of repetitive calculations. Therefore computerization of this process, named PROSET2000 is in progress in KEPCO. PROSET2000 is based on a power system protection database. The database must accomodate a variety of protective device data efficiently, which need be viewed and updated with ease. This paper suggests several database management functions for PROSET2000.

The accurate analysis of power system requires detailed load model. There are two basic approaches in modeling the load characteristics. One is to directly measure the voltage and frequency sensitivity of the load P and Q at substations and feeders. The other is to build up a composite load model from each load component. Each of these methods has advantages and disadvantages. This paper presents load composition for KEPCO's power system to develop load models by the component-based load modeling.

Power distribution system planning for maximum customer satisfaction and system efficiency requires accurate forecast of future demand in service area. Spatial load forecasting method provides a more accurate estimation of both magnitudes and location of future electrical load. This method considers the causes of load growth due to addition of customers and per capita consumption among customers by land use (residential, commercial and industrial). So the land-use study and it's preference for small area is quite important. This paper proposes land-use preference estimation method based on fuzzy logic. Fuzzy logic is applied to computing preference scores for each land-use and by these scores the customer growth is allocated in service area. An simulation example is used to illustrate the proposed method.

본 논문은 초 중 고등학교 교과서에 수록되어 있는 전기 분야의 내용을 분석하고 잘못된 내용을 수정하기 위한 것이다. 전기 분야 교과서의 분석을 통하여 현재 우리 나라의 초 중 고등학교 학생들이 어떤 내용으로 전기를 배우고 있는가를 고찰하고 전기 분야에 대한 청소년들의 인식을 높일 수 있는 방법을 제시하고자 한다. 또한 현(現) 전기 관련 종사자들이 초.중.고등학교 교육 과정의 전기 관련 분야에 대하여 관심을 가지는 계기가 되고, 다가오는 21세기 우리 나라 전기 분야 발전의 기초를 다지는 계기가 되고자 한다.

The power demand has increased the groth of industry and improvement of life. In the past, the focus of an electric power company has been on the supply aspect of a management strategy, such as the stable provision of electric power through the construction of power equipment and least Cost planning. There has been a change of method in energy management. The balance of it seems to put forward to Demand Side Management(DSM) from Supply Side Management(SSM). Therefore, this paper is made a study for the method of energy grade of building.

This paper shows the accuracy of 61.8% rule which is based on the fall-of-potential method in field measurement of earth resistances, and proposes the measurement method which is applicable to the industries. This paper also finds the minimum distance to obtain the horizontal position in the earth resistance curves, and Proposes the standard form for measurement of earth resistance using the fall-of-Potential method.

본 논문에서는 변압기 유중 가스 분석 자료와 고장에 관련된 특징을 학습시킨 신경 회로망을 이용하여 전력용 유입 변압기의 새로운 고장 진단 방법을 제안하였다. 본 논문에서 제안한 신경 회로망을 이용한 고장 진단 방법(유중 가스 분석 방법)은 입력으로 가스 구성비 분석(IEC 기준) 및 주요 가스 분석(한국 전력 공사 기준) 자료를 채택하였다. 또한, 출력으로 전력용 유입 변압기의 고장 유무 및 고장 종류의 특징을 신경 회로망으로 추출하였다. 따라서 입력된 유중 가스 분석 결과에 따라 전력용 유입 변압기의 진단 결과(고장 유무 인식 및 해석)가 제시되도록 구성하였다. 제안된 신경회로망을 이용한 변압기 고장 진단 방법은 한국 전력 공사의 변압기 유중 가스 기록으로 효용성을 입증하였다. 따라서 유중 가스 분석만으로 현실성 있는 변압기 진단 및 상태 추정이 가능하게 되었고, 이것의 적용으로 적절한 유지 및 보수 대책 방안을 제시할 수 있게 되었다.

The line charging is becoming larger due to the expansion of underground cable and extra high voltage lines. It causes reactive power surplus at light load condition which may force generators to operate reluctantly in the under excited mode. This paper proposes the pratical criteria and methodolgy for the shunt reactor planning while suppressing generator's under excited operation.

Highly Integrated Total Energy System for system operational planning and analysis is a totally integrated computerized system for various parts of power system operation planning and power system analysis. It is developed by KEPCO for about 8 years, named HITES. Nowadays restructuring, deregulation, privatization and competition of electricity market is introduced in the world. This paper describes HITES application for two typical models of a competitive electricity market.

This paper presents a new economic dispatch algorithm to improve the unit commitment solution while guaranteeing the near optimal solution without reducing calculation speed. The conventional economic dispatch algorithms have the problem that it is not applicable to the unit commitment formulation due to the frequent on/off state changes of units during the unit commitment calculation. Therefore, piecewise linear iterative method have generally been used for economic dispatch algorithm for unit commitment. In that method, the approximation of the generator cost function makes it hard to obtain the optimal economic dispatch solution. In this case, the solution can be improved by introducing a inverse of the incremental cost function. The proposed method is tested with sample system. The results are compared with the conventional piecewise linear iterative method. It is shown that the proposed algorithm yields more accurate and economical solution without calculation speed reduction.

Carried out simulation for yearly peak and March load time of the KEPCO Power System in 1999. Analysis of the problems in power system operation by powerflow, fault and stability study. Establishment of power system optimal operating plan by installation of power system stabilizer.

This paper presents a sequential framework that calculates the total transfer capabilities of power transmission systems. The proposed algorithm enhances the Power System Transfer Capability Program (PSTCP) in conjunction with the Continuation Power Flow(CPF) that is used for steady-state voltage stability analysis and modified Arnoldi-Chebyshev method that calculates rightmost eigenvalues for small signal stability analysis. The proposed algorithm is applied to IEEE 39-bus test system to calculate TTC.

This paper proposes the methods of short-term load forecasting using Kohonen neural networks and back-propagation neural networks. Historical load data is divided into 5 patterns for the each seasonal data using Kohonen neural networks and using these results, load forecasting neural network is used for next day hourly load forecasting. Normal days and holidays are forecasted. For load forecasting in summer, max-, and min-temperature data are included in neural networks for a better forecasting accuracy. To show the possibility of the proposed method, it was tested with hourly load data of Korea Electric Power Corporation. (1993-1997)

The main purpose of HITES(Highly Integrated Total Energy System) is to build and develop an integrated energy system for power system operational planning and analysis which consists of load forecast, economic generation schedule, stability analysis and relational database system. The HITES can be utilized to supply a stable electric power and operate KEPCO's power system facilities economically. This system was put into operation in 1999. This paper describes the main feature of the HITES, main functions, numerical methods adopted in this system and network configuration.