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Dielectric testing techniques, in both time and frequency domains, are currently widely used by power utilities for assessment of the condition of transformer oil-paper insulation systems. However, it has been reported that results of these tests are highly influenced by the operating temperature during measurements. The distribution, migration and equilibrium of moisture between oil and paper in a complicated insulation system is highly temperature dependent. It requires adequate experience and proper understanding to interpret the dielectric response results in the presence of temperature variations and thermal instability. Proper analysis of the dielectric test result is only possible with an understanding of the physical behavior of the insulation system in response to temperature. A circuit model, which describes the dielectric behavior of the transformers main insulation system, has been investigated in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been observed between the operating temperature and the equivalent model parameters that can be used as additional information for better interpretation of the dielectric test results. This paper thus reports a detailed study on the effects of temperature on dielectric measurements of a transformer under controlled laboratory conditions. Some results of practical on-site testing are also presented to demonstrate the possibility of errors that may be introduced in dielectric test results analysis unless temperature effects are taken into consideration. [ABSTRACT FROM AUTHOR]

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions: [ABSTRACT FROM AUTHOR]

The latest of a series of classified lists of power system relaying references, begun in 1927, is presented. This bibliography is in continuation to the bibliographies of relay literature, which were published previously and are contained in the following volumes of the IEEE Transactions. [ABSTRACT FROM AUTHOR]

In this paper, postmortem aging investigations on insulation material of power transformers are presented. A methodology for taking paper samples in a systematical manner and a scheme for calculating an average degree of polymerization (DP) for the entire transformer out of the DP values of the individual paper samples will be shown. The typical DP profile in the axial direction of transformer coils will be explained using calculated distribution of losses within the coils of a 740-MVA generator stepup transformer. Further, correlations between the furan (2-FAL) concentration in the oil and the average DP of the investigated German GSU transformers and grid transformers are derived and compared with existing correlations. [ABSTRACT FROM PUBLISHER]

This paper discusses a recent event in the western American power system when a forced oscillation was observed at a frequency that was close to a well-known 0.38-Hz inter-area electromechanical mode frequency of the western system. The event motivates a systematic investigation in this paper on the possibility of resonant interactions between forced oscillations and electromechanical inter-area oscillatory modes in power systems. When the natural oscillatory mode of a power system is poorly damped, and the forced oscillation occurs at a frequency close to system mode frequency at critical locations for the mode, resonance is observed in simulation test cases of the paper. It is shown that the MW oscillations on tie-lines can be as high as 477 MW from a 10-MW forced oscillation in Kundur test system because of resonance. This paper discusses the underlying system conditions and effects as related to resonance in power systems caused by forced oscillations and discusses ways to detect such scenarios using synchrophasors. Simulated data from Kundur two-area test power system as well as measurement data from western American power system are used to study the effect of forced oscillations in power systems. [ABSTRACT FROM AUTHOR]

This section introduces a series of articles on electric power technology and policy. While the ultimate objective of the electric power industry remains the providing of a sustainable high quality of service to its users, the needs of this service have become more complex. The paper by Felix F. Wu et al. reviews the functions and architectures of control centers. The paper by Joe H. Chow et al. makes the case that system reliability is an integral part of a properly designed electricity market, even though wholesale prices are its most visible part.

This two-part paper considers the coordination of a population of thermostatically controlled loads (TCLs) with unknown parameters to achieve group objectives. The problem involves designing the bidding and market clearing strategy to motivate self-interested users to realize efficient energy allocation subject to a peak energy constraint. The companion paper (Part I) formulates the problem and proposes a load coordination framework using the mechanism design approach. To address the unknown parameters, Part II of this paper presents a joint state and parameter estimation framework based on the expectation maximization algorithm. The overall framework is then validated using real-world weather data and price data, and is compared with other approaches in terms of aggregated load response. Simulation results indicate that our coordination framework can effectively improve the operational efficiency of the distribution system and reduce power congestion at key times. [ABSTRACT FROM AUTHOR]

This paper presents an analysis based on recent Electric Power Research Institute research in which a comparison is made between the “loss factor” calculated directly from annual simulations and a loss factor estimated variously from established equations and published papers and articles. The analysis provides new insights into the use of loss factors in estimating feeder losses. Sources of possible errors are identified and quantified. [ABSTRACT FROM PUBLISHER]

Economic dispatch (ED) considering valve-point effect, multiple fuel options, prohibited operating zones of generation units is a more accurate model compared to a conventional ED model. It is non-smooth and thus evolutionary algorithms (EAs) are so far the only feasible approaches for the model. In Part II of the paper, a new method, the dimensional steepest decline method (DSD), is proposed for the ED with non-smooth objectives. The DSD is based on the local minimum analysis of the ED problem presented in Part I of the paper. The fuel cost's decline rate between each two adjacent singular points is utilized to find the optimal solutions in a serial sequence. The computational complexity of the DSD is analyzed. The DSD has been applied to solve different types of ED problems on different test systems, including large-scale systems. The simulation results show that DSD can obtain more accurate solutions and consume much less time and its advantage is more obvious on large-scale systems, in comparison with the state-of-art EAs. [ABSTRACT FROM PUBLISHER]

This paper presents the outcomes of laboratory evaluation of the performance of a sample of LED lighting systems (lamp/driver and dimmer combinations) in presence of audio frequency injection control (AFIC) signals used by electricity distribution system network service providers (DNSPs) for control of certain loads. The testing presented in this study has been undertaken in response to a significant number of customer complaints that have been received by DNSPs related to the performance of LED lighting systems with dimmers incorporated. In a number of cases, performance issues have been verified in the field to occur during periods where AFIC signaling voltages are present in the electricity distribution network. In order to determine the contributing factors that AFIC signaling may have on the performance of the LED lighting system, a light-based flicker evaluation testing system has been developed to investigate LED lighting system performance under controlled conditions. One of the main objectives of the study was to use light-based flicker indices to identify the effect on different combinations of LED lamps/drivers and dimmers by varying the voltage magnitude and frequency of the AFIC signal as well as the position (i.e., voltage output) of the dimmer. Visual observations were also carried out to investigate the correlation between measured flicker indices and visually observed flicker. This paper presents the test results that have been analyzed in terms of types of technologies used in LED lamp/driver and the variables in the AFIC signal. [ABSTRACT FROM AUTHOR]

This paper proposes a deep learning (DL) method for the identification of spectral patterns of time-varying waveform distortion in photovoltaic (PV) installations. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. This paper shows that the DL method can be used as a starting point for further data analysis. The main contributions of the paper include: (a) providing a novel DL method for finding patterns in spectra; (b) guiding the manual post-processing based on the patterns found by the DL method; and (c) obtaining information about the emission from four PV installations. [ABSTRACT FROM AUTHOR]

This paper presents a new non-deterministic approach for multiyear distribution network reinforcement planning (DNRP) considering the uncertainty sources pertaining to loads, electricity prices, investment costs, and operation costs. Accordingly, the underlying idea of the information-gap decision theory (IGDT) is used to obtain a robust solution protected against different realizations of each uncertain variable lying in its robust region. The proposed model is capable of adjusting the robustness of the optimal solution in terms of a specific parameter designated as the budget of uncertainty. As the uncertain loads, investment and operation costs competitively tend to maximize their robust regions for a particular value of the budget of uncertainty, the normalized normal constraint (NNC) method as a proficient multi-objective optimization method is exploited in this paper to solve the proposed multiobjective IGDT-based DNRP (IGDT-DNRP) model. Mainly, the NNC method presents a set of Pareto optimal solutions rather than a single optimal solution. Accordingly, a posteriori out-of-sample analysis is introduced in this paper to find the best solution among the set of Pareto optimal solutions. The proposed IGDT-DNRP model is implemented on the IEEE 33-bus distribution network under different circumstances. Simulation results illustrate the effectiveness of the proposed nondeterministic approach. [ABSTRACT FROM AUTHOR]

Most businesses are feeling the impact of rising energy costs. As energy costs increase, it is becoming more important for plant owners to find ways to reduce energy consumption at their facilities. In addition, the stricter environmental regulations and ambitious \CO2 emission reduction goals of various countries are driving businesses toward more energy-efficient solutions. This paper discusses the vital role that optimal design and application of Trace Heating Systems plays in reducing their energy consumption. This paper presents a case study where an existing trace heating design is optimized to reduce energy consumption by 91%. Energy conservation strategies implemented include selection of an improved insulation system, a control and monitoring strategy, the appropriate trace heating technology, optimal trace heating designs, and the best power distribution option. The results of this paper are important tools to evaluate opportunities to save energy in both existing and new trace heating installations found at many industrial facilities and to reduce total operating costs. [ABSTRACT FROM AUTHOR]

Electricity distribution companies are in-charge-of supplying stable electric energy to urban customers over a wide geographical area. In these distribution networks, large number of Distribution-Transformers (DTs) are installed on towers or in electric-rooms with the ratings below 1000 kVA, which are the most important assets of distribution companies. Periodic maintenance and test services are not economically feasible for all in-operation transformers. Hence, estimating the remaining useful life and scheduling the maintenance times of DTs are of great technical and economic importance. An analytical approach is presented in this paper for predicting lifetime of DTs based on degree of polymerization. An appropriate Machine-Learning (ML) algorithm trained by measured data is selected for forecasting driven load according to the ambient temperature and humidity and day-hour schedules. The relation of Hot-Spot-Temperature in IEC60076∼7 is modified based on the measured data for accounting unbalanced-loading. Neutral-current is predicted using a trained ML-model. Another approach is proposed for determining times of oil filtering services aiming to minimize the maintenance cost and maximizing the remaining life. The proposed lifetime estimation method is validated by comparing its results with the damaged DT data of a sample network chosen as the case studies for this research, i.e., Bushehr province, Iran. [ABSTRACT FROM AUTHOR]

This paper describes the design of the ERCOT modeling extensions to the IEC 61968/70 standards to enable Common Information Model (CIM) schema support of dynamic ratings methodologies. Implementation of dynamic ratings was driven by current economic and environmental constraints placed on the construction of additional electrical transmission infrastructure, thus creating a need to operate the existing equipment closer to its physical limitations. In order to effectively utilize these dynamic limits, the necessary data constructs must be modeled, so ERCOT extended the CIM representation of the balanced three-phase power system model used to operate its various grid functions, in order to support the modeling and use of dynamic ratings in its operational real-time and congestion hedging market models. This paper also explains how the process utilized in the identification and extension of the CIM model for this purpose is flexible enough for generic application within the power industry. [ABSTRACT FROM AUTHOR]

The groundings of the power distribution, signaling, and power systems of a railway system are individually performed to realize fail safe, and the groundings are often installed in close proximity. Thus, when a grounding electrode is invaded by a lightning current, its ground potential rises together with the potential of the adjacent grounding electrodes; hence, there is a possibility of a large overvoltage being applied to the connected devices. In this paper, we have investigated the potential spread between two rod-shaped electrodes widely used in the grounding of the power, signal, and distribution systems of a railway system using the finite-difference time-domain method. The results of this paper are organized in such a way that the extent of the potential spread to the neighboring grounding electrodes can be understood from information such as the grounding resistivity at the installation location of the ground electrode and the wavefront duration of the lightning current, and these findings will be useful for grounding design. We also investigate the effect of the insulator between two neighboring electrodes to prevent the potential spread. [ABSTRACT FROM AUTHOR]

Active electricity distribution systems (AEDS) play an important role on the social welfare that is highly relies on the reliability of these systems. In this regard, maintenance management tries to decrease component failures via repairing component that are more possible to be failed in operation time. In this manuscript, a stochastic MINLP maintenance scheduling model is proposed in which the reliability of AEDS's equipment is considered through employing a three-state Markov model. This model helps us to embed the uncertainty of AEDS's equipment service restoration time by considering online monitoring system for it and FLISR functions in AEDS. In this paper, minimizing the total cost of AEDS is determined as objective function considering total customer interruption cost, total cost of energy not supplied, total cost of prevented maintenance actions, total corrective maintenance actions cost implemented in the AEDS and total cost of implementing online monitoring for AEDS's component in maintenance scheduling. The proposed framework is applied in two different cases, Case I is maintenance scheduling without online monitoring system and Case II is maintenance scheduling with online monitoring system. The aforementioned cases are implemented in an IEEE Test System as well as a real scale distribution network. Moreover, several sensitivity analyses are implemented for indicating the efficiency of the proposed model. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) is an ideal power delivery solution for many light-load applications, such as for the Internet of Things. A regulated solution for WPT may utilize a power distribution unit (PDU). Previous works have designed planar inductors for integration with switched-inductor buck regulators, but these inductors will not be as efficient for light-load applications. This paper reevaluates the inductor loss for light-load applications by taking into account the frequency spectrum of the inductor current. Using this revised analysis, a planar inductor with screen printed NiZn ferrite epoxy composite magnetic core is designed for an RF near-field coupling system with 1–10-mW load power. In measurement with a 6-MHz buck converter, the PDU with designed inductor demonstrated up to 3% improved efficiency compared to surface-mount technology inductor in the pulse-frequency modulation mode and pulsewidth modulation mode. The designed embedded inductor was subsequently demonstrated in an integrated, compact RF near-field coupling system with peak 43% system efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a novel rectifier array for a wide dynamic range of RF-dc conversion. The rectifier array consists of multiple rectifier cells optimized for operation at different power levels and uses an adaptive power distribution method to divide the RF input power among these rectifier cells according to the RF power levels. The adaptive power distribution takes advantage of the power-dependent input impedances of the rectifier cells and is implemented with passive devices. This method both improves the rectification efficiency and minimizes the impedance mismatch as the input power level varies, and therefore, significantly enhances the dynamic range. The rectifier array can be designed using either the same type or different types of rectifying devices and can be expanded by including more cells in the network to further increase the dynamic range. In this paper, three different implementations of such rectifier array circuits are described, including a two-diode rectifier array designed with the same type of diodes, a two-diode rectifier array designed with different types of diodes, and a three-diode rectifier array with different types of diodes. The performances of these circuits are validated with measurement and compared with each other. Significant enhancement of dynamic range over conventional rectifiers is demonstrated. [ABSTRACT FROM AUTHOR]

The paper addresses the problem of determining the maximum distributed energy resource (DER) capacity that can be connected to low-voltage (LV) networks without creating voltage-rise problems. That maximum capacity depends on the network characteristics and on the candidate sites for DER connection. When sites are multiple and LV networks are poorly characterized, such maximum capacity cannot be determined with power-flow or other admittance-matrix-based approaches. This paper proposes an approach to estimate voltage rise caused by DER under reduced network characterization. Such approach is built upon customary voltage and impedance measurements to be made at the sites of DER injection and gives sufficiently accurate results under most practical situations. The paper validates the accuracy of the proposed approach against exact power-flow results for well-characterized networks and load situations and provides guidelines for DER connection based on maximum capacity nodal allocation. [ABSTRACT FROM PUBLISHER]

The active power distribution network operation with the integration of various renewable distributed generations (DGs), storage units, and dynamic loads are attracting a lot of interest due to substantial benefits in maximizing the penetration of available renewable energy resources (RES). However, the risk of voltage violation in the active distribution system (ADS) is exacerbated due to increasing penetration of DGs. It has become a bottleneck to maximize the DG penetration into the system. This bottleneck can be handled by effective voltage regulation and reactive power support into ADS. Nowadays, power electronic devices are frequently used for voltage and reactive power support over the conventional approaches. In this paper, an approach to maximize the penetration of RES, such as solar, wind, etc., into ADS by maximum utilization of existing solar photovoltaic inverters (SPVI) in the system is presented. Optimal utilization of SPVI may enhance the voltage stability of the ADS and wind power penetration into the system. The proposed SPVI control approaches are depended on active power generation of solar photovoltaic (SPVG), rating and capability of SPVI, and required reactive power in the ADS. In this paper, the problem of maximum penetration of RES is formulated as an optimal power flow embedded nonlinear optimization problem subject to the physical limitations of the SPVI. The results of the analysis performed on an IEEE 33 bus system show that the proposed SPVI control strategies can improve the voltage profile of the ADS with minimization of curtailment of wind power generation. [ABSTRACT FROM AUTHOR]

Emerging environmental awareness, government subsidies, and deferred utility investments have created an environment that favors the proliferation of distributed energy resources (DERs) in distribution systems. While beneficial, these DERs create operational challenges to the power utility, ranging from additional safety risks to unstable system operation. Among those, traditional feeder overcurrent protection can become desensitized due to the additional fault contribution output by DERs. In some cases, it may not be possible to protect the entire distribution line. This effect is introduced in this paper as the Apparent Effect, which accounts for the reduction in fault contribution from the substation. Its extent varies depending on the DER technology, i.e., synchronous, induction, doubly-fed induction generators, or inverter-based DERs. Substantial investment may be required to overcome this effect and maintain feeder protection dependability. This paper characterizes this issue analytically and suggests the application of system reconfigurations that can result in mitigating the problem. [ABSTRACT FROM AUTHOR]

This paper studies the feasibility of utilizing the reactive power of grid-connected variable-speed wind generators to enhance the steady-state voltage stability margin of the system. Allowing wind generators to work at maximum reactive power limit may cause the system to operate near the steady-state stability limit, which is undesirable. This necessitates proper coordination of reactive power output of wind generators with other reactive power controllers in the grid. This paper presents a trust region framework for coordinating reactive output of wind generators with other reactive sources for voltage stability enhancement. Case studies on 418-bus equivalent system of Indian southern grid indicates the effectiveness of proposed methodology in enhancing the steady-state voltage stability margin. [ABSTRACT FROM PUBLISHER]

This brief paper presents a mathematical formulation for a team of cooperating microgrids (TCM) proposing a robust distributed control strategy based on partially nested information. This brief paper faces one of the main problems in a TCM, which is to react to the unpredictable production/demand processes, optimizing power flows, and energy storage in each microgrid (MG). This brief paper focuses on a high-level control of the TCM through properly coordinating power that is exchanged among MGs. The robust distributed control strategy operates in order to minimize the maximum divergence both from an agreed power exchange among MGs and from a technical reference value of the energy storage system of each MG. The proposed approach is based on some quite recent results on robust control for cooperative teams. The robust control approach is tested through a case study. [ABSTRACT FROM PUBLISHER]

This paper presents a new method for studying electromechanical transients in power systems using three phase, combined transmission and distribution models (hybrid models). The methodology models individual phases of an electric network and associated unbalance in load and generation. Therefore, the impacts of load unbalance, single phase distributed generation and line impedance unbalance on electromechanical transients can be studied without using electromagnetic transient simulation (EMTP) programs. The implementation of this methodology in software is called the Three Phase Dynamics Analyzer (TPDA). Case studies included in the paper demonstrate the accuracy of TPDA and its ability to simulate electromechanical transients in hybrid models. TPDA has the potential for providing electric utilities and power system planners with more accurate assessment of system stability than traditional dynamic simulation software that assume balanced network topology. [ABSTRACT FROM PUBLISHER]

This paper summarizes simulation based technical feasibility and cost benefit analyses of a range of off-the-shelf electrical losses reduction intervention solutions in the Isle of Wight (IoW) 11 kV distribution network in the United Kingdom (UK), assessed over a period of 45 years. Based on presented results, the paper provides a brief commentary on the merits, drawbacks, risks and recommendations associated with each considered network intervention. Among considered network interventions, the transformer auto stop-start scheme, where one of the transformers among a pair at a primary substation would be switched depending on the substation's varying load, was found to be the optimal solution, i.e., in reducing technical losses significantly and may also have a reasonable Net Present Value (NPV) with a good rate of Return on Investment (RoI) when fully implemented. [ABSTRACT FROM PUBLISHER]

The unbalanced nature of distribution systems requires a multiphase load-flow solution capable of handling arbitrary network topologies and providing accurate results. The need for detailed analysis of secondary grid systems found in dense urban areas and the modeling of distribution networks including the subtransmission level requires using highly efficient and large-scale system-capable methods. In this paper, three different load-flow solution algorithms are presented using the modified-augmented-nodal-analysis formulation. The load-flow solution algorithms are compared for the IEEE 8500-node distribution test feeder using a proposed regulator tap control strategy. [ABSTRACT FROM PUBLISHER]

For transmission of large amounts of electric energy across long sea crossings, the so-called mass-impregnated HVDC subsea cable has for a long time been, and still remains, the state-ofthe- art technology [1]. The electrical insulation of such cables consists of Kraft paper (or polypropylene laminated paper as in a recent development) impregnated with high-viscosity oil (the "mass"). They are also referred to as mass-impregnated nondraining (MIND) cables. The insulation is enclosed by a lead sheath that prevents water ingress. External layers of polyethylene, steel tapes, steel wire armour, polypropylene yarn, and an asphaltic compound provide mechanical strength and protection against corrosion. [ABSTRACT FROM PUBLISHER]

Smart buildings form an integral part of the smart grid that lowers electricity cost. This objective can be achieved by using suitable enhanced algorithms and techniques. The motivation of this paper is the request for an economical decision-making system from a commercial company in Singapore. This paper presents an economical building management system (EBMS) concept inspired by the building management system and machine learning. EBMS improves the decision-making process through rule-based algorithm within the system. Machine learning algorithm is included as part of EBMS to enhance the computational calculation for the electricity distribution. It includes the function of self-making decision for purchasing electricity based on forecasting system for electricity price or real-time electricity price data when facility managers are not present. EBMS uses multiagent system to communicate, interact, and negotiate with multiple agents for energy supply and demand in the building. Simulation studies have shown the potential of EBMS concept to provide a cost reduction solution up to 61.42% savings for smart buildings. Better electricity purchasing contract option can be decided based on the forecasting system for building power consumption. [ABSTRACT FROM AUTHOR]

This paper presents an evaluation of the performance of different methods for estimating the parameters required for the application of the Disruptive Effect Model to the analysis of the breakdown characteristics of 15 kV distribution insulators subjected to lightning impulses. The tests involved the application of both the standard (1.2/50 μs) and non-standard lightning impulse voltage waveshapes (1.2/4 1.2/10 3/10 μs) and 7.5/30 μs)of positive and negative polarities. The obtained Vxt characteristics are compared with those predicted by the Disruptive Effect Model using the most common procedures for estimating the parameters necessary for its application, including a novel method which is presented in the paper. An analysis of the results relevant to the various procedures shows that the parameters obtained according to the proposed method lead to a better agreement between theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Bidirectional inductive power transfer (BIPT) systems enable power transfer between stationary electricity sources and movable consumers in each direction through electromagnetic coupling. Due to its complexity, a mathematical model is required to design and to control these systems. This paper presents the mathematical analysis and the frequency-domain analysis for two different compensated (series–series and parallel–parallel) BIPT systems. This paper contains the modeling procedure of the BIPT system’s coils in the frequency domain. The prediction of its equivalent circuit values, magnetic stray field values, and coil positioning tolerance are determined as well using the JMAG field simulation software. Furthermore, the transmission characteristics and the efficiency of the two compensation topologies are discussed. [ABSTRACT FROM AUTHOR]

Distributed energy storage (DES) offers a number of benefits to improve the power system reliability. This paper presents an improved corrective security constrained optimal power flow (CSCOPF) with DES system. The proposed DES model takes into account the current state of charge (SOC) and the energy capacity model of the DES. The corrective control actions employed in the paper include not only the traditional long-term rescheduling control actions, but also the short-term post-contingency fast corrective control of the DES. A hybrid method is developed to solve the improved CSCOPF problem, and the effectiveness of the proposed method is evaluated and demonstrated in the paper by three example power systems. [ABSTRACT FROM AUTHOR]

The operational availability of mining shovels is the focus of this paper. The hypothesis is that energy quality is responsible for the frequent shutdowns of the shovels. Previous engineering studies have highlighted a large presence of harmonics and reactive power in the mine loop electric system. A common solution proposed was to use a combination of active filters, larger mobile substations, shorter mining cables, and equipment location constraints. The aim of this paper is to produce a precise diagnosis of the source and nature of the energy quality issues. Mine loop electric quality monitoring, system modeling, equipment technologies, and shovel's histograms are considered. Results are measured against IEEE standards and shovel's voltage regulation susceptibility. With the diagnosis, the goal was to produce a reliable cost-effective solution. Different alternatives are crosschecked with this paper proposal. The solution presented provides energy quality well within the shovel's susceptibility and improves energy efficiency. The lower energy consumption pays the investment required and is currently under construction. [ABSTRACT FROM AUTHOR]

Planned and unplanned outages on distribution networks may cause major economic loss to customers and can result in substantial reparation payments by utilities. This paper analyzes the use of a battery energy storage system (BESS) to partially or completely avoid these outages. The analysis is conducted with a multiday high-demand scenario where the load demand at peak times exceeds the current capacity of the line. This would result in an outage unless the current from the substation can be reduced. Three basic scenarios representative of different degrees of sophistication of feeder automation were studied, i.e., a conventional feeder controlled by one or more reclosing breakers; a modern distribution feeder equipped with a limited number of remote-controlled breakers that will disconnect nonvital loads belonging to residential, commercial, and industrial customers; and a modern distribution feeder equipped with numerous remote-controlled breakers that will selectively disconnect commercial, industrial, and residential loads based on their degree of criticality. This paper concluded that the total or partial avoidance of outages by way of BESS usage is feasible; however, the use of “smart grid” control technology can provide more benefit than BESSs in the scenarios studied. [ABSTRACT FROM AUTHOR]

Recurrence quantification analysis (RQA) is a nonlinear data analysis technique that can quantify the number and duration of a dynamical system of being in nearly the same area in phase space trajectory. This paper proposes three applications of RQA to analyse power system dynamics. These are denoising of PMU data, localization of power system events, and transient stability contingency ranking of power system. All three applications have been demonstrated using a multimachine test system. [ABSTRACT FROM AUTHOR]

This paper aims at proposing a mixed-integer linear formulation to incorporate reliability-oriented costs into the expansion planning model of electricity distribution networks. In this respect, revenue lost associated with the undelivered energy caused by network interruptions as well as costs incurred by the widely used reward–penalty regulations is considered as the major reliability-related costs from distribution companies point of view. A set of mixed-integer linear equations is proposed to calculate the most common distribution system reliability indices, i.e., expected energy not served, system average interruption frequency index, and system average interruption duration index. It is found that these equations can also facilitate the formulation of radiality constraint in the presence of distributed generation units. Moreover, application of the proposed method is investigated through various case studies performed on two test distribution networks with 24 and 54 nodes. [ABSTRACT FROM AUTHOR]

This paper shows that existing delay-based testing techniques for power gating exhibit both fault coverage and yield loss due to deviations at the charging delay introduced by the distributed nature of the power-distribution-networks (PDNs). To restore this test quality (TQ) loss, which could reach up to 67.7% of false passes and 25% of false fails due to stuck-open faults, we propose a design-for-testability logic that accounts for a distributed PDN. The proposed logic is optimized by an algorithm that also handles uncertainty due to process variations and offers tradeoff flexibility between test application time and area cost. A calibration process is proposed to bridge model-to-hardware discrepancies and increase TQ when considering systematic variations. Through SPICE simulations, we show complete recovery of the TQ lost due to PDNs. The proposed method is robust, sustaining 80.3%–98.6% of the achieved TQ under high random and systematic process variations. To the best of our knowledge, this paper presents the first analysis of the PDN impact on TQ and offers a unified test solution for both ring and grid power gating styles. [ABSTRACT FROM PUBLISHER]

Unlike most electrical systems, electrical submersible pump (ESP) system grounding has its unique feature: it must be divided into two zones, i.e., surface and downhole zones, grounding practices for the two zones are significantly different. In this paper, the current practice and future trend for ESP system grounding is presented, which is based on an extensive literature review, including the industry practice, published technical papers, and the patent search. This paper will be extremely useful for field engineers and ESP system design engineers to understand requirements, techniques, and future development directions for ESP system grounding. [ABSTRACT FROM PUBLISHER]

In order to improve low voltage (LV) network visibility without extensive monitoring and integrate low carbon technologies (LCTs) in a cost-effective manner, this paper proposes a novel three-stage network load profiling method. It uses real-time information monitored from selective representative areas to develop network templates. The three stages are: clustering, classification and scaling. It can be used to identify the loading conditions of unmonitored LV systems with similar fixed data to those monitored LV substations. In the clustering stage, hierarchical clustering and K-means are used to cluster substations into groups based on the shape of the monitored load profiles. The classification tool designed with multinomial logistic regression maps an unmonitored LV substation into the most probable templates by using routinely available fixed data. Finally, clusterwise weighted constrained regression is employed to estimate peak for individual LV substations and the developed templates. The three-stage profiling is demonstrated on a practical system in the U.K. under the umbrella of a smart grid trail project. Ten LV templates are developed by using the metered data from 800 monitored LV substations. A comprehensive comparison between the estimated peaks using the three-stage process and the metered peaks suggests that the methodology can achieve superior accuracy. This is part I of the paper, introducing clustering and classification. The scaling (peak estimation) process will be introduced in part II of the paper. [ABSTRACT FROM PUBLISHER]

Risk of blackouts is more than expected and must be considered in the power system studies. The interest of this paper is to minimize the blackouts risk during minimizing the costs in probabilistic transmission expansion planning (TEP). In this paper, a long-term reliability analysis, which was developed by self-organized criticality theory, is used in a multi-objective optimization to include risk of blackouts in TEP. The objective functions are costs and expected energy not supplied. Also, a new formulation for calculating transmission operating cost as a part of cost function is proposed. The problem is solved by a multi-objective particle swarm optimization to find an optimal Pareto set from which the decision-maker can choose the most desirable one, regarding existing budget. The proposed method is applied to the IEEE 118-bus test system to investigate its applicability and scalability. The results are compared with security-constrained TEP, which uses famous deterministic criterion known as N-1. The proposed approach produces more efficient plans for suppressing cascading blackouts with less network investment. Moreover, the results provide motivation for considering the risk of cascading blackouts in TEP, which afford substantial saving to society. [ABSTRACT FROM AUTHOR]

Air circuit breaker (ACB) is widely used in power distribution system. The movable contact of ACB consists of multiple parallel contacts and the arc will be ignited between arcing contact and static contact when the short-circuit current appears. This paper focuses on the arc evolution process at various currents in multiple parallel contact systems. A 3-D magnetohydrodynamic model of a multiple parallel contact structures is developed. In this model, the anode consists to five parallel contacts, and they are separated by insulation material. The near-electrode layer with a nonlinear voltage–current density characteristic is modeled to describe the near-electrode voltage drop, and the difference between near-anode and near-cathode layers is considered. The magnetic vector potential approach is adopted to calculate the time-varying electromagnetic field produced by the current loop. The arc evolution processes at various currents are analyzed by current density and arc voltage. It is noted that the anode arc root appears on multiple contacts with the increase of current. The arc evolution process mainly depends on the arc resistance characteristic. [ABSTRACT FROM AUTHOR]

Switchgear is an important power system protection equipment. Internal overheating of high-current switchgear has become the most common problem in the power system. In this paper, two different methods of simulation model are adopted to study the temperature rise issues of the 12-kV medium voltage switchgear. First, the electromagnetic field is calculated by using ANSYS APDL, then coupling with fluid dynamics software CFX to give the temperature and flow field distribution of the switchgear. Second, FLUENT and Maxwell 3-D are used to get the temperature and flow field distribution. It can be proven that CFX simulation of flow field is more suitable for the complex models. In the meantime, it has huge differences with FLUENT software when the temperature rise of the switchgear is calculated. In this paper, the influences of inlet velocity, the number of ventilation holes, and their positions are further studied, which could provide theoretical guidance for reducing temperature rise of the switchgear. [ABSTRACT FROM PUBLISHER]

This paper examined the extent of the dependence of the interrupting capability on the shape of the contact system in a molded case circuit breaker (MCCB). Thus, a simple analysis method was suggested for estimating the interrupting capability and used to investigate the magnetic flux density distribution in a contact system caused by a short-circuit current. However, the MCCB produced by a joint-research company turned out to have the poor interrupting capability and a low magnetic flux density distribution for driving arc plasma between two contacts in the contact system. To build up additional interrupting capability without making many changes, a new arc runner was devised to prevent arc plasma from returning to its original position in the contact system. The arc voltage characteristics were tested with a simplified synthetic testing facility using an LC resonant circuit. The result showed that the new MCCB had a much higher arc voltage than the existing MCCB. This implies that investigating the arc voltage is fairly comparable to predicting the arc plasma extinction and the interrupting capability. [ABSTRACT FROM AUTHOR]

Microthrusters are used for microsatellites to provide precise motion control in space by applying very low thrust pulses, which must be properly calibrated on earth. The range of thrust levels required varies from one thruster to another, depending on its use. Thus, microthrusts that stand capable of reading thrusts of multiple ranges, depending on the configuration, are in demand. This paper discusses the features and the calibration method for a typical miniaturized thrust stand. This device is essentially a torsional pendulum whose sensitivity can be varied. As a source of torsion, a piece of wire is used. For the purpose of this paper, the thrust stand was configured to achieve a micro-Newton resolution. [ABSTRACT FROM AUTHOR]

This paper will present a new approach that is advantageous to medium-voltage (MV) distribution design configurations for large industrial and power distribution system configurations [specifically main-tie-main (MTM)] for large industrial and power station installations. Sixty years of traditional low-cost design approaches (typical MTM and operated with open tiebreaker) are re-evaluated to demonstrate that traditional low capital cost design may miss improvement opportunities. Those opportunities can be major capital expenditure reduction, power quality improvement, MV motor soft starter deletion, and improved system stability to name a few. Many designers may not have considered the component interrelationships and/or their tradeoffs when in an integrated system. The designer and/or user should consider the advantages of higher short-circuit capacity (SCC) systems by integrating fault current limiters and MV switchgear. Utilizing higher SCC systems permits power system designer optimization opportunities not possible before using conventional design methods. This paper will provide documentation of substantial savings of capital investment and energy under higher SCC conditions. The savings in one system component will offset another's increased cost. An obvious benefit of stiffer systems is ease of direct-on-line starting of large motor-driven compressor trains. The future need for motor soft starters minimizing system impact will be challenged. This paper may change fundamental system design methodology for system designers by removing several performance tradeoffs. This paper, in its original version, was previously presented at the 2010 IEEE/IAS/Petroleum Chemical Industry Conference. It was expanded with new sections for the 2017 IEEE/Industry Applications Society (IAS)/Pulp, Paper Forestry Industries Conference to include pre-emptive prefault adjustable power quality and multisourced networked power systems. [ABSTRACT FROM PUBLISHER]

An online approach based on application of search coil for transformer winding fault detection is presented in this paper. Earlier attempts report use of search coil for the detection of transformer interturn fault. This paper extends application of search coil for detection of winding displacement in addition to interturn fault identification. Experimental results based on specially designed 10-kVA transformer are presented to analyze search coil voltages during healthy and faulty conditions. The algorithm detects phase ($U$ , $V$, $W$), side (LV, HV), and precise location of the fault. Discrimination between interturn fault and winding radial displacement is also achieved by search coil voltage analysis. The results are experimentally verified based on impedance analyzer plots. Experimental analysis indicates that the proposed method is independent of load on the transformer, vector group, nature of winding, balanced or unbalanced source voltage, source voltage harmonics, inrush, and overexcitation conditions. [ABSTRACT FROM AUTHOR]

Transmission and distribution (T&D) networks are a critical part of the power grid. As moving towards a smart-grid, it is essential to modernize the T&D networks and make it “Smart-grid ready”. The concept of flexible ac transmission systems (FACTS) has been well-known for three decades. Rapid advancements in power electronics technology in the past decades have led to a new generation of FACTS devices. The Modern FACTS technology helps the transition of transmission networks to “smart”. With increasing penetration of distributed generation, the distribution network is seeing unprecedented variation in terms of its fundamental operation and control, from renewable energy integration to microgrid, from active control of power quality, volt/var and frequency to self-healing and islanding operation. As a key part of smart-grid at the distribution level, we summarize the current efforts as a concept of resilient ac distribution systems (RACDS). The concepts of both FACTS and RACDS for a smart grid are introduced in this paper. Different configurations, key benefits, operating principles and world-wide installations of FACTS and RACDS devices are presented in detail. The ongoing and future direction of R&D leading to newer generations of FACTS and RACDS are also discussed. [ABSTRACT FROM PUBLISHER]

In this paper, the finite-elements method was used to analyze the approximation being typically used in the international standards for the calculation of the touch voltage, appearing at earth faults in power networks. The calculations in this paper were performed on the series of earthing systems applied in practice and the results are compared with the results of the widely accepted approximate method from standards. The origin of discrepancy in the results is analyzed and evaluated. The outcome of this paper is the justification of the application of Thevenin's theorem and the development of the higher accuracy equations for the resistance between feet and remote earth in case of the application of high resistivity additional surface material. [ABSTRACT FROM PUBLISHER]

This paper discusses and compares phase-shifted pulse-width modulation (PS-PWM) and level-shifted PWM (LS-PWM) in a modular multilevel single-delta bridge-cell (SDBC) inverter for utility-scale grid-tied photovoltaic applications. This three-phase SDBC inverter provides the capability of operating even under power-distribution imbalances not only among three clusters, but also among cascaded bridge cells in each cluster. The main focus of this research lies in analyzing the capability of operation under severe power-distribution imbalances and presenting power-balancing methods based on zero-sequence current injection, which result in an extended power-balancing capability. This paper highlights that LS-PWM is superior to PS-PWM in both power-balancing capability and harmonic performance at the ac side of the SDBC inverter when operating under power-distribution imbalances. Experimental results obtained from a three-phase 10-kW downscaled system show good agreement with those from the theoretical analysis. [ABSTRACT FROM AUTHOR]

Widespread three-phase imbalance causes inefficient uses of low voltage (LV) network assets, leading to additional reinforcement costs (ARCs). Previous work that assumed balanced three phases underestimated the reinforcement cost throughout the whole utility by more than 50%. Previous work that quantified the ARCs was limited to individual network components, relying on full sensory data. This paper proposes a novel methodology that will scale the ARC estimation at a utility level, when the data concerning the imbalance of circuits or transformers are scarce. A novel statistical method is developed to estimate the volume of assets that need to be invested by identifying the relationship between the triangular distribution of circuit imbalance and that of circuit utilization. When there are more data available in future, accurate probability distributions can be constructed to reflect the network condition across the whole system. In light of this, two novel generalized ARC estimation formulas are developed that account for generic probability distributions. The developed methodology is applied to a real utility system in the UK, showing that: 1) three-phase imbalance leads to ARCs that are even greater than the reinforcement costs in the balanced case; 2) a 1% increase in the demand growth rate, the maximum degree of imbalance (DIB) and the maximum nominal utilization rate leads to over 10%, approximately 1% and 2% increases in the ARCs, respectively; and 3) the ARC is not sensitive to the minimum DIB values and the minimum nominal utilization rates. [ABSTRACT FROM PUBLISHER]