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Focuses on the reliability and power quality at Champion International Corp. paper mill in Deferiet, New York. Numerous process interruptions experienced by Champion; Voltage sags emanating from the Niagara Mohawk Power Corp. transmission system; Causes and location of faults; Mitigation techniques.

Since power transformers are valuable components of power networks, reliable determination of the remaining lifetime of a transformer is very important for power utilities. Power transformers consist of oil, a core, wire, and paper (cellulose), and their performance and remaining useful lifetime depend on the state of the oil-impregnated paper. Changing the oil over the lifetime of a transformer is possible, but it is not possible to change the insulation paper. Thus, the end of the paper lifetime will also be the end of the transformer lifetime (typically more than 40 years). The health condition of an in-service power transformer can be assessed by chemical and electrical tests of the oil and the paper [1]. [ABSTRACT FROM PUBLISHER]

The article highlights various departments of the journal including the Industrial and Commercial Power Systems Department, the Industrial Power Conversion Systems Department and the Manufacturing Systems Development and Applications Department.

Load profile classification is very important in load forecast, planning and management. Although customers are generally grouped by utilities into residential, commercial classes and respective subclasses, there is a lack of systematic framework that can be used to characterize different classes with signatures that are both human-readable and machine-readable. The work presented in this paper attempts to formulate the theoretical framework for customer classification using the annual load profiles. This paper demonstrates how to extract characteristic attributes in frequency domain (CAFD) and use these CAFDs to formulate a hierarchy of load profiles that can be used as the systematic framework for customer load classification. As signatures for customer classes and subclasses, the CAFDs are obtained by using a data mining method called CART (classification and regression tree). The paper presents a load profile classification test to establish the efficacy of the proposed approach which is significant improvement over current practices that provide mostly qualitative labeling. [ABSTRACT FROM AUTHOR]

The need for economic, reliable, and effective delivery of electric power has lead to the search for fast, efficient, and effective methods for diagnosing the insulation of high-voltage (HV) equipment in the power industries. The recent dielectric techniques that have been carefully considered by major industries for transformer insulation condition assessment are the recovery voltage method (RVM) and the polarization and depolarization current (PDC) measurement. However, due to the complexity of the transformer insulation structure and various degradation mechanisms under multiple stresses, insulation condition assessment is usually performed by experts with special knowledge and experience. In this paper, an expert system (ES) is developed, which imitates the performance of a human expert, to make the complicated insulation condition assessment procedure accessible to plant maintenance engineers. The structure of the ES is described in detail including knowledge base, inference engine, and human-computer interface. Examples of the application of the ES are also presented to confirm that the system can provide accurate insulation diagnosis. [ABSTRACT FROM AUTHOR]

Provides instructions and guidelines to prospective authors who wish to submit manuscripts. [ABSTRACT FROM AUTHOR]

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles (EVs), locomotive traction, ship propulsion, “more-electric” aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various nontraditional purposes. [ABSTRACT FROM AUTHOR]

This paper proposes a new cableless transportation system that associates a magnetic actuator with the piping system in which it travels. To achieve high-speed transport within the pipe, the proposed actuator must show excellent movement characteristics. An aluminum pipe was cut in half longitudinally, and an alternating current was passed through the cut piping. The proposed cableless actuator powered by an electric current supplied by an electric brush was demonstrated to be capable of high-speed movement in a curved pipe. A scheme of attaching a cargo container to a nodal point of the actuator using a flexible rod was also proposed. The experimental results show that the actuator can be driven through the pipe even when the curved pipe is nearly U-shaped. Furthermore, the cableless actuator transporting a cargo mass of 30 g can be driven at a speed of 87.9 cm/s in a curved aluminum pipe with a curvature angle of 22.5°. The method established in this paper is considered to be applicable to the high-speed transport of lightweight reagents, bacteria, and microfluidic chips. [ABSTRACT FROM AUTHOR]

Development of smart grid technologies has created a promising atmosphere for smart cities and energy trading markets. Especially, traditional electricity consumers evolve into prosumers who produce as well as consume electricity in modern power electric systems. In this evolution, the electric power industry has tried to introduce the notion of local energy markets for prosumers. In the local energy market, prosumers purchase electricity from distributed energy generators or the other prosumers with surplus electricity via a local power exchange center. For this purpose, this paper proposes joint geometric clustering and truthful auction schemes in the local energy markets. The proposed clustering scheme is designed for distribution fairness of the distributed energy generator for serving prosumers, where the scheme is inspired by expectation and maximization based unsupervised learning. Moreover, this paper proposes an auction mechanism for truthful electricity trading in a local energy market. In order to guarantee truthful electricity trading, the proposed auction mechanism is constructed based on the Vickrey–Clarke–Groves auction, which was proven to guarantee truthful operations. The Hungarian method is also considered in addition to the auction. The simulation results for the auction verify that the utilities of local market energy entities are maximized when the prosumers are truthful. [ABSTRACT FROM AUTHOR]

Water is damaging for power transformers since it accelerates aging processes, reduces dielectric margin, decreases partial-discharge inception voltage, and, therefore, increases the probability of unexpected failures. Taking into account that power transformers are the most expensive equipment in an electrical plant and that the electrical supply guarantee is closely related to their reliability, it seems clear that transformer water content is a variable that must be kept under control. Since water is a byproduct of aging reactions in cellulosic insulation, the amount of water contained in a transformer usually increases from levels below 0.5% in weight, after its manufacturing, to levels of 6% in weight at the end of its life. However, it is not unusual to find high humidity levels in not so-old transformers, for example, in those that have been subjected to repairs in field. These days, some techniques are available to dry transformers in the field. Most of these methods achieve proper drying of transformer oil, but a great amount of water usually remains in cellulosic insulation and water in oil rises slowly some months after finishing the process. In these cases, drying treatments, which are very expensive; would have limited effectiveness. In this paper, a finite-element study is presented that analyzes different field-drying methods that are currently widely used. The efficiency of these methods will be studied and compared, and recommendations about drying parameters will be given. [ABSTRACT FROM AUTHOR]

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]

Preventive diagnosis and maintenance of transformers have become more and more popular in recent times in order to improve the reliability of electric power systems. Dielectric testing techniques such as return voltage measurement (RVM) and polarization-depolarization current (PDC) measurement are being investigated as potential tools for condition assessment of transformer insulation. A better understanding and analysis of the dielectric test results are only possible with a clear understanding of the physical behavior of the insulation system in response to moisture and aging. A circuit model, which describes the dielectric behavior of the transformer's main insulation system, has been parameterized in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been developed between the physical condition of the insulation and the equivalent model parameters that enable a clear and transparent interpretation of the dielectric test results. [ABSTRACT FROM AUTHOR]

Pricing multi-interval economic dispatch of electric power under operational uncertainty is considered in this two-part paper. Part I investigates dispatch-following incentives of profit-maximizing generators and shows that, under mild conditions, no uniform-pricing scheme for the rolling-window economic dispatch provides dispatch-following incentives that avoid discriminative out-of-the-market uplifts. A nonuniform pricing mechanism, referred to as the temporal locational marginal pricing (TLMP), is proposed. As an extension of the standard locational marginal pricing (LMP), TLMP takes into account both generation and ramping-induced opportunity costs. It eliminates the need for the out-of-the-market uplifts and guarantees full dispatch-following incentives regardless of the accuracy of the demand forecasts used in the dispatch. It is also shown that, under TLMP, a price-taking market participant has incentives to bid truthfully with its marginal cost of generation. Part II of the paper extends the theoretical results developed in Part I to more general network settings. It investigates a broader set of performance measures, including the incentives of the truthful revelation of ramping limits, revenue adequacy of the operator, consumer payments, generator profits, and price volatility under the rolling-window dispatch model with demand forecast errors. [ABSTRACT FROM AUTHOR]

This paper is Part II of a two paper series on electrical machine iron loss predictions. The Part II paper is focused on application of, and experimental data comparisons for, a new and unique method for predicting machine iron losses using transient finite element methods. A significant difference of the new method is the manner in which the predictive surface function of loss versus frequency and flux density is arrived at given lamination steel experimental loss test data. [ABSTRACT FROM AUTHOR]

As high-speed railways develop rapidly worldwide, the problems of neutral section and power quality are becoming increasingly prominent. These problems affect the normal operation of the power grid and the electric locomotives. The co-phase power supply schemes were proposed by researchers, which can solve these problems well. Among them, the MMC-based scheme (MMC-5 L) is a representative one. The existing scheme, when applied to the auto-transformer (AT)-fed system which is usually adopted by high-speed railways, needs to install an auto-transformer on the output side. To eliminate the auto-transformer and to obtain the more suitable and superior co-phase power supply schemes to AT-fed system, two improved schemes are proposed in this paper based on the novel MMC-based scheme (MMC-6 L) we proposed before. While establishing the mathematical model, creating the control system, and carrying out simulation verification of the proposed schemes, the proposed schemes are compared with MMC-6 L and MMC-5 L in terms of topological characteristics, control system complexity, power loss, and functionality. The results show that while the proposed schemes can fulfill the functions of the co-phase power supply scheme well like the MMC-5 L and MMC-6 L, they are more suitable and superior for the AT-fed system in terms of control system complexity and power loss. Among them, MMC-5L1CB performs best in power loss, and MMC-4L2CB performs best in control system complexity. [ABSTRACT FROM AUTHOR]

The electric drive power density and fault tolerance capability are of fundamental importance in many applications such as aerospace and traction applications. The modularization and the physical integration of the electric motor and the power converter components can lead to a high power density and a high fault tolerance drive system. The power density of a highly modular and integrated drive based on an axial flux permanent magnet synchronous machine and GaN converter is investigated in this paper. Several power density boosting techniques are provided and investigated using CFD simulations. These techniques incorporate optimization of the converter topology, the geometry of the shared cooling structure of the electric machine and the power converter and optimal selection of the materials in the path of heat transfer from the machine and the power converter to the cooling ambient. The power density of the reference integrated design is increased from 1.12 kW/ $l$ to 2.14 kW/ $l$. The CFD computations are validated by extensive measurements on a modular integrated setup. [ABSTRACT FROM AUTHOR]

This paper is concerned with the use of a three-level inverter for a synchronous reluctance machine (SynRM). The SynRM suffers from a poor power factor due to poor machine saliency. This makes it harder to operate the three-level neutral-point-clamped inverter due to a strict requirement to have the two dc-link capacitor voltages balanced. This paper proposes a new nearest three vector modulation algorithm which can balance the two dc-link capacitors even at poor machine saliency ratio (poor power factor). In this paper, a method of sizing the two dc-link capacitors based on the machine power is also proposed. A comparison between two- and three-level inverters was conducted. The SynRM registered lower $d$-axis current ripple with a three-level inverter, indicating lower core losses in the machine. [ABSTRACT FROM PUBLISHER]

Energy harvesting has attracted increased attention recently. Energy sources are present all around us, such as, mechanical vibrations, stress, strain, waste heat, sunlight or room light, electromagnetic rays, and chemical or biological sources. Vibration generators based on piezoelectric elements have been highlighted as low-power sources; however, their output power is very low, around the milliwatt or microwatt level, and thus, improving their performance is necessary to make the generated power usable. This paper investigates the use of passive devices to improve output characteristics of the vibration generators. The proposed circuits are a resonator and a passive rectifier. The proposed resonator consists of a parallel inductor and capacitor for $LC$ resonance. The $LC$ resonance equivalently reduces the internal capacitor of the piezoelectric elements. As a result, the output voltage and power are increased compared with that of conventional circuits. In addition, a boost-type current-improving passive rectifier is applied as the passive rectifier. The validity of the proposed circuit is numerically and experimentally verified. [ABSTRACT FROM AUTHOR]

In the process of electromagnetic launch, the melting on the armature surface tends to change the state of the armature/rail (AR) contact. Once the contact state is damaged, transition will appear easily. For this reason, it is necessary to analyze the factors affecting the melting characteristics of the armature surface. According to the Reynolds equation listed for the liquid metal film (LMF) on the AR contact interface, and by coupling the temperature, stress, and electromagnetic fields, this paper presents a thermoelastic magnetohydrodynamic model, which is used to analyze effects of the current waveform, and the length and angle of the armature tail on the surface melting rate and LMF thickness. The results show that for the same armature, if we want to achieve the same velocity within the same time range, the smoother the current waveform, the slower the surface melting rate and the thinner the minimum LMF thickness, and that for armatures of different key dimensions, in a certain range, the longer the armature tail, the slower the surface melting rate, but the larger the total melting amount and the thicker the minimum LMF thickness, and that the angle of armature tail has little effect on melting characteristics of the armature surface. What has been done in this paper is of great importance to improving the AR contact state and optimizing the performance of the electromagnetic launcher. [ABSTRACT FROM AUTHOR]

Near threshold computing (NTC) systems have been inherently plagued with heightened process variation (PV) sensitivity. Choke points are an intriguing manifestation of this PV sensitivity. In this paper, we explore the probability of minimum timing violations, caused by choke points, in an NTC system, and their nontrivial impacts on the system reliability. We show that conventional timing error mitigation techniques are inefficient in tackling choke point-induced minimum timing violations. Consequently, we propose a comprehensive error mitigation technique, Trident, to tackle choke points at NTC. Trident offers a $1.37\times $ performance improvement and a $1.11\times $ energy-efficiency gain over Razor at NTC with minimal hardware and power overheads. [ABSTRACT FROM AUTHOR]

The control of reactive power exchange between grids of different voltage levels has always been a concern for system operators. With production moving from the transmission to the distribution level, its importance increases. This paper proposes a novel approach to estimate reactive power capability of the grid as a whole. A linearized analytical model for an estimation of available reactive power exchange at the interface between two grids has been developed. The maximum estimation error for the scenarios we tested was only 2%. The model gives the relation between important grid parameters and the supported reactive power. The conclusions drawn from the model are confirmed on typical Swedish distribution network with scattered wind power and small industry consumers. Common scenarios in development of distribution grids are applied to show relevant parameters influence. One studied scenario is replacement of overhead lines with cables. It is shown that this particular change enhances the reactive power capability of the grid which is directly seen from the analytical analysis without running any optimal power flow. The analytical model proposed in this paper gives fundamental understanding of the reactive power capability of radial distribution grids. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear dynamic model of grid-connected combined heat and power (CHP) system that can effectively simulate the thermoelectric interactions and examine the impact of the CHP on the power grid. Based on the theorems of mass balance and energy balance, this paper studies and analyses the principles and dynamic characteristics of the main CHP components, including gas internal combustion engine, synchronous generator, waste heat exchanger, water storage tank, exhaust-heat boiler, and gas fired boiler. Then, the nonlinear time-domain models for each component are built against input and output parameters in order to facilitate the study of CHP operation under various conditions. Subsequently, a simulation method that can deal with the coupling of all models with different time constants is proposed. Finally, dynamic simulation analysis of the developed CHP model is carried out on the MATLAB/Simulink. Extensive demonstration results show that the developed models are accurate to represent the thermoelectric interactions in the gird-connected CHP and capture the impact of these gird-connected CHPs on the power grid. This study is particularly beneficial to the design of new control strategies for CHPs to maximise its efficiency and stability value to the grid. [ABSTRACT FROM AUTHOR]

As the deregulation of the electric power industry moves forward, there is an increasing need for cost cutting and it is becoming exceedingly important to keep track of the residual life and identify the timing of replacement for power transmission equipment that has aged for several tens of years in the field. This paper, taking up the theme of "insulation degradation phenomena and lifetime evaluation for power transmission equipment", conducted cross-sectional comparison of different types of equipment although this kind of evaluation was made independently for these equipment types so far. This paper covered six types of equipment: gas insulated switchgear (GIS), gas insulated transformers, oil filled (OF) transformers, OF cables, crosslinked polyethylene (XLPE) cables, and power capacitors. As a result of examining the characteristics such as electric, thermal, mechanical, and hygroscopic degradations, each of these equipment types was found to have distinctive Voltage-time (V-t) and Voltage-number (V-N) characteristics, which sometimes greatly varied from those of others. Since thermal degradation is dominant for gas insulated transformers and oil filled transformers, their lifetimes depend on the reduction of mechanical strengths of Polyethylene Terephthalate (PET) or insulating paper. Therefore, it is effective to diagnose decomposition products such as CO, CO2 and furfural generated in the thermal degradation mechanism. On the other hand, the influence of electric degradation has more significant impact on the other equipment types except OF cables. Such GIS components as epoxy spacers, XLPE cables, and power capacitors for which long-term ac voltages are dominant, are commonly characterized by the long-term V-t characteristics with a large gradient (small n-value). In terms of insulation structures, there is a possibility of reducing the degree of degradation by improving solids or the interface between solids and electrodes. [ABSTRACT FROM AUTHOR]

This paper, as an outcome of the EU project AREUS, heralds an optimization procedure that reduces up to 30% of energy consumption and up to 60% in peak power for the trajectories that have been tested on real industrial robots. We have evaluated a number of cost functions and tested our algorithm for a variety of scenarios such as varying cycle times, payloads, and single/multirobot cases in both ac- and dc-operated robot cells. The significance of our work is not only in the impressive savings, simplicity of implementation, and preserving path and cycle time, but also in the variety of test scenarios that include different kinds of KUKA robots. We have carried out the optimization and experiments in as realistic conditions as possible. [ABSTRACT FROM AUTHOR]

This paper presents the flexible dc capacitor voltages balancing control method for star-connected cascaded H-bridge converters. In this paper, the power flows are analyzed by investigating all the converter's control freedoms. Based on the analyses, users can accomplish the dc capacitor voltage balancing with both negative-sequence current and zero-sequence voltage. These two kinds of control options are further integrated together with the defined weighting factor $K$. The low-voltage ride-through operation of a proposed control method is also discussed in this paper. The control method is verified with a 220-V 1-kVA static synchronous compensators based on the star-connected cascaded H-bridge converters, and the experimental test results show that all the dc voltages are well regulated at the commanded value with different weighting factor $K$. [ABSTRACT FROM AUTHOR]

Dynamic wireless charging (DWC) is one of the most promising and economical power supply solutions for electric vehicles (EVs), which can address range anxiety and downsize the volume of onboard batteries. To solve the null power phenomenon and transfer power pulsation phenomenon in DWC scheme, this paper proposes a new magnetic coupler array to implement continuous charging and reduce the output power variation. The transmitters are placed with a proper interval to eliminate the adjacent coupling and enlarge the coil array’s effective length. ANSYS Maxwell is utilized to demonstrate the finite element analysis (FEA) of the DWC system. A larger receiver coil is designed to significantly mitigate power pulsation and increase the magnetic coupling as the receiver moves along the array. With the well-designed receiver coil, the output power pulsation is $\pm$ 1.52 $\%$. For the high-power capacity scenario, a multilevel connected DC-DC converter is designed on the receiver side to regulate the transfer power. Besides, a passivity-based control (PBC) is developed for the receiving DC-DC converter based on the Euler-Lagrange (EL) model, and a current sharing compensator is employed to balance each phase inductor current. Finally, a 500- $\text{W}$ prototype is constructed, and experimental results are represented to validate the proposed optimized coil array and the proposed PBC method. [ABSTRACT FROM AUTHOR]

This paper depicts an accident that happened in 2010 in a Brazilian chemical plant. A combination of different events, installations, and commissioning errors coupled with equipment failures involving the primary substation resulted in catastrophic failure. A single-phase failure of a 138-kV disconnect switch, during closing, initiated events and phenomena that resulted in a complete plant shutdown. This paper will walk the reader through the events, forensics analysis, and power system analysis that allowed the authors to identify what happened, how it happened, and what to do to prevent it from happening again. This paper will show how the anatomy of the problem, involving equipment failure, single-phase arcing, switching transients, overvoltage, capacitive coupling, transferred surge voltages, ungrounded system, transient overvoltage due to an arcing ground fault on an ungrounded system, insulation coordination, flashover, and lack of adequate surge protection, all of which resulted in a catastrophic failure of an arc resistant switchgear and a potentially serious arc flash incident. The research followed some steps that will be commented on here as well as the lessons learned. [ABSTRACT FROM AUTHOR]

The goal of all circuit protection devices is to mitigate and minimize collateral damage when a failure occurs to either the source (ac line) or the equipment. The circuit protection device is often given little attention, i.e., until erroneous trips hamper performance or unexpected damage occurs within the equipment. Then, the devices are often reviewed for performance characteristics and operating conditions. To meet this need, various devices have been designed for this purpose, and various standards have been written to provide guidance for the usage of those devices. The focus of this paper will be on the interplay between adjustable-speed drive (ASD) short-circuit current rating and protective device sizing, as well as the scaling of such systems, i.e., if a fuse sized for a 10-A circuit should have the same guidelines as that used for a 1000-A circuit. This paper will review the impact of Underwriters Laboratories 508A and 508C, and the National Electric Code on the ASD protection requirements. This paper evaluates a test setup scheme to measure the fuse performance. The peak current and I^2\t test results with both test schemes from three protection devices, a time-delay (TD) Class J fuse along with two non-TD Class J and T fuses, are presented and explained. A novel method of comparing the results is offered by viewing the collateral damage associated with a failure. This methodology has a minor impact at low power ratings, but it has major implications with high power ratings, where equipment is often field repairable. [ABSTRACT FROM AUTHOR]