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In this research, a new approach to safeguard against Loss of Field (LOF) in a synchronous generator, in the presence of a series compensation capacitor, is introduced. LOF can lead to detrimental effects on both the generator and the power network. Impedance-based negative and positive offset MHO relays are employed for the rapid recognition of LOE occurrences in the network. However, issues arise when a series compensation capacitor is integrated into the system, causing maloperation of the protection relays. The introduction of the series compensation capacitor alters the total impedance value, necessitating adjustments to the relay settings for precise functionality. The variation in the overall impedance of the system leads to the underreaching and overreaching of a relay. The study provides detailed explanations and comparisons of both types of MHO relays, along with their respective settings. A simulation is applied in DIGSILENT to assess the effect of series compensation capacitors on offset MHO (negative and positive) relay LOF protection. Ultimately, the article concludes by summarizing the pros and cons of both relay schemes. [ABSTRACT FROM AUTHOR]

Microgrids are integral to power grids; they enhance grid reliability by integrating distributed generators (DGs) to fulfill the local load requirements, lowering energy generation costs, and providing eco‐friendly energy resources to reduce carbon emissions. Despite their benefits, new capabilities also introduce protection‐related complexities, including bidirectional power flow, varying fault currents, false tripping, relay reach limitations, coordination issues, and the requirement for proper grounding. This article offers a detailed review of protection issues in AC, DC, and hybrid AC–DC microgrids, investigating existing approaches to address these issues. Furthermore, the constraints and hurdles associated with these approaches and the future trends and intelligent approaches required to develop a reliable and efficient protection strategy are also identified in this article. This article is categorized under:Energy and Power Systems > MicrogridsEnergy and Power Systems > Distributed Generation [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a topologically protected electroacoustic transistor. We construct a reconfigurable phononic analog of the quantum valley-Hall insulator composed of electrically shunted piezoelectric disks bonded to a patterned plate forming a monolithic structure. The device can be dynamically reconfigured to host one or more topological interface states via breaking inversion symmetry through selective powering of shunt circuits. Above a threshold, the amplitude of wave energy at a chosen location in one topological interface creates a second interface by dynamically switching power between two groups of shunts using relays. This enables the flow of wave energy between two locations in the reconfigured interface analogous to the voltage-controlled electron flow in a field effect transistor. The amplitude of wave energy in the second interface is used for bit abstraction to implement acoustic logic. We illustrate the various states of the transistor and experimentally demonstrate wave-based switching. The proposed electroacoustic transistor is envisioned to find applications in wave-based devices and edge computing in extreme environments and inspire novel technologies leveraging acoustic logic. [ABSTRACT FROM AUTHOR]

In this work, a mathematical model of a three-phase nonlinear transformer is suggested. The model enables simulating the transformer operation with allowance for its nonlinearity and covers needs of the relay protection. Our model has been developed on the basis of a mathematical model with phase coordinates, where differential equations are composed by the Kirchhoff's phase-voltage law. Based on this model, we first compose a mathematical model for simulating steady-state operation modes of a transformer, taking into account the asymmetry and nonlinearity of its ferromagnetic core. In this model, the initial values of inductances and mutual inductances of loops are determined from the main phase inductance calculated by the experimentally found no-load current, and their current values are determined from the currents in windings and the magnetic fluxes in legs of the transformer core. The magnetic fluxes are calculated by the nodal-pair method. This improved mathematical model is verified through a comparison between the calculated harmonic components of the phase currents and the experimental results. The harmonic components are calculated with the use of Fourier expansion of the calculated phase currents. Their experimental values are determined with a spectrum analyzer. The calculated and experimental harmonic components of the currents of phase A during no-load and rated-load operation of the transformer are tabulated. The comparison of these results shows that the mathematical model of a three-phase transformer we suggest makes it possible to simulate currents in transformer windings under steady-state operation modes with accuracy acceptable for relay protection. [ABSTRACT FROM AUTHOR]

This article provides an overview of modern numerical relays used in the protection of power transformers. It discusses various protection schemes and their corresponding relays, highlighting the importance of proper protection for the safe and efficient operation of electrical power systems. The article covers differential protection, overcurrent and earth fault protection, standby earth fault protection, and restricted earth fault protection. It also addresses factors such as CT ratios matching, magnetizing inrush current, tap changer imbalance current, and zero sequence currents in designing effective protection schemes. The document further delves into the mathematical formulation and calculation of differential protection, as well as the use of high-impedance REF schemes and standby earth fault protection. It concludes by emphasizing the significance of efficient power system protection schemes in minimizing faults and ensuring stable power systems. [Extracted from the article]

This study aims to develop a weight-adjustment scheme for a double exponentially weighted moving average (dEWMA) controller using deep reinforcement learning (DRL) techniques. Under the run-to-run control framework, the weight adjustment of the dEWMA is formulated as a Markovian decision process in which the candidate weights are viewed as the DRL agent's decision action. Accordingly, a composite control strategy integrating DRL and dEWMA is proposed. Specifically, a well-trained DRL agent serves as an auxiliary controller that produces the preferred weights of the dEWMA. The optimized dEWMA serves as a master controller to provide a suitable recipe for the manufacturing process. Furthermore, two classical deterministic policy-gradient algorithms are leveraged for automatic weight tuning. The simulation results show that the proposed scheme outperforms existing RtR controllers in terms of disturbance rejection and target tracking. The proposed scheme has significant practical application prospects in smart semiconductor manufacturing. [ABSTRACT FROM AUTHOR]

This paper proposes a comprehensive 26-bus microgrid (MG) test system designed to validate or propose new protection coordination schemes. The proposed MG test system comprises various components facilitating the simulation of diverse configurations and operating modes. It also presents a predefined overcurrent protection scheme which is validated with and without Distributed Generation (DG), offering detailed specifications and settings for the test network. The MG test system outlined in this paper incorporates multiple DG sources in different buses, multiple voltage levels, and two operating modes (with and without DG). Additionally, the overcurrent protection scheme considers multiple functions and devices simultaneously. The detailed features of the proposed protection coordination scheme enable the simulation of various fault types and contingencies. The paper also presents specific details of the MG test system under different single-phase and three-phase faults, reporting bus voltages in nodes, transformer and line loadability, short-circuit currents, and operating times. The MG test system is meant to serve as a valuable tool for researchers to conduct comparative studies and develop new strategies regarding the operation and planning of MGs. [ABSTRACT FROM AUTHOR]

Modern fault ride-through (FRT) standards in many countries require distributed generators to remain connected for a specified period during the fault by providing reactive current, to support voltage and prevent a massive renewable outage. As a result, short-circuit current is not constant, but it varies depending on the current and disconnection order of distributed generators (DGs). This time-varying short-circuit current complicates the estimation of the time it will take for an overcurrent relay or fuse to trip. The existing short-circuit calculation algorithms usually assume that the fault current is constant throughout the whole period of fault. This assumption may result in incorrect conclusions regarding the tripping time of protective devices in networks with high renewable penetration. This paper incorporates modern FRT standards into the fault analysis by considering the influence of fault current variations on the protective devices (relays, fuses), significantly increasing the accuracy of the estimated tripping time. Simulations carried out in a 13-bus and the IEEE 8500-node network indicate that the traditional short-circuit calculation approaches may miscalculate the tripping time of protective devices, with deviations up to 80 s, when applied to networks complying with modern FRT standards. [ABSTRACT FROM AUTHOR]

Exponentially weighted moving average (EWMA) and Shewhart control charts are commonly utilized to detect the small to moderate and large shifts in the process mean, respectively. This article introduces a novel Bayesian AEWMA control chart that employs various loss functions (LFs), including square error loss function (SELF) and LINEX loss function (LLF). The control chart incorporates an informative prior for posterior and posterior predictive distributions. Additionally, the control chart utilizes various paired ranked set sampling (PRSS) schemes to improve its accuracy and effectiveness. The average run length (ARL) and standard deviation of run length (SDRL) are used to evaluate the performance of the suggested control chart. Monte Carlo simulations are conducted to compare the performance of the proposed approach to other control charts. The results show that the proposed method outperforms in identifying out-of-control signals, particularly under PRSS schemes compared to simple random sampling (SRS). The proposed CCs effectiveness was validated using a real-life semiconductor manufacturing application, utilizing different PRSS schemes. The performance of the Bayesian AEWMA CC was evaluated, demonstrating its superiority in detecting out-of-control signs compared to existing CCs. This study introduces an innovative method incorporating various LFs and PRSS schemes, providing an enhanced and efficient approach for identifying shifts in the process mean. [ABSTRACT FROM AUTHOR]

With the rapid development of wireless power transmission (WPT) technology and the demand for a wide range of applications, the common two-coil system is becoming increasingly mature. However, the monotonous structure of two-coil systems limits their development. By incorporating relay coils, the distance of power transmission, efficiency, and electromagnetic field (EMF) leakage can be effectively improved. In this paper, the three-coil system is analyzed, and the relay coil parameters are optimized by an evolutionary algorithm. After that, based on the coil optimization, the compensation capacitance of the relay coil is analyzed and an analytical formula of the compensation capacitance of the optimized relay coil is obtained. The results show that the parameter-optimized system reduces current by 86.9%, increases efficiency by 10%, and suppresses EMF leakage by 18 dB. Meanwhile, the capacitor optimization further improves the transmission efficiency of the system. [ABSTRACT FROM AUTHOR]

SABRE (Signal Amplification By Reversible Exchange) has become a widely used method for hyper-polarizing nuclear spins, thereby enhancing their Nuclear Magnetic Resonance (NMR) signals by orders of magnitude. In SABRE experiments, the non-equilibrium spin order is transferred from parahydrogen to a substrate in a transient organometallic complex. The applicability of SABRE is expanded by the methodology of SABRE-relay in which polarization can be relayed to a second substrate either by direct chemical exchange of hyperpolarized nuclei or by polarization transfer between two substrates in a second organometallic complex. To understand the mechanism of the polarization transfer and study the transfer efficiency, we propose a theoretical approach to SABRE-relay, which can treat both spin dynamics and chemical kinetics as well as the interplay between them. The approach is based on a set of equations for the spin density matrices of the spin systems involved (i.e., SABRE substrates and complexes), which can be solved numerically. Using this method, we perform a detailed study of polarization formation and analyze in detail the dependence of the attainable polarization level on various chemical kinetic and spin dynamic parameters. We foresee the applications of the present approach for optimizing SABRE-relay experiments with the ultimate goal of achieving maximal NMR signal enhancements for substrates of interest. [ABSTRACT FROM AUTHOR]

This paper presents a 250 kHz bidirectional battery charger circuit using a GaN HEMT. The charger is subjected to a high-/low-side constant voltage at 200 V/20 V. The charger circuit is a hybrid of the LLC and flyback circuit topologies. Both the power output analysis and efficiency control of this circuit are simplified when the magnetization current is minimized using the low-resistance GaN HEMT. The switching frequency is controlled to match the series resonance in a way that is analogous to conventional LLC circuit controls, while the duty ratio that determines the power output and the dead time, which determines the zero voltage switching, is controlled in an analogous manner to the flyback circuit control. The charging and discharging modes were altered by applying a double-throw relay that changes the transformer turn ratio, which is different from conventional LLC designs using the switching frequency adjustment. A nominal turn ratio with Np = 35 and Ns = 3.5 for a 200 V/20 V converter can only produce an internal series resonance with no current flowing in any charging direction. The proposed circuit using a transformer with multiple windings (Np = 35, Ns,F = 4, and Ns,R = 3) was fabricated to deliver 125 W output power from the power grid battery to the vehicle battery in the forward (charging) mode and 90 W in the reverse (discharging) mode. The conversion efficiency was calculated to be as high as 97% in the forward mode and 95% in the reverse mode. The high conversion efficiency is due to the characteristics of the GaN HEMT, including low resistive and switching losses. The equations derived in this paper associate these losses with the series resonant frequency and power conversion rate, which highlight the advantages of using a GaN HEMT in this CLLC design. [ABSTRACT FROM AUTHOR]

Much attention has been paid to the optimized protection of microgrids (MGs) and active distribution networks (ADNs). However, the literature shows a research gap in proposing a hybrid scheme, utilizing the voltage-based and overcurrent-based relays, while the voltage relay characteristics are smartly selected. This study aims to address such a research gap. This article presents an optimal hybrid protection coordination method for ADNs and MGs. Considering that any system fault is associated with a voltage drop, a new protection method is formulated from voltage analysis under fault conditions. The proposed method is independent of the type, size, and location of distributed generation (DG) units, as well as the operation of the distribution system connected to the grid. This method uses only the local voltage to determine the relay's tripping time and is a low-cost protection method, in addition to the directional overcurrent relays (DOCRs). Optimizing the voltage-based relay characteristics is one of the most important contributions, which leads to improving the protection system speed and its selectivity concerns. The effectiveness of the proposed method has been verified by several simulation tests performed on the medium voltage (MV) distribution system under different fault conditions and DG size and location. The simulation results show that the protection method has appropriate speed, and the protection settings could be independent of the operation modes/topologies and the locations of faults. The comparative results illustrate the advantages of the proposed hybrid protective scheme. [ABSTRACT FROM AUTHOR]

As the demand for energy is increasing exponentially due to the growing population, it needs to be properly monitored and controlled. On the other hand, nowadays, we are facing a lack of technical knowledge in monitoring and controlling energy consumption. Over the past several years, there has been a rapid increase in both the utilization of energy loads and the use of various forms of power electronic equipment. As a result, contamination of the electricity supply is becoming an increasingly critical issue. The purpose of this study is to provide the design and implementation of a virtual instrument tool that uses LabVIEW for real-time online monitoring of power quality. Readings are traditionally extracted manually from devices of this kind. A smart energy meter can help overcome these problems, allowing people to take readings from any location globally, thanks to technology that makes use of the Internet of Things. In addition to the amount of energy being consumed, the smart energy meter will provide information on other characteristics such as voltage, current, power, and frequency. This enables us to achieve the ideal level of load control. For load management, LabVIEW is the tool of choice. Users can tailor their pricing plans to their financial situations using this technology. The PZEM-004T sensor is utilized for measuring parameters, and the Node MCU is the component that transmits the data to the server. Users can exert influence over the system through both mobile applications and web applications. This system also helps detect surge conditions of appliances and can break them using a relay. [ABSTRACT FROM AUTHOR]

Copyright of Automotive Digest is the property of Automotive Digest Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrical utility substations are wired with intelligent electronic devices (IEDs), such as protective relays, power meters, and communication switches. Substation engineers commission these IEDs to assess the appropriate measurements for monitoring, control, power system protection, and communication applications. Like real electrical utility substations, complex electrical substation grid testbeds (ESGTs) need to be assessed for measuring current and voltage signals in monitoring, power system protection, control (synchro check), and communication applications that are limited by small-measurement percentage errors. In the process of setting an ESGT with real-time simulators and IEDs in the loop, protective relays, power meters, and communication devices must be commissioned before running experiments. In this study, an ESGT with IEDs and distributed ledger technology was developed. The ESGT with a real-time simulator and IEDs in the loop was satisfactorily assessed and commissioned. The commissioning and problem-solving tasks of the testbed are described to define a method with flowcharts to assess possible troubleshooting in ESGTs. This method was based on comparing the simulations versus IED measurements for the phase current and voltage magnitudes, three-phase phasor diagrams, breaker states, protective relay times with selectivity coordination at electrical faults, communication data points, and time-stamp sources. [ABSTRACT FROM AUTHOR]

The need for power is increasing every day in the world. In order to meet the power demand, numerous power plants are being built. Adding new power plants on available transmission lines leads to overloading problem. As a solution to this, series capacitors are used in transmission lines. Series capacitors increase the active power transfer capability. Also, it has a positive effect on system stability and voltage profile. However, on the contrary to the positive effects of series capacitor, it has some negative effects on distance relays which protect the transmission lines. In case of a short-circuit fault, the distance relays, depending on the location where the fault occurred and the capacitor effect might not see the fault that occurs on the line it protects or might see the fault on another line. In this study, a management relay was developed in order to prevent maloperations of distance relays due to capacitor effect. The developed relay identifies the faulted line in case of a short-circuit fault and sends tripping/blocking signal to the distance relays that might malfunction. At the end of the study, the verification of the management relay is carried out with various scenarios, and it is seen that the relay functions effectively during short-circuit simulations. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fault detection continues to be a relevant and ongoing topic in multiterminal High Voltage Direct Current (MT-HVDC) grid protection. In MT-HVDC grids, however, high DC-fault currents result from a failure of a complex protective threshold in traditional protection schemes, making Voltage Source Converter (VSC) vulnerable to such potent transient currents. In this innovative single-ended DC protection scheme, multiple time window segments are used to consider the effects of the transient period across limiting inductors at each end of the link. Multiple segments of 0–0.8, 0.8–1.5, and 1.5–3.0 ms reduce relay failure and improve the sensitivity to high fault impedance while requiring minimal computational effort. It employs feature extraction tools such as Stationary Wavelet Transform and Random Search (RS)-based Artificial Neural Networks (ANNs) for detecting transmission line faults within DC networks. Its goal is to improve the accuracy and reliability of protective relays as a result of various fault events. Simulations showed that the proposed algorithms could effectively identify any input data segment and detect DC transmission faults up to 500 ohms. Accuracy for the first segment is 100% for fault impedance up to 200 ohms, whereas the second and third segments show 100% accuracy for high impedance faults up to 400 ohms. In addition, they maintain 100% stability even under external disturbances. [ABSTRACT FROM AUTHOR]

Conventional distribution networks have evolved into active distribution networks due to the high penetration of distributed energy resources. These new networks have several protection issues; some are related to the high fault and load current variations due to the various operating conditions. This situation is faced by adaptive protection development, as proposed in this study, where variations among active distribution network operating conditions are considered to estimate the adaptive pickup current. This is used to estimate the overcurrent relay's time dial setting, avoiding miscoordination. The proposed protection approach uses fast calculations and local measurements; consequently, a low computational burden is required to update the adaptive relay parameters for each operating condition without using communication infrastructure. The obtained results in the IEEE 34-nodes test feeder demonstrate the advantages of the proposed approach, accomplishing the coordinating time interval for phase and ground faults. These results show a high performance of primary and backup protection at different operating conditions of the proposed test system compared to the performance of the conventional protection approach. The proposed approach's high performance, low computational burden, and communicationless characteristics make it suitable for immediate real-field implementation. [ABSTRACT FROM AUTHOR]

The fault of the tie line between the photovoltaic (PV) station and the grid is a serious fault for the PV station. It will cause the PV station to operate into an unintentional island. The uncontrolled Island voltage and frequency will inevitably lead to the disconnection of the inverter in the station. This situation will bring great losses to PV operators and impact to the power grid. In order to deal with the tie line fault, this paper analyzes the operation characteristics of PV stations in case of tie line fault firstly. Then a tie line fault ride‐through method based on cooperative strategy of small capacity energy storage (ES), relay protection and PV inverters is proposed. The islanding switching control strategies of PV and ES are designed respectively. The cooperative strategy of protection, PV controller and ES controller is formulated as well. The real‐time digital simulator (RTDS) closed‐loop test platform including line protection device, ES controller and PV controller is built to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In modern power systems, the installation of a shunt capacitor bank is one of the cheapest and most widely used methods for improving the voltage profile. One shunt capacitor bank is composed of mass capacitor units and have ground, ungrounded, delta, wye connections that make configuration of capacitor banks is various. In the case of long-term operation, the failure of a single capacitor unit of a capacitor bank is likely to cause uneven voltage, which will lead to the breakdown and burning of the whole group, resulting in huge losses. The relay protection device can detect the simultaneous voltage and current of the capacitor. By utilizing these data from the relay, the abnormal state of the shunt capacitor banks at the initial stage of the fault can be found through monitoring the slight change in capacitance. Timely and early maintenance and repair would avoid capacitor bank faults and potentially greater economic losses. Capacitor banks have different connection modes. For ungrounded wye-connected capacitor banks with an unknown neutral point voltage, the capacitance parameters of each branch cannot be calculated. A parameter symmetry based on the calculation method for capacitor parameters is proposed. For long-term monitoring and observation of the capacitor capacitance value, the fault state and abnormal state of the capacitor are identified based on statistical methods. The simulation established by PSCAD verified that a relay protection device can realized an effective monitoring of the early abnormal state of the capacitor bank. [ABSTRACT FROM AUTHOR]

Active distribution networks integrate distributed energy resources into traditional power grids, mainly guided by the intention of addressing climate change concerns. However, integrating distributed energy resources has introduced several challenges for traditional overcurrent protection, including variations in pre-fault and fault current magnitudes and bidirectional power flows. These challenges make it difficult to guarantee reliable protection of active networks in grid-connected and islanded modes. In response to the challenges posed by these new networks, this paper presents an adaptive protection approach that leverages local measurements and data clustering to identify the network operating states accurately. In this approach, reference relay coordination is obtained by considering all distributed energy resources that supply the network during the grid-connected operating state, providing optimal settings for each relay. Next, based on the current operating state, the adaptive relay pickup current is estimated based on local measurements, which is used to adjust the time dial setting of each directional overcurrent relay. The proposed approach is contrasted with the conventional relay, considering several operating states, including DER switching, grid-connected, and islanded modes, for single-phase and three-phase faults and several fault resistances, using the IEEE 34-node test feeder. The results demonstrate the proposal's high performance in avoiding relay miscoordination. Finally, the proposed approach is also simple and suitable for immediate implementation in existing digital relays, as it has a low computation burden and does not require communication systems. • Proposes an approach for communication-less adaptive protection to update the relay settings adequately. • The approach detects the ADN OS originated by the connection/disconnection of DERs, starting from a reference case and using clustering and classification approaches. • The relay parameters are online estimated from the local pre-fault current and voltage measurements. • The proposed solution does not use a centralised computation scheme. • The protection approach uses straightforward computation, resulting in a low computational burden. [ABSTRACT FROM AUTHOR]

This article shows practical rules which were developed for the adjustment of Numerical Overcurrent Functions (NOCF) of microprocessor-based protective relays in order to avoid their maloperation due to Transformer Magnetizing Inrush Currents (TMIC). The TMIC waveforms are decaying and nonsinusoidal, and their effects are different on instantaneous, definite-time, or inverse-time NOCF; thus, specific rules are necessary for each type of NOCF. Experimental methods, specifically developed to perform tests of NOCF with TMIC, were applied to four commercial relays from different manufacturers. As each relay has different types of curves, a total of 26 inverse-time curves were included in the set of tests. In practice, the specific behavior of a relay cannot be assumed as known during the coordination of protection; therefore, the rules are based on the worst cases of results (i.e., in order to avoid the incorrect trip of any of the analyzed relays). The input data for the developed rules are the estimated cumulative RMS values of TMIC, assumed as known since there is a long tradition of their estimation. The estimated cumulative RMS values of TMIC, at different time intervals, should be divided by the numerical factors which were specifically proposed for each type of NOCF (to obtain suitable limits to avoid their inappropriate operation). In order to illustrate the application of the proposed rules, the solutions to two cases related to a simple example are shown at the end of this article. [ABSTRACT FROM AUTHOR]

Power metering, relay protection, lightning current measurement, fault current measurement, and traveling current measurement in the field of power systems, as well as high-current measurement in the field of pulse power, require safe, high-accuracy, large-range, and wide-frequency-band current sensors. Current transformers and Rogowski coils can basically meet the requirements of measurement accuracy and range, but they are not good enough to meet the two requirements of safety and broad frequency bands. In this study, a non-contact broad-band current sensor is designed, which is based on the improvement of the traditional Rogowski coil to realize non-contact measurement of current. The equivalent circuit of the sensor was established, and the output characteristics of the sensor were calculated from the theoretical level as well as the design parameters were optimized. The sensor samples were made, and the usability of the sensor and the correctness of the theoretical calculation model were verified by 50 Hz AC current and 1.6 ÎĽs/3.4 ÎĽs impulse current tests. The non-contact current sensor designed in this paper has the advantages of simple structure, low cost, safety and reliability, large range, and wide operating band, and can be widely used for AC current or impulse current measurement in power systems and pulsed power fields. [ABSTRACT FROM AUTHOR]

The power demand in textile industries is fulfilled by the utility grid and diesel generators. However, due to the low reliability and high cost of power from these resources, the industries now install solar-powered microgrids on their premises. The issues such as bidirectional power flow and changing fault current level are obvious with PV installations. The protection system in traditional textile grids employs overcurrent relays, but these relays are not suitable for PV integrated systems. Furthermore, in industrial microgrids sensitivity and selectivity are two essential requirements, which are not available in overcurrent relays. To overcome these challenges, this paper proposes a comprehensive distance protection strategy for PV-powered textile microgrids. The proposed scheme utilizes a backward and forward configuration of distance relays, tested for different types of faults and variable fault currents in different scenarios. It is observed that the designed strategy gives the best performance for any kind of fault, and there is no overlapping of protection zones during the operation. The paper also presents the distance relay setting criteria to provide the full-proof protection of textile microgrids. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Protective relays in electric power grids recognize the types of electrical faults in a few seconds. The most common detection method to detect the types of electrical faults is based on measuring the angle between the zero and negative sequence currents. However, it is not completely accurate because the phase-to-phase-ground and phase-to-ground electrical faults could have the same detection conditions. Therefore, engineers need to plot the events after an electrical fault to observe the nature of the incidents in detail. In this study, the phase-to-ground fault apparent (PGFA) admittance method with phase/ground boundaries identified the types of electrical faults located in distribution power lines and feeders. This method was based on measuring the PGFA admittance magnitudes for the faulted and nonfaulted phases, resulting in greater than zero and near zero, respectively. The PGFA admittance algorithm was built with MATLAB/Simulink software and tested with signature library and grid simulation events. The PGFA method with phase/ground boundaries was evaluated with the confusion matrix. The measured and predicted values matched in more than 90% of the tests, and the PGFA admittance method with phase/ground boundaries presented an accuracy of 94.3% and a precision of 100%. [ABSTRACT FROM AUTHOR]

This paper presents a novel hardware-in-the-loop (HIL) approach as used to investigate the impact of the reduction in inertia on the Great Britain (GB) electrical power system with regard to rate of change of frequency (RoCoF) settings for Loss-of-Mains (LoM) protection. Furthermore, the research as presented in this paper updates, enhances, and validates a reduced model of the Great Britain transmission system, as originally developed in DIgSILENT PowerFactory by the National Grid Electricity System Operator. The enhanced model has been developed for integrated use with the OPAL-RT real-time HIL simulation toolkit and is validated against phasor measurement unit (PMU) data from actual disturbance events using novel automated interfacing between both integrated simulation platforms, PowerFactory from DIgSILENT and ePHASORSIM from OPAL-RT. The corresponding simulations show that the updated reduced model is capable of capturing the dynamic behaviour of the GB transmission system, including both local and inter-area oscillations, with satisfactory accuracy. Finally, the paper presents HIL study results with the reduced model to investigate the influence of decreasing system inertia on the response of LoM protection relays. The studies show that decreasing system inertia may have a significant impact on LoM relays using RoCoF detection, particularly relays using the legacy G59 setting of 0.125 Hz/s. Initial studies have also demonstrated the potential for a previously unrecognised interaction between system oscillations and the 500 ms operating delay, as specified in G59 and G99 Engineering Recommendations. Consequently, faster local oscillations (>1 Hz) reset the relay and decrease the sensitivity, whereas slower inter-area oscillations (<1 Hz) appear to cause the relay to overestimate the average RoCoF. [ABSTRACT FROM AUTHOR]

Multiple breaks are favorable for arc extinguishment of relays switching heavy load. However, the existed asynchronous mechanical separation of contact pairs and associated unbalanced arcing behavior limit the electrical lifetime to some extent. In this article, the typical contact voltage and contact current waveforms of double breaks within power relays are presented. Based on the variations in bounce energy, contact resistance, and arc energy as a function of switching cycles, the effect of contact gap on the electrical lifetime of power relays is analyzed explicitly. Furthermore, the failure process of power relays with two bridges is characterized by the recorded breaking time difference of bridges. The observed significant asynchronous breaking phenomena in the end of electrical lifetime experiments attribute to the contact welding failure of power relays. [ABSTRACT FROM AUTHOR]

Summary: In this study, two novel distributed space‐time block coding based cooperative generalized spatial modulation networks are proposed, and their theoretical analyses are derived. The first network is a three‐node cooperative system, consisting of a source (S), a relay (R), and a destination (D). In this design, S sends a GSM symbol to R and D in the broadcast phase. In the relay phase, if R decodes the received signal correctly, it encodes the orthogonal counterpart of the GSM symbol, and sends it to D. If R has a decoding error, it sends a failure to S, and S realizes the R's transmission. The second network is designed with two relays. Here, S sends the GSM symbol to R1, R2, and D in the broadcast phase. In the relay phase, if both relays decode the incoming signal correctly, R1 regenerates the GSM symbol coming from S, and R2 encodes the orthogonal version of it. After encoding, both send them to D in a successive manner. If any or both relays fail, S sends the symbol of R2 in the relay phase. Theoretical and asymptotic analyses as well as simulation results are provided for both networks. It is seen that derived analytical expressions match with the simulation curves. Moreover, since we use the GSM in the proposed methods, their data rates are higher for the same number of transmit antennas. Even for the same spectral efficiency, they provide a significant diversity gain and a better error performance than the existing methods. [ABSTRACT FROM AUTHOR]

The article presents a study on the polydiketoenamines (PDK) depolymerization via acid-catalyzed hydrolysis. It describes how mixed-polymer and mixed-material recycling are enabled by chemospecific PDK deconstruction, and molecular engineering of triketone monomers yields from PDK resins. It discusses the application of circular design PDK resins with sustainable manufacturing.

Transformation of the distribution network, integrated with Distributed Energy Resources (DER), into a MicroGrid (MG) is an attractive approach in improving the reliability and resilience of the network. In this paper, by introducing the important and necessary aspects of the MG formation problem, an effective methodology for transformation of a distribution network into the MG is proposed. In the presented methodology, optimal allocation of DERs within MG is obtained by optimization of power losses and voltage stabilization along feeders. Moreover, the short-circuit constraints are also taken into account simultaneously while allocating DERs. The reason for the latter is that the integration of DERs alters the amplitude and direction of the short circuit current, which can cause the overall fault current to exceed the designed fault-level capability of the circuit breakers. This issue may put CBs at risk of failure and degrading MG resilience. In this regard, resilience-oriented evaluation of the MG formation, from the perspective of considering short circuit level and coordination of OCRs, is also performed. Another advantage of short circuit studies is devising complete and economic overcurrent-based protection plan for MG in both operating modes (grid-connected and islanded). It should be pointed out that adopting an appropriate control routine is a key element in the MG formation. Hence, a control strategy, based on Energy Storage System (ESS) utilization, is suggested in this paper. This feature, which is another contribution of the paper, will guarantee seamless transition to island mode and stable operation of the MG. The proposed formulation of the MG formation is solved using a modified multi-objective PSO and the Pareto-optimal set is obtained. However, since the optimal solutions are nondominated to each other, a Fuzzy Satisfaction Method (FSM) is utilized to find the optimal solution among the Pareto-set. Utilization of the proposed methodology leads to the successful transformation of the distribution network into a MG, which not only considers the load flow constraints but also preserves the optimal coordination of the protective relays and resilience of the MG. In addition, seamless transition and stable operation of the MG in island mode is achieved. [ABSTRACT FROM AUTHOR]

This paper analyses the formation mechanism of the transmission distortion of electronic voltage transformer, and points out that the integrator will magnify the transient transfer error and superimpose the dynamic additional component on the output signal, which may cause the transfer distortion of voltage signal in serious cases. To restrict the electronic transformer transient variable error effect on distance relay, a distance relay method using instantaneous value after equal transfer processes is proposed. It directly uses output differential signals of the capacitor voltage divider and Rogowski coil. The capacitor voltage divider and Rogowski coil are decomposed into several typical variable link in series. The virtual digital transfer link, which is constructed by the digital filter, is used to compensate for the difference parts of the transfer link, so that the voltage and current signals pass through the same transfer link. It can mitigate the influence of voltage and current signal transfer difference on the calculation accuracy of distance relay. The simulation results show that the proposed distance relay method has fast operation speed and is less affected by abnormal voltage and current signal transfer, and its performance is better than existing distance relay methods. [ABSTRACT FROM AUTHOR]

In this paper, a cooperative orthogonal frequency division multiplexing system with multiple untrusted amplify‐and‐forward relays is considered. Since there exists no direct link between source and user because of the shadowing effect, a positive system secrecy rate cannot be obtained. Addressing this issue, a cooperative user‐aided jamming technique to improve the secrecy performance is employed. With the aim of maximising the system secrecy rate, a joint resource allocation problem of power allocation, relay assignment and subcarrier pairing is formulated. By using the signal‐to‐noise ratio based approach and the Lagrange dual method, this nonconvex problem is solved efficiently. To reduce the calculation complexity, a suboptimal algorithm, which decouples the power allocation with the relay assignment and subcarrier pairing is further proposed. Numerical results are presented to demonstrate the advantage of the two proposed algorithms and the impact of relays' location and number of subcarriers on the secrecy performance. Moreover, it is shown that the secrecy performance of the proposed scheme is decreased with respect to the number of untrusted relays. [ABSTRACT FROM AUTHOR]

Several schemes are available in the literature to protect transmission lines (TLs). These schemes are either transmission network-specific or require modifications in case of any changes in the TL structure. FACTS devices are often incorporated in TLs to increase power transfer and improve controllability and stability. There have been many developments in the field of protection of FACTS-TL. However, the search for a scheme that can successfully adapt to the system changes and can be applied to almost any transmission network to identify the line faults is still ongoing. With advancements in communication technology and global positioning system-enabled time-tagged data, the voltage and current data can be synchronized and, therefore, the pilot relaying may become more viable. Utilizing these technological advances, a digital pilot relaying scheme, for the protection of TLs with or without series compensation and any type of short-circuit fault under any loading condition, is proposed in this paper. [ABSTRACT FROM AUTHOR]

• A new protection methodology based on current-voltage characteristics. • Optimal OCR coordination under smart inverter control strategies. • Comparative analysis through the influence of diverse control techniques. The integration of distributed generation (DG) based on inverters into power systems has increased significantly, necessitating a thorough understanding of its impact on fault analysis and the performance of distribution networks' protection mechanisms. This study addresses this issue by examining how various inverter management modes influence protective relay systems within IEEE 9-bus redial and mesh networks, CIGRE and IEEE 33-bus networks featuring Photovoltaic (PV) farms and Battery Energy Storage Systems (BESS), by IEEE1547–2018 and German grid code standards. By analyzing grid-connected scenarios with five distinct PV control modes, the research introduces a novel protection methodology termed the Photovoltaic Overcurrent Relay (PVOCR). This method introduces a current-voltage characteristic to optimally coordinate Overcurrent Relays (OCRs), aiming to reduce their operational time and eliminate mis-coordination events. The proposed PVOCR is evaluated against standard inverse time, SOCR, and modern adaptive voltage, VOCR, relay schemes across various fault scenarios differing in type and location. Furthermore, the PVOCR scheme effectively operates across all PV inverter modes without experiencing miscoordination events, whereas the SOCR and VOCR schemes encountered such issues during the operation of Control 4. These results underscore the potential utility of the PVOCR methodology in enhancing the reliability and efficiency of protection systems in inverter-based DG networks. [ABSTRACT FROM AUTHOR]

Detection of high impedance faults (HIFs) in low and medium voltage distribution networks has always been challenging due to their lower magnitude and random current characteristics. Conventional overcurrent relays are ineffective in detecting HIFs because of the low fault current associated with them. Consequently, existing HIF detection schemes predominantly rely on features extracted from the frequency, time–frequency, or symmetrical component domains. However, these methods are often limited in their effectiveness under specific conditions, such as particular voltage levels, conductor types, or environmental factors, due to the multifaceted nature of HIF currents, which depend upon a variety of factors such as type of materials, voltage level, wetness of the surface, shape of the conductor, and even the weather conditions. On the other hand, due to the intrinsic presence of arcing in the HIF phenomenon, the resultant fault current consistently assumes a random character, and this inherent randomness can be leveraged as a potential feature for fault detection. This paper proposes a new HIF detection method by analyzing the randomness or unpredictability of the fault current signals. The Detrended fluctuation analysis (DFA) is innovatively employed to assess the unpredictability of the lower frequency component of the zero-sequence current by examining its instantaneous amplitude envelope. The accuracy of the proposed approach is verified with extensive simulation data of fault events under diverse operative conditions. The security of the proposed scheme is also verified under several no-fault transient circumstances, such as capacitor switching and load perturbation. The computational efficiency of the method has been verified through the process-in-loop (PIL) simulation using cost-effective hardware. • Novel application of modified detrended fluctuation analysis to the HIF detection. • The proposed protection method uses of randomness in the zero-sequence current. • Randomness of lower frequency current signal is calculated through DFA and DEMD. • A new HIF simulation model is also presented in this work. • Computational efficiency of the method is tested through process-in-loop simulation. [ABSTRACT FROM AUTHOR]

• The impact of distributed capacitance is eliminated due to the capacitance current can be ignored at the low frequency. • The low-frequency components only exist between the BES and the fault point, and will not flow to the opposite grid. • The least square algorithm is employed to solve the overdetermined equations, improving the accuracy of calculation. The fault current of the photovoltaic (PV)/battery energy storage (BES) hybrid power generation system contains harmonic components, which might cause the maloperation of the distance relay. The time-domain distance protection has attracted more attention recently. However, the distributed capacitance of long transmission lines negatively affects the performance of time-domain distance protection, which hinders its application. To solve this problem, this paper proposes an improved time-domain distance protection based on fault active control. By leveraging the fault active control capability of the BES inverter, a specific low-frequency characteristic voltage is modulated through the phase-locked loop (PLL). By injecting the low-frequency characteristic voltage, the influence of line distributed capacitance can be ignored. Thus, the accuracy of time-domain distance protection based on the equivalent R-L model of transmission lines is guaranteed, which is the first advantage of injecting the low-frequency characteristic voltage. The other advantage is the low-frequency components only exist between the BES and the fault point, and will not flow to the grid on the opposite side of the line. The accuracy of time-domain distance protection has been further improved. In Addition, the faulty line's derivative equations for different fault types are deduced based on fault active control. Finally, the least square algorithm is used to calculate fault distance. The proposed scheme's feasibility and effectiveness are verified through simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for electrical power necessitates the continuous enhancement of power system reliability and stability. In this context, determining the maximum loadability limit of different nodes of power network maintaining stability of the system is a critical aspect of power system planning and operation. This study presents a mathematical model-based novel approach that calculates the maximum loadability limit of multiple nodes in a power network while considering voltage security constraints. The proposed method integrates advanced load flow analysis techniques with voltage security assessments to identify critical loading of different points of the network at which voltage stability limits are reached at weakest nodes. Considering voltage security constraints, the algorithm offers a more accurate representation of the power system's operational capabilities. Through comprehensive simulations on various test systems (33-bus RDS and 118-bus RDS), the effectiveness and robustness of the proposed load flow algorithm are demonstrated. The results illustrate its ability to determine the maximum loadability limit across multiple nodes while ensuring voltage stability, thus aiding power system operators and planners to take informed decisions to enhance the reliability and resilience of modern electrical grids. This research contributes to the ongoing efforts to optimize power system operation, ultimately fostering a more sustainable and secure energy future. [ABSTRACT FROM AUTHOR]

This work considers quantize–forward (QF) relay channels with $M$ -ary phase shift keying at the source and $q$ -bit uniform phase quantization at the relay. A cooperative linear combining (CLC) detection which linearly combines the received signals at the destination is proposed in the QF relay channel by deriving an equivalent signal-to-noise ratio for the source-relay-destination link. Furthermore, the proposed detection is simplified by approximating $Q$ function in two directions: small $q$ and large $q$. The CLC detection and its simplified version are also extended to multi-relay channels. Simulation results verify that the CLC and simplified CLC detections achieve reasonable performance with less complexity than the maximum-likelihood detection. It demonstrates that applying $(\log _{2} M+2)$ -bit uniform phase quantization at the relay and the simplified CLC detection at the destination can be an appropriate choice in terms of performance, complexity, and memory. [ABSTRACT FROM AUTHOR]

In this paper, the maximization of the achievable information rate is proposed for the multi-relay amplify-and-forward cooperative simultaneous wireless information and power transfer communication systems, where the nonlinear characteristic of the energy harvesting (EH) circuits is taken into account for the receivers of the relay nodes. The time switching (TS) and power splitting (PS) schemes are considered for the EH receivers and the achievable rate maximization problems are formulated as convex and non-convex optimization problems, respectively. The optimal TS and PS ratios for the relay nodes along with the maximum achievable rates for the system are obtained, respectively, by solving the optimal problems with efficient algorithms. The asymptotic maximum achievable rates at low and high input signal-to-noise ratios (SNRs) for both the PS and TS schemes are also analyzed. It is demonstrated that the PS scheme is more susceptible to the variation of the relays' location and the channel parameters than TS scheme, whereas the TS scheme is more susceptible to the mismatch of the resource allocation than PS scheme. Specifically, compared to the linear EH model, the nonlinear EH model achieves significant performance gain for the TS scheme, whereas inconspicuous performance improvement is achieved for the PS scheme. [ABSTRACT FROM AUTHOR]

The electrical market scenario has changed drastically in the last decade. In the presence of increased competition and less tolerant players, more sophisticated methods are required to balance the diversity and differential pricing while promoting cooperation among the agents. In the monopolistic environment, the central utility incurred the total cost of the transmission expansion. But as the current scenario demands, there are several public and private market players. The growth will benefit all the players, so the total cost in transmission expansion can be divided among players as per the benefit received by each player. In this paper, a transmission system expansion planning problem in the cooperative environment using cooperative game theory (CGT) is framed for the power sector, in which various players can cooperate in a coordinated manner to maximize their benefit but ultimately strengthen the power grid. In this paper, we have modeled, analyzed and compared various cost allocation methods of cooperative game theory specifically for the cost allocation in a transmission expansion planning problem. The present work focuses on forming coalitions to calculate the costs using the forward search and frog leap optimization approach. We have compared the SCRB, BSV, ENSC, and ACA methods for transmission expansion planning while attempting to satisfy the axioms. We have also observed that bilateral Shapely value efficiently allocated the costs due to its decentralized approach and the sequencing of coalition formations to achieve the best possible cost allocations. [ABSTRACT FROM AUTHOR]

Battery energy storage system (BESS) plays an important role in the grid-scale application due to its fast response and flexible adjustment. Energy loss and inconsistency of the battery will degrade the operating efficiency of BESS in the process of power allocation. BESS usually consists of many energy storage units, which are made up of parallel battery clusters with a cell-pack-cluster hierarchical structure. This article presents a power allocation strategy based on cluster switching to relieve the stated problem in two levels. Cluster switching is identified as a new control approach to eliminating the imbalanced state of charge (SOC) in the cluster level. In the unit level, an optimization model is constructed for power allocation, where the objective function consists of two aspects: minimizing battery energy loss and maximizing SOC consistency. Finally, the effectiveness of the power allocation strategy for BESS in peak shaving and frequency regulation is validated by simulation and scaled-down experiment. The results prove that the power allocation strategy can reduce the battery energy loss and prevent from overcharging/overdischarging to extend the battery lifetime. [ABSTRACT FROM AUTHOR]

Purpose. Earthing relays are utilized very commonly in open-pit mines for disconnecting the failure part of 6 kV electric system from earthing incident. Much previous research is mentioned on searching either an optimal method for improving the effect of relays or improvements of reducing the overvoltage caused by grounding separately. The paper presents a new approach to not only improving the relays’ sensitivity but also to limiting the over-voltage. A new algorithm is also proposed to control automatic connection of an additional resistor in order to achieve both above mentioned purposes of 6 kV earthing relay. Methodology. The propose controlling diagram is implemented on PROTEUS to get 3U0 signals. The main components appeared when 6 kV feeders were faulted to earth. Afterward, the detecting signal is utilized as input for simulation diagram in MATLAB to get and analyze the wave forms of responded zero sequence voltage. Findings. The paper presents a new algorithm utilizing a resistor that is auto-controlled to auto-connect the open-triangle coil of 6 kV measurement transformer at the moment of earth fault. This automatic connection aims to increase the relay sensitivity as well as reduce the overvoltage. The finding results are sensitivity factors of relay and voltage magnitudes of healthy phases, which will be compared with corresponding values when there is no connection of resistor to prove the effectiveness of the method. Originality. A useful method is proposed for increasing the earthing current to enhance the sensitivity of earthing relay. Practical value. The proposed control diagram could be used to design a device aiming to improve the safety of 6 kV grid in open pit mines when earth faults occur. [ABSTRACT FROM AUTHOR]

With the integration of high proportional photovoltaics (PVs) into distribution networks, the superposition of uncertain output power of PVs and stochastic load demand fluctuations have posed a serious challenge to voltage stability. In this paper, a multitimescale decomposition-coordination-based voltage control method is proposed under the cloud-edge cooperative architecture. The distribution network is firstly decomposed into several subnetworks. In each subnetwork, the edge computing device is equipped to realize the distributed control and provide external computing resources for the cloud center. Then, a multitimescale control scheme containing the interval dispatch stage and the real-time time-window stage is proposed. In the interval dispatch stage, a cloud-edge collaborative calculation strategy considering balanced resource allocation is well designed to obtain the global optimal power flows and the corresponding reference operating points of the voltage control equipment. Meanwhile, in the real-time time-window stage, a consensus-based voltage correction mechanism under the optimal power flow boundary constraints is designed to avoid the voltage violations caused by unexcepted power fluctuations deviating from the representative scenarios. Simulation results with the improved 33-bus and IEEE 123-bus systems have demonstrated the effectiveness of our proposed method. [ABSTRACT FROM AUTHOR]