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With the expansion in recent power systems, the boost in renewable energy resources with multiple interconnections, overloading of existing power networks, increased load growth, and equipment failures, power system transient instability issues have exponentially increased. Transient stability in power systems is of particular importance even while performing the steady state analysis of a power system. Power system transient stability assessment is mandatory regularly for power system operation and has a major impact on power system planning. Potential risks of blackouts and failures in power systems can be avoided or minimized with the prompt prediction of transient instability. This research work presents a predictive approach for power system transient instability. The case study is a 735kV, 29-bus, 7-powerplant network involving precise modeling of generators. In particular, the proposed method is represented by different machine learning models through extraction and regression, in which the variables of the power-generating units are used as primary sources/features. Data cleaning and sorting out techniques are being used for refining data. Feature extraction has also been implemented for further cleansing of the data. The result is in the form of concrete and robust classifier models that can overcome power systems’ instability concerns through prompt prediction.

The standard 1.2/50 lightning impulse test has been important for factory testing equipment and evaluating their performance in electrical systems. In practice, however, such equipment is subject to non-standard waveform (NSW) of high frequencies, which may not be covered by standard tests. To overcome this difficulty, the present article outlines a method that simulates NSW in laboratory tests. Based on multiresolution wavelet analysis, the method considers the correlation between amplitude and entropy in the decomposition levels between waveforms. To that end, changes are proposed to the following parameters of standard impulse tests: amplitude, cut-off instant, and front time. The results show that, mostly, the combination of a lightning impulse waveform (LIW) with impulse waves cut at different times, sufficiently represent the NSW. Only when the NSW's density falls predominantly in a frequency range above 3.125 MHz, will there be need for a complementary LIW with a steep front time. The method's application allows manufacturers and concessionaires to subject the equipment to conditions that properly represent the NSW effects, through lightning impulse tests carried out at the factory. [ABSTRACT FROM AUTHOR]

The paper presents the results of experimental registrations and numerical simulations of the transient overvoltages caused by single phase intermittent arc earth fault in 35 kV network with isolated neutral. Experimental laboratory investigation is performed in order to implement appropriate arc fault model for arcs with low and discontinuous current. Single phase to earth arc fault is created in field in 35 kV network. Numerical model of the system is created in EMTP-ATP software. Overvoltage waveshapes and overvoltage factors are calculated and compared to measured values. Good agreement between the measured and calculated results is achieved. [ABSTRACT FROM AUTHOR]

In this article, we discuss the relationship between subcycle and instantaneous power metrics in polyphase ac systems. While both approaches have very low computational cost, which makes them suitable for real-time control of industrial processes, the two-sample subcycle scheme offers several distinct advantages over the purely-instantaneous approach. In particular, we show that: a) the level of steady-state fluctuation of subcycle power metrics that use only two time-domain samples is significantly lower than that of purely-instantaneous metrics, and b) the subcycle scheme generates several additional power metrics, which can be used to detect onset of faults, and accurately determine their duration. We illustrate our points using both synthetic and (real-life) industrial examples. In addition, we examine the connection between the two-sample subcycle scheme and other near-instantaneous approaches, based on derivatives of currents and voltages. We again observe a significantly lower numerical sensitivity for the two-sample subcycle quantities. Furthermore, two-sample quantities have a unique feature that they can naturally be extended to more samples, with concomitant reduction in fluctuations, better accuracy and with only moderate increase in computational cost. We posit that the subcycle approach has promise in detection, control, and classification applications. [ABSTRACT FROM AUTHOR]

To ensure successful islanding of microgrids after a fault has occurred, the transient stability should be analyzed under a set of expected operating conditions during the design and operation of microgrids. Transient stability analysis is conventionally performed with time-domain analysis which is computationally expensive and does not quantify the stability margin. Energy-based methodologies can determine the stability margin, however existing methodologies require significant simplifications to be applied to the microgrid model. The energy-based stability analysis methodology proposed in this paper enables the analysis of high-dimension nonlinear microgrid systems and quantification of the stability margin within reasonable time. The performance of the methodology is validated by analyzing a case study microgrid and comparing the results to time-domain analysis and to a state-of-the-art methodology proposed in the literature. The results indicate that the proposed methodology has a significantly lower computational burden and similar accuracy compared to existing energy-based methodologies. The methodology is able to improve the probability of stable islanding of the case study microgrid from 74% up to 94% when only optimizing the design, and up to 100% when optimizing design and control actions. [ABSTRACT FROM AUTHOR]

DC cables are supposed to withstand a number of operations involving supply-voltage peak-value time variations, such as energization, switch off and polarity inversion. It is known that voltage-supply time variations cause electric field transients in cable insulation that can last for a long time before steady-state conditions are achieved, and during this time the electric field distribution is not only driven by electrical conductivity, as in steady state, but also by permittivity, as in AC. This paper shows that highly energetic degradation phenomena, that is, partial discharges, PD, can occur during voltage transients that a DC cable has to withstand during life. This results in a cumulative damage which can cause premature insulation breakdown, at times well shorter than those expected based on a cable design which is PD free under steady-state conditions. Quantification of the damage caused by PD, based on aging and residual life models, is proposed in the paper, and it is shown that damage can be significant enough to pose a threat for cable life when operation transient rate is e.g., a few per day, and that the faster the slew rate of the supply voltage variation, the highest the cumulative damage due to PD. [ABSTRACT FROM AUTHOR]

This paper presents the results of pilot tests performed on a real medium voltage (MV) underground network in Switzerland with the aim of assessing the performance of a fault location system. The deployed fault location platform is based on a very sensitive and precise acquisition system which is capable of capturing perturbations or events on a dedicated portion of a given MV network. Thanks to a post processing algorithm based on the tenets of time reversal theory, FasTR method, an accurate localization of relevant events can be worked. Due to the fact that each acquisition system shares a clock reference based on a GPS antenna, the localization accuracy is within tens of meters. To the best of the Authors knowledge, this is the first time that the FasTR-based fault location technique is validated through live tests. The pilot network is a three branch system part of live radial MV distribution feeder consisting of a total of 2.6 km long underground three-phase cables. The branched lines are composed of coaxial cables of different types. The tests involve solid- and resistive-type single-phase-to-ground fault occurrences triggered along one of the laterals when the network is operational. The obtained results demonstrated the capacity of an on-deck portable system to make an on-line accurate detection of transient faults in a complex network. [ABSTRACT FROM AUTHOR]

This study proposes an alternative method to calculate the transient responses of multi‐conductor overhead transmission lines based on ABCD representation, recursive convolutions and numerical method for rational approximation in the frequency‐dependent curves. In the classical universal line model, the characteristic admittance matrix Yc(ω) and propagation matrix H(ω) are represented by rational functions. In H(ω), previous and correct identification of the modal travelling times is required. However, these modal travelling times are estimated numerically, which do not offer good accuracy in some cases. This fact has a considerable effect on the rational representation of H(ω) itself and consequently on the transient responses. In the alternative method, a previous estimation of the modal travel times is unnecessary because when using the ABCD representation for each propagation mode, a direct relation exists between the currents and tensions of the receiving and sending ends. These relationships are fitted by smooth rational functions, and then, using recursive convolution methods, the authors obtain the explicit equations of the currents and voltages to calculate the transient responses. The results demonstrate that the alternative method is accurate when compared with the frequency‐domain solution of the transmission line transformed to the time domain using the numeric Laplace transform and with the Bergeron method. [ABSTRACT FROM AUTHOR]

Transmission faults caused by recent wildfires in California have induced the disconnection of utility-scale converters in photovoltaic (PV) power plants. Postmortem investigations reported that tripping commands were caused by phase-locked loops (PLLs) and dc-side dynamics, which are typically unmodeled in classical transient stability studies. Since existing simulation packages rely on simplified models that neglect these dynamics, they have a limited capability to predict converter behavior during faults. To address this shortcoming, we set forth a positive-sequence model for PV power plants that is derived from physics and controls first principles. As seen on utility-scale three-phase converters, the model includes PLLs, dc-side dynamics, and closed-loop controllers. Instances of the developed model are integrated into illustrative power systems containing conventional generators. Numerical simulations of the obtained multi-machine multi-converter power systems are assessed via a suitable set of stability and performance metrics. [ABSTRACT FROM AUTHOR]

The renewable energy source based generating technologies and flexible demand and storage devices exhibit significant temporal and spatial uncertainties in generating and loading profiles and introduce additional level of uncertainty in network operation. The dynamic behaviors of such a network can be affected and the stable operation may be compromised. This paper proposes a probabilistic analysis approach for the evaluation of the effect of uncertain parameters on power system voltage and angular stability. Load margin, the damping of critical eigenvalues and the transient stability index have been chosen as the relevant stability indices for voltage stability, small-disturbance stability, and transient stability analysis, respectively. The Morris screening sensitivity analysis method coupled with a multivariate Gaussian copula to account for parameter correlations is used for the priority ranking of uncertain parameters. The approach is illustrated on a number of case studies using modified IEEE 68-bus NETS-NYPS test system. The results obtained in this paper reveal that the critical parameters appear as groups if the input dataset is correlated, and, hence even a parameter (which may be uninfluential individually) can have a significant impact on system dynamic behavior due to its correlation with other influential parameters. [ABSTRACT FROM AUTHOR]

Transient processes at neutral bus of ultra-high value direct current (UHVDC) converter station received insufficient attention, because of the lower amplitude compare to poles. However due to the lower insulation level, electromagnetic transient processes at neutral bus may cause serious fault, and become an important issue that should be studied carefully in the design stage. A method to analyse the electromagnetic transient based on time-domain wide-band circuit simulation is proposed in this study. Models of major equipment are described. The electromagnetic transient of a ±800 kV converter station is calculated. The transient under different operation statuses is compared. Effects of suppression method such as arresters and capacitors are analysed. [ABSTRACT FROM AUTHOR]

Transient processes at neutral bus of ultra-high value direct current (UHVDC) converter station received insufficient attention, because of the lower amplitude compare to poles. However due to the lower insulation level, electromagnetic transient processes at neutral bus may cause serious fault, and become an important issue that should be studied carefully in the design stage. A method to analyse the electromagnetic transient based on time-domain wide-band circuit simulation is proposed in this study. Models of major equipment are described. The electromagnetic transient of a ±800 kV converter station is calculated. The transient under different operation statuses is compared. Effects of suppression method such as arresters and capacitors are analysed.

This study introduces an active distribution network with high penetration of inverter-based distributed generations (IBDGs) to improve the steady state, dynamic and transient performance of the distribution network. The size and location of the IBDGs, capacitor bank, on-load tap changers position and voltage regulator set points have been optimised to minimise the system losses, improve voltage profile and maximise the dynamic reactive power reserve. In addition to that, the adaptive master/slave roles are deployed in planning the active distribution network to achieve the best utilisation of each device based on its capability and response time in steady state, dynamic and transient operation. Indeed, the optimisation algorithm allows the IBDGs to operate in an inductive mode of operation during steady state resulted in maximising the dynamic reactive power reserve. Consequently, the IBDGs react with large dynamic margin in response to grid fault leading to enhanced voltage recovery and improved transient response. A comprehensive system optimisation and transient analysis are carried out to demonstrate the performance of the distribution network for enhancing the voltage profile, increasing the penetration level of renewable energy distributed generation, IBDGs, and improving the transient recovery in response to severe grid fault.

Battery energy storage system (BESS) services will be of great help when operating power systems at high renewable energy penetrations. This paper demonstrates the requirements for effective frequency and inertia services. Some system operators currently apply scalars to financially reward improved performance. This paper demonstrates a method of validating and improving these scalars by considering the delay time and ramp time of the BESS. The importance of the method used to measure the rate of change of frequency is discussed in the paper. While the rate of change of frequency services improves with reduced delivery times, limits are identified where further reductions produce a negligible impact. This demonstrates the tangible benefits of a rapid response, and that current technology could meet the criteria. A variety of BESS capacities are trialed, which demonstrate consistency in performance and the occurrence of diminishing returns [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) grid‐connected inverter is the core component of PV generation system; quickly and accurately obtaining the parameters of inverter controller has great significance in analysis of transient characteristics of PV generation system. Parameter identification relies on disturbance signals and measurements selection, and the trajectory sensitivities of inverter controller parameters are calculated with different system outputs as the measurements, the disturbance signals include AC three‐phase short‐circuit fault and DC voltage reference jump, accordingly, a two‐step identification method is proposed, the first step use a three‐phase fault to identify all voltage loop parameters and the proportional coefficient of current loop, and the second step consider a DC voltage reference jump disturbance to identify the integral coefficient of current loop and the setting inductance value. The adaptive differential evolution is taken as the identification algorithm, which adopts adaptive strategies for algorithm parameters in order to speed up the convergence and enhances the balance between the global search and local mining. The simulation analysis validates the effectiveness of this method. In addition, the impact of the inductance error on the identification is discussed. [ABSTRACT FROM AUTHOR]

An expression of the compensation torque is derived to reduce the difference between the fifth-order generator model and the seventh-order model. It is appended to the swing equation in the fifth-order model, with the voltage equations and the flux linkage equations unchanged. Based on the singular perturbation theory, the stator transients are approximated. The fast current components of three rotor windings are represented by equivalent d- and q-axis stator current increments that create the same stator flux linkage. The relationship between this torque and damping is clarified from a physical viewpoint. Simulations on two systems show that the compensation torque reduces the model difference. The proposed damping preserving model overcomes the difficulty in determining the damping torque coefficient and is applicable to online transient stability analysis. [ABSTRACT FROM PUBLISHER]

This letter presents a closed-form expression for ground return admittance for a system of underground cables. It is based on the approximation of the infinite integral found using a quasi-TEM (transverse electromagnetic) formulation of the electromagnetic field. The results indicate that the frequency behavior of the closed-form expression provides useful responses up to a few megahertz, thus being a suitable alternative to the numerically challenging infinite integrals. The agreement of the closed-form results and those obtained using the infinite integrals is very good regardless of the ground conductivity considered. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to modeling magnetic cores for high-frequency transient analyses in power system applications. A method is presented to obtain a frequency-dependent, nonlinear equivalent circuit model of magnetic cores, suitable for simulations of transients in high-frequency and high-current conditions. The model can be used in any Electromagnetic Transients Program (EMTP)-like simulation software for power system transient analyses and hardware design of transient mitigation solutions. The model has been developed based on the frequency characteristics of the complex impedance of a magnetic core, measured for different operating points on the magnetization curve. Based on the measured characteristics and on some basic material properties, a nonlinear equivalent model composed of a set of lumped elements was established. The presented method is generic; however, the results are presented for a magnetic core of nanocrystalline type and the model implementation is shown in EMTP simulation software. The exemplary model is dedicated for the frequency range $f=$ 1 kHz $\div $100 MHz, and for the current range $I=0\div 10$ kA. The model accuracy was validated with selected measurement results, and the accuracy of the method is thoroughly discussed. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis of possible transient overvoltages that can be generated during vacuum circuit-breaker (VCB) operation at the connection point of a photovoltaic powerplant. A typical switching event that is related to the VCB concerns energization and de-energization of the unloaded transformer. However, at the typical photovoltaic powerplant, the transformer is fed by an inverter equipped with LC (or LCL) filters that are necessary for limitation of harmonics and ripple in voltage and current. From the point of view of switching operations, the inductance and capacitance of the low-voltage (LV)-side connected filter affect the natural frequency of the transformer, which is reflected by different transient system response during VCB operation. In this paper, laboratory measurement of overvoltages generated during distribution transformer switching by means of VCBs is analyzed. The impact of the LC filter connected at the LV side on the overvoltages suppression was studied. Electromagnetic Transients Program–Alternative Transients Program simulations were conducted in order to verify the possibility of transients elimination by means of the additional series-connected RL choke at the transformer medium-voltage side. [ABSTRACT FROM PUBLISHER]

Historically, failures of distribution transformers due to transient overvoltage phenomena have led to the development of resistor–capacitor snubber circuits for the protection of the transformer and winding insulation. These transients are most often observed when dry-type transformers are close coupled to vacuum switching devices. Typically, snubber circuit design has been specific for the particular application, and complex engineering studies were required. However, the design of a snubber circuit itself may be performed without these detailed studies. If snubber studies are required, the procedures for system modeling and simulation are explained in a step-by-step manner. [ABSTRACT FROM AUTHOR]

The generalization of the probabilistic lightning limiting parameter (LLP) method for high-voltage substation lightning performance estimation due to the discharges into connected overhead lines (OHLs) is described. The method improvement is made only for the case of lightning strokes to the shield wire of OHL, causing back-flashover in front of the substation. The improved LLP method is illustrated at the insulation coordination study of the 400-kV line with long connecting cable with direct entry into the gas-insulated substation of the hydroelectric plant. The number of surge arrester sets and sensitivity analyses of the number of connected step-up transformers influence to the mean time between failures of the 400-kV transformer and equipment insulation are investigated. [ABSTRACT FROM AUTHOR]

This paper proposes a new passive antiislanding method for three-phase (3φ) distributed generation units (DGUs). The proposed method is based on extracting signatures from the instantaneous 3φ apparent powers determined at the point of common coupling (PCC). This new method is found on the fact that the instantaneous 3φ apparent powers have components continuously exchanged between loads and sources. The islanding condition creates transient high-frequency components in the instantaneous 3φ apparent powers.These high-frequency components contain signature information capable of identifying the islanding condition. These transient high-frequency components can be extracted using the wavelet packet transform (WPT), when applied to the direct and quadrature (d-q-axis) components of the instantaneous 3φ apparent powers. The d-q WPT-based antiislanding method is implemented for testing on a 3φ permanent magnet generator-based wind energy conversion system. Test results demonstrate an accurate, fast, and reliable response to the islanding condition occurring when supplying different load types at different levels of power delivery to the host grid. [ABSTRACT FROM AUTHOR]

The principal function of a protection relay is to protect the electric power system (EPS) from intolerable phenomena, such as fault produced by lightning, which can produce deleterious effects on EPS. Both impedance estimation protection and transient-based protection have become the most used protection relays for the lightning stroke classification. However, it is clear that currently these techniques suffer from drawbacks, which cannot correctly classify lightning stroke signals with speed and precision balanced, and cannot correctly distinguish the lightning stroke with and without a fault. Therefore, in order to avoid maloperation, protection schemes must be able to classifier lightning strokes correctly. This paper presents a novel methodology to provide effective lightning transmission-line protection. Principal component analysis is used to extract different patterns for lightning strokes due to shielding failure and backflashover. This work discloses that the transient voltages projected on the principal component coordinates clearly illustrate lightning strokes with and without a fault. In this manner, two pattern classifiers, based on spectral energy and artificial neural network, are useful for effectively classifying lightning stroke types. On the other hand, to evaluate the robustness of the proposed methodology, this research is also compared with the technique based on the wavelet transform, which has been the major tool used for the analysis of lightning strokes. Results show that the methodology proposed is fast and effective, which is not affected by operational conditions. Thus, this methodology can be applicable for high-speed protection systems. [ABSTRACT FROM AUTHOR]

Transformers connected at the medium-voltage level in cable grids, such as wind park collection grids and industrial grids, are exposed to the stress of very fast transients. These electric transients are mainly generated during breaker switching operations and the rise time of the transient voltage in such systems is much shorter compared to the rise times of transients generated in transmission systems at a high-voltage level. In this paper, the internal voltage stress is studied during very fast transients generated during transformer energization. Instead of using a breaker, the energizing tests are performed using a low-impedance pulse generator that can generate lightning impulse-shaped waveforms and voltage steps with rise times varying between 35 and 500 ns. Experiments show that during very fast transients with a 35-ns rise time and 1-p.u. magnitude, the interturn voltage exceeds the level obtained with a lightning impulse-shaped voltage waveform of 4.4 pu. Furthermore, during a specific switching scenario with delta-connected transformers, where the winding is excited from both ends, the same 1-p.u./35-ns voltage step generates an interturn voltage that exceeds the 1-p.u. level, which is more than 2.5 times higher voltage stress than during a lightning impulse test. [ABSTRACT FROM AUTHOR]

This paper analyzes long duration overvoltages due to backfeeding currents from the low-voltage network to the medium-voltage network through network protectors in heavily meshed underground distribution networks. Overvoltages above 3 p.u. may be developed as a result of a simultaneous occurrence of three phenomena: neutral displacement, Ferranti effect, and current chopping. A detailed model of a typical distribution network is utilized for the study. Time-domain simulations are performed using an Electromagnetic Transients Program-type program. The results demonstrate that overvoltages due to backfeeding last longer during peak load operating conditions, and the largest peak overvoltages occur at no load. [ABSTRACT FROM AUTHOR]

This paper describes two wide-area protection schemes for controlled islanding of the Uruguayan electrical power system. The first scheme relies only on local signals available for distance protection relays, whereas the second scheme is based both on local and remote synchrophasor measurements. The paper compares results in terms of load shedding amount necessary to maintain system integrity, with and without the proposed protection schemes. The investigation is based on comprehensive transient stability studies using actual dynamical models. Past occurrences that led the system to widespread blackouts have motivated the investigations presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents an orthogonal decomposition method, which is used to extract information from the current transient signals generated after a fault. The orthogonal basis functions are obtained under the condition of maximizing variability (variance) of input signals which, in turn, allows for finding an optimal representation of fault data. The results of the decomposition bring remarkable patterns described by transient signals into sight. Directionality, which appears as one of the foremost features, is highly related to the fault inception angle. This relation is then used to determine the fault direction just by comparing the steady-state prefault voltage angle and the angle of the vector resulting from the representation of the current signal in the space given by the first two orthogonal functions. Time windows shorter than 2 ms are used. Thus, the methodology can be applied in high-speed protection schemes. [ABSTRACT FROM PUBLISHER]

This is the second part of a two-paper series. The first paper presented the transient modeling methodology for various components of wind power plants (WPPs). This paper presents a general methodology for transient analysis of WPPs and discusses case studies which investigate some of the most important high-frequency interactions between different components of the WPP. The focus has been on switching transients, and lighting transients have been excluded. Transient case studies conducted on a typical WPP are presented which discuss the impact of fast system surges on the performance of the circuit breaker and impact of fast surges caused by the circuit breaker on the adjacent power components. These case studies investigate the opening and closing of the collector grid vacuum circuit breaker for loaded and unloaded conditions. Simulation results provide a close match with the field measurements conducted on a laboratory prototype of a typical WPP. Differences caused by modeling assumptions or insufficient accuracy of measurement devices are highlighted. To understand the most onerous overvoltages that can be experienced in the test system, a couple of additional simulation case studies are reported. These case studies discuss the interruption of inrush current with an unloaded transformer and interruption of a small inductive current following the transformer energization. [ABSTRACT FROM PUBLISHER]

This paper is the first of a series of publications detailing the development of an AI-based adaptive autoreclosing (AA) algorithm. In part 1, a detailed model of the Scottish 132 kV network has been constructed on a real-time digital simulator. The system model is discussed, including the network topology, line and source modeling, and the doubly fed induction generator-based wind farm model. An initial investigation on the penetration of harmonics from local wind farms is conducted using short circuit faults on two transmission lines in the network. This is necessary to ascertain to what extent wind farms may interfere with the AA scheme. Along with validating the model, the results suggest that penetration of harmonics is only significant on lines adjacent to the wind farms. [ABSTRACT FROM AUTHOR]

This is the first part of a two-paper series and presents the modeling methodology for all of the main components of a typical wind power plant for power system transient studies. The models developed are intended for investigation of the temporary overvoltages, switching overvoltages, and lightning overvoltages. The component models developed include the high-frequency models of the vacuum and SF6 circuit breakers, three core cables for the collector grid, and quad core cables for the wind turbine tower, turbine transformer, doubly fed asynchronous generator, and surge arrester. The models developed are wideband in nature and can be used for all studies, except the transformer model which requires two variations for the low–mid frequency range and mid–high frequency range. Detailed user-defined models developed for both vacuum and SF6 circuit breakers take account of the restrikes, reignitions, prestrikes, low-frequency high-current interruption, and high-frequency low-current interruption. The generator and transformer transient models include a representation of the various high-frequency capacitive couplings. The success criteria for each individual component model are discussed, and the model performance is validated against these criteria. [ABSTRACT FROM AUTHOR]

In view of frequent and severe overvoltage failures of 40.5-kV vacuum circuit breakers (CBs) while switching off the shunt reactors in the 35-kV distribution systems in China, a series of field tests was carried out to determine the mechanism of this kind of disruption. The transient process and phenomena were analyzed and summarized based on the overvoltage waveforms obtained from the field tests. The experimental results indicated that the probability of reignition is greater for a 40.5-kV CB than in a 12 kV one. The interphase overvoltage was especially critical. The causes of severe overvoltages were analyzed, and it was indicated that the difference of CBs, multireignitions by the interphase coupling, and the different application conditions were the main effect factors. In addition, some suggestions were given. [ABSTRACT FROM AUTHOR]

In this paper, the problem of calculating transient electromagnetic fields due to frequency-dependent multiconductor overhead transmission lines above lossy ground and underground cables buried in lossy soil is studied by decomposing the transmission line into a number of small segments. A modified finite-difference time-domain technique is applied to find the current passing through each segment of the excited transmission line. The contribution of each segment on the total electric and magnetic fields is calculated using two frequency-domain analytical techniques. The theoretical background and extent of validity of each technique are presented, and the results derived by applying each method are compared with those obtained using a commercial software package. The time-domain solution is then obtained using Fourier and Inverse Fourier transforms. Finally, the effects of different electrical and geometrical parameters, such as conductivity and relative permittivity of the ground and conductor sag of the transmission line, are studied. [ABSTRACT FROM AUTHOR]

This paper focuses on the education aspect of potential functions and presents the concept as a general approach for formulation of dynamic processes in different areas of engineering, e.g., dynamics of motion, electrical fields, power systems, control, and robotics. In power systems, the potential functions have been used in transient stability analysis in capacities such as 1) transient energy function and 2) the theoretical backbone of the equal-area criterion. The unified representation introduced in this paper is to help students (especially global learners by providing them with the big picture of the subject) discover similarities between different disciplines, which facilitates inter-application of the analytical methods. Recognizing the importance of digital computer based simulation techniques in education, the paper also introduces a software tool for assisting students/researchers in experimenting with different forms of potential functions and their application to a dynamic environment consisting of mobile robots, targets, and obstacles. [ABSTRACT FROM PUBLISHER]

Transient motor current signature analysis is a recently developed technique for motor diagnostics using speed transients. The whole speed range is used to create a unique stamp of each fault harmonic in the time-frequency plane. This greatly increases diagnostic reliability when compared with nontransient analysis, which is based on the detection of fault harmonics at a single speed. But this added functionality comes at a price: well-established signal analysis tools used in the permanent regime, mainly the Fourier transform, cannot be applied to the nonstationary currents of a speed transient. In this paper, a new method is proposed to fill this gap. By applying a polynomial-phase transform to the transient current, a new, stationary signal is generated. This signal contains information regarding the fault components along the different regimes covered by the transient, and can be analyzed using the Fourier transform. The polynomial-phase transform is used in radar, sonar, communications, and power systems fields, but this is the first time, to the best knowledge of the authors, that it has been applied to the diagnosis of induction motor faults. Experimental results obtained with two different commercial motors with broken bars are presented to validate the proposed method. [ABSTRACT FROM AUTHOR]

This paper investigates the applicability of decision tree, hidden Markov model, and probabilistic neural-network (PNN) classification techniques to distinguish the transients originating from the faults from those originating from normal switching events. Current waveforms due to different types of events, such as faults, load switching, and capacitor bank switching were generated using a high-voltage transmission system simulated in PSCAD/EMTDC simulation software. Simulated transients were used to train and test the classifiers offline. The wavelet energies calculated using three-phase currents were used as input features for the classifiers. The results of the study showed the potential for developing a highly reliable transient classification system using the PNN technique. An online classification model for PNN was fully implemented in PSCAD/EMTDC. This model was extensively tested under different scenarios. The effects of the fault impedance, signal noise, current-transformer saturation, and arcing faults were investigated. Finally, the operation of the classifier was verified using actual recorded waveforms obtained from a high-voltage transmission system. [ABSTRACT FROM AUTHOR]

The modeling of inrush currents that occur upon energization of a transformer is a challenge for Electromagnetic Transients Programs due to limitations in available transformer models and the ability to determine and specify initial flux. The estimation of transformer model parameters is also an issue. This paper presents a transformer model for low- and mid-frequency transient studies with a focus on the behavior in saturation and the estimation of residual fluxes. The comparison of the simulation results with analytical calculations and measurements proves the capability of the model to accurately represent energization and de-energization transients of a three-legged-core distribution transformer. A novel property is the ability of auto initialization after disconnection, made possible by the implementation of a hysteretic core model which properly simulates and remembers residual flux from the previous de-energization. Special attention is paid to parameter estimation. Detailed core and winding design data are not used as they are seldom available from the manufacturer. Sensitivity analysis is performed to verify the influence of each parameter on the inrush current envelope curve. It is observed that the parameter that most influences the current amplitude is the slope of the magnetization curve at extreme saturation. [ABSTRACT FROM PUBLISHER]

This paper presents a detailed model for simulation of a Superconducting Magnetic Energy Storage (SMES) system. SMES technology has the potential to bring real power storage characteristic to the utility transmission and distribution systems. The principle of SMES system operation is reviewed in this paper. To understand transient and dynamic performance of a SMES system, a detailed SMES system benchmark model is given with extensive simulation results. This system is demonstrated using an electromagnetic transient program—PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

This paper deals with parameter determination and is aimed at reviewing the procedures to be performed for deriving the mathematical representation data of the most important power components in electromagnetic transient simulations. It presents a conveniently arranged summary on the current status and practice in this field and emphasizes needed improvements for alleviating and augmenting the precision of modeling tasks in detailed transient analysis. [ABSTRACT FROM PUBLISHER]

The wavelet transform is beginning to be used widely in power engineering. Its effectiveness for analyzing transients with time localized information is now well known. Multiresolution analysis is especially suitable for feature enhancement of transients and thus makes it possible for power disturbances to be classified. In addition, the wavelet transform works well where the Fourier transform fails. A graphical insight is demonstrated in this letter. [ABSTRACT FROM PUBLISHER]