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The effects of furfural generation and partitioning on the aging assessment of oil-paper insulation of power equipment were investigated. Oil-paper samples with various furfural contents were prepared using an accelerated thermal aging experiment. The mass of the furfural generated during the aging of insulation paper was calculated and used to establish the quantitative equation between the accumulated furfural and the degree of polymerization (DP) of the insulation paper. Results showed that the reciprocal of the DP value was linearly related to the amount of furfural generated by the insulation paper. Effects of temperature, moisture, and temperature on the furfural partitioning ratio between oil and paper were analyzed using a furfural partitioning experiment, and a furfural partitioning model was established. Results showed that the furfural partitioning ratio in oil was positively correlated with temperature and moisture but negatively correlated with the DP of the insulation paper. A method for assessing the age of an insulation paper by integrating the furfural generation and partitioning models was proposed and applied on a 500-kV reactor that was returned for factory maintenance. The application result indicated that the method could accurately assess the overall aging condition of the oil-paper insulation of the power equipment. [ABSTRACT FROM AUTHOR]

Traction transformers are one of the most important equipment in the traction power supply system. Thermal aging of transformer insulation system determines its reliable life. To achieve an estimation of the insulation life of traction power transformers operated under real load condition, the effects of traction loads on the thermal aging of oil-paper insulation in traction transformers were investigated. First, the design principles for the accelerated thermal aging experiment were studied and proposed by considering magnitude (i.e., load rate) and frequency (i.e. spare time and lasting time) of the traction load. Then, an experimental system was established in the laboratory to conduct extensive accelerated thermal aging experiments, in which the traction loads were mimicked by using positive temperature coefficient (PTC) heating plates and a programmable logic controller (PLC). Finally, the experimental results were analyzed and discussed to reveal the effects of traction load on the thermal aging of oil-paper insulation in traction transformers. [ABSTRACT FROM AUTHOR]

Oil-immersed paper is a weak link in internal insulation of oil immersed power transformer, whose aging state distributes inhomogeneously. However, most of the current assessment methods fail to consider the spatial distribution of aging areas inside transformer. Aiming at this problem, this paper proposes the inversion detection method to obtain the resistivity of oil-immersed paper in various regions nondestructively, and uses the resistivity of oil-immersed paper to assess directly the insulation state of oil immersed power transformers. Finite element method is applied to establish the mapping relationship between the resistivity of oil-immersed paper in different regions, and the dielectric loss factor obtained from the port of transformer. Back propagation neural network is used to learn inversely this mapping relationship so as to calculate the resistivity. Applying the proposed method on a 10-kV transformer, the calculated results are close to the measured values. The study shows that the inversion method can effectively calculate the oil-immersed resistivity in various regions, which represent the aging state in different regions of the transformer. [ABSTRACT FROM AUTHOR]

Reliability and power quality are two of the most discussed topics in the utility industry today. Many groups have performed power quality studies with varying results. One large industrial customer in northern New York State which experienced numerous process interruptions due to power system disturbances was the focus of this study. Monitoring methods, results, inadequacies of standards, and unique mitigation techniques used to conquer their problems are discussed in this paper.

The paper presents results of a laboratory study on the effect of temperature and moisture level of paper-oil insulation on the parameters of the Cole-Cole model. It also discusses how to determine the values of coefficient \alpha and time constant \tau (parameters of the Cole-Cole model) of the characteristics resulting from the experimental frequency spectroscopy method (FDS) of paper-oil insulation. [ABSTRACT FROM PUBLISHER]

Oil-paper insulation ageing of transformer has characteristics of spatial locality due to uneven temperature distribution. The transformer is sealed, it is difficult to obtain the local ageing state of oil-paper insulation by sampling directly. Currently, there are no effective detection method to detect the insulation state of local regions. The oil-immersed paper resistivity inversion method can nondestructively assess the local state of oil-paper insulation. However, the current inversion methods still have shortcomings and need to be improved. In this paper, combining the back propagation neural network (BPNN) and Newton downhill method (NDM), an improved inversion method is proposed to optimize the current inversion method, so as to reduce the effect of initial value on it and make calculated results converge better. Finally, a 3D 10 kV transformer model is established to verify the effectiveness of the proposed method. The resistivity calculated by the improved method show that the method can provide initial resistivity values for technicians and improve the convergence and accuracy of current inversion method, which is more suitable for extending to the engineering practice. [ABSTRACT FROM AUTHOR]

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. Index Terms--Conductivity, depolarization current, dielectric response, dissipation factor, equivalent model, polarization current, recovery voltage, temperature, transformer insulation.

Special measures may be needed to select line insulators for transmission and distribution lines in locations exposed to freezing conditions. This first part of the paper describes the environmental and electrical stresses encountered in service that influence the risk of flashover on line insulators. Part II of the paper describes the strength of typical line insulation in these conditions and deals with selection and mitigation methods. Index Terms--Climate, contamination, flashover, fog, high voltage, ice, insulation coordination, line insulators, snow.

Knowledge about moisture content in oil impregnated paper insulation is essential when estimating remaining lifetime of power transformers. Direct evaluation of moisture content is rarely possible due to inaccessibility of the internal insulation system in transformers. Therefore, various indirect estimation techniques are utilized. Frequency domain spectroscopy (FDS) measurements of transformer insulation belong to this group. To perform high quality interpretation of results of FDS measurements a good knowledge on dielectric responses in oil impregnated pressboard and paper is required, especially as it refers to their variation with water content and temperature. The aim of this paper is to provide an open access to the frequency domain spectra of oil impregnated paper and pressboard samples, which can then be used in modeling of the results of diagnostic measurements in power transformers. Index Terms--Conductivity, dielectric frequency response, modeling, moisture content, oil-paper insulation.

Activation energy is popularly used for the estimation of remaining life of transformer insulation. It is defined as the average rate of all reactions that happen with cellulose. Existing literature shows that the activation energy of oil–paper insulation can be obtained from polarization depolarization current (PDC) and return voltage measurement (RVM) data that are measured at a specific temperature. It is practically difficult to ensure the same measurement temperature for both PDC and RVM data. On the other hand, PDC data and its analysis get influenced by de-trapping current. This de-trapping current is generated by ionic charge carriers that get freed from trap sites during PDC measurement process. Formation of these trap sites is related to physical, chemical reactions that happen at oil–paper interface. This paper proposes a methodology which uses de-trapped charge, dislodged from deep and shallow traps, to assess insulation condition and for the prediction of activation energy. Thus, eliminating the need of RVM data. The proposed method is tested using data collected from various real-life in-service transformers. [ABSTRACT FROM AUTHOR]

The effects of moisture, oxygen, and acidity upon the aging of Kraft and thermally upgraded ('Insuldur[R]') papers have been studied in detail. The results for Kraft are consistent with the kinetic model and parameters proposed earlier by Emsley et al., and with the principle that moisture promotes acid-hydrolysis by causing carboxylic acids to dissociate. Moisture is released during the aging of Kraft and, hence, its aging is auto-acceleratory. In contrast, Insuldur consumed moisture under the same conditions, aged more slowly, and its aging was less accelerated by added moisture. 2-Furfuraldehyde (2FAL), which is a dehydration product of pentosans and, hence, an index of moisture production, is also released from Kraft during aging, but not from Insuldur. Acids are, however, produced from both types of paper. Theoretical explanations for these findings are proposed, and their practical implications for transformer maintenance are discussed. Index Terms--Acids, aging, hydrolysis, maintenance, oil, oxidation, paper, transformer, 2-Furfuraldehyde, water.

Dynamics of water penetration in mass impregnated cable insulation has been studied. For experimental purposes, artificial damage has been inflicted to a 40-cm-long cable sample and water ingress has been continuously monitored by frequency response measurements. A similar experiment has been conducted on 2.8-m-long cable sample, where both frequency response and time-domain reflectometry (TDR) measurements have been performed. After termination of both experiments, actual moisture content has been measured radially and axially. Based on dielectric measurements, a model of water ingress has been developed and diffusion coefficients have been estimated for mass impregnated cable paper. Index Terms--Dielectric response, Karl Fischer titration, mass impregnated cable, moisture content, oil paper insulation.

Dielectric spectroscopy (dielectric response measurements) has been applied for nondestructive estimation of humidity in oil-paper cable insulation. The experiments have been based upon two field-aged cables, 20 and 50 years old. Paper samples from these cables have been characterized and subjected to environments with different relative humidity. Dielectric loss and capacitance have been measured in a frequency range 1 MHz to 1 kHz and related to the moisture content determined by Karl Fisher titration. A method has been verified where the moisture content is correlated to the minimum value of loss tangent (tan [delta]). A number of field measurements have been performed where the method has been applied to estimate the moisture content in the distribution cables. Index Terms--Dielectric response, Karl Fischer titration, mass impregnated cable, moisture content, oil paper insulation.

Special measures may be needed to select line insulators for transmission and distribution lines in locations exposed to freezing conditions. This second part of the paper describes the strength of typical line insulation in these conditions and then deals with selection and mitigation methods based on the in-service stresses described in Part I. Index Terms--Climate, contamination, flashover, fog, high voltage, ice, insulation coordination, line insulators, snow.

An extensive revision of the IEEE C37.011 'Application Guide for TRV for AC High-Voltage circuit Breakers' has been in process for the last four years. The main aim was to introduce the two- and the four- parameter description of the transient recovery voltage (TRV) as used in IEC Switchgear standards that have been introduced in the revisions of Standards C37.04 and C37.06. These two standards are being concurrently revised, but IEEE C37.011 provides the necessary explanations on TRV characteristic in advance. Non-specialist engineer users of the guide will better understand these standards. Index Terms--Circuit breaker, standard, transient recovery voltage (TRV).

Test methods for evaluating flashover voltage of ceramic and nonceramic insulators under ice, snow, and cold-fog conditions are recommended. The paper describes the procedure to be followed at various stages of an evaluation test including preparation of the test object, insulator precontamination, ice, snow, and cold-fog deposits as well as voltage applications and flashover voltage evaluation. Some relevant parameters for ice accretion, flashover voltage evaluation, artificial pollution, and power source requirements are taken tram IEC 60129, IEC 60507, and IEEE Std.-4-1995 on standard techniques for high-voltage testing. Index Terms--Contamination, flashover, fog, high voltage transmission, ice, insulator, snow, statistical interpretation, test methods.

Recently developed monitoring-systems show the need as also the possibilities for online- and offline-onsite-diagnostics. The limit in sensitivity for electrical pd-measurements according to IEC 60270 which is reached using filters for sinusoidal disturbances and compensation for corona impulses is still not satisfactory. The acoustic partial discharge measurement (pd-measurement) is also a well known and reliable method often used by transformer manufacturers in testing. In laboratory setups a gain in sensitivity of the acoustic in comparison to the electrical pd measurements could be established. This is reached by adapting the sensors to the propagation path, a modern but moderately priced acquisition hardware and the introduction of new signal processing algorithms. The developed sophisticated measuring systems show remarkable results in online acoustic pd-measurements onsite. Index Terms--Acoustic measurements, partial discharges, signal processing, transformers.

Many utilities still have paper-insulated pipe type cables in service. In the near future they may have to replace some of these systems due to local increases in electric power demand or aged cable insulation. In many cases the steel pipes are well protected against corrosion and thus suitable for further use. For Retrofitting in such installations, XLPE-insulated cables offer several advantages. Felten & Guilleaume Energietechnik AG has developed a new three-core XLPE-insulated 64/110 kV cable with reduced insulation thickness (10 mm), that can be pulled into a pipe. In co-operation with VEW ENERGIE AG, the cable performance is being investigated in a field test, that started in October 1996. This long-term loading cycle test will last for three years. The test voltage, applied between conductor and earth, amounts to 127 kV. The temperature is measured with the help of an optical-fiber measurement system. This device is computer controlled and works as a remote monitoring system. Keywords: Retrofitting, power cables, cross linked polyethylene insulation, paper insulation, pipe cables, optical-fiber measurements, temperature measurement, cable ratings, power cable installation, trenchless technology

Power capacitors are widely used for regulating voltage and improving the power factor, and the type in most frequent use today are capacitors made of oil-impregnated paper film, a growing number of which will soon have been in operation in the field for 20 years, which has prompted us to make study of techniques for diagnosing deterioration in oil-impregnated paper film capacitors. It was found that thermal stress causes deterioration of the insulating paper, which increases the amount of dissolved CO and C[O.sub.2] in the oil, and lowers the partial discharge inception voltage, determining the useful lifetime of the capacitor. Based on this idea, techniques have been proposed for diagnosing deterioration, consisting of caution level and danger level, from actual stress in the field. Further, a trial calculation was made for the number of years and months it takes for a capacitor to reach the caution level, from an investigation of capacitors in service for years.

Disconnecting switch operations in gas insulated equipment cause transient voltages with risetimes as steep as 5 to 20 nanoseconds and magnitudes as high as 2.5 pu. There is very little information on the effect of these transients on oil-paper insulated equipment. There have been reports, however of transformer and bushing failures caused by these transients. The electrical breakdown characteristics of oil-paper insulation under steep front impulse were studied in this project, which was co-sponsored by the Canadian Electrical Association and B.C. Hydro. [V.sub.50] (50% breakdown probability voltage) breakdown data was obtained with steep front (10 ns/2500 [[micro]second]), lightning and switching impulse waveforms. Insulation breakdown voltage vs breakdown time (V-t) data and multiple impulse breakdown data were obtained with the steep front impulse waveform. The [V.sub.50] results showed that the breakdown strengths were lower for steep front impulses than for lightning impulses. The multiple impulse breakdown results showed that oil-paper insulation breakdown strength can be lower than 100 kV/mm. These results are alarming, since they suggest that oil-paper insulated equipment subjected to steep front transients will fail at voltages below the lightning impulse design level (BIL). The Volt-time data had a discontinuity. The breakdown process at risetimes below about 50 ns was different from the breakdown process at risetimes above 50 ns.

The electric characteristics and insulation design strength of a liquid-nitrogen-impregnated synthetic insulation was considered. It found to detect the impregnation of liquid nitrogen by measuring the electrostatic capacitance of the cable. [Epsilon] tan [Delta], an index of the dielectric loss, was 0.31% for cellulose paper and 0.18% for semisynthetic paper, PPLP and OPPL. It is found that the decline of the thickness dependence of the breakdown strength of the liquidnitrogen-impregnated insulating cable is steeper than that of the OF cables. It is possible to design the insulation strength of the 66 kV cable to be 10 kV/mm.

This paper exploits smart inverters of distributed energy resources (DERs) for the mitigation of fault-induced delayed voltage recovery (FIDVR). According to the IEEE Standard 1547-2018, smart inverters with voltage ride-through and var injection capabilities are promising technologies for mitigating FIDVR. This paper quantitatively investigates the effectiveness of smart inverters for FIDVR from a system-wide perspective. It shows that the penetration of smart inverters and induction motors are important factors affecting mitigation success. In addition, the over-voltages at the end of FIDVR due to load disconnections can be prevented with coordinated control of DERs and automated switching capacitors. The control scheme of smart inverters used for FIDVR is extended from the distributed volt/var droop control to include low- and high-voltage ride-through capabilities. The IEEE 13-bus feeder, the 8500-node test feeder, and the IEEE 390-node low-voltage network test system are used to illustrate the impact of DER penetration. For example, one can determine the residential air conditioner penetration level (for a given system at certain DER penetration level) that makes a system susceptible to FIDVR. The effects of solar intermittency are also studied. [ABSTRACT FROM AUTHOR]

This paper briefly describes the special publication, 'Fault and Disturbance Data Requirements for Automated Computer Analysis', prepared by Working Group I 11 of the Relaying Practices and Consumer Interface Protection Subcommittee of the IEEE Power System Relaying Committee. The publication describes the analysis objectives and the data necessary to facilitate automated analysis. The address for ordering a copy from the IEEE is in the reference section.

Compared to conventional ac cables, the current rating of HVDC cable circuits is more complicated because the permissible current is not only limited by the operating temperature, but also by the electrical stress within the insulation. Therefore the IEC60287 current rating standard is considered insufficient for some HVDC applications because it fails to include the stress limitation. This paper presents an analytical methodology to calculate an electrical stress-limited rating for HVDC cables, which considers the maximum dielectric stress as the current limiting factor. This paper represents the first part of a project which has comprehensively reviewed cable rating calculations for mass impregnated HVDC cable systems. [ABSTRACT FROM PUBLISHER]

In this paper, we discuss a better method to measure the paper water content of transformers using cellulose isotherms. The advantage of the new method is that the transformer oil and cellulosic insulation do not need to be in thermodynamic equilibrium. Instead, the temperature needs to be cycling in order to determine when the direction of water migration, whether out of or into the oil changes. The reversal in water migration can be used to determine the vapor pressure of the water adsorbed by the cellulose. This method was tested using 12 different conditions similar to those within a normally operating transformer. The results showed close agreement when this method is used. The significance is that isotherm equations can now be used even when insulation media are not in equilibrium. [ABSTRACT FROM PUBLISHER]

Voltage rise caused by high levels of distributed generation is manifesting as voltage regulation challenges for many electricity network service providers. In this environment it would be ideal to reduce supply voltage magnitudes, however, many network operators are hesitant to do so due to concerns related to consumer appliance performance at reduced supply voltage magnitudes. Voltage regulation requirements are defined by network standards and network service providers must ensure voltages remain within specified limits. Through an evaluation of domestic appliance performance when supplied at various voltage magnitudes, this paper examines the impact of varying voltage levels on residential appliances. Equipment energy demand, operation and actuation were monitored for each applied voltage magnitude. While no equipment failures were recorded, appliance behaviour varied significantly with applied voltage magnitude. Individual appliance conservation voltage reduction (CVR) factors have also been established. The results highlight the importance of good voltage regulation and provide substantiated appliance performance figures for future studies. The outcomes of this paper allow electricity network service providers to understand the implications of supply voltage magnitude on domestic appliance performance, whether it be understating of the impact of higher voltage magnitudes caused by distributed generation or implications of reducing voltage magnitudes to provide headroom for distributed generation integration. [ABSTRACT FROM AUTHOR]

Utilities prefer to perform a condition-based assessment of power transformer insulation in the least possible shutdown time. It is essential to estimate the values of various insulation condition sensitive performance parameters with higher accuracy. In the present work, a technique for the estimation of performance parameters, moisture content of paper, dissipation factor of the entire oil-paper insulation, paper conductivity, and activation energy is proposed. The evaluation of these parameters using reported techniques requires complete measurement of polarization and depolarization current profile, which requires around 20000 s of measurement time. The present method uses a forecasted polarization current profile obtained from 600 s of measured polarization current data. Detrended Fluctuation Analysis is applied to the forecasted polarization current data obtained from various in-service power transformers to obtain a suitable parameter. It is shown that this parameter maintains well-defined relationships with parameters; moisture content of paper, dissipation factor of oil-paper insulation, paper conductivity, and activation energy. The proposed technique is beneficial for utilities as it eliminates the requirement of measuring depolarization current and return voltage measurement for estimating activation energy. [ABSTRACT FROM AUTHOR]

Traditionally, water mobility inside the cellulosic insulation, as those used in power transformers, has been modeled using the so-called Fick's diffusion theory, considering that the water movement in this porous material only depends on local conditions, such as temperature and moisture concentration. However, recent experimental works have demonstrated that the moisture movement inside the cellulose insulation could be also influenced by a global condition, that is, the insulation's thickness. In this paper, the influence of the insulation thickness in the mobility of moisture inside the cellulosic materials, such as Kraft paper and pressboard, is analyzed. In addition, the improvement in moisture dynamics estimation obtained when this variable is included into the diffusion models has been proved. [ABSTRACT FROM PUBLISHER]

In this paper, we present an update to the models used to calculate the remaining life of transformer paper insulation. A drawback to the current IEEE method is that it does not take into account the availability of water and oxygen on the life expectancy of Kraft paper insulation. We therefore set out to test an algorithm which does take these into account. For our investigation, we loaded three test transformers and ran them to near their end of life. Kinetic equations were applied to model the fall in the degree of polymerization of paper. Our model showed better agreement with the test results than that given from using the IEEE standard. The IEEE standard gives life expectancy for Kraft paper being aged in minimal oxygen under dry conditions, which is not necessarily representative of an old transformer. Wet paper and using high levels of oxygen can age nearly 40 times faster. The IEEE method needs to take the synergistic effect of water and oxygen on increasing the rate of paper aging into account. [ABSTRACT FROM PUBLISHER]

In recent years, there is an increased use of passive filters in both transmission and distribution systems due to the proliferation of power electronic devices. However, the problem of filter design has not been well addressed in the past and one example is the application of high-pass filters in a filter package. Three types of HP filters are widely used to mitigate multiple harmonics, i.e., 2nd HP filter, 3rd HP filter and C-type filter. There is still a lack of research to clearly reveal the characteristics of each filter, which makes it difficult for the designer to select the optimal filter topology under different circumstances. The main goal of this paper is to solve the problem of how to select a proper configuration among three HP filter candidates for a given harmonic problem. Unlike the conventional optimization-based filter studies, this paper investigates three HP filters in an analytical way. As a result, the paper provides a deep insight into the inherent characteristics of the filter and the conclusions drawn in the paper are universal; thus can be used in different applications, ranging from low voltage levels to high voltage levels. The research results lead to a recommended application scope of each HP filter, which is very useful to guide the design of filter packages and help designers to evaluate the design results. [ABSTRACT FROM AUTHOR]

The simulation of electric field transients in HVDC cables can be a fundamental tool to support insulation system design when operation dynamics, which includes voltage polarity inversions and load variation, becomes significant during the expected cable life. The field behavior during voltage and temperature transients is associated with intrinsic and extrinsic ageing processes that can affect the cable design life. Traditional models employed for electric field simulations consider only the non–linear, steady–state dependence of conductivity on temperature and field magnitude, but they neglect the transient behavior of permittivity and conductivity, that is, polarization and charge trapping phenomena. These processes impact on the duration of the field transient and thus ageing. This paper discusses the numerical implementation of an electro–quasistatic model that can be used to perform transient simulations of electric fields in HVDC cables insulation. With respect to the model traditionally employed, the presented one is extended with Debye's equations for dielectric polarization processes. The model is implemented numerically using finite differences, or the Occhini equivalent circuit: this paper demonstrates that the two approaches are equivalent. Numerical simulations show that, during transients, polarization processes slow down the electric field dynamics and reduce its maximum intensity. [ABSTRACT FROM AUTHOR]

In this paper, the initial stage and the return stroke current waveform parameters of rocket-triggered lightning flashes to the ground and to the distribution line have been analyzed. The results show that the average current, the charge transferred and the action integral associated with the Initial Stage with return strokes are greater than the corresponding values without return strokes. For the initial stage, the presence of the distribution line greatly reduces the maximum current, average current, charge transfer, and action integral by a factor of 0.35, 0.42, 0.51, and 0.19, respectively. For the return stroke, the presence of the distribution line has little effect on the other parameters except for a 2.4-fold increase in the 10-90% risetime. The presence of the distribution line affects the initial stage parameters more significantly than the return stroke parameters, probably because the lightning channel equivalent impedance of the initial stage is much smaller than that of the return stroke. The lightning channel equivalent impedance of the initial stage estimated in this paper is about 145 ohms and the estimated lightning channel equivalent impedance for the return stroke is greater than 2000 ohms. [ABSTRACT FROM AUTHOR]

Conventionally, the 2-parameter Weibull model, Arrhenius-Weibull model, has been used vastly for transformer aging-dependent unavailability modeling. However, this model only uses the lifetime feature to describe the transformer's degradation process and to calibrate the Weibull parameters, which harms the accuracy of aging-dependent unavailability forecasting. In response, this paper develops a 3-calibratable-parameter Weibull model for evaluating the transformer aging-dependent unavailability. In the proposed model, both the individualized aging threshold and lifetime are taken into the calibration of the Weibull parameters to accurately characterize the heterogeneity in transformer populations. First, a degree of polymerization (DP) analysis and Monte Carlo Simulation (MCS) based approach is proposed for estimating the transformers’ uncertain aging thresholds and lifetimes. Then, the Maximum Likelihood Estimate and Particle Swarm Optimization are jointly adopted to model the relationship among the calibratable Weibull parameters, aging threshold, and lifetime. Finally, the analytical formula of aging-dependent unavailability is derived from the established 3-calibratable-parameter Weibull model using an integral-discretization method. A real utility application example in China's Chongqing power system has been presented to validate and demonstrate the practicality and usefulness of this method. [ABSTRACT FROM AUTHOR]

Moisture is one of the key variables that must be considered when determining the load profiles that can be safely applied to a transformer. The presence of high amount of water accelerates the aging rate of the transformer's solid insulation, shortening the life expectancy of the equipment. Moreover, the dynamic processes of moisture migration between paper and oil must be considered in order to avoid a potential cause of failure, such as the formation of bubbles in the paper–oil interface, or the moisture saturation and the subsequent formation of liquid water in oil. These processes are linked to the changes in temperature; however, within the transformer, both processes have very different time constants, which complicates the analysis. In this paper, a mathematical model is presented, which allows us to study the moisture dynamics in a transformer. The model considers a multi-physical approach incorporating a thermal module and a moisture dynamic module that makes it possible to analyze the behavior of the moisture for a certain load profile. Some application cases are included in this paper to illustrate the model operation. [ABSTRACT FROM AUTHOR]

A bibliography on the subject of relay literature which includes the articles "An Innovative Template Design for Low Impedance Bus Zone Protection," by M. Ally, "Advances in Breaker-Failure Protection," by H. J. Altuve, and "Modern Techniques for Protecting Busbars in HV Networks," by Z. Gajic is presented.

This paper presents extensive verification, sensitivity, and application studies for an online substation grounding grid condition monitoring method proposed in a companion paper. The studies are conducted using a realistic substation grounding grid and associated feeder configurations commonly encountered in North America. The verification studies confirm that the proposed method is able to estimate the substation grounding impedances with acceptable accuracy. Main factors impacting measurement accuracy are identified and quantified through sensitivity studies. The findings lead to a guide for the implementation and operation of the proposed method. An application case is presented to demonstrate how the gradual deterioration of substation grounding grid can be monitored using the proposed method. [ABSTRACT FROM AUTHOR]

One of the issues faced by asset managers in the electric power industry is the condition and remaining life assessment of the high voltage (HV) assets. In contrast to other power equipment, transmission power cables are mainly subjected to corrective maintenance. To support the asset management of service aged transmission power cable circuits, this paper discusses an approach of integrated knowledge rules for condition-based maintenance based on laboratory investigations and field examples. There are very few recent publications on this subject in spite of aging power cable infrastructure; therefore, this paper aims at showing practical applications of condition-based maintenance of this important component of the transmission and distribution systems. [ABSTRACT FROM AUTHOR]

Ladder network synthesis is very significant for winding fault diagnosis within transformer. To synthesize the network reversely based on the measurable frequency response analysis (FRA) data is the only applicable way. To date the iron core and non-tested winding, which result in the frequency-dependent network components and multiple ladders in some frequency ranges, are usually not considered in the reverse process and thus the synthesis precision is largely limited. This paper proposes to synthesize multiple ladder networks in different frequency regions to handle this problem. Firstly, the sensitivities and frequency-dependent features of network components are analyzed, based on which the topology and components of the networks in diverse frequency ranges are determined afterwards. Further, the network synthesis strategies in different frequency ranges are elaborately designed. Finally, the synthesis method is applied on a distribution transformer successfully, with the fact that the extracted network parameters meet all the constraints and its FRA curve matches well with the measured one. An intact method of multiple-network synthesis for transformer winding in wide frequency range, considering the iron core and non-tested winding, is offered in this paper. [ABSTRACT FROM AUTHOR]

Presents a classified list of power system relaying references. 'Superimposed Quantities: Their True Nature and Application in Relays,' by G. Benmouyal and J. Roberts; 'Fast Harmonic Computation for Digital Relaying,' by A. Gomez Exposito and J.A. Rosendo Macias; 'System Reliability Improvements Through Fiber Optic Systems,' by J. Benckenstein.

This paper presents a novel approach to speed up electromagnetic-transients (EMT) simulation, using graphics-processing-unit (GPU)-based computing. This paper extends earlier published works in the area, by exploiting additional parallelism inside EMT simulation. A 2D-parallel matrix-vector multiplication is used that is faster than previous 1D-methods. Also, this paper implements a GPU-specific sparsity technique to further speed up the simulations, as the available CPU-based sparsity techniques are not suitable for GPUs. In addition, as an extension to previous works, this paper demonstrates modelling a power-electronic subsystem. The efficacy of the approach is demonstrated using two different scalable test systems. A low granularity system, that is, one with a large cluster of buses connected to others with a few transmission lines is considered, as is also a high granularity where a small cluster of buses is connected to other clusters, thereby requiring more interconnecting transmission lines. Computation times for GPU-based computing are compared with the computation times for sequential implementations on the CPU. This paper shows two surprising differences of GPU simulation in comparison with CPU simulation. First, the inclusion of sparsity only makes minor reductions in the GPU-based simulation time. Second, excessive granularity, even though it appears to increase the number of parallel-computable subsystems, significantly slows down the GPU-based simulation. [ABSTRACT FROM PUBLISHER]

As is known, cable plays a significant role in electric power transmission of the ship. From the safety perspective, this paper aims to predict the ship cable life more accurately and analyze its reliability under small sample conditions. To achieve this goal, based on the non-equidistant grey model (NEGM (1, 1)), an optimized equal-dimension dynamic NEGM (1, 1) is proposed in this paper. In the improved model, the raw data smoothness and the background value are optimized to apply to grey model parameters. Equal-dimension dynamic prediction algorithm (EDDPA) is adopted to predict the lifetime of ship CXF type cable. Compared with the aging model from literature and NEGM (1, 1), the prediction effectiveness and reliability of the proposed model are more considerable. Interestingly, with the increase of recurrence times, the numerical results show this model has higher prediction performance. Finally, the reliability and confidence interval of the life evaluation of ship CXF cable are given to provide more valuable information for the cable management. [ABSTRACT FROM AUTHOR]

This paper is devoted to electric arc furnace (EAF) modeling using a random differential equation based on the power balance equation. The proposed approach broadens and improves the model through the introduction of stochastic processes in place of existing coefficients. The paper presents a method which enables the estimation of EAF model coefficients with the help of measurement data - voltage and current waveforms recorded during the melting stage of an EAF work cycle. The estimation process is conducted with a Monte Carlo method and genetic algorithm, which is applied iteratively to each of the defined frames of the input signal. The estimated coefficients have been analyzed with respect to their time variability as well as the probability distributions of their values and increments. The results have been extensively visualized. Next, the identification of the stochastic processes representing the model coefficients has been carried out. Based on the previous results and autocorrelation functions, the density functions and parameters of discrete-time stochastic processes were identified. The paper presents solutions validated with statistical tests. [ABSTRACT FROM AUTHOR]

Visual surveillance for autonomous power facility inspection is considered to bethe prominent field of study in the power industry. This research field completely focuses on either object detection or image fusion which lacks the overall consideration. By considering this, a single end-to-end object detection method by incorporating the image fusion named Fast Detection Fusion Network (FDFNet) is proposed in this paper to output qualitative fused images with detection results. The parameters in the FDFnet are greatly reduced by sharing the feature extraction network between image fusion and object detection tasks, due to which a huge reduction in computational complexity is achieved. On this basis, the object detection algorithm performance on various types of power facility images is compared and analyzed. For experimentation purposes, an IR (infrared) and VIS (visible) image acquisition system has also been designed. In addition, a dataset named CVPower with different sets of images for power facility fusion detection is constructed for this research field. Experimental results demonstrate that the proposed method can achieve the mAP of not less than 70%, process 2 frames per second, and produce high qualitative fused images. [ABSTRACT FROM AUTHOR]

This article presents a bibliography of the papers related to relay literature. The papers listed in this bibliography include references to the subjects of service restoration, testing and methods of calculation well as to the field of relaying. The references also include the title, author, publication information and a summary of the subject matter. Some of the entries in this bibliography are: "Symmetrical Components Estimation through Non-Recursive Newton-type Numerical Algorithm," "Signal Processing Module for Power System applications," "Variable-Window Algorithm for Ultra-High-Speed Distance Protection," "Wavelet-Based ANN Approach for Transmission Line Protection," and "Enhanced Transmission Line Protection Settings."

Nowadays, there is an increasing interest in using transformer monitoring systems. Some monitoring systems use models to predict the value of certain variables. One of the key variables to be monitored is moisture content in oil, as moisture has a high influence on transformer exploitation. In this paper, the theoretical foundation of a model for monitoring moisture in transformer oil is reported. The Moisture Model estimates moisture content in transformer oil under certain working conditions. Comparing the value of estimated moisture with the measured one, the model is able to detect failures producing an abnormal water content in the transformer. The Model considers the equilibrium relations between paper and oil, the transients that take place until the steady-state equilibrium is attained, and the water increase caused by the insulating paper ageing. In addition, the Model can alert to the possibility of oil saturation and the consequent free water formation in the transformer. In this paper, the theoretical foundation of the Moisture Model is described; in a companion paper, its experimental verification is reported. [ABSTRACT FROM AUTHOR]

The paper deals with a final experimental validation of three-dimensional Multiconductor Cell Analysis (MCA) developed by the Electric Energy Transmission Laboratory of the University of Padova. This final confirmation comes from the measurement campaign carried out on one of the longest (100 km) HVAC submarine three-core cables: the Sicily-Malta interconnector. The considered frequency measurements range from 0 to 40th harmonic order with both positive and zero sequence supplies. In this overall harmonic interval and with both supplies, the comparison between measurements and MCA results highlights a very good agreement (maximum differences of 10%). These differences are negligible if measurement uncertainties are considered. [ABSTRACT FROM AUTHOR]

Multiple strokes are the main factors affecting the safe and stable operation of power equipment. As the core lightning protection equipment, arresters are also frequently thermally collapsed due to multiple strokes. This paper investigates thermal effects of polymer-housed metal-oxide surge arrester (PMOSA) under multiple strokes. The comparative experiments of PMOSA lightning impulse are carried out through multiple strokes of experiment platform, including continuous lightning stroke and multiple strokes. Furthermore, the temperature distribution of the housing surface is obtained by infrared imager for thermal effect analysis. Subsequently, some typical DC parameters are tested to explore the association of impulse aging and thermal effects of the arrester under multiple strokes. Finally, a thermal-electric coupling model (TECM) is constructed to investigate the influence of some factors on the temperature of PMOSA from the perspective of materials and structure. The research in this paper can provide a theory reference and brief data support for improving the heat dissipation performance of arresters under multiple strokes based on structural optimization design and material modification. [ABSTRACT FROM AUTHOR]

Cable fault location is generally much more difficult if cable defect has not reached the level of serious breakdown. Traditional methods such as time domain reflectometry (TDR) and partial discharge detection cannot solve this problem well due to their low sensitivity. This paper proposes a new non-destructive detection method based on the impedance spectroscopy (IS), which can effectively locate soft faults in the cable. In this paper, a numerical model for cable with distributed parameters is established firstly. Based on this model, cable faults are extracted from the imaginary part of impedance spectrum with Discrete Fourier Transform (DFT). The Chebyshev window is introduced to suppress interference and enhance signal-to-noise ratio, which improves the sensitivity and accuracy of fault location significantly. Experiments and simulations show that this method can well locate multi-segment defects in cables with good accuracy. The window function successfully amplifies the normalized amplitude of faults and improves the positioning accuracy. Compared with other method, this method reduces distortion points effectively. The fault location error is within 0.53%, which has great potential for field application. [ABSTRACT FROM AUTHOR]