南水北调中线工程35kV输电线路继电保护整定研究

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Currently, power plants operating on renewable energy sources (RES) are increasingly being integrated into the Unified Energy System of Russia. At the same time, the majority of electricity generated by RES power plants is produced by wind (WPP) and solar (SPP) power plants.

Aiming at the problems of low information fusion and slow real-time protection of traditional transmission line relay protection methods, a fault-tolerant transmission line relay protection method based on the concept of three-type and two-network is proposed, which divides the grid into correlation domains, calculates the actual current by using the charge variation coefficient, establishes the protection matrix according to the complexity and logic of the fault, calculates the differential of the current, and refers to the concept of “shared type” to establish a new method of information sharing and joint analysis of transmission line relay protection. Shared” concept, to establish a new method of transmission line relay protection fault tolerance information sharing and joint analysis, introduce the use of the method to control the discharge gap of the transformer, non-singular matrix and gain matrix to establish the set of conventional control rate and fault automatic repair control rate, set the actual fault tolerance control rate, to realize the improvement of transmission line relay protection fault tolerance method, and through the test results and comparison with the traditional method, it is shown that the proposed transmission line relay protection fault tolerance method has been improved, and the proposed method can be applied to the transmission line relay protection. The experimental results and comparison with the traditional method show that the proposed transmission line relay protection fault tolerance method is more perfect.

Since China entered the era of high-voltage AC and DC hybrid power grids, many high-voltage transmission lines have been successfully constructed. Due to the high voltage and long transmission distance of high-voltage transmission lines, once a fault occurs, it will cause serious losses. The research on the relay protection method of high-voltage transmission lines based on time-frequency analysis is proposed, which has important contribution value to ensure the stable development of the power grid. The fault signal of the high-voltage transmission line is extracted based on time-frequency analysis. The fault transient component of a high-voltage transmission line is detected by decomposing the fault signal characteristics. The phase correlation protection based on the fault transient component is realized to realize the relay protection of the high voltage power transmission line. The simulation results show that the accuracy of the proposed method is 100%, which verifies the reliability of this method.

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Abstract This paper evaluates, mathematically and experimentally, a transmission line differential protection function based on incremental currents, which are not influenced by pre-fault conditions, such as charging and loading levels. In the mathematical analysis, the trajectories for each phase, for all types of faults, are demonstrated by analytic deduction of incremental current ratios. For the experimental assessment, the Alternative Transients Program (ATP) was employed to submit a 500 kV 200 km long transmission line into a wide variety of faults. In addition, a 500 kV transmission line of the Brazilian interconnected system was also modeled via ATP, so that different faults scenarios could be applied to it. Also, for this last set of cases, the algorithm was embedded into a real commercially available relay to assess its performance. In order to carry out a broad evaluation of the incremental algorithm performance, sensitivity analyses were made. The results reveal that the incremental function operates for a bigger variety of faults including ones that the conventional function does not operate.

With the development of modern power systems, higher requirements are imposed on relay protection technology. Traditional relay protection and fault diagnosis technologies have been unable to meet the requirements of the continuous development of power systems, and relay protection systems based on artificial intelligence(AI) technology have received increasing attention. Therefore, this document first analyses the weaknesses of traditional broadcast line protection and uses the adaptability and self-learning of artificial intelligence(AI); to propose the concept of protection of a relay line based on AI. In combination with the artificial nervous network, the AI-based relay protection system shall be studied and the experimental model shall be developed. This paper validates it with simulation experiments. The research results show that for the analysis of the ANN test results of the subnetwork, the actual output of the subnetwork is very close to the ideal output, and the error does not exceed 0.2%. The system has good performance and high reliability.

When a fault occurs on the transmission line, the relay should send the faulty signal to the circuit breaker to trip or isolate the line. Timely detection is integral to fault protection and the management of transmission lines in power systems. This paper focuses on using the threshold current and voltage to reduce the time of delay and trip time of the instantaneous overcurrent relay protection for a 330 kV transmission line. The wavelet transforms toolbox from MATLAB and a Simulink model were used to design the model to detect the threshold value and the coordination time for the backup relay to trip if the primary relay did not operate or clear the fault on time. The difference between the proposed model and the model without the threshold value was analysed. The simulated result shows that the trip time of the two relays demonstrates a fast and precise trip time of 60% to 99.87% compared to other techniques used without the threshold values. The proposed model can eliminate the trial-and-error in programming the instantaneous overcurrent relay setting for optimal performance.

Power system transmission line protective relays are supervised by a number of elements to ensure the security and selectivity of protection decisions. Supervising elements are important for fault direction determination and they are typically designed based on the properties of sequence currents and voltages. Superconducting fault current limiters (SFCLs) could potentially affect the profiles of sequence currents and voltages, which could have further influence on the performance of supervising elements. This article is one of the first works that investigate the impact of resistive SFCLs on supervising elements in power system transmission line protection. A resistive SFCL and an electric power system are modeled in an electromagnetic transients simulation program. Single-line-to-ground faults are simulated on the transmission line. The acquired fault voltages and currents are processed by a transmission line impedance-based protective relay model to investigate the responses of supervising elements. The results are analyzed and discussed.

The dynamic variation of impedance during different operating modes of a thyristor-controlled series capacitor (TCSC)-compensated transmission line imposes protection challenges to conventionally used distance relays. The problem becomes further complicated when these lines are connected to present-day large-capacity doubly fed induction generator (DFIG)-based wind farms. In this article, a cutting-edge relaying algorithm is suggested for the protection of such crucial lines by extracting useful features from the local current signals using a single-pole filtering technique. The extracted features are further used to generate red–green–blue images for the convolutional neural network classifier for improved detection and classification of faults. The performance of this method is validated on several fault and nonfault data generated on 2-bus, WSCC 9-bus, and IEEE 39-bus test power systems considering TCSC- and DFIG-based wind farms in the network through a real-time digital simulator. The operation of the actual relay is validated through SEL 451, and the algorithm is accomplished by OPAL-RT (OP5600). The high fault detection accuracy (100%, 100%, and 100%) and classification accuracy (99.30%, 99.50%, and 99.20%) and the comparative study can claim the strength of the proposed method.

Power systems are becoming increasingly complex due to the integration of several power electronic devices. Protection of such systems and augmentation of reliability and stability depend on limiting the fault currents. Analysis of faults is essential for the selection of appropriate relays and other safety systems. In this research work fault analysis, fault detection, and data prediction of long transmission lines are discussed. Different parameters are analyzed at each point of distance using MATLAB/Simulink for long transmission lines. Through these results, it is concluded that with the increase in distance, the parameters change, so the detection response of the Mho relay also varies. Moreover, in this research work, the Mho relay response at different points is tested through Simulink software for long transmission lines. As it is concluded that manually it is very difficult to test the response of Mho relay at each point, the artificial intelligence technique of long short-term memory (LSTM) is used for the prediction of the data for the next long transmission line. Lastly, in this work, a long short-term memory network is used to predict the parameters. The LSTM is then used to find the predicted data of subsequent transmission line from previous data. The artificial intelligence technique successfully utilized for the detection of long transmission line fault.

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This study proposes a protection relay using a microcontroller to detect and classify faults in transmission lines based on the wavelet transform. An experimental model was constructed from an actual 115 kV transmission system prototype. The current signal was observed based on the fault type, phase, and position. Clark’s transform and the discrete wavelet transform (DWT) were applied to transform signals for analysis. Moreover, the performance of fault detection based on the output signals of Clark’s transform (alpha sequence, beta sequence, and zero sequence current) was compared to the performance of the alternative proposed fault detection method, which is based on the combining factor between alpha and beta sequence current. In addition, the influence of DWT level on fault analysis is also considered and is used to confirm the accuracy of fault detection. Results show that the proposed method is efficient for fault detection and classification. This finding allows the researcher to choose the appropriate analytical method. Moreover, it can also be used as the basis for overcurrent relay algorithm design in the effort to develop more advanced technologies.

This paper discusses the practical considerations for the selection of type of protection on a transmission line for inverter-based resources (IBRs) application. Phasor based differential (87), distance (21), overcurrent (51, 67), undervoltage (27) and multi-function (11) schemes are considered. Various aspects of protection such as ability to trip locally, reliability (dependability and security), selectivity, speed, simplicity, and economics are compared to select the line protection scheme. The results of cost-benefit analysis are presented in this paper for the project case study which is a $\mathbf{1 0 0}$ MW solar cut in on high voltage (HV) bulk electric system (BES) in southeast United States (USA). Vendor application guides and recent solutions are considered in this paper to shortlist existing issues with relay protection for transmission lines, both at in-and-out station and bulk power stations. The paper also discusses the evolution of philosophy and standards for the particular utility to add perspective to the chosen solution. A decision ladder is proposed which can be applied to select the protection scheme for transmission lines with similar challenges.

Nowadays, line protective relays utilizing traveling-wave (TW) technology are increasingly being adopted in power system. Similar to any protection solution, the ease of testing is crucial for user comprehension of the technology and application in the field. However, the testing tools available today, including laboratory simulators and relay test sets, do not reproduce signals bandwidth necessary for testing line protection and fault locators based on TW technology. This paper will explore the utilization of a system composed of both software and hardware capable of accurately modeling all components of an electrical system, including transmission lines with variable and frequency-dependent parameters, and reproducing waveforms up to the megahertz range on secondary levels. The study will demonstrate the effectiveness of an ultra-high-speed (UHS) transmission line protection system that operates in the time domain, utilizing incremental magnitudes. This protection system is based on the principles of traveling waves (TW) to identify and locate faults. Consequently, an Intelligent Electronic Device (IED) will undergo numerous contingency situations to assess the performance of the protection function based on traveling waves. The evaluation will consider parameters such as correct fault location (with errors limited to the transmission tower span length) and protection function delay (values approximately around 1ms).

In some countries, it is a common practice to re-set the relays after installation when a fault occurs. This reprogramming of settings can create damage to the equipment, or it might result in a wrong configuration. The aim of this work proposes an alternative to these problems through the virtualization of the protective equipment. The design presented in this paper reproduces the operation of a distance protection relay for offline Playback type tests on files, or pre-recorded failures extracted with COMTRADE files from field relays. Both features are introduced and validated using ATPDraw and transient simulation models of a basic power system. Results show the main advantages and contributions of virtualization as a tool for tranmission line protective relay testing.

Fault resistance influences the operation of distance relays, thus causing it to give inaccurate impedance measurement, thus resulting to under-reach condition. .Trip report of fault occurrence in Alaoji-Afam 330kV line showed the effect of fault resistance on the relay operation. This paper seek to improve distance relay performance in terms of reliability, speed and selectivity on Alaoji-Afam 330kV transmission line, when fault resistance is present through adjustment of protected zone reach using NEPLAN software to model and simulate distance relay used for this study. Several simulations were run and the results showed good improvement of distance relay operation in handling fault conditions. Adjustment of the protected zone reach was done to compensate for the effect of high fault resistance on distance relay operation.

The Static VAR Compensator (SVC) has the capability of improving reliability, operation and control of the transmission system thereby improving the dynamic performance of power system. SVC is a widely used shunt FACTS device, which is an important tool for the reactive power compensation in high voltage AC transmission systems. The transmission lines compensated with the SVC may experience faults and hence need a protection system against the damage caused by these faults as well as provide the uninterrupted supply of power.The research work reported in the paper is a successful attempt to reduce the time to detect faults on a SVC-compensated transmission line to less than quarter of a cycle. The relay algorithm involves two ANNs, one for detection and the other for classification of faults, including the identification of the faulted phase/phases. RMS (Root Mean Square) values of line voltages and ratios of sequence components of line currents are used as inputs to the ANNs. Extensive training and testing of the two ANNs have been carried out using the data generated by simulating an SVC-compensated transmission line in PSCAD at a signal sampling frequency of 1 kHz. Back-propagation method has been used for the training and testing. Also the criticality analysis of the existing relay and the modified relay has been done using three fault tree importance measures i.e., Fussell-Vesely (FV) Importance, Risk Achievement Worth (RAW) and Risk Reduction Worth (RRW).It is found that the relay detects any type of fault occurring anywhere on the line with 100% accuracy within a short time of 4 ms. It also classifies the type of the fault and indicates the faulted phase or phases, as the case may be, with 100% accuracy within 15 ms, that is well before a circuit breaker can clear the fault. As demonstrated, fault detection and classification by the use of ANNs is reliable and accurate when a large data set is available for training. The results from the criticality analysis show that the criticality ranking varies in both the designs (existing relay and the existing modified relay) and the ranking of the improved measurement system in the modified relay changes from 2 to 4.A relaying algorithm is proposed for the protection of transmission line compensated with Static Var Compensator (SVC) and criticality ranking of different failure modes of a digital relay is carried out. The proposed scheme has significant advantages over more traditional relaying algorithms. It is suitable for high resistance faults and is not affected by the inception angle nor by the location of fault.

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Relay protection settings are typically calculated in the offline phase and remain unchanged for a relatively long period of time during online operation of power systems. Therefore, it is necessary to consider the extreme operating conditions (EOCs) of the systems during the setting calculation. Traditional EOC Search (EOCS) methods based on local enumeration are time-consuming and have high computational overheads, which cannot meet the requirement of the new-type power system. This paper proposes a Multi-Action Reinforcement Learning Method and Multi-Action Exploration Strategy to solve the EOCS problems. The algorithm optimizes the traditional reinforcement learning framework by exploring several actions with the highest value in each state, thereby accelerating the convergence of the neural network. The proposed methods are verified on the IEEE 39-bus system. The experimental results show that the Multi-Action Reinforcement Learning Method can effectively solve the EOCS problem. The correctness of the calculation method for the optimal number of action explorations is also validated.

The application of intelligent question-answering (QA) technology in the power industry is continuously evolving, but existing systems still face challenges in terms of the effectiveness and accuracy of user queries. This paper proposes an optimization approach for guided keyword templates in the context of relay protection setting calculations within intelligent QA systems. By designing templates, the system helps users formulate clearer and more precise questions, thereby improving the quality of the answers. To address the issues of ambiguity and incompleteness in user queries, five categories of guided keyword templates are designed, along with two evaluation metrics: clarity enhancement and guidance enhancement. The experimental results show that the optimized queries significantly improve both the clarity and guidance of the questions, enhancing the quality of the system’s responses. The guided keyword template system designed in this paper demonstrates its advantages in improving question quality and provides valuable insights for the optimization of intelligent QA systems and for improving QA in other domains.

To address the limitations of traditional centralized relay protection setting calculations in smart grids, a microservice-based adaptive optimization method for protection setting computation is proposed. The system employs a containerized microservice architecture to decouple and deploy functional modules independently. It integrates a hybrid optimization model combining Non-dominated Sorting Genetic Algorithm II with Deep Deterministic Policy Gradient, aiming to simultaneously optimize selectivity, sensitivity, and quick action of protection responses. Simulations results demonstrate that the proposed model achieves significantly better performance in key metrics such as trip time error, coordination preservation rate, and minimum sensitivity margin, along with faster convergence and higher concurrent processing capacity, thus providing a practical and scalable solution for relay protection setting in dynamic grid environments.

With the continuous expansion of the power grid scale and the extensive integration of new energy, the operation mode of the system become increasingly complex, and the task of relay protection setting calculation has multiplied. Traditional manual setting calculation methods are time-consuming and costly, and the accuracy is often limited by calculation errors. Moreover, most of existing setting calculation software is mainly targeted at transmission lines and converting substations, with few research at new energy stations such as wind power. Therefore, an automatic calculation method and system for relay protection setting in new energy station suitable for large-scale power system is proposed in this paper, which can significantly improve calculation efficiency, effectively eliminate calculation errors, and ensure the stable operation of the system.

In complex ring networks, a significant amount of time is typically required to determine the coordination relationships of backup protection settings during online adjustment, which affects the efficiency of the online setting process. To address this, the paper introduces a data-driven approach by applying artificial intelligence technology—specifically, for the first time—into the field of online setting. A fast computation scheme for online backup protection setting based on Generative Adversarial Networks (GANs) is proposed. Firstly, a conditional GAN based on the Wasserstein distance is constructed, using system operating modes as conditional labels. The coordination pairs of backup protection settings are transformed into matrix indices, forming a backup protection coordination matrix, which serves as real sample data for GAN training. The generator and discriminator networks of the GAN are primarily composed of Convolutional Neural Networks (CNNs), and batch normalization is applied to the outputs of the neural networks to improve training stability. Next, the specific implementation of the GAN-based online setting scheme for backup protection is presented. Parallel computing techniques are employed to accelerate the computation of both the CNN and the setting values, further enhancing the efficiency of the online adjustment process. Finally, the IEEE 39-bus system is used as an example to compute backup protection coordination matrices under various operating conditions, thus constructing the dataset required for GAN training and validating the proposed scheme. Simulation results show that the proposed method can learn the complex coordination relationships among various backup protection settings from real sample data via GANs. It can generate the corresponding coordination matrix according to different operating modes, thereby achieving fast computation for online backup protection setting.

Pumped storage is a key way to meet the regulatory needs of the power system. Currently, SFC starting has become the main starting method for large pumped storage power plants. This article introduces the typical structure and operation principle of SFC in pumped storage power plants. Based on existing guidelines, the relay protection configuration and setting principles of the SFC system in pumped storage power plants are elaborated. Starting from engineering practice, a relay protection setting calculation scheme for SFC input and output transformers is proposed and put into operation on site, ensuring the reliable and stable operation of the SFC system in pumped storage power plants.

With the increasing scale of the power grid and the increasingly close connection between power grids, the traditional regional data modeling based protection setting calculation method is facing huge challenges. A quasi real-time boundary fusion technology is urgently needed to seamlessly splice the setting calculation data of each region to form an integrated power grid data model to solve the network wide, high-precision, multi-mode relay protection fault analysis and setting calculation requirements, build a strong "first line of defense" for the power grid. Aiming at the problems faced by the relay protection setting calculation of large interconnected power grids, this paper proposes an automatic data fusion algorithm for setting calculation based on multi-agent technology, which effectively solves the problems of too many zone fusion data and ineffective fusion due to data differences, and verifies the effectiveness of the algorithm through examples.

As the core component of the modern power transmission system, the stable operation of the UHV power grid is of great significance to ensure the overall safety of the power system. As a key line of defense in the ultra-high voltage power grid, relay protection can detect and isolate faults in time, thus limiting the impact of the accident to the minimum range. Setting calculation is an important basis for relay protection, which involves a series of complex calculation and analysis processes. This paper deeply analyzes the key technology of ultra high voltage power grid relay protection setting calculation, discusses the specific factors of the substation configuration on the setting calculation, carefully analyzes the principles of the setting calculation, comprehensively analyzes the related protection device configuration strategy, and further study the potential problems existing in the setting calculation and its effective countermeasures. Through the in-depth discussion and research of these key technical problems, it provides a set of scientific and reasonable norms and guidance methods for the relevant personnel in the setting and calculation of the relay protection of the ultra-high voltage power grid, so as to effectively guarantee the long-term stable operation and safe power supply of the power system.

The conventional relay protection setting calculation method considers the internal interference of the transformer and obtains the setting value quickly, which leads to large harmonic interference of the transformer and affects the secondary setting calculation results. Therefore, the setting calculation method of the power transformer relay protection based on the Electrical Transient Analysis Program (ETAP) is designed. The harmonic transfer characteristics of the power transformer are extracted, and the harmonic interference of the power transformer is proposed. Then the ETAP software is adopted to establish the calculation principle of the power transformer relay protection setting and improve the calculation accuracy of the secondary setting. Through comparative experiments, it is verified that the second fixed value of the algorithm is close to the actual fixed value and can be applied to real life.

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Nuclear power plants have a complex structure and changeable operation mode, which induces low setting calculation efficiency. After analyzing the technology, architecture, and functional logic of a variety of relay protection setting calculation systems and combining the characteristics of the setting calculation of nuclear power plants, the relay protection setting calculation system in nuclear power plants based on B/S architecture and cloud computing is studied in this paper. The system adopts three-tier B/S architecture, applies two key technologies, the cloud computing task distribution synchronization mechanism and the cloud component automatic assembly mechanism, and introduces a particle swarm optimization algorithm to provide technical support for nuclear power plant setting calculation; the running example of the nuclear power plant system fully proves the efficiency and reliability of the relay protection setting calculation system of the nuclear power plant, which has high practical value.

New energy station relay protection fixed value check is an important means to ensure the reliable operation of power transmission and transformation equipment. Informatization and standardization, as important means to improve operation and management efficiency of power generation enterprises, are the general trend.Therefore, it is necessary to study the intelligent check method of relay protection fixed value. Firstly, the on-line check and intelligent setting system architecture of relay protection setting are studied. The popular SpringBoot architecture is used as the back-end framework to develop the system, and Vue.js is chosen as the front-end framework. Basic configuration and system management, relay protection fixed value calculation, relay protection fixed value management, trip management and other modules are researched and developed, and achieve overall design goals through interrelationships between these modules.

With the development of the power distribution system and equipment diversification, the accuracy of setting values is required to be at a high level to realize well protection coordination for the relay protection system. The inaccurate setting values and defective protections may lead to lots of severe accidents, such as, the arc flash accident, which has been paid more attention recently. In this paper, a relay protection method considering the influence of arc fault is proposed. Then, the electrical engineering software is used to perform a more accurate setting calculation and protection coordination. Also, the arc flash hazard is weakened by the arc flash protection device. Based on the results, the modified configuration of relay protection can protect the power distribution system more effectively.

In order to improve the automated management of the mine power supply system, this paper designs and develops a mine power supply system relay protection setting calculation and verification system. The system uses Web technology to unify the production and management, realizing multi-device collaborative work anytime, anywhere. In the system calculation process, a variety of power system operation mode combinations can be considered and different principles can be set up to perform the relay protection setting calculation and verify the results to ensure that the relay protection calculation system is practical and reliable.

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This paper proposes a design method of distribution network relay protection setting optimization system based on improved genetic algorithm. Firstly, the limitations of the traditional genetic algorithm in the optimization process are analyzed for the complexity and adaptability problems in the process of distribution network relay protection rectification, and targeted improvement measures are proposed. The convergence speed and global search ability of the algorithm are improved by optimizing the operations of selection, crossover and mutation. Then, the fitness function is designed to better meet the actual needs of relay protection setting, and an integrated optimization system is developed for automated calculation and verification of relay protection setting values. The system test results show that the optimization system has significant advantages in improving the reliability and efficiency of relay protection setting, which provides a strong guarantee for the safe and stable operation of distribution networks.

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Recently, demonstration projects on an MVDC distribution network have been actively carried out to increase the capacity of an existing AC distribution system. However, since there are no specific protection guidelines for an MVDC station, which is a key facility for power conversion, operation methods of protection devices are required. In particular, if an MVDC station is operated without considering the coordination of protection devices in a distribution substation, customers in the same distribution line may be adversely affected by a fault section expanding when a fault occurs. Therefore, this paper proposes an operation algorithm for protection coordination of protection devices in an MVDC station by taking into account fault types and scenarios in order to properly operate protection devices in a ±35-kV MVDC distribution system. We also modeled a ±35-kV MVDC demonstration system by using PSCAD/EMTDC S/W. It was composed of a distribution substation, MVDC station, and protection devices. The evaluation results of operation characteristics for protection devices based on the proposed algorithm and various fault scenarios confirmed that the proposed algorithm is a useful method to operate protection devices in an MVDC station because 38.7 cycles of the coordination time interval is satisfied by securing 17 cycles as technical guide.

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Recently, demonstration projects of hybrid MVDC distribution technology have been actively conducted in connection with existing distribution systems, which convert 22.9kVAC into ±35kVDC through a converter station and accept renewable energy sources. This is done as a counter-measure to solve the hosting capacity problem caused by the rapid introduction of renewable energy sources. This paper proposes a protection coordination operation method for each fault scenario for stable operation of a ±35-kV hybrid MVDC distribution system in fault points on an AC distribution feeder and MVDC distribution feeder. We modeled a ±35-kV hybrid MVDC distribution system using PSCAD/EMTDC, which is composed of a distribution substation, MVDC distribution feeder, converter station, inverter station

In the process of power construction, it is inevitable that the line distance is too short. In order to meet the demand of power network reliability and improve the coordination ability of substation relay protection, in this paper, by analyzing and studying the coordination problem of back-up protection of ultra-short line system between stations, a kind of coordination method of system back-up protection is put forward, which can effectively reduce the influence of ultra-short distance line on the reliability of system protection, it is proved that the ultra-short distance line is not the factor that restricts the site selection, and it has certain guiding significance for the design of subsequent substations.

The trigger type superconducting fault current limiter (SFCL) decreases the fault currents without steady-state power loss by using the switching operation of high temperature superconducting (HTSC) elements. However, the application of SFCL can lead to malfunction in overcurrent relays (OCRs), which disrupts the protection coordination of OCRs. In this paper, compensation method consists of the impedance symmetrical components is suggested for the single line ground faults. The proposed method considers situations that the fault currents flow in reverse direction due to the looped structure of the power distribution system. This paper validates the suppression of OCR malfunction and recovery of the protection coordination of OCRs using the compensation method in a loop power distribution system incorporating SFCL under single line ground fault conditions.

The electric power transmission system requires a reliable protection mechanism to ensure continuity and dependability, particularly in 150 kV transmission lines. One of the key protection devices used is the distance relay, which detects and isolates faults based on impedance measurements. This study was initiated following a fault on the PLTMG Baubau–Raha transmission segment, which caused a power outage of 8.7 MW lasting 2 hours and 23 minutes. The objective of this research is to analyze the coordination settings of distance relays and evaluate the performance of the teleprotection system in responding to disturbances, as well as to estimate energy loss and its economic impact. The methodology includes collecting primary data from PT PLN (Persero) and simulating fault conditions based on the actual relay settings installed at three substations: PLTMG Baubau, Baubau, and Raha. The analysis revealed that the relay zone settings and timing delays were functioning correctly, and the Permissive Underreach Transfer Trip (PUTT) teleprotection scheme successfully accelerated fault isolation in a selective manner. Simulations also confirmed that the system accurately identified fault locations based on impedance values detected by the relays. Additionally, calculations showed a total energy loss of 20,732.1 kWh, equivalent to IDR 29,939,622.4. This study emphasizes the importance of proper relay coordination and teleprotection systems in enhancing the reliability of power transmission networks.

AC microgrid protection schemes are often compromised by dynamic changes introduced by diverse Distributed Generators (DGs). These dynamic variations, resulting from different DG types and sizes in Grid-Connected Mode (GCM), Islanded Mode (IM), and network topologies emerging from line and DG outages, significantly alter the fault current levels and lead to miscoordination of conventional Directional Over-Current Relays (DOCRs). Hence, this paper introduces an adaptive protection strategy utilizing a novel pickup scaling coefficient, which adjusts relay settings based on local voltage and current measurements. Further, the proposed method is the first AC microgrid protection strategy capable of maintaining consistent relay operating times and Coordination Time Intervals (CTIs) across different topologies, including GCM, IM, line, and DG outages and varying DGs' injections, by determining a single optimal set of DOCR settings. Extensive simulations for various faults, including high resistance faults, in different scenarios of modified IEEE $13-$bus distribution network with synchronous and inverter-interfaced and comparison with previous works validate the proposed adaptive pickup, ensuring improved sensitivity, selectivity and reliability of the proposed method under diverse operating conditions. Further, Controller-Hardware-Loop (CHIL) simulations using TI-LAUNCHXL-F28379D DSP board and Real-Time Digital Simulator (RTDS) validate the real-time feasibility of the proposed method for varying scenarios.

A protection strategy utilizing agent technology for adaptive relaying of Directional Overcurrent Relays (DOCRs) has been proposed in this paper. In this approach, communication plays a vital role by providing real time information of the changing system conditions. In this study, communication channel has been simulated in Java Agent Development Framework (JADE) platform. The change in topology has an adverse impact on the protection coordination of the DOCRs and hence, the settings of DOCRs should be updated. In this study, for 9-bus test system communication channel flow has been established between different agents of the system, namely, relay agents, DG agents, equipment agents etc through Agent Communication Language (ACL) standard. Different test cases have been considered, namely, DG connection/disconnection, line outage, change in microgrid operation and relay coordination upon occurrence of fault for enhancing the protection strategy. In this study communication channel between different agents has been carried out through series of simulation on JADE platform for different contingencies in the quest to validate the sequence of events that occur upon fault inception. Hence, the DOCRs adaptively update their settings utilizing the communication channel and mitigate any maloperation of the relay. This ensures greater reliability and efficiency in mitigating the relay coordination problem.

This paper analyzes the impact of photovoltaic (PV) penetration in 20 kV distribution networks on protection coordination. PV penetration continues to rise, driven by utility-scale generation and customer installations that supply local demand and inject excess power into the grid. One of the main technical consequences of PV integration is the alteration of fault current characteristics during faults, which changes relay operating times and can cause loss of coordination between protection devices. The study evaluates four penetration scenarios on 20 kV distribution feeders in East Jakarta, with simulations performed in DIgSILENT PowerFactory to assess their impact on protection coordination. The simulation results show that PV penetration increases fault current by $\mathbf{1 . 2} \boldsymbol{\%}$ at the nearest bus and decreases the current by 5.8% on the external grid, with the operating time which can increase up to 41.8% under high penetration scenario. The results suggest that increasing PV penetration must be carefully coordinated with protection settings to ensure the protection devices work properly.

This article addresses the challenge of fast and reliable dc fault protection in multiterminal direct current (MTdc) grids by coordinating a cost-effective hybrid-modular multilevel converter (H-MMC) with a hybrid dc circuit breaker (H-dcCB). The proposed method introduces a dc-fault-severity criterion that enables adaptive fault management at each station, thereby minimizing power fluctuations and shortening grid restoration time. The presented strategy employs an optimized full-bridge submodule (FB-SM) ratio in H-MMCs along with dc circuit breakers (dcCBs) that have low-peak-current-tolerance requirements, while maintaining selective dc fault protection. Simulations utilizing frequency-dependent overhead line (OHL) models in MATLAB/Simulink demonstrate that the fault current is limited to below 2.5 p.u. and cleared within approximately 4 ms. Experimental validation on a scaled-down three-terminal dc grid confirms the theoretical analysis and simulation results.

Conventional protection schemes are susceptible to dynamic changes in AC microgrids having diverse Distributed Generators (DGs). These changes, caused by different DG types, significantly alter the fault current levels, leading to conventional Directional Over-Current Relays (DOCRs) miscoordination. The feasibility of using a single set of settings in conventional DOCRs for Grid-Connected Mode (GCM) and Islanded Mode (IM) of operation of AC microgrid is often hindered in the presence of inverter-interfaced DGs due to relatively low short-circuit levels in IM. Hence, this paper uses a novel local voltage measurement-based pickup setting of DOCRs, where the relay operating time is a function of relay voltage and current. A protection coordination problem is also solved to obtain a single set of optimal settings for these DOCRs, which are feasible for various operating scenarios, including GCM, IM, line, and DG outages in an unbalanced AC microgrid. Simulations for different faults in the modified IEEE 13-bus network with synchronous and inverter-interfaced DGs and comparison with previous works validate the reliability and reduced relay operating times in the proposed method. The Controller Hardware-In-Loop (CHIL) simulation using the Real-Time Digital Simulator (RTDS) and dSPACE DS1104 DSP board validates the proposed method's real-time efficacy.

Zero-sequence overcurrent (ZOC) protection is the last line of defense for protection when differential protection and distance protection both fail to detect and isolate the ground fault. Therefore, ZOC protection plays an important role in the secure and stable operation of the power system. Nowadays, traditional definite-time ZOC (DT-ZOC) protections can hardly cope with various fault scenarios in an increasingly complex grid structure. Even though the inverse-time ZOC (IT-ZOC) protections have been widely applied in high-voltage power systems to improve the performance, there still exists the possibility that the transformer protection over-level trips when fault happens in a line, due to the mismatch of IT-ZOC protections under some specific conditions. This paper reveals the typical scenarios of incompatibility between the IT-ZOC protections of transformers and lines, Then, a definite-inverse-time composite ZOC protection method is proposed, so as to avoid the above risk and support the ground fault backup protection of large power grids. Case studies are presented to demonstrate the effectiveness and strengthens of the proposed method.

In the global quest for carbon neutrality, the integration of renewable energy sources within industrial parks has become a prevalent trend, significantly influencing power system operations, with particular implications for relay protection mechanisms. This study provides an in-depth analysis of how the proliferation of renewable energy in industrial parks affects line relay protection and explores strategies for enhancing the effectiveness of these protections. The research begins with an assessment of the existing power grid infrastructure in industrial parks, the intrinsic characteristics of renewable energy, and the current relay protection configurations. It then delves into the challenges arising from the increased deployment of renewable energy, such as the intricacies of protection scheme design, the recalibration of protection settings, and the need for interprotection coordination. To tackle these issues, the paper introduces a suite of targeted solutions and recommendations for improvement. The findings demonstrate that with strategic and informed adjustments to relay protection configurations and strategies, the integration of renewable energy can be managed effectively, thereby safeguarding the integrity and security of the power system

The implementation of low-voltage-ride-through (LVRT) requirements for distributed generation (DG) sources in medium voltage (MV) distribution networks introduce challenges for the existing protection systems. These challenges stem from coordination issues between line protection systems (fuses and reclosers) when the DG may continue to operate in line with LVRT requirements during faults in the network. To address this challenge, we propose an enhanced voltage protection module (EVPM) for DG interconnection protection relays (IPR). EVPM employs a space phasor model (SPM) of three-phase voltages at the point of common coupling (PCC) to detect faults in the distribution network and the consequent recloser operation. This allows for prompt isolation of the DG from the faulty network in coordination with the reclosing relays, by over-riding the LVRT requirement. This reduces the time required for reclosing and ensures recloser fuse coordination without changing the settings of the existing protection systems based on DG penetration levels. To assess the EVPM performance under different scenarios, transient simulation studies are carried out in three case study networks. The results validate the efficacy of the proposed EVPM.

Due to the influence of the control strategy of the battery energy storage station (BESS), the degree of voltage sag, and the battery state of charge (SOC), the fault current characteristics of the BESS outlet line differ significantly. Traditional overcurrent protection faces the risk of failure to operate. To evaluate the operational performance of overcurrent protection of outlet line connecting BESS, this work first analyzes the topological structure and control strategy of BESS and further investigates the fault current characteristics of its outlet line. Based on this, the operational performance of overcurrent protection relay is studied. In addition, an overcurrent protection method of outlet line connecting BESS considering the battery SOC is proposed. By calculating and setting the SOC boundary, reliable protection of outlet line within different SOC intervals is achieved. Finally, a grid-connected model of BESS is built based on an electromagnetic transient simulation software to verify the operational characteristics of the proposed method.

Abstract An electrical power system must have an optimal protection system for enhanced reliability. Numerous studies have attempted to address issues with protection schemes, such as coordination constraint violations due to change in network configuration. Furthermore, in a few articles, the N-1 line contingency is considered without considering the line contingency selection criterion, resulting in a large number of constraints to deal with in the optimization problem. This paper proposes a new relay coordination scheme for dual setting directional overcurrent relay (DOCR) and distance relay based on the severity index of line outages, which is calculated by using an active and reactive performance index. The proposed protection strategy is improved with the help of an intelligent selection of the relay characteristics coefficient for dual setting DOCR along with the other relay settings. Another significant contribution is to provide a comparative analysis of standard and user-defined relay characteristics using genetic algorithm and grey wolf optimization algorithms. The modified IEEE-14 bus test system and IEEE-39 bus test system is used to validate the efficacy of the proposed protection scheme.

Transmission line protection is crucial for ensuring power system stability and reliable operation. This work presents a comparative study of two conventional protection schemes: the traditional Overcurrent Protection Scheme (OCPS) and Differential Current Protection Scheme (DCPS). A standard 9-bus system is adopted as the test model to evaluate and highlight the limitations of both approaches. The literature review explores existing studies and advancements in transmission line protection, with emphasis on OCPS and DCPS. The methodology details the comparative framework, including system layout, parameter settings, and simulation setup in MATLAB/Simulink. Simulations under diverse fault conditions assess the performance of OCPS and DCPS in the 9-bus network. Results are presented and analyzed to identify strengths and weaknesses of each method. Based on these findings, conclusions are drawn and recommendations for improvements and future research directions are provided.

This paper presents an optimized inverse-time overcurrent relay (OCR) setting and coordination methodology for interconnected high-voltage and medium-voltage (HV/MV) transmission systems, validated on a real 110 kV/15 kV utility substation network. Analytical feeder impedance equivalences and phase-to-phase fault current models were developed to evaluate relay performance under multiple fault locations ranging from 0% to 100% of feeder length. Standard inverse (SI), very inverse (VI), and extremely inverse (EI) IEC overcurrent relay characteristics were applied to both incoming and outgoing feeders. The study incorporates practical power system parameters, including short-circuit MVA, positive and negative sequence impedances, X/R ratio, transmission line length, current transformer (CT) ratios, full-load current, line capacity, grid frequency, and real power. Relay pickup currents and a fixed time multiplier setting (TMS = 0.05 s) were carefully selected to ensure safe, reliable, and rapid fault clearance. Fault current levels at each feeder location were computed based on feeder impedance variation, CT ratios, and pickup settings to determine optimal relay operating times and coordination intervals. Simulation results demonstrate that the proposed OCR coordination scheme achieves fast and selective fault isolation, with coordination interval times of 0.062–0.0927 s, 0.0720–0.0949 s, and 0.0661–0.0764 s for extremely inverse, very inverse, and standard inverse relay characteristics, respectively. The extremely inverse characteristic provided the fastest response for remote faults, while standard inverse relays ensured stable operation near the substation. MATLAB/Simulink-based validation confirms improved relay selectivity, reduced coordination delays, and effective mitigation of cascading outages. The results indicate that properly optimized inverse-time OCRs can provide a cost-effective, reliable, and practical protection solution for HV/MV transmission networks, particularly in developing and interconnected power grids where simplicity and coordination speed are critical.

The extensive integration of photovoltaic (PV) power generation has significantly transformed the structure of power grids, leading to increasingly complex fault current characteristics. Inverse‐time overcurrent protection is notable for its ability to adjust operation time based on the magnitude of fault currents, thereby enabling an adaptive response to varying fault severities. Therefore, inverse‐time overcurrent protection is extensively employed in power line protection systems that feature a substantial integration of distributed PV generation. However, the configuration of this protection mechanism often relies heavily on engineering experience, thereby constraining its practical applicability. This paper proposes an optimisation algorithm for inverse‐time overcurrent protection based on the improved grey wolf optimiser (GWO). The simulation example verifies the feasibility and superiority of the proposed model under both two‐phase and three‐phase faults. The results demonstrate that the improved GWO not only enhances the sensitivity and operational speed of the protection mechanism but also ensures selectivity, thereby markedly improving the accuracy and reliability of fault response. The proposed optimisation scheme effectively addresses challenges posed by distributed PV systems, such as bidirectional power flows and dynamic fault characteristics, by reducing the overall operating time while maintaining protection selectivity and sensitivity.

Traditional instantaneous overcurrent protection schemes encounter significant challenges in power lines, particularly when line impedances are low, resulting in minimal differences in fault current magnitudes for faults occurring at various segments in the power line. This condition compromises selectivity, leading to poor relay coordination, misoperation, and delayed fault clearing. This study presents an advanced solution through the design and strategic placement of Resistive-type Superconducting Fault Current Limiters (r-SFCLs) along power line segments to enhance protection selectivity and system reliability. The r-SFCL dynamically introduces substantial impedance upon fault detection, effectively reducing fault current magnitudes downstream and creating distinct, easily discriminated current levels at each segment. This clear differentiation enables instantaneous overcurrent relays to operate swiftly and selectively. A detailed self-activated r-SFCL model, incorporating realistic superconducting behavior, is developed and simulated within a practical 33 kV power line system using MATLAB/Simulink. Simulation results under various fault conditions show marked improvements in relay sensitivity and instantaneous selectivity. Strategically inserting multiple r-SFCLs across line segments yields a selectivity margin greater than 25% between fault current magnitudes of line segments, ensuring accurate fault localization and fast clearing without affecting normal load stability. These findings confirm the usage of r-SFCLs as effective and practical devices to enhance instantaneous overcurrent protection, strengthening system resilience and reliability in modern distribution networks.

Partially or fully electrified of advanced equipment has become the main development trend. SSPC (Solid State Power Controller) play a crucial role in ensuring the safe and reliable operation of distribution systems. Inverse time overcurrent protection curve algorithm technology is the key technology to implement SSPC. In this paper, proposes an innovative “heat accumulation” inverse time overcurrent protection algorithm of considering the influence of initial environmental temperature and load line heat dissipation, and the theoretical derivation process of the algorithm is given. The protection time accuracy is improved by about \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10\%$$\end{document}. The power consumption in multiple scenarios is simulated and analyzed, and the simulation results verify the correctness and accuracy of the algorithm. This provides a new idea for the design of SSPC inverse time overcurrent protection technology.

Adjusting the secondary side operating voltage of power distribution transformer helps minimize voltage drop and maintain quality at the distribution line's endpoint. However, this adjustment alters the transformer ratio, especially in transformers with an on-load tap changer, causing an increase in high-voltage side current that could exceed the nominal current when the medium-voltage side is fully loaded. Analyzing protection parameters, operational schemes, and historical voltage trends helps identify transformers at risk of malfunction due to voltage variations. To address this, adjusting overcurrent protection parameters on either the high-voltage or medium-voltage side is recommended. For medium-voltage adjustments, an adaptive scheme based on tap changer conditions or operating voltage can further enhance protection. This approach prevents malfunctions while ensuring reliable operation with minimal load limitations.

With the capability of limiting the increasing short-circuit current of power grid, high voltage built-in high-impedance transformer (HVBHT) has been widely used in recent years. However, due to its special structure, the magnetizing inrush with high magnitude and slow decay is likely to occur during no-load energization, which may lead to the mal-operation of zero-sequence overcurrent protection of the upstream transmission line. This phenomenon has become a serious problem in the actual production in China. To solve this problem, a modified time difference method is proposed based on the substation area information, so as to accurately identify the magnetizing inrush, internal fault as well as current transformer saturation. Subsequently, a countermeasure on preventing line zero-sequence overcurrent protection from mal-operation due to HVBHT energization is proposed. Simulation results based on PSCAD indicate that the proposed protection scheme can cope with various kinds of energization and fault situations effectively. Thus, the correct operation of zero-sequence overcurrent protection can be ensured. Compared with other existing identification methods of magnetizing inrush, the proposed method shows great superiority.

The transmission lines are an indispensable part of the electrical power system and have a large impact on the quality of life in our communities. They transport electricity from power plants to homes and businesses. They are the backbone of modern society, providing power for everything from lights to refrigerators to electric cars. They are an essential part of the nation’s infrastructure, and when they are functioning properly, they help to keep our country moving forward. But like any complex system, transmission lines are not without fault. They can experience a variety of faults such as line to line faults, line to ground faults, double line to ground faults and three phase symmetrical faults. These faults can cause a variety of problems for the electrical system, from power outages to safety hazards. To protect transmission lines from these faults, different type of overcurrent relays are used which are normally located at substations. When a fault occurs on transmission line, the overcurrent relays are activated and the transmission line is shut down. The overcurrent relays are also used to notify the transmission line operator of faults so that the transmission line can be protected as early as possible. This paper presents the modelling and simulation of inverse type overcurrent relays using MATLAB/SIMULINK. A relaying decision is obtained based on the simulation results to determine the suitable overcurrent characteristics for the different types of faults.

Traditional uniform zero-sequence inverse-time protection schemes struggle to simultaneously achieve rapidresponse and selectivity for $\mathbf{2 2 0 k V}$ short-line series systems with ground faults through transition resistance. To address this challenge, this study first reveals the distribution patterns and variation characteristics of voltage sequence components during such faults. A novel protection criterion is then proposed, which constructs variable time factors using the distinct differences between zero-sequence and negative-sequence voltages measured at protection terminals during internal versus external faults. This approach dynamically modifies the conventional inverse-time characteristic curve. The proposed method fundamentally eliminates transition resistance's adverse effects by enhancing rapid-response capabilities while ensuring protection selectivity. Simulations show that it effectively resolves both selectivity mismatch and compromised rapid-response caused by implementing identical protection characteristics network-wide. Additionally, it demonstrates higher sensitivity and offers a novel technical pathway for improving grid protection performance.

As the Transmission Line (TL) is an important part in the power system; this paper presents the design and practical implementation of overcurrent protection for threephase TL system using Programmable Logic Control (PLC). The PLC then on-line monitring the vlaue of the load current in each phase and detect the overcurrent and simaltinouslly isolate the fault by sending an output signal for tripping the coil of the Circuit Breaker (CB). Display unit of the PLC is used for displaying the load current, in addition to alert maessage with the type of the occoured fault. The proposed contrroller program also cancel of the trip signal of the CB during a definite time of the inrush and stating load current. In addition, an automatic reclosing system for return the CB to the work when the overcurrent is released. PLC-based protection methods cost less, provides greater precision with a safe way of operation when compared with the other protection controllers system. Function Block Diagram (FBD) language is employed for implementing the proposed software controller. Simulation is made for the proposed controller via LOGO! Soft Comfort V7.0 software programs for virtual implantation of the program before downloading to the PLC.

Power system protection plays a very significant role in the reliable operation of the power grid, by safeguarding the personnel, equipment, and property against any undesirable events. These protection systems are traditionally analyzed using computer simulation and physical testing. However, the sampling-based nature of these analysis techniques does not allow us to cover all the possible scenarios and thus the resulting protection systems may not guarantee complete protection. This fact can lead to partial or complete power loss/blackouts, which can have devastating consequences. Formal verification methods have been successfully used to overcome the incomplete analysis issues in many domains of engineering. We believe that their introduction in the analysis of protection systems can lead to more reliable power grid operations. With this motivation, we propose to formally verify the correctness and reliability of the conventional and dual setting directional overcurrent relays. In this regard, we propose the development of the generic Markovian models of the conventional and dual setting directional overcurrent relays. To illustrate the effectiveness of the developed models a simple three bus distribution system network is analyzed to formally verify the efficiency and reliability of these models using PRISM, which is a probabilistic model checking tool. Furthermore, the failure and success probabilities of isolation of the faulty section are also determined.

Section II and section III of distance protection are widely used as backup protection for 220kV transmission line. In order to ensure that the line distance protection can act correctly and cooperate with each other, it is necessary to set the impedance and time setting value of distance protection. At present, the time setting values of section II and III of power grid distance protection are fixed action time limits calculated by manual calculation or computer setting calculation program offline. In this paper, an on-line setting technology for section II and section III of distance protection is proposed. The operation time of section II and section III of distance protection is determined by measured fault impedance. As long as the distance protection section II and section III operates, the operation time can be calculated according to the formula proposed in this paper, and the operation time of protection section II and section III of the upper and lower level lines can meet the coordination relationship, and the operation time difference meets the requirements. Through modeling and simulation, it is proved that the method proposed in this paper is feasible.

The modern power system is equipped with protection system based on advanced technology through the use of digital multifunction relay, control system and intelligent selectivity, whose purpose is to ensure maximum security and service continuity of protection relay in the presence of various fault currents. Distance protection is an important protection required in high voltage transmission lines. In this paper, experimental platform tests have been performed and proposed for setting and evaluation the performances of distance protection named Micom P442 installed in Biskra-Batna of the Algerian transmission power system. The performances of the distance protection have been evaluated under various short circuits. In this study, experimental result based single phase fault to ground is analysed and discussed. Experimental results based on the proposed platform tests in terms of precision in detecting faults at various locations and trigger times confirm the efficiency and particularity of the proposed experimental platform tests.

The traditional three section distance protection is widely used in transmission lines with voltage level of 110kV and above, and the setting of impedance and time is the key. At present, the setting of three-section distance protection depends on manual calculation or off-line setting by professional software, which requires a lot of work and often leads to insufficient sensitivity or lack of coordination. In this paper, a distance protection scheme based on adaptive on-line setting method is proposed. This scheme does not need to set the impedance setting value and time setting value of the distance protection, instead, it only needs to calculate the fault distance using the local current and voltage information. On the basis of the calculated fault distance, the operation time limit can be calculated online by using the time limit calculation formula proposed in this paper. The protection operation time of the upper and lower lines can be adaptively coordinated and has an ultra-long protection range. This scheme can not only greatly improve the performance of distance protection, but also realize the cost reduction and efficiency improvement of relay protection setting, which brings considerable practical and economic benefits.

The AC line fault near the LCC-HVDC inverter station usually causes commutation failures (CFs). The accuracy of power frequency phasor extraction will be affected by the distortion of fault voltage and current waveform, resulting in deterioration of power frequency phasor distance protection performance. The adaptability of the traditional power frequency phasor distance protection is analyzed by simulation. Then, according to the AC line RL model, a time domain distance element based on the polarity comparison of the instantaneous voltage at the protection installation and the instantaneous voltage of the setting point compensation is proposed. The proposed time domain distance element is not affected by the nonlinear output characteristics of the inverter station. Finally, the effectiveness of the time domain distance protection is verified by simulation.

The objective of this work is to determine the fault location for one zone. Impedance relays constitute a vital component of power systems, specifically within the real value of transmission system, which was accomplished through the utilization of MATLAB/SIMULINK. The sim power system toolbox was employed to enable the intricate modeling of the distance relay, transmission line, and fault simulation. Within the modeling phase, the specific fault type chosen was single line to ground (SLG), Line-to-Line, while the protection scheme was established as the impedance type distance characteristic. This technique represents an interactive simulation environment that facilitates the design and evaluation of relaying algorithms. Moreover, the fundamental principles governing digital distance relays, as well as several pertinent filtering techniques, are meticulously elucidated within the confines of this paper. In order to enhance the user experience and ensure ease of interaction, thereby augmenting the functionality of the developed model. It is important to note that distance or impedance relays constitute a vital component of power systems, specifically within the realm of transmission systems. Finaly, it has been concluded that the fault impedance became less than the set value and a trip signal sent with short time to the circuit breaker.

Transmission lines connecting wind farms (WFs) to the main grid experience considerable variations in operating conditions due to changes in wind generation level, number of units in service (NUS), and network topology. These variations significantly challenge the dependability and security of conventional fixed Zone-2 distance protection, particularly when Zone-2 is employed as an overreaching element in teleprotection schemes such as permissive overreach transfer trip (POTT). This paper proposes a setting-group (SG)-based adaptive Zone-2 protection method for WF-connected transmission lines. The proposed approach maximizes Zone-2 fault coverage at both ends of the protected line while rigorously preserving selectivity with adjacent protection zones over a wide range of fault resistances, WF operating conditions, and network topologies, including N-0, N-1, and selected high-impact N-2 scenarios. A hybrid optimization framework is developed to simultaneously determine optimal Zone-2 quadrilateral characteristics for each available SG and to assign the appropriate SG to each operating scenario. To reduce computational burden, a systematic scenario-reduction technique is used to identify only those network elements whose outage significantly affects the relay-measured apparent impedance. Simulation results on a modified IEEE 39-bus test system demonstrate that the proposed method substantially improves Zone-2 coverage compared to conventional fixed-setting schemes. In particular, the method significantly increases the overlap of Zone-2 coverage between line-end relays, yielding marked performance gains for POTT-based protection while also enhancing protection dependability under non-teleprotected operation.

Generally, wind speed alters continuously during a day and leads to fluctuating output power of a wind farm (WF). Connecting such a WF to the transmission line of grid causes a malfunction in the performance of the backup zone of the distance relays due to the random nature of generation and the number of connected wind turbines (WF penetration). In this study, a new adaptive setting groups‐based method has been proposed to set the second zone of the distance relay in the grid with a WF equipped with a doubly fed induction generator. In this method, the authors have also taken into account the uncertainty of wind fluctuations and the availability of WT. A Markov model is developed to implement these features. To determine the impedance setting of each of the set groups of the second zone in the distance relays of the remote bus, the obtained impedances are clustered in four clusters by using the combination of K‐means and particle swarm optimization algorithms. Finally, the details of the analysis results of this issue have been compared with other methods available in the literature. The validity and accuracy of the proposed approach also have been assayed and confirmed.

© 2013 Zellagui and Chaghi, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Impact of Series FACTS Devices (GCSC, TCSC and TCSR) on Distance Protection Setting Zones in 400 kV Transmission Line

The Gas-insulated Line (GIL) is a technical equipment that allows power transmission underground at high voltage level. The UHV GIL-overhead hybrid transmission line is an essential way for power transmission in complicated landscapes. Because of the distributed capacitance of the UHV transmission line and the difference of the structure and the electrical parameters between GIL and overhead transmission line, the distance protection based on uniform lumped parameters cannot be applied to this hybrid transmission line directly. In order to overcome the shortcomings, this paper studies and proposes a new principle of distance protection for the UHV GIL-overhead hybrid transmission line based on frequency domain lossless transmission line equation, with the distributed capacitance accounted. Then, the paper presents a setting scheme for this distance protection with the hybrid line parameters considered. Finally, tests are carried out on the Power Systems Computer Aided Design (PSCAD) platform, and the accuracy and reliability of the distance protection method proposed are verified by simulation results.

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Transmission line protection is a very important part of the power system. In order to effectively study the distance protection of high-voltage transmission lines, this paper introduces the setting and operation of distance protection., build the mode with Simulink tool box in the software of Matlab, and simulate the mode by S functions. The simulation results illustrate the Matlab software can effectively reflect the behavior of the distance protection when there are some faults in the simulated transmission line, which proves a simple and effective method to research the relay protection in the power system.

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This study evaluates the performance of distance relay in the presence of inverter-based resources. In particular, it investigated the dynamic response of an inverter-based resource that is endowed with low voltage ride through capability and the performance of a distance relay at various time scales of operation following fault inception. Analytical evaluation and electro-magnetic transient simulation demonstrates that the influence of inverter-based resources varies significantly depending on the study’s time scale and the protection zones of the distance relay. The research also explores the effect of grid strength on the distance relay operation. A few considerations that may help improve the overall reliability of the distance relay operation in the presence of inverter-based resources are discussed. The results of this study suggest an intentional delay in zone 1 setting, revised reach settings, and underline the importance of electro-magnetic transient studies to ensure reliable operation of the relay. Furthermore, this study can assist protection engineers in proper relay configurations, particularly when the relay is exclusively fed by an inverter-based resource.

This thesis mainly analyzes the applications of distance protection zone I for short transmission line or weak-infeed. It demonstrates the calculation method of shortest length of transmission line that distance protection zone I can be applied at power source side and gives suggestions of setting calculation. Moreover, it analyzes the large error between measured impedance value and actual fault impedance, because distance protection zone I may work improperly when distance protection used for weak-infeed side.

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This paper presents a study on the performances of distance relays setting in 400 kV in Eastern Algerian transmission networks at Sonelgaz Group (Algerian Company of Electricity) compensated by shunt Flexible AC Transmis- sion System (FACTS). The facts are used for controlling transmission voltage, power flow, reactive power, and damping of power system oscillations in high power transfer levels. The direct impacts of SVC devices i.e. Thyristor Controlled Reactor (TCR) and the Thyristor Switched Capacitors (TSC) insertion, on the total impedance of a transmission line (ZAB) protected by MHO distance relay are investigated. The modified setting zones protections (Z1, Z2 and Z3) have been calculated in order to improve the performances of distance relay protection and prevent circuit breaker nuisance tripping. The simulation results are performed in MATLAB software and show the direct impact of the thyristors firing angle (α) on the total impedance of the protected line.

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As the most typical application of superconducting technology, the Saturated Iron core Superconducting Fault Current Limiter (SISFCL) is a kind of ideal high voltage limiter, which can achieve noticeable limiting endless stream and has wide application prospect. However, the selectivity and sensitivity of the distance protection (DP) in the high voltage transmission network would be affected by the impedance characteristics of SISFCL. For these problems, firstly the structure and the working principle of the SISFCL are introduced briefly. Secondly, the impact mechanisms of 220 kV SISFCL on the original distance protection for the transmission line (TL) are analyzed. Then two methods of eliminating influences are deduced from the previous analysis and an improved setting method based on SISFCL for distance protection is proposed. Finally, we used EMTDC/PSCAD software to build the 220 kV SISFCL and distance protection model in the transmission network. The simulation results demonstrate that the proposed setting strategy can effectively improve the selectivity and sensitivity of distance protection and provide a reference for the practical applications of SISFCL applied to the transmission line.

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This paper presents the evaluation of a line protection scheme for interconnected power subtransmission systems by comparison of the feasibility of relay time coordination, under different criteria. The protection scheme consists of distance relays as primary protection and directional overcurrent relays as back-up relays at 69 kV. A coordination computer program that uses linear programming and goal programming techniques is employed to determine the relay settings. Three cases are considered: (1) independent coordination of inverse-time relays and distance relays; (2) combined coordination of inverse-time directional overcurrent relays considering distance relays; and (3) combined coordination of definite-time-high-current setting directional overcurrent relays. The test case consists of a system located in the Eastern zone of Venezuela with 108 buses, 86 lines, 61 transformers and 97 directional overcurrent relays. It is shown that all three cases have advantages and disadvantages regarding the feasibility and viability of relay coordination, however the case with definite-time-high-current setting directional overcurrent relays is simpler for time coordination achievement.

The precise operation of relay protection devices for transmission lines is contingent upon the accuracy of setting values. The current approach to the operation and maintenance of relay protection setting values lacks sufficient intelligence, predominantly depending on specialized soft-ware. In response to these challenges, this study introduces an auxiliary method for relay protection setting based on LLaMa2-7B. The proposed model not only provides setting values for relay protection but also offers recommendations based on transmission line data. Initially, a dataset comprising 252 relay protection setting lists for 110kV-220kV transmission lines from a regional grid was assembled and preprocessed. Subsequently, the LLaMa2-7B model was modified and fine-tuned for training, enabling it to focus on the task related to protection setting values prediction while maintaining general language generation capabilities. Cross-validation and task separation techniques are employed to enhance predictive accuracy. Finally, case results indicate that the model's root mean square error in predicting setting values, with line parameters and control words as input, is as low as 0.45%, which is a 12.83% reduction compared to the direct fine-tuning method using the dataset. This proposed method facilitates the precise prediction of relay protection set-ting values, thereby aiding in the validation and calibration process.

Relay protection setting coordination diagrams can effectively visualize the setting coordination relationships between buses in power systems. A clear and aesthetically pleasing coordination diagram is easier for operators to interpret. However, there is currently no method available for automatically generating such diagrams based on the connection relationships between buses. Therefore, this paper proposes an automated method for generating coordination diagrams that meets practical needs. The proposed method first employs a simple Kamada-Kawai (KK) force-directed layout algorithm to generate an initial layout of the buses. Then, a graph neural network (GNN) is utilized to further optimize the layout, particularly to alleviate overcrowding in dense areas. Once the bus layout is completed, a connection line layout algorithm is applied to determine the paths of the connecting lines between buses. After these steps, the overall layout of the coordination diagram is finalized. Finally, case studies verify the effectiveness of the proposed method.

To address the challenge of traditional relay protection settings becoming mismatched due to topological changes such as switching of transmission lines, this paper proposes an adaptive setting scheme for relay protection based on the modular design concept. The scheme introduces a System Topology Online Identification Module (STIM) that can monitor the status of line circuit breakers in real-time and dynamically adjust the core settings of downstream distance protection modules according to a preset logic. To verify the effectiveness of the proposed scheme, this paper builds a 220 kV double-ended transmission system with parallel lines in MATLAB/Simulink. The simulation results show that when the system switches from a double-circuit line to a single-circuit line operation, the traditional fixed-setting protection will refuse to operate for internal faults at specific locations due to setting mismatch; however, the adaptive scheme proposed in this paper can instantaneously update the protection settings under the new topology, achieving rapid and accurate fault clearing for the same fault. Research proves that this scheme can significantly improve the adaptability and reliability of protection under dynamic changes in the power grid topology.

With the development of smart grid construction, the accuracy and timeliness of traditional relay protection will be severely tested. In order to make the verification and management of relay protection value more scientific and effective, an orderly check of the relay protection value based on the comprehensive importance of each line is proposed. Firstly, based on the complex network theory, the improved flow betweenness index is proposed to judge the vulnerability of the branch from the structural point of view after the power disturbance. Then, based on the entropy theory, the weighted flow transfer entropy index considering the load rate of the branch is proposed, which overcomes the shortcomings of the original indicator that only consider the uniformity of the transfer flow distribution. Finally, the comprehensive importance assessment index including the above two indicators is established to more comprehensively measure the importance of the branch in the power system. The effectiveness of the method is proved by simulation of IEEE 39 node system, which is of guiding significance for the research on the online verification sequence of protection setting.

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In order to make high-voltage transmission line anti-icing without interrupting power supply, OLTC anti-icing devices can be used for reducing the line voltage and increasing operating current to undermine the conditions of icing formation. The relevant relay setting values of the anti-icing line needs to be modified accordingly. In this paper, the research on how to reset the value of the 110kV and 220kV lines had been done after the OLTC equipment was implemented, and the principle of relay protection setting related to the change of line operating voltage and current had been given. A digital simulation of an area which encountered the icing disaster in 2008 had been done and the results shows that the reset relay protection setting of relevant relay protection is reasonable.

The relay protection system is an indispensable part of the power system, and it is the first line of defense to ensure the safe and stable operation of the power system. In order to guarantee the safe and stable operation of the power grid, four basic requirements of selectivity, rapidity, sensitivity, and reliability are put forward for the relay protection device, and the setting calculation of the action setting value of the relay protection device is of great significance. To solve the problem that the traditional step-by-step coordination setting method is inefficient and difficult to get the optimal result, we propose a relay protection setting optimization method based on the improved discrete Cuckoo algorithm in this paper. This method makes full use of the simple structure of the Cuckoo algorithm parameters and the constraint interval coding, aiming at the shortest setting time and the optimal sensitivity, and can quickly and accurately obtain the optimal solution of the relay protection setting value. Compared with the traditional relay protection setting method such as the genetic algorithm, the optimization method based on the improved discrete Cuckoo algorithm has fast convergence speed and high optimization efficiency and is suitable for the setting global optimization of the large-scale complex power grid.

The normal operation reliable power supply system of a nuclear power plant is equipped with a diesel engine power supply, in which the wiring is complicated and the operation modes are numerous. Therefore, in addition to the basic settings according to the standards, the relay protection settings of the power plant also need to be configured based on actual operating conditions, especially the grounding protection setting, contradicting the previous habit of protective design. This paper analyzes and calculates the protection settings of diesel engines and the coordination of the upper and lower reaches of the diesel engine. The protection configuration of the normal power supply line, the standby power supply line, and the bus connection switch are determined.

This paper focuses on the commissioning strategies of substation relay protection and deeply analyzes its principles and technologies. Relay protection, as a crucial defense line for ensuring the safe and stable operation of substations, the rationality and effectiveness of its commissioning strategies are of utmost importance. The article elaborately expounds on protection principles such as current protection, voltage protection, and differential protection, as well as conventional and digital commissioning technologies, including key points of setting value verification, secondary circuit inspection, and network communication commissioning. Through the analysis of commissioning cases of 110 kV and 220 kV substations with different voltage levels and the research on the application of commissioning strategies under complex faults, the effectiveness and problems of the existing strategies are clarified. Based on emerging technologies such as artificial intelligence and big data, optimization directions are proposed, aiming to enhance commissioning efficiency and accuracy. The research results are of great significance for ensuring the reliable operation of substations and improving the stability of the power system, providing valuable references for subsequent related research and practices.

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At present, the 380V AC power supply system of substations generally lacks independent microcomputer-based protection for the incoming and outgoing feeders, relying instead on electronic trip units to perform protection functions. Although this approach simplifies wiring, the large measurement error of electronic trip units makes it difficult to achieve proper grading coordination between the inlet line and feeder line protections. When a fault occurs in an outgoing feeder, it often results in a cascading trip, causing a voltage loss across the entire 380V bus section. Moreover, locating the fault point is difficult, which severely affects the reliability of substation power supply. This paper proposes a highly integrated microcomputer-based protection device that can realize the protection functions for both incoming and outgoing lines within a single unit. This design saves panel installation space while providing high protection setting accuracy and low time-delay error, thus resolving the grading coordination problem between inlet line and feeder protections. In addition, a bus protection scheme with a blocking mechanism is adopted. It operates independently of external signals, featuring simple and reliable logic, and ensures rapid protection response in the event of bus faults.

These days, the concept of distributed generations is being widely adopted due to the increased interest in the smart grid and its applications. The integration of distributed generators (DGs) resulted in the transformation of the distribution networks topology from radial to the looped/meshed networks. However, the addition of DGs not only alters the magnitude of fault current but it also results in bi-directional power flow. Thus, the line protection in a DG based power system is mainly based on the directional overcurrent relays (DOCRs) to address the issue of bi-directional power flow. With the technological advancement, the conventional DOCRs are now being replaced by the multi-functional digital relays. This makes it possible to use dual setting DOCRs. In this study, the combined deployment of conventional and dual setting DOCRs is investigated to decrease the number of relays and current transformers (CTs) used for line protection in the IEEE 14 bus distribution system. Since a single dual setting DOCR can have two different tripping curves for forward and backward current directions, the number of costly DOCRs can be reduced compared to the conventional line protection system. To analyze the applicability of the replacement, the proposed protection logic is simulated in the Electrical Transient and Analysis Program (ETAP). Three cases are considered in the simulation. Since, relays and CTs are expensive protection devices, reducing the number of relays and CTs without compromising the level of protection will provide a cost-effective protection solution.

No abstract available