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This paper summarizes the work performed by the Task Force —within Performance Characteristic Subcommittee of IEEE PES Transformers Committee— to investigate potential revisions to IEEE Std C57.142-2010. Although the scope of this document does not implicitly exclude HV and EHV systems, the existing document primarily includes examples and information on distribution voltage systems. A Task Force was formed to investigate the need to include information about power system transient events on HV systems more explicitly in this existing document. The Task Force was charged with the following tasks:-Establish system voltages encompassed by C57-142-2010 Guide. -Gather field data, reports, and literature on HV and EHV failures related to substation transients and transformer interaction. -Solicit input from the other technical committees on this subject. -Review IEC and CIGRE work in this area. -Recommend course of action on revision of the present Guide. -Recommend high level changes to the Guide. -Prepare final paper for the Subcommittee. In the course of this work several failure scenarios were identified. These are categorized and the failures are described in this paper. The final recommendations to the Subcommittee are summarized and recommendations are presented for the course of action on the revision/addition of HV and EHV material to the current C57.142 Guide. [ABSTRACT FROM AUTHOR]

This paper presents frequency domain (FD) Norton-type equivalents of single- and three-phase photovoltaic (PV) generators, aimed at transient calculations. The proposed equivalents can be interfaced with a general frequency-dependent network and/or nonlinear loads and include voltage/current sources representing initial conditions aimed at partitioned-time transient simulation. The transient solution is performed via the numerical Laplace transform (NLT) in a sequential scheme by using time sub-windows with corresponding initial conditions and using reduced number of samples. The proposed approach overcomes the issue of computationally heavy simulations as in classical implementations of NLT. Two case studies involving PV generator and nonlinear load are presented to illustrate the performance of the proposed FD PV models. [ABSTRACT FROM AUTHOR]

Different from typical circuit breakers, breakers used to switch AC filters in convertor stations have to operate frequently according to the real-time operation mode and daily load changes. Therefore, the performance of filter breakers decreases very quickly, which leads to frequent accidents. Both preinsertion resistors and controlled switching devices can suppress switching transients. In this paper, a comparative analysis of whether a controlled switching device and preinsertion resistor should be adopted is carried out using PSCAD. The transient is calculated as the combined result of the switching angle and preinsertion resistor value, and the optimal configurations are proposed. After determining the resistor value and whether a controlled switching device should be included, the reference voltage of the arrester should be reevaluated. [ABSTRACT FROM AUTHOR]

The possibility of operating distributed generation (DG) in islanded mode brings several benefits but still faces some problems, especially related to the transition from a grid-connected to an islanded operating condition. When connected to the main grid, DG units operate in PQ mode. During this transition, their controls must be changed to regulate frequency and voltage. The delay for islanding detection, associated with abrupt changes in the control references, may result in large and detrimental transients. This paper proposes a new control structure for a distributed synchronous generator (DSG) to allow a smooth transition from the grid-connected to the islanded operation mode. The proposed control structure uses a compensation loop that was conceived based on the main ideas of the anti-windup bumpless transfer (AWBT) theory (although it is not, strictly speaking, an AWBT controller). The results show that the proposed structure ensures smaller excursions of the DSG variables during the transition and, therefore, the possibility of a successful formation of the islanded system is extended to a wider range of operating conditions. Moreover, with the proposed control, the success of this transition does not depend on the islanding detection time, which is the main contribution of this paper. [ABSTRACT FROM AUTHOR]

Aging of power system assets challenges utilities to maintain reliable service while minimizing their maintenance costs. Although malfunction of devices in the transmission or distribution networks can have catastrophic consequences, their failure is seldom unforeseen. Typically, the device aging occurs gradually over time until its health condition reaches a point of complete breakdown. The overall objective of this paper is to devise a non-invasive, online condition monitoring technique of circuit switchers for shunt capacitor banks. It aims to detect abnormal operation of these devices based on features derived from raw voltage and current waveforms, such that a predictive maintenance strategy may be employed before a complete failure occurs. The data analyzed in this paper are collected at a transmission capacitor bus, where the banks are equipped with pre-insertion impedance. Through a baseline range of values for selected parameters, the proposed technique is able to detect missing pre-insertion impedance during the capacitor energizing and failure of pre-insertion impedance switch out a few cycles after the energizing operation. [ABSTRACT FROM AUTHOR]

Identifying the location of partial discharges (PDs) and providing clear information on insulation vulnerabilities in power systems can help utility companies to improve their maintenance efficiency. This paper presents a PD monitoring and locating system for medium-voltage switchgears using a set of transient earth voltage (TEV) detectors. A time-of-flight methodology was used to identify the switchgear affected by PD among a row of switchgears. A time sharing access mechanism, which was implemented by multiple high-frequency surface mounting relays integrated into each TEV detector, was applied to automatically identify the site of PD and minimize the number of expensive high-speed acquisition cards. The operation principle and implementation of the modular system were formulated, and the efficiency of the proposed system in identifying the switchgear with PD among three 10 kV metal-clad switchgears was confirmed experimentally. [ABSTRACT FROM AUTHOR]

Transient voltage and current stresses are essential for the design and protection of multi-terminal DC (MTDC) transmission systems, especially under the short-term dynamics after severe grid faults. In this paper, we propose a discrete-time model for the modular multilevel converter based MTDC (MMC-MTDC) system considering the DC-side disturbances in the system. Based on the piecewise linear modeling, the state variables such as the transient voltage on the sub-module (SM), arm current, etc., can be calculated analytically for the critical short term (within 10 ms) after the severe DC fault while the system protection is yet to be activated. Parameter sensitivity analysis is also performed to give a better system design guideline. The estimation results are validated by detailed electromagnetic (EMT) circuit simulations and the scaled-down experimental laboratory prototype. [ABSTRACT FROM AUTHOR]

Fast and detailed calculations of harmonics, generated by three-phase uncontrolled rectifiers with finite dc smoothing, can be performed by using detailed analytical procedures (DAPs). Several DAPs are developed for continuous- and discontinuous-conduction modes (CCM and DCM) when balanced operation of the system is assumed. The authors of this paper have recently proposed a new DAP (model 1a) in which nonideal conditions, such as unbalances and even harmonic voltages on the ac side, are taken into account. However, only CCM is assumed in model 1a. The main objective of this paper is to overcome this limitation of model 1a so that a new DAP (model 1b) for DCM is presented, which is capable of considering unbalanced operation. Moreover, the boundary of the DCM is also estimated for model 1b under nonideal conditions. [ABSTRACT FROM PUBLISHER]

Switching of shunt capacitors can cause transient overvoltage. The voltages are traditionally evaluated with electromagnetic transients (EMT) simulation programs. It is a very time-consuming process mainly due to the need to convert a power-flow (or short-circuit) case to the EMT case. This paper proposes an idea to conduct capacitor switching studies directly inside commercial power-flow/short-circuit tools such as PSS/E, thus avoiding the data-conversion process. The idea is to conduct switching studies in the frequency domain. The frequency response of the study network is determined using the short-circuit solution engine of the host commercial software. This paper presents the theory, unique issues, and implementation details of the idea. The effectiveness of the proposed method is verified by comparing the results with those of the EMT simulations. [ABSTRACT FROM PUBLISHER]

A novel scheme is proposed to monitor the operation of capacitors scattered in MV distribution systems. It first codes each capacitor with a distinctive switching character by setting a unique combination of a three-phase switching order and time interval. As a result, the transient of the three-phase reactive power during capacitor switching will appear in a unique way. Then, the reactive power disturbances monitored in the substation are decoded to identify which capacitor is being switchedonandoff. A detailed decoding method is developed to realize this identification without being impacted by the switching interference of loads and other reactive power compensation devices. Moreover, the implementation of the proposed scheme in the field is elaborated, and the resultant three-phase voltage unbalance is analyzed in this paper. Compared with existing methods, this scheme only requires one power quality monitor located at the substation to monitor the operations (energizing or de-energizing) of downstream distribution capacitors without extra communication devices. The operation information is valuable for tackling power quality problems caused by capacitor switching and optimizing the distribution grid operation. [ABSTRACT FROM AUTHOR]

On transmission lines where switching surges are not mitigated with closing resistors and/or surge arresters, high-speed reclosing on a line with trapped charge will produce high overvoltages that have been measured above 3 p.u. Careful simulations of these switching events using available electromagnetic transient (EMT) programs consistently produce significantly higher voltages than the measurements. This indicates a phenomenon present on the line that acts to reduce the switching surge magnitudes but is not typically modeled. This paper aims to identify the required simulation practices in reproducing the field measured overvoltages in EMT simulations and investigates the sensitivity of results to modeling approaches and electrical parameters. Field measurements from a switching surge test of a 230-kV line without surge mitigation have been used for model comparisons. Variations in frequency-dependent line modeling, ground resistivity, skin effect, shunt conductance, parallel lines, and source-side detail have been tested in an unsuccessful attempt to decrease the difference between the field measurements and the higher simulation overvoltages. It is demonstrated that even though the pattern of the transient voltage waveforms can be reproduced very well using frequency-dependent line models, the magnitude of the maximum overvoltage is significantly overestimated unless the effect of corona is considered. Two types of corona models are tested, and both demonstrate that corona is the primary factor that allows the simulations to correctly reproduce high peak overvoltage measurements. [ABSTRACT FROM AUTHOR]

This paper proposes a modified bridge switch-type flux-coupling nonsuperconducting fault current limiter (BSFC-NSFCL) for suppressing the fault current and voltage sag. A flux-coupling reactor and a bidirectional bridge switch are combined to perform the functions of steady-state line current sharing and fault current suppression. The modified BSFC-NSFCL mainly utilizes the magnetic flux cancellation effect to make the limiter behave as a short circuit on the circuit during normal operation. Hence, there is almost no impact on the power system when the limiter is used. When a fault event occurs, the bridge switch turnsoffimmediately, and then, the magnetic flux cancellation effect disappears. Thus, the impedance of primary coil inserts into the circuit to restrict the fault current and voltage sag phenomena. Once the fault is removed, the bridge switch turnsonagain, and the BSFC-NSFCL recovers to the normal operation. The modified NSFCL is more cost-effective and easy to be implemented than the flux-coupling superconducting fault current limiter. Theoretical analysis for the BSFC-NSFCL has been fully developed and proven by MATLAB software. Finally, the analytical, simulated, and experimental results have been carried out to verify the feasibility and performance of the proposed BSFC-NSFCL. [ABSTRACT FROM AUTHOR]

Zero-missing is a phenomenon in shunt-compensated cable systems, in which the current through the line breaker does not cross the zero point for several cycles. This paper deals with a thorough investigation on countermeasures of the zero-missing phenomenon in transmission systems and determines the requirements, benefits, and risks of applying each method. The effectiveness of countermeasures is studied on a simulated cable project with different cable lengths in an actual grid model of the Dutch 380 kV transmission system. Results are analyzed based on three criteria related to the IEC standards and the Dutch grid code. In addition, the switching sequence of circuit breakers is specified to maximize the effectiveness of the countermeasures. A statistical switching analysis is performed for the insulation coordination study since the application of some countermeasures increases the probability of high transient switching overvoltages. Moreover, the closing variation threshold of circuit breakers is calculated as a function of the circuit impedance and the shunt compensation degree. [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]

This paper highlights an immediate need for renewable generation developers, manufacturers, utilities and industry standardization institutes to jointly address a challenge of capacitor switching transient immunity in inverter-based wind or solar farms. The need was identified from wide-area operation records which showed partial or full generation loss in coincidence with routine utility-owned capacitor switching. The lack of a clear industry guideline has caused confusion to all involved parties. This paper recommends all entities to address this challenge collaboratively through enhanced equipment specification, design, and test before a well-defined industry guideline becomes available. [ABSTRACT FROM PUBLISHER]

Active front-end (AFE) rectifiers are becoming widely used in medium-to-high-power adjustable speed drives (ASDs) to achieve regenerative operation and meet the energy efficiency and harmonic requirements. The typical control methods used with AFE rectifiers include voltage-oriented control (VOC), direct power control (DPC) and virtual-flux-based methods. This paper presents a dynamic average-value model (AVM) of the AFE rectifier system which is based on the voltage-source converter (VSC) operated with DPC. The developed AVM and the modeling methodology presented in this paper highlight the specifics of the hysteresis bang-bang type DPC that is used to track the real and reactive power references. The proposed AVM of the AFE rectifier system is demonstrated to significantly reduce the computing effort while accurately capturing the fast transient performance of the system. [ABSTRACT FROM AUTHOR]

This paper presents the work carried out by the IEEE Working Grou[ on field-measured overvoltages and their analysis for validating power system component models to be used in switching transients studies. The work uses measurement data obtained from field tests performed by Bonneville Power Administration in June 1995 where switching overvoltages were measured on one of its 230 kV lines. This paper includes a description of the switching tests and the main results derived from field measurements. Details of the switching procedures that were followed to calibrate component models used to match field-recorded waveforms can be found in the Part II paper. [ABSTRACT FROM AUTHOR]

The model of a modular multilevel converter (MMC) determines the extent of critical circuit information that electromagnetic transient simulations can reveal. In this paper, two MMC models are proposed for efficient real-time hardware-in-the-loop (HIL) emulation on the field-programmable-gate-arrays (FPGA). The nonlinear switch-based model employing the insulated-gate bipolar transistor (IGBT) dynamic curve-fitting model considers factors affecting its transient performance so that device-level behavior such as power loss and junction temperature can be reproduced accurately in the electro-magnetic-thermal simulation of a power converter for its design evaluation. Meanwhile, regarding the MMC submodule as a transmission line stub achieves faster computation speed and enables the formation of a hybrid arm to save FPGA hardware resources. As the large network that the MMC presents is burdensome for real-time execution with a small time-step, circuit simplification based on partitioning and merging is conducted. Hardware implementation of a three-terminal high-voltage direct-current system containing an MMC-based dc–dc converter is carried out and the efficacy of proposed models is validated by comparing HIL emulation results with the offline simulation tool PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Shunt power capacitors are essential to system operation and reliability as a critical reactive power source to increase system capacity, support voltage magnitude, improve power quality, and reduce reactive current flow. To mitigate capbank switching transients, the synchronous switching with preinsertion resistor technology is developed and used at an extra-high voltage transmission system. In this paper, the coupling relationship between several key factors that contribute to switching transients is studied. Optimization solutions are developed to improve the switching process. Field operations with an updated setting are compared with original setting records to prove the correctness of the study. [ABSTRACT FROM PUBLISHER]

In this paper, the commutation and switching mechanisms between the operating low-voltage (LV) switch and parallel external branches are presented. Experiments for the limitation of electric arc energy during inductive current interruption were performed for three scenarios: 1) for standalone operated switch (base case), 2) for passive method of arc energy limitation (widely applied RC branch connected in parallel to operated switch), and 3) active method of electric arc energy limitation (current commutation into the external semiconductor branch controlled by the microprocessor system). A typical three-phase electromechanical LV switch with double arc quenching chamber was selected as the tested object. The following parameters were investigated: electric arc resistance, electric arc power, electric arc energy, as well as power and energy generated at the external branch connected in parallel to the operating switch. Measurements were performed for current interruption in a single-phase circuit. In addition, observations of a burning electric arc in the quenching arc chamber were registered by an ultraspeed camera (for two cases: base case and hybrid switching). [ABSTRACT FROM AUTHOR]

During the switching of disconnectors in gas-insulated switchgear (GIS), repeated strikes occur in the contact gap and lead to very fast transient overvoltage (VFTO). Severe VFTO may bring damage to transformers and other equipment. The switching speed of the disconnector is one of the important factors which influences VFTO. There are still different opinions on this factor. Very little quantitative study was done before this paper. In this paper, the whole repeated strike process associated with the switching operation of the disconnector was simulated and analyzed. The polarity and the probability characteristics of breakdown voltage were analyzed. The impacts of the switching speed of the disconnector on VFTO were studied by statistical methods. Comparisons were made between simulated and measured results. The simulation result shows that within a certain range of speed, disconnectors with a lower switching speed generate lower trapped charge voltage after opening operation and lower VFTO magnitude during the opening and closing operations. [ABSTRACT FROM AUTHOR]

Understanding mechanisms of switching transient overvoltages in modern electrical power systems is a necessity to ensure a proper design of power plants and switchgear and the required level of reliable and secure system operation. High fidelity plant modelling and accurate transient analysis is a prerequisite for understanding the mechanisms of how overvoltages are created and whether or not the voltage withstand capabilities of system components will be exceeded. This research is focused on switching overvoltages typical for an offshore wind farm power collection grid configuration that comprises vacuum circuit breakers (VCBs), cables and transformers. An in-depth understanding of the prestrike effects in VCBs is a prerequisite for studying switching transient overvoltages. In this paper, the impact of VCB parameters (e.g., stray capacitance and withstand voltage ability)and cable length on the transformer terminal voltage during closing operation was studied. A wind farm power collection system was modelled in ATP-EMTP environment. To validate the results obtained through computer simulation, field measurements from an actual system were used. [ABSTRACT FROM PUBLISHER]

The hybrid direct-current circuit breaker (DCCB) consists of a mechanical switch (MS) branch and a static DCCB branch. Once a short-circuit fault is detected, the current should commutate from the MS branch to the static DCCB branch first. In this paper, two current commutation measures have been investigated. A hybrid DCCB prototype with current commutated by the arc voltage of the SF${}_{6}$ switch is developed. Based on the prototype, current commutation and interruption tests have been carried out. The results show the current of 3.4 kA can be commutated within 2.4 ms, and be interrupted within 6 ms. Then, a current commutation drive circuit (CCDC) is proposed as the other current commutation measure. Equivalent current commutation tests have been carried out. The results show with the CCDC, both positive current and negative current can be commutated within tens of microseconds. Using a CCDC in series with a mechanical vacuum switch as the MS branch, a 44 kV/3.4 kA hybrid DCCB prototype is developed. Based on the prototype, current commutation and interruption tests are carried out. According to the results, the current of 3.4 kA can be commutated within 100 $\mu $s, and be interrupted within 2 ms. [ABSTRACT FROM PUBLISHER]

This paper investigates the conditions for transformer winding resonances with an emphasis on oscillatory excitation voltages originating from various switching events in the power grids. A section of the Eastern Regional Power Grid in India has been simulated in this paper by using the Alternative Transient Program for the purpose of defining high-frequency transient voltages which may occur during various switching events. The investigation reveals that such oscillatory voltages could excite natural frequencies of a 400/220/132-kV power transformer, which closely matches the terminal excitation frequencies. Short time Fourier transform (STFT) has been used to analyze the frequency contents of the oscillatory terminal excitation as well as the voltage response of the windings. The results of the STFT confirmed the presence of resonant frequency in the oscillatory terminal voltage and in the 400-kV main and tap changer windings of the transformer. It has been demonstrated that the voltage stresses in the windings under certain critical switching operations can exceed the stresses developed under the standard 1.2/50-\mus lightning impulse at the transformer's basic insulation level voltage. The reduction in winding voltage stresses under resonance is possible by deploying some remedial measures involving winding design modifications which have also been suggested in this paper. [ABSTRACT FROM PUBLISHER]

In this paper, a new concept for analyzing the dielectric severity supported along transformer windings when a transformer is submitted to a nonstandardized transient voltage waveform induced by switching operation of a vacuum circuit breaker (VCB) is examined. There are two new factors considered for evaluating the severity supported by the insulation windings in factory and in service. One factor is based on the methodology suggested by the authors called time-domain severity factor and another one is the frequency-domain severity factor. Both methodologies are here applied to two case studies in order to show and compare their capabilities and sensibilities to detect the risk of dielectric failures. The analyzed case studies, performed as practical applications, consist of: 1) a power transformer submitted to damped oscillatory waves at the resonant frequency and 2) a power system consisting of a power transformer connected to a VCB. [ABSTRACT FROM AUTHOR]

This paper summarizes the important factors that affect statistical switching transients studies during transmission-line energization. These factors include the number of repetitions to ensure the statistical characteristic of the study, the variation range of the mean closing time of the circuit-breaker contacts, the model used for the representation of the transmission line, and the influence of transposition. In addition, a statistical analysis of mitigation methods to reduce overvoltages during transmission-line energization maneuver is presented, specifically the use of surge arresters, of controlled switching, and of a preinsertion resistor. The shunt compensation degree is considered as an independent parameter. Digital simulations were performed with PSCAD. [ABSTRACT FROM AUTHOR]

This paper discusses the channel gain characteristics of a two-conductor power-line communication system under a given transient analytical model. The channel frequency responses are derived with different transmission-line lengths and terminal loads. Compared with previous works on power-line communication, the transient model can more accurately describe the variation of the channel frequency responses, especially when transients occur on the transmission line. Simulation results show higher accuracy is achieved compared with the results under the traditional lumped-circuit \pi model. [ABSTRACT FROM AUTHOR]

This paper presents an average-value model of a line-commutated converter-based HVDC system using dynamic phasors. The model represents the low-frequency dynamics of the converter and its ac and dc systems, and has lower computational requirements than a conventional electromagnetic-transient (EMT) switching model. The developed dynamic-phasor model is verified against an EMT model of the CIGRE HVDC Benchmark. Simulation results confirm the validity and accuracy of the average value model in predicting the low-frequency dynamics of the ac- and dc-side quantities. Merits and applicability limitations of the average model are highlighted. [ABSTRACT FROM AUTHOR]

In this paper, a new noncommunication-based scheme is presented for the protection of three-terminal transmission lines. Using this scheme, simultaneous operation of circuit breakers (CBs) at all terminals is provided for all internal faults. This scheme can discriminate between external and internal faults based on initiated transients by faults, considering the high-stop filtering property of busbars through modeling their stray capacitances and employing a newly defined mathematical morphology (MM) filter to analyze the captured transients. Moreover, the transients generated by lightning or switching are identified and prohibited to enter the algorithm. The presented scheme has been applied on one of three-terminal lines in Iran's Transmission Grid. The effects of fault resistance, fault inception angle, (internal) fault location, and fault type on the performance of the proposed scheme are evaluated, where the high dependability, accuracy, and speed are verified. [ABSTRACT FROM AUTHOR]

Electric power distribution systems of many commercial and industrial sites often employ variable frequency drives and other loads that internally utilize dc. Such loads are often based on front-end line-commutated rectifiers. The detailed switch-level models of such rectifier systems can be readily implemented using a number of widely available digital programs and transient simulation tools, including the Electromagnetic Transient (EMT)-based programs and Matlab/Simulink. To improve the simulation efficiency for the system-level transient studies with a large number of such subsystems, the so-called dynamic average models have been utilized. This paper presents the average-value modeling methodologies for the conventional three-phase (six-pulse) front-end rectifier loads. We demonstrate the system operation and the dynamic performance of the developed average models in discontinuous and continuous modes, as well as under balanced and unbalanced operation. [ABSTRACT FROM PUBLISHER]

Capacitor switching transients are harmful to the capacitor and the switching device. For reducing these transient phenomena, this paper proposes a symmetrical structure transient limiter (SSTL). The proposed SSTL can automatically provide high impedance at the instant of capacitor energization, and, thus, the switching transients can be effectively suppressed. After the restriction, owing to the compensation of all power losses caused by the diodes and reactors, the SSTL acts as a short circuit during the steady state and, thus, has no effect in the circuit. As a result, the capacitor voltage and current waveforms will not be distorted. Moreover, due to the freewheeling effect in the SSTL, no transient overvoltage will appear across the switch contacts at the instant of capacitor de-energization even though the reactors are inserted into the circuit. Theoretical analyses of the proposed SSTL for the energization state, steady state, and de-energization state have been completely carried out. Also, the selections of the related components are depicted. Finally, the experimental results obtained using different methods of capacitor switching verify the feasibility and performance of the proposed SSTL. [ABSTRACT FROM AUTHOR]

Numerical overcurrent relays used to protect capacitor banks can better discriminate between faults and switching inrush compared to their electromechanical counterparts. However, there is still scope and use for faster and reliable operation. This paper describes the implementation of a filter based on mathematical morphology that creates distinct signatures for capacitor inrush and faults. These signatures are then used to propose a rule-based classification method that can be easily implemented in microprocessor-based relays. Extensive simulations are carried out to test the classification method using waveforms generated from PSCAD/EMTDC simulation of a standardized test system. The classification method is shown to be very reliable, general, and significantly faster than methods currently used or previously proposed. [ABSTRACT FROM AUTHOR]

In this paper, a new method is proposed that can be used to discriminate faults from switching transients. The method is primarily intended for use in systems where fast fault detection and fast fault clearing before the first peak of the fault current are required. An industrial system, in which high short-circuit power is desired but in which high short-circuit currents cannot be tolerated is an example of such a system. A phase-locked loop (PLL) is used to perform the discrimination. Computer simulations have been performed and it has been demonstrated that the output of the PLL is completely different for a fault compared to a switching transient. This difference can be used for discrimination between a fault and a switching transient. [ABSTRACT FROM AUTHOR]

This paper describes two new approaches for the determination of the direction of switched capacitor banks as well as an efficient technique for estimating the distance of switched capacitors from the monitoring location in distribution systems. At first, two new indices based on branch voltage and current changes immediately after the capacitor switching instant are proposed for determining the direction of switched capacitor banks. The wavelet transform is used to detect the exact instant of switching. Then, a new technique based on linear circuit theory is proposed to estimate the distance of the switched capacitor bank from the monitoring location using capacitor switching transient data. Simulation results show that the error of the estimated distance is acceptable. A combination of the approaches for direction finding and the technique for distance estimation provide a novel method for determining the location of switched capacitor banks in real distribution systems. The method is valid in all normal, back-to-back, and abnormal switching of wye- and delta-configured capacitor banks. Also, the size of the capacitor bank has no effect on method accuracy. The efficacy of the proposed method is validated by using the IEEE 13-bus and 34-bus distribution systems. [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]