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In this part of the paper (Part II), available technical solutions to minimize or prevent wildfires caused by power networks are reviewed in more detail. These methods include fundamental changes to power system equipment, periodic checkups and maintenance, identification of faults via voltage/current waveforms, changes to protection and relaying settings and coordination, and installation of new power system apparatus. The strengths and drawbacks of each method are discussed. The discussion section brainstorms some future possible solutions that smart-grid technologies can enable. The paper concludes that there has neither been enough research in universities nor enough investment by industry to develop viable preventive solutions for wildfires that initiate from the daily operation of electrical power grids. This, in the authors’ opinion, is the crucial time for investment in research and development to tackle the lethal wildfire problem while electric power networks offer “the lowest hanging fruits to pick.” [ABSTRACT FROM AUTHOR]

Lightning is considered one of the main causes of faults in overhead distribution networks. Direct strokes usually lead to flashovers due to the insulation levels that are used. Induced overvoltages caused by indirect lightning are usually lower and can be efficiently reduced by metal–oxide surge arresters. Hence, its associated flashover rate can be reduced. In this paper, a heuristic method is proposed to optimize the number of surge arresters as well as their locations. The method presented is based on genetic algorithms and an economic approach is taken into account by means of evaluating the cost of insulation flashover. [ABSTRACT FROM AUTHOR]

This paper reviews and applies the balanced realization (BR) theory to obtain reduced-order models from dynamic system equivalents of electric power networks. BR allows obtaining reduced-order models via a process in which the original asymptotic stable system is internally balanced. The balanced system is truncated according to its dominant dynamics. It can be proven that the truncated, that is, reduced-order, system is also stable. This paper applies the BR method to dynamic system equivalents represented as frequency-dependent network equivalents (FDNEs). Furthermore, it shows that an assumed reduced-order FDNE can be further reduced via the BR process. Four case studies, involving one transmission network and three wind power plants, are presented. [ABSTRACT FROM PUBLISHER]

This paper presents a practical approach to obtain reduced-order models for electric networks expressed in the dynamic harmonic domain (DHD). The proposed method reduces the DHD system of ordinary differential equations first in the harmonic sense via a voltage-based frequency-scan procedure and subsequently in the state sense via truncated balanced realizations. The harmonic-selection and truncation stage substantially reduces the original full-size system. The state-reduction process is applied to the already harmonic-reduced system, achieving further reduction. Two networks are used as case studies to demonstrate the reduction properties of the proposed model-order reduction methodology. [ABSTRACT FROM AUTHOR]

This paper presents induced voltage measurement results along a conductor pair inside a 4.5″, 9-m-long galvanized steel tube, with an intermediate screwed joint. The excitation was done by an external parallel conductor where a 60-Hz current flows, followed by an impulsive current (5 kA, 8/20 μs). Some measurements with the external joint short-circuited cast a great doubt about the validity of all Schelkunoff transfer impedance concept. The paper focuses also the recommended calculation procedures using Circuit Theory. This paper also shows that there are strong evidences that the classical Maxwell equations were developed to represent wireless propagation such as light and wireless communication. The paper suggests as well the convenience of a deeper verification on the validity of applying Maxwell equations to solve metallic circuit problems. [ABSTRACT FROM AUTHOR]

This paper presents a new method for the classification and characterization of voltage dips and swells in electricity networks. The proposed method exploits unique signatures and parameters of three-phase voltage signals extracted from the polarization ellipse in 3-D coordinates. Five ellipse parameters, which include azimuthal angle, elevation, tilt, semi-minor axis, and semi-major axis, are used to classify and characterize voltage dips and swells. Seven types of voltage dips, which include a total of 19 groups of dips incorporating different kinds of balanced (three-phase dips) and unbalanced (single-phase or double-phase) dips, are identified and successfully classified using the 3-D polarization ellipse parameters. Two types of voltage swells, which include a total of 6 groups, are also classified using the proposed method. The proposed method is validated using real measurement data, recorded waveforms provided by the IEEE 1159.2 working group, and the data of unbalanced dips associated with phase-angle jumps, voltage drops, and rotations due to loading effects. [ABSTRACT FROM AUTHOR]

A new wind turbine transformers protection method against high du/dt switching transients taking place during a wind turbine operation is described. High-frequency transients, characterized by a high rate of voltage rise (du/dt) and overvoltage at the wind turbine transformer high-voltage terminals may be a result of operations of the turbine switchgear typically comprising a vacuum circuit breaker. The protection concept described in this paper is a follow up of research activities on a transients suppressing method dedicated for distribution transformers. The principle of operation of the protective device proposed and parameters optimization procedures for windmill transformers are provided in this paper. The performance of the device was verified by means of Alternative Transients Program–Electromagnetic Transients Program simulations. The physical device was built and experimentally verified by full-scale functional tests reflecting a real wind turbine power network. [ABSTRACT FROM AUTHOR]

Different microsources have different frequency regulation functions and capabilities. The droop control can allocate power among the microsources according to the operation demand during system dynamics; however, the steady-state frequency often deviates from the rated value because of the droop characteristics. To ensure the precise condition of power and the stability of frequency even in a low-voltage network, this paper puts forward an improved droop control algorithm based on coordinate rotational transformation. With the ability to accurately regulate the unbalance power, this method realizes self-discipline parallel operation of microsources. Furthermore, an adaptive inverse control strategy applied to modified power conditioning is developed. With an online adjustment of modified P-f droop coefficient for the frequency of microgrid to track the rated frequency, the strategy guarantees maintaining the frequency of microgrid at the rated value and meeting the important customers' frequency requirements. The simulation results from a multibus microgrid show the validity and feasibility of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In Part I of this two-part paper, fundamental concepts of interlaminar fault and its consequences on magnetic cores were presented. An equivalent configuration, which was proved by FEM modelling, was proposed for magnetic cores with interlaminar fault. In this Part II paper, based on the equivalent configuration of the core and equivalent circuit of eddy current path, an analytical model is developed to estimate eddy current power loss of magnetic cores with interlaminar faults in a wide range of magnetizing frequency. Important factors, such as skin effect, nonuniform flux density distribution, complex relative permeability and nonlinear relation of B (H), which are often neglected in the literature, are highlighted. Packs of two, three, and four Epstein-size laminations of conventional grain oriented were shorted together artificially to measure the extra power loss caused by the interlaminar fault and support the analytical modeling. It was found that in the magnetic cores affected by interlaminar fault, the skin effect is a determinant factor in the magnetic properties determinations, even at low frequencies. [ABSTRACT FROM AUTHOR]

Penetration of distributed generations (DGs) are becoming more widespread in the current electric power networks. One of the most important issues regarding utilization of DG in power systems is related to their impact on fault-current level. In this regard, a multiagent-based fault-current limiting scheme for microgrids is presented in this paper. A typical microgrid is divided into several sections. A number of superconducting fault-current limiters, which are located in suitable locations of the network, can suppress transient fault currents. Fault location is identified using several fault-location identification units (FLIUs), which are installed in suitable places. In each FLIU, fault current is estimated using a Kalman filter and then the residual signal is generated from the calculated and measured fault current. In the fault condition, the faulty section is identified by analyzing the information of FLIUs in the network. Then, the impact of the faulty section on the sound sections is minimized by utilizing the proposed fault-current limiting scheme. Capabilities of the proposed method are evaluated using different simulations on a benchmark microgrid. [ABSTRACT FROM PUBLISHER]

Identifying harmonic sources in a given power system is an important task for utility power-quality (PQ) management. This paper presents a new class of harmonic source identification problems: how to quantify the harmonic impact of several known harmonic-producing loads on the harmonic levels observed at a network location. This paper first defines the problem and proposes a harmonic impact index to theorize the problem. This paper then presents a statistical-inference-based method to estimate the index. The data required for this analysis are the harmonic voltage and current magnitudes continuously collected by the existing PQ monitors. The characteristics of the proposed method are investigated through case studies. Finally, additional applications and improvements of the proposed method are discussed. [ABSTRACT FROM AUTHOR]

This paper presents a new solution method that combines state-space and nodal analysis for the simulation of electrical systems. The presented flexible clustering of state-space-described electrical subsystems into a nodal method offers several advantages for the efficient solution of switched networks, nonlinear functions, and for interfacing with nodal model equations. This paper extends the concept of discrete companion branch equivalent of the nodal approach to state-space described systems and enables natural coupling between them. The presented solution method is simultaneous and enables benefitting from the advantages of two different modeling approaches normally exclusive from one another. [ABSTRACT FROM AUTHOR]

This paper is concerned with calculating the optimum rating for two dynamic voltage restorers (DVRs) when used in an interline DVR (IDVR) structure. An IDVR consists of two or more DVRs which have a common dc link and, thus, can exchange active power. This can increase the compensation range of an IDVR compared with separate but otherwise similar DVRs. The basic operation of the DVR and IDVR is briefly explained. The limitations of IDVR operation in terms of active power exchange are explained and, based on that, the expressions governing the steady-state operation of IDVR are derived. The compensation range of an IDVR is compared with that of two separate DVRs. This paper also explores how the limitations in absorbing power from a healthy feeder can narrow the compensation range of an IDVR. After identifying and formulating various limitations in IDVR operation, a design procedure is presented to determine the optimum size (or rating) of the DVRs in an IDVR structure. In the proposed approach, all possible scenarios concerning healthy and faulty feeders are taken into consideration. Examples along with graphs and tables aid in conveying the proposed approach. [ABSTRACT FROM AUTHOR]

A wooden pole is the most popular choice as the physical support structure for an electrical distribution network. A recent increase in the failures of wooden poles that lead to pole fires warrant further investigation into the performance of wooden poles and pole design. This paper examines the leakage current distributions on the radial, heartwood and sapwood section of the wood pole and the effect of the metal insertion in wooden structures using an electrical ladder network model. This paper presents the findings from two wooden pole models: a basic wooden pole and a complete wooden pole with cross-arm and supporting bars attached. The results show that the bulk of the leakage current flows through the internal section under wet weather conditions and the metal insertion along the radial of the wood increase the magnitude of the leakage current. The model takes into consideration the pole dimension, rain parameter, moisture content, air resistance, and preservative effect (chromated copper arsenate) on the wooden pole. [ABSTRACT FROM AUTHOR]

This paper presents a gradient-based nonlinear optimization wrapper for an electromagnetic transient simulation program to assist in the design of hardware and control parameters of flexible ac transmission system (FACTS) apparatus. A new second-order sensitivity analysis method is introduced that quantifies the sensitivity of the optimal solution to parameter uncertainties. Using this approach, the sensitivity of the harmonic elimination capability of a pulsewidth-modulated voltage-source converter to variations in switching angles is investigated. This paper also adapts the method of Pareto optimization to the simulation-based design of FACTS apparatus when multiple design objectives are to be satisfied. The developed Pareto optimization tool generates a Pareto frontier plot to visualize the design tradeoffs between the multiple objectives. The effectiveness of the tool is demonstrated through a design example that selects optimal values for the dc-bus capacitor and the control settings of a STATCOM. [ABSTRACT FROM AUTHOR]

This paper presents an active islanding detection method for electronically-interfaced distributed resource units at the distribution voltage level. The proposed method is based on injecting a disturbance signal into the system through either the direct axis (d-axis) or the quadrature axis (q-axis) current controllers of the interface voltage-sourced converter. Signal injection through the d-axis controller modulates the amplitude of the voltage at the point of common coupling (PCC), whereas signal injection through the q-axis controller causes a frequency deviation at PCC, under islanded conditions. Monitoring strategies to detect islanding are also presented for the proposed injection method. The feasibility of the proposed method is evaluated under the UL1741 anti-islanding test configuration. The studies reported in this paper are based on time-domain simulations in the PSCADIEMTDC environment. The studies show that the proposed islanding detection method succeeds in detecting the islanding phenomenon as fast as 33.3 ms for the parameter setting of the test system, and always meets the two-second UL detection requirement. The paper also concludes that the proposed method has the salient feature of offering a potential application in a micro-grid scenario, where fast "islanding detection" and not necessarily the "anti-islanding function" is required. [ABSTRACT FROM AUTHOR]

Power quality indices have been developed to assess the performance of a single site or an entire system. They can guide utilities to improve their systems and can be used by manufacturers to decide about equipment immunity. This paper is the third part of a joint paper aimed at predicting the voltage sag performance of distribution networks by estimating voltage sag indices. Two types of indices are analyzed in the present paper, they give, respectively, the average number of events and the average interruption duration of each kilovolt ampere served at the low-voltage level over the assessment period. Their values are obtained from a stochastic prediction using a time-domain simulation tool. The methodology used to obtain these indices and the analysis of the influence of the protective devices are the main contributions of this paper. The limitations of the present work are also discussed. [ABSTRACT FROM AUTHOR]

The increasing capacity of power systems and the continuing growth in interconnections within transmission networks to improve the reliability may cause the short-circuit fault current level of the equipment in the system, including the existing circuit breakers, to exceed their rated capacities. Therefore, the equipment must be either upgraded or replaced, which is costly and requires time-intensive procedures. Fault current-limiting techniques offer benefits to the system in such cases. Using passive elements, such as current-limiting reactors, is a well-known practice in power systems: however, they impact the power flow under normal operation, cause voltage drop, and might reduce the transient stability. Alternatively, resonant fault current limiters (RFCL) offer a dynamic solution based on proven technologies of current-limiting reactors and series capacitors. This paper presents a comprehensive framework to design RFCLs in bulk power systems. The presented approach uses a combination of mathematical analyses and numerical time-domain simulations to design the RFCL elements, and its effectiveness is assessed in test power systems. [ABSTRACT FROM PUBLISHER]

A novel methodology is presented in this paper for conducting transient and steady-state analysis of electric networks containing nonlinearities and switching plants components. The method is termed the extended harmonic domain (EHD) method as may be seen as an extension of the harmonic domain (HD) method used in steady-state analysis. It is shown in the paper that EHD is a natural approach for conducting dynamic and steady-state studies of the evolution of harmonics in power circuits containing nonlinear components and flexible ac transmission systems (FACTS) devices. It is also shown in the paper that EHD provides a suitable basis for extending the well-known steady-state power quality indices to the transient range. To illustrate the use of the theory, a three-phase linear circuit and a three-phase PWM-STATCOM are modeled using EHD. The results are compared against those provided by industry standard tools as PSCAD/EMTDC and Matlab. [ABSTRACT FROM AUTHOR]

The widespread use of distributed generators (DGs) in utility distribution feeders brings about several challenges to the operation, planning, and design of general distribution networks. In this paper, the task of accurate determination of available delivery capability (ADC) subject to thermal limits, voltage limits, and voltage stability limit is formulated. A rigorous numerical method to calculate the ADC of large-scale distribution networks with renewables is presented. This numerical method computes three critical points which are the saddle-node bifurcation point or structure-induced bifurcation point, voltage violation point, and thermal-limit violation point. To gain the speed and robustness for the proposed method, the continuation method is integrated into the proposed numerical method. For illustrative purposes, the proposed method is applied to the IEEE 14-bus test feeder and the IEEE 8500-node test system. [ABSTRACT FROM AUTHOR]

Islanding detection is important to ensure the reliability and safety of distributed generation (DG). In this paper, a new active islanding detection method (IDM) is proposed, and it depends on individually estimating an overall transient stiffness measure for any multi-DG system to establish a clear separation between prior- and post-islanding stiffness. For the multi-DG system to avoid spectrum overlapping, each of its DGs is required to perturb at distinct frequencies. By using this concept of perturbation separation, the proposed technique can be applied to multi-DG systems without requiring any communication among the DGs. Simulation results show that the proposed technique is scalable and robust against different loading conditions and variations of grid stiffness levels as well as with respect to the number of connected DGs and different types of DG controllers. It is also shown that the proposed technique can successfully distinguish islanding conditions from other disturbances that may occur in power system networks. [ABSTRACT FROM AUTHOR]

Monitoring of voltages and currents at system buses gives the network operators information about the performance of their network, both for the system as a whole and for individual locations and customers. There is also demand from the customers and the regulatory agencies to provide information on the actual power-quality (PQ) level. Developments in enabling technology have made it possible to monitor at a large scale and to record virtually any PQ parameter of interest. While many network operators are installing monitoring equipment and while more and more monitors are available, there is a lack of knowledge and agreement on a number of aspects of the monitoring process and on processing the recorded data. As a response to this lack of uniformity in approach, data acquisition, and processing, in February 2011, CIGRE and CIRED established the Joint Working Group C4.112: “Guidelines for Power quality monitoring—measurement locations, processing and presentation of data.” In order to identify the current international industry practice on PQ monitoring, the group carried out a survey in 43 countries across the world. This paper summarizes the key findings from 114 responses to the questionnaire and identifies prevalent industrial practice in PQ monitoring around the world. [ABSTRACT FROM AUTHOR]

Modeling of frequency-dependent components and subnetworks is often based on a terminal description by an admittance matrix in the frequency domain. One challenge in the extraction of state-space models from such data is to prevent possible error magnification when the model is to be applied in time-domain simulations. The error magnification is a consequence of inaccurate representation of small eigenvalues of the admittance matrix. This paper resolves the problem by introducing a similarity transformation matrix which better reveals the eigenvalues of the admittance matrix. The chosen transformation preserves the passivity and symmetry of the original data, allowing the modeling to be performed by standard methods for model extraction and passivity enforcement. The approach is demonstrated for the wideband modeling of subnetworks and power transformers. The new technique is shown to accurately capture the large and small eigenvalues alike, thereby avoiding error magnifications in time-domain simulations. [ABSTRACT FROM PUBLISHER]

This paper presents a general fault-location method for large transmission networks which uses phasor measurement unit (PMU) voltage measurements where the injected current at a fault point can be calculated by using the voltage change and its relevant transfer impedance on any bus. A two-stage fault-location optimization model is proposed, along with defining a matching degree index. The first stage is the fault region identification stage, which uses the matching degree index to determine the suspicious fault region in order to reduce the search area. The second stage is used to identify the exact fault line and fault distance. A method to determine optimal PMU placement is also proposed in this paper. Case studies verify that the proposed fault-location algorithm and optimal PMU placement scheme can locate faults in large transmission networks quickly and accurately without requiring fault-type classification or fault phase selection. [ABSTRACT FROM AUTHOR]

This paper addresses the waveform alteration problem of open-circuit voltage (OCV) and short-circuit current (SCC) of the combination wave generator (CWG) due to the effect of the power-line coupling/decoupling network (CDN). A model of CWG and CDN was implemented in the OrCAD/PSPICE program, and simulations have been conducted in detail on how CDN's component values affect OCV and SCC waveforms. The results show the time duration will decrease and undershoot will increase for OCV and SCC after CDN is connected to the CWG. The fictive impedance of the CWG will increase due to the effect of the CDN. To meet the requirement of IEC 61643-1, methods of obtaining normalized surge waveforms are discussed and the corresponding drawbacks are also analyzed. Finally, the amendment suggestions about broader tolerances of surge waveforms in IEC 61643-1 after CDN is connected to CWG are presented in this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a new and effective communication protocol for the implementation of an automatic meter reading system using power-line communications (PLC) and presents analytical models to study its performance. The proposed protocol utilizes a novel packet routing system which combines “Request” and “Data” packets that enable meter units to send their metering data to the data concentrator and, at the same time, re-broadcast the “Request” to other meter units. It employs a carrier-sense multiple access with collision avoidance medium-access control protocol for the contention-based data transmission. The performance of the proposed protocol in terms of data-collection delay and throughput under impulsive noise interference is analyzed and compared with that of the neighbor relay polling (NRP) protocol. The proposed protocol does not require a central controller to initiate all data transmission unlike polling-based protocols and can be applied to PLC systems with unstructured networks. The proposed protocol ensures significantly lower data-collection delay than the NRP protocol. It will be able to achieve 100% throughput for light and moderate impulsive noise environments and 75% throughput for a heavy impulsive noise environment using broadband PLC with a cluster size larger than 60. [ABSTRACT FROM AUTHOR]

This paper proposes a new synchronous machine model based on the application of Park's transformation to the discretized equations of the phase-domain model. The proposed approach maintains the precision of the phase-domain model and eliminates its computational inefficiencies through a constant admittance matrix. The model includes magnetic saturation. Precision analysis is performed within the accuracy constraints of the surrounding network. [ABSTRACT FROM AUTHOR]

The use of power networks as a communication medium is currently under development. Power line communication (PLC) is a recent technology that allows interconnecting high-speed multimedia equipment while using the conventional domestic electric network. This paper deals with the use of this technology over pulsewidth-modulation (PWM) networks in motor-drive applications. The originality stands on the frontier of two distinct domains—communication and energy. First, the performance of the PLC technology conceived for domestic applications is evaluated when used over a PWM network. Operating limits and main difficulties encountered are underlined. Based on the requirements of the PWM network, new PLC modems are developed and tested. Experimental results presented in this paper show the capacity of these modems to overcome the hostile environment due to the inverter and to guarantee reliable communication over the PWM network. [ABSTRACT FROM AUTHOR]

New opportunities for optimally integrating the increasing number of distributed-generation (DG) units in the power system rise with the introduction of the microgrid. Most DG units are connected to the microgrid via a power-electronic inverter with dc link. Therefore, new control methods for these inverters need to be developed in order to exploit the DG units as effectively as possible in case of an islanded microgrid. In the literature, most control strategies are based on the conventional transmission grid control or depend on a communication infrastructure. In this paper, on the other hand, an alternative control strategy is proposed based on the specific characteristics of islanded low-voltage microgrids. The microgrid power is balanced by using a control strategy that modifies the set value of the rms microgrid voltage at the inverter ac side as a function of the dc-link voltage. In case a certain voltage, which is determined by a constant-power band, is surpassed, this control strategy is combined with P/V-droop control. This droop controller changes the output power of the DG unit and its possible storage devices as a function of the grid voltage. In this way, voltage-limit violation is avoided. The constant-power band depends on the characteristics of the generator to avoid frequent changes of the power of certain DG units. In this paper, it is concluded that the new control method shows good results in power sharing, transient issues, and stability. This is achieved without interunit communication, which is beneficial concerning reliability issues, and an optimized integration of the renewable energy sources in the microgrid is obtained. [ABSTRACT FROM AUTHOR]

This paper presents an optimization model for the calculation of the minimum number of phasor measurement units (PMUs) in electrical power networks. The problem constraint is a predefined probability of observability associated with each bus. The mixed-integer programming is used for the proposed optimization and an efficient linearization technique is proposed to convert the nonlinear function representing the probability of observability into a set of linear expressions. The PMU placement is staged in a multi-year planning horizon due to financial and physical constraints. The average probability of observability is maximized at the intermediate planning stages, subject to a limited number of PMU placements, that would satisfy the horizon year schedule. In addition, network expansion scenarios associated with intermediate stages are taken into account. Numerical studies are conducted on a nine-bus system and the IEEE 57-bus system and the results are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents modeling guidelines and a benchmark system for power system simulation studies of grid-connected, three-phase, single-stage Photovoltaic (PV) systems that employ a voltage-sourced converter (VSC) as the power processor. The objective of this work is to introduce the main components, operation/protection modes, and control layers/schemes of medium- and high-power PV systems, to assist power engineers in developing circuit-based simulation models for impact assessment studies, analysis, and identification of potential issues with respect to the grid integration of PV systems. Parameter selection, control tuning, and design guidelines are also briefly discussed. The usefulness of the benchmark system is demonstrated through a fairly comprehensive set of test cases, conducted in the PSCAD/EMTDC software environment. However, the models and techniques presented in this paper are independent of any specific circuit simulation software package. Also, they may not fully conform to the methods exercised by all manufacturers, due to the proprietary nature of the industry. [ABSTRACT FROM AUTHOR]

This paper proposes a novel peak load management scheme for rural areas. The scheme transfers certain customers onto local nonembedded generators during peak load periods to alleviate network under voltage problems. This paper develops and presents this system by way of a case study in Central Queensland, Australia. A methodology is presented for determining the best location for the nonembedded generators as well as the number of generators required to alleviate network problems. A control algorithm to transfer and reconnect customers is developed to ensure that the network voltage profile remains within specification under all plausible load conditions. Finally, simulations are presented to show the performance of the system over a typical maximum daily load profile with large stochastic load variations. [ABSTRACT FROM AUTHOR]

Availability of wind energy which differs across locations primarily determines the appropriate location for installing windfarms. However, the grid location of windfarms must always be considered in an attempt to accurately quantify the benefits which can be achieved from windfarms during their lifetime operation to the supply network. The value of wind power is significantly affected by their penetration and concentration, and is further affected by their location within a network. This is because the location and penetration level of wind generation will result in a significant impact on power-flow distribution across the network. The objective of this paper is to measure the impact of grid location of windfarms on economic and operational parameters of a power system in the lifetime of a windfarm project. This paper first develops an assessment tool to quantify the economic and operational impact of wind power in the grid. This is followed by developing different scenarios in which different penetrations of wind power are installed at different locations in the grid, and it shows how the value of wind power is affected by location and network constraints. [ABSTRACT FROM AUTHOR]

This paper analytically determines the nondetection zone (NDZ) of an active islanding detection method, and proposes a solution to obviate the NDZ. The method actively injects a negative-sequence current through the interface voltage-sourced converter (VSC) of a distributed generation (DG) unit, as a disturbance signal for islanding detection. The estimated magnitude of the corresponding negative-sequence voltage at the PCC is used as the islanding detection signal. In this paper, based on a laboratory test system, the performance of the islanding detection method under UL1741 anti-islanding test conditions is evaluated. Then, determining the NDZ of the method and proposing the countermeasure, the existence of the NDZ and the performance of the modified method to eliminate the NDZ is verified based on simulation results in PSCAD/EMTDC software environment and experimental tests. [ABSTRACT FROM AUTHOR]

The number of semiconductor switches in a modular multilevel converter (MMC) for HVDC transmission is typically two orders of magnitudes larger than that in a two or three level voltage-sourced converter (VSC). The large number of devices creates a computational challenge for electromagnetic transient simulation programs, as it can significantly increase the simulation time. The paper presents a method based on partitioning the system's admittance matrix and deriving an efficient time-varying Thévenin's equivalent for the converter part. The proposed method does not make use of approximate interfaced models, and mathematically, is exactly equivalent to modelling the entire network (converter and external system) as one large network. It is shown to drastically reduce the computational time without sacrificing any accuracy. The paper also presents control algorithms and other modelling aspects. The efficacy of the proposed method is demonstrated by simulating a point-to-point VSC-MMC-based HVDC transmission system. [ABSTRACT FROM AUTHOR]

Power-line networks are promising mediums by which broadband services can be offered, such as Internet services, voice over Internet protocol, digital entertainment, etc. In this paper, an analysis of delay spread, coherence bandwidth, channel capacity, and averaged delay in the frequency bands up to 100 MHz for typical indoor power-line networks are studied. Earlier studies for indoor power-line networks considered frequencies up to 30 MHz only and earlier works have shown that at these frequency bands, the data rates are generally low and are inefficient for digital entertainment in comparison with wireless local-area networks standards, such as IEEE 802.11n. In this paper, it is shown that at 100 MHz, the average channel capacity for typical indoor power-line networks can be up to 2 Gb/s and it is found that by increasing the number of branches in the link between transmitting and receiving ends, the average channel capacity decreases from 2 Gb/s to 1 Gb/s (when the number of branches was increased by four times for a power spectral density of -60 dBm/Hz). At the same time, the coherence bandwidth decreased from 209.45 kHz to 137.41 kHz, which is much better than the coherence bandwidths corresponding to 30-MHz systems. It is therefore recommended to operate the indoor power-line networks at 100-MHz bandwidths for a wide variety of broadband services. [ABSTRACT FROM AUTHOR]

In this paper, numerical and analytical approaches for the study of busbar systems are analyzed and compared. In the first part of this paper, the multiconductor model (MC) is presented for studying a general busbar system and the equation are formalized for "current-driven" and "voltage-driven" problems. Afterward, the "MC method" has been applied for solving a "current-driven" problem related to an industrial busbar system. The evaluation of current distribution and electrodynamic forces of the. system has been compared with the one obtained by using a classical finite-element method. Finally, the total current in the massive conductors of the system has been compared with the measurement. In the second part, an analytical approach for evaluating the electrodynamic forces is presented. The "adjacent massive conductors" configuration considered in the IEC standard 865/93 is fully detailed and the "nonadjacent massive conductors" configuration, not considered in the standard, has been developed. [ABSTRACT FROM AUTHOR]

Abstract-This paper presents allocation of energy losses to consumers connected to radial distribution networks in a deregulated environment. A detailed comparison of the proposed "Exact Method" with three alternative algorithms, namely, pro rata, quadratic allocation and proportional allocation are presented. Pro rata procedure is based on the load demand of each consumer, quadratic and proportional allocations are based on identifying the real and reactive parts of current in each branch and the losses are allocated to each consumer, and the proposed "Exact Method" is based on the actual contribution of real power loss by each consumer. A case study based on a 30-node distribution system is provided. [ABSTRACT FROM AUTHOR]

In a previous paper [1], the voltage induced onto a 1-km above-ground pipeline by transmission line transients was shown to be significant in comparison to the induced voltage resulting from power system currents. This paper enhances the previous work in three distinct areas. First, both aerial and buried pipelines are considered. Above-ground pipelines are shown to be more at risk from transient-induced voltages. Second, parallelisms of up to 10km are simulated. The results show that increasing parallelisms do not result in higher induced voltages once a critical distance has been reached. Third, a backflashover from a tower in the vicinity to a pipeline is modeled. This allows conductive coupling to take place at the same time as inductive and capacitive coupling. Backflashovers are shown to be an important consideration in determining the maximum voltages observed on a nearby pipeline. [ABSTRACT FROM AUTHOR]

In this paper, a new method called arbitrary-difference precise-integration (ADPI) algorithm is proposed to calculate the electromagnetic transients in single-phase nonuniform transmission line. The new method employs arbitrary difference in space domain and precise integration in time domain, respectively. It not only can create the difference equations arbitrarily according to the characteristics of the nonuniform transmission line but also can remove the Courant-Friedrich-Levy (CFL) stability condition restraint. The method presented in this paper is used to calculate the electromagnetic transients in a vertical conductor. The results show that compared with other methods such as finite-difference time-domain (FDTD) and electromagnetic transients program (EMTP) method, this new algorithm provides higher efficiency since the time step used in the simulation is no longer restricted by the stability condition. [ABSTRACT FROM AUTHOR]

This paper presents the computer simulation of the Multistage Model for Distribution Expansion Planning with Distributed Generation, as described in Part I. The simulations deal with the planning of an electrical power distribution network in three stages, in five different situations: 1) each of the three stages planned independently; 2) multistage planning; 3) multistage planning with distributed generation; 4) multistage planning with distributed generation and constraints on investment; and 5) multistage planning with distributed generation considering three load levels. The influence of additional constraints is analyzed in terms of the computational effort required to find the optimum solution to the problem. [ABSTRACT FROM AUTHOR]

This paper presents the effects of load impedance, line length and branches on the performance of an indoor voltage broadband power line communications (BPLC) network. The power line network topology adopted here is similar to that of the system found in Tanzania. Different investigations with regard to network load impedances, direct line length from transmitter to receiver, branched line length, and number of branches has been carried out. From the frequency response of the transfer function (ratio of the received and transmitted signal), it is seen that position of notches and peaks in the magnitude and phase responses are largely affected by the above said network parameters/configuration, mainly in terms of attenuation and dispersion. These effects are observed in the time domain responses also. The observations presented in the paper could be helpful in the suitable design of the BPLC systems for a better data transfer and system performance. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of characterizing voltage sags from measured three-phase voltages. A new algorithm based on three-phase voltage magnitudes and their phase angles is proposed in this paper. This new algorithm is named the three-phase three-angle algorithm (TP-TA). The proposed algorithm is compared with the well known symmetrical component (S-C) and the six-phase (S-P) algorithms defined to identify voltage sags type C and D. Numerical examples and recorded voltages were used to validate the proposed algorithm and compared with the other two, yielding better results for the TP-TA algorithm. [ABSTRACT FROM AUTHOR]

This paper is the second part of a joint paper aimed at predicting the voltage sag performance of distribution net- works by estimating voltage sag indices. This part explores the characteristics of voltage sags caused by faults in a distribution network considering the effect of the protective devices installed in the network. The work is based on a Monte Carlo procedure implemented in a time-domain simulation tool. Several scenarios with a different coordination between protective devices have been analyzed. As expected, the main conclusions are that the protection system can have a significant influence on voltage sag characteristics and proper coordination between protective devices can reduce voltage sag impact on end-user equipment. [ABSTRACT FROM AUTHOR]

This paper is the first part of a work aimed at predicting the voltage sag performance of distribution networks using digital simulation and an EMTP-like tool. The paper discusses modeling guidelines for representing power distribution components in voltage sag simulations and details the approaches selected in this work. Different models for representing some components can be used to obtain voltage sag characteristics with similar accuracy. Test results are included to illustrate the performance of the developed models and support the selection of different modeling approaches. [ABSTRACT FROM AUTHOR]

This paper explores the approach of having a common Power Factor Correction circuit for domestic and commercial loads. This leads to lower harmonic distortion without the need to install (expensive) active rectifiers in each end-user device. The need for power-factor correction as well as a number of design options is discussed in this paper. The design and cost estimation of a common Power Factor Correction scheme and some reliability issues are discussed. [ABSTRACT FROM AUTHOR]

The design, evaluation and implementation of a busbar current differential protection relay suitable for use with measurement type current transformers (CTs) is described in the paper. The relay operates in conjunction with a saturation detection algorithm, which effectively detects the start and end of each saturation period using a technique based on the third-difference function applied to the current signal. A blocking signal is activated immediately after the onset of saturation and is maintained active until the saturation period plus an additional delay of one cycle has expired. For internal faults that result in CT saturation, the relay issues a trip command before the blocking signal is activated. For external faults, that result in CT saturation, the blocking signal arrives first and the trip command remains inactive. Test results indicate that the relay successfully discriminates between internal and external faults, even when the remanent flux in a CT is high and the fault capabilities of the measurement CTs are severely limited. The paper concludes by describing how the relay was implemented on a prototype relay based on a digital signal processor. Compared to a conventional busbar differential protection scheme, the new relay achieves greater stability on external faults and enhanced sensitivity for internal faults. [ABSTRACT FROM AUTHOR]

This paper deals with the line voltage drop calculation in presence of disturbances in the electric network, like unbalance, harmonic, and interharmonic components. The Park approach permits to define a calculation expression with a structure very close to the classical one typically employed in case of balanced systems and also permits to underline the role of the imaginary power that quantifies in one term only the effects of disturbances on the voltage drop. In order to text the effectiveness of the proposed methodology, two applications on real industrial plants are presented in the second part of the paper. The comparison with the classical theory and calculation made by using commercial soft- ware gives rise to interesting comments and discussion on the proposed approach. [ABSTRACT FROM AUTHOR]

The low-voltage distribution grid is an essential link for the integration of distributed renewable sources. It is expected to experience stronger loading and load variation in the near future. At the same time, part of the low-voltage network is an aging infrastructure. Distribution system operators are therefore becoming increasingly interested in being able to diagnose their low-voltage assets. This paper describes corrosion phenomena that are observed in aluminum conductors after a damage is inflicted to a cable section. Such a damage is suspected to initiate long-term degradation. Short-duration intermittent current peaks are observed in laboratory experiments and similar peaks are now also recorded in the field. The perspectives for online monitoring, by registering these events, are investigated by having a large number of measurement devices installed on connections in service. The research is directed to gain a better understanding of the relation between the current peaks and cable circuit failures as well as the underlying degradation mechanisms. [ABSTRACT FROM AUTHOR]

It is well known that metal–oxide arresters (MOAs) do not have the capability of protecting the equipment in extra-high voltage networks, when they face the threats from very fast transients (VFTs). This “inaction” on the part of MOA is mainly brought by stray capacitance, which not only delays the conduction of MOA under VFTs but also brings a nonuniform voltage distribution across its structure and thereby impacts its life, especially, that of its top unit. This phenomenon prompts an urgent take on the factors that threaten the functioning of MOA under VFTs. After performing a thorough review of the studies made earlier, this study focuses on the further improvements required. This paper mainly deals with the accurate calculation of stray capacitance, its adverse impacts on MOA during its conduction phase, voltage distribution across the arrester with the aid of a finite-element method (FEM) and the Electromagnetic Transient Program (EMTP), and, finally, it explores the modifications required to get adequate protection for the equipment exposed to VFTs. [ABSTRACT FROM AUTHOR]