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This paper proposes and evaluates a method that improves the adaptability and efficiency of genetic algorithms (GAs) when applied to the minimal loss reconfiguration problem. This research reduces the searching space (population) when a new codification strategy and novel genetic operators, called accentuated crossover and directed mutation, are used. This allows a drastic reduction of the computational time and minimizes the memory requirements, ensuring a efficiency search when compared to current GA reconfiguration techniques. The reduced population is created through the branches that form 'system loops.' This means that almost all individuals created for the GA are feasible (radial networks) generating topologies that can only be limited by the system's operational constraints. The results of the proposed reconfiguration method are compared with other techniques, yielding smaller or equal power loss values with less computational efforts. Index Terms--Genetic algorithms (GAs), losses, minimal loss reconfiguration, optimization methods, power distribution.

This paper presents an investigation of a method for determining the dynamic properties of a power system. The investigation is based on the injection of perturbations in the supply voltage magnitude and the analysis of the resulting active and reactive power responses. A large dc/ac converter (HVDC-Light installation) has been used to generate the perturbations. The frequency range of the perturbations was from 0.03 to 20 Hz. The method is experimentally verified on a small 10-kV grid with 5 MW of wind power, subjected to the above perturbations. Both theoretical and experimental results indicate that a large concentration of wind turbines does not cause any power quality disturbances or serious oscillations, although the grid is fairly weak. Index Terms--Grid interaction, model, modeling, power quality, wind turbine.

The test and the characterization of medium or high-power electronic converters, under nominal operating conditions, are made difficult by the requirement of high-power electrical source and load. In addition, the energy lost during the test may be very significant. The opposition method, which consists of an association of two identical converters supplied by the same source, one operating as a generator, the other as a receptor, can be a better way to do these test. Another advantage is the possibility to realize accurate measurements of the different losses in the converters under test. In the first part of this paper, the characteristics of the method concerning loss measurements are compared to those of the electrical or calorimetric methods, then it is shown how it can be applied to different types of power electronic converters, choppers, switched mode power supplies, and pulsewidth modulation inverters. In the second part, different examples of studies conducted by the authors, and using this method, are presented. They have varying goals, from the test of soft-switching inverters to the characterization of integrated gate-commutated thyristor (IGCT) devices mounted into 2-MW choppers. Index Terms--Integrated gate-commutated thyristor (IGCT) characterizations, inverter losses measurement, opposition method, reliability test in power electronics.

The second part of this paper presents a practical implementation and application of the methodology for the stochastic assessment of the annual financial losses due to interruptions and voltage sags discussed in the first part of this paper. The costs of interruptions and voltage sags are determined separately and then combined in order to estimate the total financial losses in the network. The methodology is illustrated on a generic realistic distribution network with all relevant network components modeled appropriately. Finally, different network topologies are compared taking into account total financial losses in the network. It is shown that the inclusion of the financial losses due to voltage sags that may account for up to about 20% of the interruption costs may alter the network topology ranking. Index Terms--Financial losses, interruptions, power quality (PQ), reliability, voltage sags.

This paper presents a generalized methodology for stochastic/probabilistic assessment of the annual financial losses due to interruptions and voltage sags. The costs of interruptions and voltage sags are treated separately and then combined in order to estimate the total financial losses in the network per annum. The methodology proposed is applicable to both assessment of individual customer losses and assessment of total network losses. It takes into account in a probabilistic manner all the uncertainties associated with the voltage sag calculation, sensitivity of customers' equipment to voltage sags, the interconnection of the equipment within an industrial process, and customer types and the location of the process in the network. Index Terms--Financial losses, interruptions, power quality (PQ), reliability, voltage sags.

This paper presents a study on losses in cables and transformers considering nonsinusoidal conditions in commercial facilities. A mathematical development based on classical definitions available in the literature supports the proposal of a factor that is suitable to indicate where losses are significant and must be compensated. A case study is also presented and meticulously analyzed in order to validate the theoretical assumptions. Index Terms--Harmonic distortion, losses, power system harmonics, reactive power.

Distributed generators (DGs) sometimes provide the lowest cost solution to handling low-voltage or overload problems. In conjunction with handling such problems, a DG can be placed for optimum efficiency or optimum reliability. Such optimum placements of DGs are investigated. The concept of segments, which has been applied in previous reliability studies, is used in the DG placement. The optimum locations are sought for time-varying load patterns. It is shown that the circuit reliability is a function of the loading level. The difference of DG placement between optimum efficiency and optimum reliability varies under different load conditions. Observations and recommendations concerning DG placement for optimum reliability and efficiency are provided in this paper. Economic considerations are also addressed. Index Terms--Distributed generator (DG), load pattern, optimal location, power loss, power system efficiency, power system reliability.

Risk indices of loss-of-load expectation and loss-of-energy expectation were traditionally used to determine generation adequacy. However, because responsibility of generation installation and transmission upgrades rests with different entities, both generation and transmission need to be examined to evaluate the resource adequacy of today's deregulated power systems. Further, it is important to delineate the contribution to curtailments arising from insufficient installed capacity and bottlenecks in transmission system. Hence, risk-based planning and market decision-makings have to address both generation and transmission jointly. This paper presents a procedure to combine dynamic optimization and Monte Carlo simulation to generate a vector space of solution, from which optimal solutions for different objectives can then be easily obtained. Determining locational capacity and transmission requirements serves the example of such an application. This paper closes with a discussion on some possible changes to risk criteria. Index Terms--Installed capacity, loss-of-load expectation (LOLE), optimization, reliability, risk, transfer capability.

This paper presents a methodology based on the circuit theories for unbundling and allocation of transmission losses among the participants of a pool-based electricity market. Starting from a known operation point and using the basic network equations without additional assumptions, an expression of the branch losses based on nodal current injections is derived. Since the power flow equations and circuit theories are satisfied, the methodology turns explicit, in a natural way, separating the losses at each system branch and assigning the responsibility to the respective market participants. It means that the loss allocation of each branch, which is produced by each generator and consumer, is obtained. Extensions and strategies considering unsubsidized and predefined proportion-based loss allocation as well as issues related with the allocation fairness and transparency are also included. Comparisons with previous methods and validation tests of the proposed method are reported by using the IEEE Reliability Test System. Index Terms--Loss allocation, pool-based electricity markets, power flow, transmission losses, transmission open access.

The accurate evaluation of losses in power systems has important technical, economic, and regulatory repercussions. For example, losses are increasingly becoming one of the most important measures of system performance, especially in connection with private sector participation (PSP) in the distribution segment of the industry. This paper proposes a top-down/bottom-up approach for accurately estimating technical losses in power distribution systems when a complete set of modeling data is not available. The results of the recent application of this approach in a developing country are also presented. Index Terms--Losses, power distribution economics, power distribution planning.

This paper presents a particle swarm optimization (PSO) as a tool for loss reduction study. This issue can be formulated as a nonlinear optimization problem. The proposed application consists of using a developed optimal power flow based on loss minimization function by expanding the original PSO. The study is carried out in two steps. First, by using the tangent vector technique, the critical area of the power system is identified under the point of view of voltage instability. Second, once this area is identified, the PSO technique calculates the amount of shunt reactive power compensation that takes place in each bus. The proposed approach has been examined and tested with promising numerical results using the IEEE 118-bus system. Index Terms--Evolutionary computation, loss power minimization, nonlinear optimization problem, optimal power flow (OPF), particle swarm optimization (PSO).

This paper is devoted to efficiently modeling the connectivity of distribution networks, which are structurally meshed but radially operated. A new approach, based on the 'path-to-node' concept, is presented, allowing both topological and electrical constraints to be algebraically formulated before the actual radial configuration is determined. In order to illustrate the possibilities of the proposed framework, the problem of network reconfiguration for power loss reduction is considered. Two different optimization algorithms--one resorting to a genetic algorithm and the other solving a conventional mixed-integer linear problem--are fully developed. The validity and effectiveness of the path-based distribution network modeling are demonstrated on different test systems. Index Terms--Distribution networks, genetic algorithm, loss minimization, network reconfiguration.

This paper covers the experimental investigation and theoretical calculation of losses in a planar inductor under load. Finite-element software is used to perform the loss calculations. Thermally controlled experiments are performed for a range of frequencies to validate the corresponding finite-element method loss calculations. The thermal dependence of the loss mechanisms is also considered. Index Terms--Finite-element method (FEM) calculations, loss analysis, loss measurement, planar inductor, thermal measurement.

Faults on the electric power distribution system are responsible for a large portion of the interruptions that a customer will experience. To maintain a high level of system reliability, vegetation maintenance is often required. Analytical prediction of the effects of vegetation maintenance on distribution system reliability requires a model of the expected failure rate of line sections that includes the effects of vegetation. Vegetation-related failures are more likely to occur as the vegetation near the overhead power lines grows, increasing the line-section failure rate. Due to difficulties in using existing growth models, this paper proposes to use a direct model for failure-rate prediction based on factors that affect vegetation growth. Four models are considered: linear regression, exponential regression, linear multivariable regression, and an artificial neural network (ANN). The models are tested with historical vegetation growth parameter data and feeder failure rates. Results are compared and the features of each model are discussed. Index Terms--Failure-rate modeling, failure-rate prediction, line clearance, neural networks, power distribution systems, regression, reliability, tree trimming, vegetation maintenance.

A newly developed electrothermal calculation method is implemented to estimate the power loss and working temperature of insulated gate bipolar transistor (IGBT) devices. Based on the measurement of the IGBT's characteristics, the exact estimation of power loss considering the junction temperature is introduced. Then, the thermal network is used to calculate the working temperature. The comparison between experimental and calculation results shows that this method is effective as a designing step with only the time-domain voltage and current data obtained from simulation results. Index Terms--Insulated gate bipolar transistor, junction temperature, power loss.

This paper deals with pulsewidth modulation (PWM) strategies that synchronize clamped voltage segments using the current peak in the corresponding phases of a three-phase quasi-resonant dc-link (QRDCL) voltage inverter. It is shown that, instead of employing lookup tables, these strategies can be easily implemented by using the concept of hybrid modulation in this type of pulsed dc-link voltage (PDCLV) inverter. In fact, such concept leads to a systematic and straight approach to the generation of any continuous or discontinuous PWM strategy. A topology that is shown to produce fewer losses than either PDCLV inverters or the hard-switched inverter version is used to compare the losses produced when the two strategies discussed in the paper are employed. Simulation and experimental results confirm the validity of the proposed technique. Index Terms--Losses, soft switch, three-phase inverter.

This paper presents a conceptual possibilistic approach using fuzzy set theory to manage the uncertainties in the reliability input data of real power systems. In this paper, an algorithm is introduced to calculate the possibilistic reliability indices according to the degree of uncertainty in the given data. The probability distribution function can be transformed into an appropriate possibilistic representation using the probability-possibility consistency principle (PPCP) algorithm. In this algorithm, the transformation is performed by making a compromise between the transformation consistency and the human experience. Fuzzy classification theory is applied to reduce the number of load data points. The fuzzy classification method determines the closeness 1 of load data points by assigning them to various clusters and then J determining the distance between the clusters. The IEEE-RTS with 32-generating units is used to demonstrate the capability of the proposed algorithm. Index Terms--Loss-of-load expectation, forced outage rate, probability-possibility consistency principle, fuzzy clustering.

This paper discusses various methods based on network partitioning and voltage stability indices to accelerate the computation of voltage collapse points using continuation techniques. Partitioning methods derived from right eigenvector and tangent vector information are thoroughly studied, identifying limitations and probable application areas; a mixed partition-reduction technique is then proposed to reduce computational burden. Also, tangent vectors are used to define a clustering method for the identification at any operating condition of the critical area at the collapse point, and a new voltage stability index is defined based on the identification of this critical area. Finally, a predictor-corrector methodology based on this index and the continuation method is proposed for fast computations of voltage collapse points. All the different methods are compared based on the results obtained for the IEEE 300-bus test system, and a methodology is recommended based on its prospective computational savings. Keywords: Network partitioning, voltage stability index, voltage collapse, continuation power flows, on-line security analysis.

A predispatch model that minimizes generation and transmission losses on hydroelectric power systems is presented and applied to the hydroelectric power system of COPEL, a Brazilian utility located in southern Brazil. Power loss in the generation and transmission systems is minimized on an hourly basis throughout a day. Load demand as well as generation, transmission and interchange operational constraints are satisfied. Hydroelectric generation characteristics are described in detail. Power loss in hydroelectric generation is associated with a reduction in turbine-generator efficiency and effective water head. The latter is due to an increase in tailrace elevation and penstock head loss. Power loss upon transmission is calculated as a quadratic function of active power flow, as represented in a DC load flow model. The predispatch model was evaluated under typical operational conditions, achieving significant savings with respect to actual operation.

The paper presents a new approach for the estimation of harmonic components of a power system using a linear adaptive neuron called Adaline. The learning parameters in the proposed neural estimation algorithm are adjusted to force the error between the actual and desired outputs to satisfy a stable difference error equation. The estimator tracks the Fourier coefficients of the signal data corrupted with noise and decaying dc components very accurately. Adaptive tracking of harmonic components of a power system can easily be done using this algorithm. Several numerical tests have been conducted for the adaptive estimation of harmonic components of power system signals mixed with noise and decaying dc components. Key words: Power system harmonics, Neural network, Adaline, Estimation.

The concept of transmission loss penalty factors for area energy interchange is introduced. The algorithm for penalty factors is based upon the Jacobian method and reflects the current network model and operating condition. The electrical distances between energy sending and receiving points and the area inter-tie locations are considered in the calculation. A unique and important attribute of an area penalty factor is that it reflects only the portion of the internal area loss induced by the interchange with the area of interest. Because of this attribute, short-term economic transactions can be properly evaluated. Also, current trends toward open access to transmission networks bring forth tire need for accurate component modeling of transmission losses. With area penalty factors, wheeling charges can be more accurately assessed for specific transactions. Practical considerations and implementation of the algorithm are discussed, and test results on an example network are presented. KEYWORDS: Penalty Factors, Transmission Loss, Loss Sensitivity. Economic Dispatch, Interchange Evaluation

Parameters of a capacitor-start, capacitor-run single-phase induction motor with closed or semi-closed rotor slots are measured and a model for the investigation of the performance of the machine in the frequency domain under the influence of harmonic voltages is presented. An algorithm taking into account the nonlinear rotor leakage inductance is established. This algorithm is applied to estimate the current in the time domain, and the harmonic losses at rated-load operation without and with run capacitors are calculated. Computational results are compared with those from experimentation and the differences between both are discussed. Keywords - Time harmonics, single-phase induction machines

The problem of the harmonic loss evaluation is of growing interest among power system engineers, both for the increase of operating costs and the decrease of the useful life of the system components. The paper addresses this problem with a probabilistic approach to take into account the randomness of current and voltage harmonics; a method for evaluating the expected value of the operating costs and of the premature aging costs is presented. A numerical application to a test system is also discussed, showing the viability of the proposed approach and the significance of the results; in particular, the aging costs turn out to be unaffected by the type of probability density function describing the harmonics. Keywords - Power system harmonics, Harmonic effects, Probabilistic approach.

A new special stability control termed CAPS improves power system stability by exploiting the time-overvoltage capability of large shunt capacitor banks. During low voltage emergencies, several series groups of wye-connected capacitor banks are shorted to increase reactive power output. We describe successful commissioning tests on a 241.5-kV, 168-MVAr capacitor bank.

This paper describes a new approach to the evaluation of loss adjustment factors for distribution systems. Such factors are required for 'use of system' and wheeling calculations and reflect the amount by which purchases of energy at entry points to the system must exceed consumption at the point of use to account for the losses which occur in between. Renewed interest in cost-reflective methods of charging for losses has resulted from the deregulation of the electricity supply industry in many parts of the world. An algorithm is described which combines the use of graph theory with readily available loadflow results, to assign the losses in each line or transformer within the system to the consumers supplied by it. The resulting allocation is shown to account for the voltage level, location and consumption pattern of the consumer in a way which is economically efficient. A variety of strategies for apportioning losses between multiple consumers at a given location can be implemented. The algorithm is suitable for allocating both demand and energy losses. Results on a full size distribution network are presented, and are compared with traditional published loss adjustment factors.

Solid-state switches are being designed for use on ac transmission lines for tighter control of power flow and increased use of transmission capacity in accordance with an advanced concept called 'Flexible AC Transmission System' (FACTS). These necessitate using the largest available thyristors and GTO's that must perform under emergency fault conditions with assurance of long term reliability and life expectancy. This paper is concerned with reviewing concepts needed to predict on-state losses incurred at extreme variations of junction temperature and describing an empirical method being used for commercially available 100-mm thyristors.

An adaptive loss evaluation algorithm for power transmission systems is proposed in this paper. The algorithm is based on training of artificial neural networks (ANNs) using backpropagation. Due to the capability of parallel information processing of the ANNs, the proposed method is fast and yet accurate. Active and reactive powers of generators and loads, as well as the magnitudes of voltages at voltage-controlled buses are chosen as inputs to the ANN. System losses are chosen as the outputs. Training data are obtained by load flow studies, assuming that the state variables of the power system to be studied take the values uniformly distributed in the ranges of their lower & upper limits. Load flow studies for different system topologies are carried out and the results are compiled to form the training set. Numerical results are presented in the paper to demonstrate the effectiveness of the proposed algorithm in terms of accuracy and speed. It is concluded that the trained ANN can be utilized for both off-line simulation studies and on-line calculation of demand and energy losses. High performance has been achieved through complex mappings, modeled by the ANN, between system losses and system topologies, operating conditions and load variations. Keywords: capacity loss, energy loss, artificial neural network, power transmission systems

Strategically sited grid-support photovoltaic (PV) applications have been proposed to provide value (cost savings) to electric utilities experiencing transmission and distribution (T&D) system overloads. These applications can potentially defer transformer and transmission line upgrades, extend equipment maintenance intervals, reduce electrical line losses, and improve distribution system reliability. This research presents and tests a method to calculate the reduction in distribution system electrical line losses. It also describes how to optimize plant size, plant location along a distribution feeder, and load transfer from an adjacent feeder. Results at Pacific Gas and Electric Company indicate that a 0.50 MW PV plant at Kerman, California, has $37,000 in energy loss savings value over the plant's life with additional value due to capacity loss savings. These results are site specific.

This paper assesses the suitability of the sandwiched-winding matrix transformer for low-profile applications from the loss standpoint. Finite-element simulations and experiments suggest that the core loss can be adequately characterized by approximating the matrix transformer as a collection of identical uncoupled elements. Thus, a matrix transformer with a large number of elements may have higher core loss than a conventional (tall) transformer, and more core loss than winding loss. Eddy-current analysis reveals that the interconnects which parallel the elements incur a significant fraction of the winding loss. Thus, load distribution is recommended to eliminate the paralleling interconnects in matrix transformers.

A wide variety of electromagnetic phenomena occurring on ac power lines has been held responsible for literally billions of dollars per year in lost revenue. Information related to actual probability of occurrence of these power line deviations is presently limited. This paper describes the results of four years of point of utilization power quality monitoring at 112 North American locations. A quantity of 1057 site months of data collected between 1990 and 1994 was used in this assessment. The data indicate that the numbers of events occurring at typical locations may range from almost none, to thousands per month. The analysis results characterize several aspects of power quality related to the occurrence of low rms events, high rms events, transient events, and power interruptions (outages).

A new algorithm for calculation of transmission loss penalty factors for generators, suitable for real-time application, is presented. Previously published techniques for generator penalty factor calculation were derived from the power flow model with basis upon reference bus location or internal-external interchange, disregarding the electrical distance between generation and load. This new method is based purely upon the physical definition of a penalty factor, that is, losses resulting from delivering power across the transmission network from a generator bus to the loads. The penalty factors are calculated from a solved network model and thus reflect network conditions in the result. Considerations in implementation of the new technique are discussed, and test results on an example network are presented. Other applications of the formulation are explored. KEYWORDS: Penalty Factors, Transmission Loss, Loss Sensitivity, Economic Dispatch, Interchange Evaluation

The transverse alternating current (AC) losses in flat superconducting cables were investigated numerically at varying frequencies. Mathematical formulas were developed to take into account the different factors that may contribute to transverse AC losses, including the cable thickness and length. Investigations were carried out for both finite and infinite cables. Results indicate that finite cables exhibit higher loses than infinite cables at the high frequency range. It was also found that such losses are not dependent on the cable length.

The power-loss method, along with a surface integral formulation, has been used to compute the attenuation constant in microstrip and coplanar structures. This method can be used for the analysis of both open and closed structures. Using the surface equivalence principle, the waveguide walls are replaced by equivalent electric surface currents and dielectric surfaces are replaced by equivalent electric and magnetic surface currents. Enforcing the appropriate boundary condition, and E-field integral equation (EFIE) is developed for these currents. Method of moments with pulse expansion and point matching testing procedure is used to transform the integral equation into a matrix one. The relationship between the propagation constant and frequency is found from the minimum eigenvalue of the moment matrix. The eigenvector pertaining to the minimum eigenvalue gives the unknown electric and magnetic surface currents.

A numerical damping analysis program (DAMP), based upon the frequency scanning method, for application to multi-generator power systems has developed. This program permits the determination of electrical and mechanical torsional damping at arbitrary frequencies with respect to the individual generator under consideration within such a multi-machine system. Therefore, this allows the quantitative frequency domain analysis of power swing and torsional oscillation with due consideration for the effects of mutual interference among the generators. In this paper, first, the basic algorithm, modeling method, and validity of the new program are indicated. Next, the effectiveness of the program is demonstrated through SSR and other types of analyses for multi-machine systems. KEYWORDS: damping, multi-generator power system, series capacitor, subsynchronous resonance, frequency scanning

This paper presents development of an innovative tool for online power system operation. It is designed to operate in an Energy Control Center (ECC) environment. Online application consists of using the developed Optimal Power Flow (OPF) based Loss Minimization (LM) function for real time power system corrective actions by ECC dispatchers. The results of online power system operations using the LM function are reported to demonstrate economic and security gains for power system operations. Keywords: Optimal Power Flow, Loss Minimization, Suboptimal, Energy Management System (EMS), Energy Control Center.

The main purpose of this paper is to call power engineers' attention to the lin loss in the residential wiring system. This paper introduces a measurement method which will measure the node voltages and apply the approximate loss equations to calculating the line loss. This method is very effective and efficient because it does not involve measuring the line current. This paper also presents the field test data and the results of economic evaluation to demonstrate the role of the interior wiring loss in an effort to conserve energy.

A method is proposed which avoids many limitations associated with traditional B-coefficient loss coefficient calculation. The proposed method, unlike the traditional B-coefficient method, is very fast and can handle line outages. The method utilizes network sensitivity factors which are established from DC load flow solutions. Line outage distribution factors (ODF's) are formulated using changes in network power generations to simulate the outaged line from the network. The method avoids the use of complicated reference frame transformations based upon Kron's tensor analysis. The necessity of data normalization used in least squares and the evaluation of the slope of [[Theta].sub.j] versus P[G.sub.n] is not necessary with the proposed method. Using IEEE standard 14-bus and 30-bus systems, the method's results are compare against results obtained from an AC load flow program (LFED). The method's solution speed is compared to that of the LFED method, the base case database method and the conventional B-coefficient method based on [A.sub.jn]-factor. Th proposed method is easy to implement and, when compared to other methods, has exhibited good accuracy and rapid execution times. The method is well suited to on-line dispatch applications.

This paper proposes a methodology to derive the simplified model for distribution system loss analysis. According to the typical daily load patterns and the energy consumption of customers, the hourly loading of distribution transformers can be solved. A three-phase load flow program is applied to calculate the feeder power flow so that the hourly feeder loading will be the same as that obtained by the field test. The hourly primary conductor loss, secondary conductor loss, transformer copper loss and core loss are then solved according to the mathematical modeling of system components. The sensitivity analysis of system loss with respect to the feeder loading, power factor, feeder length, transformer capacity is then performed to derive the simplified loss model of distribution feeders. A distribution feeder of Taipower system is then selected for computer simulation to demonstrate the effectiveness of the proposed method. By applying the simplified loss model derived, the daily loss pattern of distribution feeders is solved according to the actual hourly feeder loading. It is concluded that the proposed methodology provides an useful tool for distribution engineers to estimate the operation efficiency of distribution systems in a very effective manner.

No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter stations and Static VAR controllers. This paper presents a measuring method to be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to a sophisticated calorimetric technique. An uncertainty of 1% was achieved at conditions simulating full load operation. Voltage across and current through the valve are recorded in discrete steps and digitized. The loss is then calculated as their product. Special current and voltage sensors were developed to cover a very high dynamic range of the measured quantities. A high resolution, multichannel digital recorder was used for simultaneous registration of two voltage and two current signals. The method is of a general application, since the valve is treated as a two port circuit. Therefore, it can be used to measure loss in other non-linear components and apparatus, where large dynamic changes of the measured quantities preclude application of conventional techniques.

Voltage sags, also known as dips, are important to industrial reliability. Modern process controls are often sensitive to voltage sags. The combination of voltage sags and sensitive equipment may cause significant production outages. Less sensitive equipment may be available, but the designer must know sag characteristics of the electric system to make the best choices between reliability and equipment cost. This paper shows how to predict voltage sag performance of electric supply systems by combining a new analysis method with reliability data. The analysis method is proposed for a new chapter in the next revision of IEEE Std 493.

A detailed time domain model for the eddy current losses in the windings of a transformer is presented. The basic elements for the derivation of the model are the turns which may be combined into sections. The model is expressed as an R-matrix. Its diagonal elements were fitted using a series Foster circuit while for the off-diagonal elements we used the basis functions of the Foster circuits to derive the time domain model in the form of state equations. For validation, the losses computed with the detailed model are compared with those obtained by considering full windings. The frequency response of the transformer model is compared with test results. Simulations are presented for illustration and further validation.

A novel window is presented and applied in electrical power system harmonic analysis. The goal of increasing the resolvability of low magnitude non-harmonic tones close in frequency to higher magnitude harmonics and the detectability of very low magnitude high frequency harmonics is pursued. The proposed window is derived from the Tseng window; its spectrum can be modeled in the synthesis stage and it is characterized by a narrow width main lobe and by sidelobes which are very low in correspondence to some specified frequencies. Numerical experiments demonstrate the performances and the usefulness of the new window in resolving periodic distorted waveforms in power systems.

A new method based on a heuristic technique for reactive loss reduction in distribution network is presented. This method allocates capacitors to certain nodes (sensitive nodes) which are selected by first identifying the branch which has the largest losses due to reactive power. Then, the node therein, which has the largest reactive power is selected. The capacitor rating is determined by differentiating the system losses with respect to the load connected to that node. The compensating capacitors are placed at these optimal locations with appropriate VAR ratings to achieve maximum benefits in dollar savings. The variation of the load during the year is considered. The capital and installation costs of the capacitors are also taken into account. This method is applied to a 38 feeder distribution system of 27.6 kV, 560 MVA of the city of Windsor, Ontario, resulting in annual saving of about CAN $145,000 after amortizing the capital and installation costs of applying the compensating capacitors, and using a figure for the cost of energy of 1.986 cents per kWh.

Internal-tin-diffusion process results in interfilament contact in Nb3Sn wires which leads to excess hysteresis loss superceding the intrinsic magnetic hysteresis loss of filaments. Reducing the twist pitch length of the filaments in the wire minimizes excess contact loss. Interfilament contact leads to a strong dependence of volume magnetization measurements on sample length below one twist pitch.