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This paper proposes the planning method for capacitor installation in a distribution system to reduce the installation costs and minimize the loss of electrical energy. The expected lifetime of devices with moving parts depends on the total number of operations, which affects the replacement period and replacement decisions for aging equipment under a limited budget. In this paper, the expected device lifetimes are included in the formulation, and the optimal operation status of the devices is determined using a genetic algorithm. The optimal numbers and locations for capacitor installation are determined based on the optimal operation status. Simulation results in a 69-bus distribution system show that the proposed technique performs better than conventional methods. Index Terms--Distribution system, genetic algorithm, operation cost, planning, shunt capacitor, under-load tap changer.

This paper proposes a coordinated control method for an under-load tap changer (ULTC) with switching capacitors in distribution systems to reduce the operation numbers of both devices. The proposed method consists of two stages. In the first stage, the dispatch schedule of capacitors is determined using a genetic algorithm with forecasted loads to reduce the power loss and to improve the voltage profile during a day. In the second stage, each capacitor operates according to this dispatch schedule and the ULTC is controlled in real time with the modified reference voltages considering the dispatch schedule of the capacitors. Simulation results show that the proposed method performs better than a conventional control method. Index Terms--Capacitor, coordinated voltage control, genetic algorithm, modified reference voltage, under-load tap changer.

The protective devices and switches play an important role in the reliability of electrical distribution systems by minimizing the impact of interruption. In this paper, a method for identifying the type and location for protection devices and switches on the prerouted distribution system using value-based optimization is proposed. The proposed method is based on the contingency analysis of various components, e.g., the faults of line sections, switches, protective devices, and the restoration through switching actions such as upstream restoration and downstream restoration. The formulation of the optimization problem in this paper is appropriate for linear integer programming, where each nonlinear term can be translated by only two additional linear constraints. The detailed design of the protection devices and the switches are determined by minimizing the total cost of reliability that comprises apparatus investment, maintenance, and interruption cost. The efficiency and validity of the proposed method are demonstrated in case studies. Index Terms--Integer programming, power distribution, power distribution planning, power distribution protection, power distribution reliability.

In this paper, a method for the fault section estimation that considers the network topology under the influence of a circuit breaker tripped by the previous fault is proposed. The proposed method uses a three-dimensional (3-D) matrix to represent the network topology and the protection systems. The proposed network matrix describes the sections that are protected by particular protective devices that can be changed according to the network topology. To deal with the uncertainties imposed on the protection systems, the fuzzy set theory was applied to the network matrix in order to examine the relationships between the operated protective devices and the fault section candidates. A systematic method for the fuzzy membership function for each relation is proposed. In the proposed method, the operated time sequences of the protective devices were employed because either the network matrix or the network topology varied whenever the operations of the circuit breakers occur. The efficiency and adaptivity of the proposed method were demonstrated in experimental studies on real power systems in the Korean electric power system, particularly in case of complicated multiple faults. Index Terms--Fault diagnosis, fuzzy set, power system.

In this paper, a new approach to maintenance scheduling of generating units (MSU) in competitive electricity markets is presented. The main contribution of this study can be focused on modeling a game-theoretic framework for the MSU problem to analyze strategic behaviors of generating companies (Gencos). The MSU problem is formulated as a dynamic noncooperative game with complete information. The player corresponds to the profit maximizing individual Genco, and the payoff of each player is defined as the profit from the energy auction market. The optimal strategy profile is defined by the Nash equilibrium of the game. Numerical results for two-Genco systems are used to demonstrate the basic ideas of the proposed scheme, and large-scale IEEE reliability test systems are also considered to show the applicability of the proposed framework. The results obtained indicate that maintenance schedule can be one of the crucial strategic behaviors whereby Genco maximizes their profit in a competitive market environment. Index Terms--Competitive market, dynamic noncooperative game, maintenance scheduling of generating unit, maintenance strategy, Nash equilibrium.

It has been possible to optimize the geometrical structures of unprotonated (NH3)n+ (n = 1-6), protonated NH4+(NH3)n-1 (n = 1-6) and proton-transferred (NH4+-NH2)(NH3)n-2 (n = 3-7) ammonia cluster cations. The harmonic vibrational frequencies were assessed.

This paper presents a theory and simulation results of real time pricing of real and reactive powers that maximizes social benefit. Conventional studies represented the responses of consumers as demand functions, and the objective of optimization was minimization of operating cost of power system. In this paper, the responses of consumers are represented as the inverse of the demand functions and power flow equations are incorporated in the constraints. This makes it possible to incorporate constant power factor demand consumer as a participant. That also makes it possible to maximize the objective function of optimization that is social benefit of participating in the electricity market and to determine the price of electricity at each bus. Not only the real time price of real power but also that of reactive power is determined simultaneously by the incorporation of power factor of loads into the constraint of optimization. Keywords: Optimization, Electricity Pricing, Demand Function, Benefit Function, Power Factor

This paper deals with analysis of the detailed dynamics of the TCSC. The system considered is a system of one machine connected to an infinite bus through a thyristor controlled series compensated transmission line. This system can be described as periodic state equations. This paper provides analysis of the periodic state equations using the state variable approach. Transient characteristics as well as steady state characteristics of the TCSC are presented using the analytical equations for three operating modes of the TCSC. The simulations are performed using the MATLAB program.

A series of strained amides such as N-formylazetidine, N-formylaziridine and their protonated tautomers were analyzed to characterize the mechanisms of N- and O-protonation in strained molecular systems. Ab initio calculations of strained N-formylazetidine and N-formylazidine indicated the presence of planar conformations that mediated the hydrolysis of strained amide systems. The stereoselectivity of the strained molecular systems containing a nitrogen lone pair was also dependent on stereoelectronic and electrostatic effects.

This paper proposes an expert system using fuzzy relations to deal with uncertainties imposed on fault section diagnosis of power systems. We build sagittal diagrams which represent the fuzzy relations for power systems, and diagnose fault sections using the sagittal diagrams. Next, we examine the malfunction or wrong alarm of relays and circuit breakers based on the alarm information and the estimated fault section. The proposed system provides the fault section candidates in terms of the degree of membership and the malfunction or wrong alarm. An operator monitors these candidates and is able to diagnose the fault section, coping with uncertainties. Experimental studies for real power systems reveal usefulness of the proposed technique to diagnose faults that have uncertainty.

This paper presents a linear quadratic Gaussian(LQG) based power system stabilizer(PSS) to control the subsynchronous resonance(SSR) that may occur in a series capacitor compensated power system. This paper investigates the dominant parameters on the SSR using the critical compensation level(CCL), and selects the design parameters to confirm the stability robustness. The complete SSR simulation system based on the IEEE first benchmark is employed in this study. Eigenvalue analysis and time domain simulations using a nonlinear system model show that the proposed PSS can control the SSR efficiently.

This paper presents a method of obtaining transmission network equivalents from the network's response to a pulse excitation signal. Proposed method is based on modal decomposition representation for the large-scale interconnected system. In this framework we use Prony analysis to identify the network function of the system and to decompose the large system into a parallel combination of simple first-order systems. As a result network function of the transmission network can be identified easily, and Thevenin-type of discrete-time filter model can be generated. It can reproduce the driving-point impedance characteristic of the network. Furthermore proposed model can be implemented into the EMTP in a direct manner. The simulation results with the full system representation and the developed equivalent system showed a good agreement. Keywords: Network Function, Modal Decomposition, Prony Analysis, Electromagnetic Transients.

An integrated fuzzy expert system is presented to diagnose various faults that may occur in a regional transmission network and substations. Fuzzy reasoning method is applied, and it is discussed in detail. Discrimination of false operations or nonoperations of protective devices as well as the fault identification scheme are also analyzed, together with the fuzzy inference process. The proposed system is designed to improve efficiency, generality, and reliability of the solution. The system will replace a fault diagnosis system that had been tested as a part of an intelligent support system on a local control center in Korea. Index Terms--Fuzzy Reasoning, Integrated Fault Diagnosis, Expert System.

The increasing penetration of plug-in electric vehicles (PEVs) may cause a low-voltage problem in the distribution network. In particular, the introduction of charging stations where multiple PEVs are simultaneously charged at the same bus can aggravate the low-voltage problem. Unlike a distribution network operator (DNO) who has the overall responsibility for stable and reliable network operation, a charging station operator (CSO) may schedule PEV charging without consideration for the resulting severe voltage drop. Therefore, there is a need for the DNO to impose a coordination measure to induce the CSO to adjust its charging schedule to help mitigate the voltage problem. Although the current time-of-use (TOU) tariff is an indirect coordination measure that can motivate the CSO to shift its charging demand to off-peak time by imposing a high rate at the peak time, it is limited by its rigidity in that the network voltage condition cannot be flexibly reflected in the tariff. Therefore, a flexible penalty contract (FPC) for voltage security to be used as a direct coordination measure is proposed. In addition, the optimal coordinated management is formulated. Using the Pacific Gas and Electric Company (PG&E) 69-bus test distribution network, the effectiveness of the coordination was verified by comparison with the current TOU tariff. [ABSTRACT FROM AUTHOR]