Operation Of Protective Relays Research Articles

THE INFLUENCE OF THE RESISTANCE OF THE NEUTRAL GROUNDING RESISTOR ON THE 20 KV VOLTAGE DISTRIBUTION MODES OF OPERATION

The article examines the impact of different modes of neutral grounding on the operating parameters of 20 kV distribution networks, in particular, the selection of the optimal resistor resistance for resistive neutral grounding. One of the main tasks is to improve the efficiency of distribution networks of the UES of Ukraine by switching from a voltage of 10 kV to 20 kV. This solution is aimed at reducing power losses, increasing the amount of transmitted energy and improving the operation of relay protection. In the context of such a transition, the choice of the method of grounding the neutral of the power transformer is particularly relevant, which significantly affects the reliability and safety of operation of electrical networks. In the study, an analysis of the effect of resistive grounding of the neutral of the transformer on the operating characteristics of the 20 kV network was performed, as well as determination of the optimal value of the resistance of the resistor. The article presents the results of a comparison of a network with an isolated neutral and resistive grounding. The main operating parameters, such as short-circuit currents, overvoltages on undamaged phases, power losses and operation of relay protection, which have a significant impact on the stability and safety of network operation, are analyzed. Modeling is performed using the PowerFactory software complex, which provides the ability to accurately reproduce the real operating conditions of electrical systems. To conduct the research, a simulation model of the distribution network was created based on a two-transformer 110/20 kV substation, which includes two sections with outgoing lines of different lengths and loads. Special attention was paid to the selection of the resistance of the neutral grounding resistor and its influence on network parameters. Four options were considered in the study: isolated neutral and resistive grounding with a resistance of 10 Ohm, 15 Ohm and 20 Ohm. It was established that in order to ensure stable and safe operation of the distribution network, it is important to correctly choose the neutral grounding method. The best option is resistive grounding with a resistance of 15 Ohms, which allows you to reduce power losses, provides a sufficient level of currents for the effective operation of relay protection, and minimizes the risks of overvoltages on undamaged phases. This study is important for increasing the reliability of the operation of distribution networks and the security of electricity supply, especially in the context of the modernization of Ukraine's UES networks.

مرحل حماية المسافة وتأثير MOV على مناطق المرحل بإستخدام الماتلاب

Transmission lines are an important part of the power system. Transmission lines are used to transmit power and are prone to many breakdowns. Therefore, protection relays are used to protect transmission lines. The purpose of the protection system is to isolate the faulty part from the healthy part, because large currents generated by faults may cause damage to electrical equipment. One of the protection relays is the distance relay and is mainly used in the transmission line. Sometimes these relays are used for backup protection. Distance relays to determine impedance need voltage and current. Transmission lines are usually protected by a distance protection relay. Distance relays are of the high-speed class and can provide transmission lines. Protection distance relays that use impedance measurements to determine the presence and location of faults, are "fooled" by a series capacitor mounted on the line, when the presence or absence of a capacitor in the fault circuit is not known in advance. This is because the capacitor cancels or compensates for some of the line inductance, so the relay may sense a fault in its first region when the fault is actually in the second or third region of the protection. Similarly, Zone one fault can be considered reverse faults. In fact, this can cause some costly operating errors. Series compensated lines are protected from overvoltage by metal-oxide-varistors (MOVs) connected in parallel with the capacitor bank. The nonlinear characteristics of MOV devices add complexity to fault analysis and distance protection operation. During faults, the impedance of the line is modified by an equivalent impedance of the parallel MOV/capacitor circuit. Worth noting is a method that determines the L and C string values of the font and the MOV effect at the time of the error. This is done by analyzing the synchronous and sub-synchronous content of the voltage and current signals separately which provides enough information to calculate the L and C series of the line. In this paper, the transmission line impedance Z, Z(f) as a function of frequency has been calculated and plotted by the sequence characteristics and the studied MOV effect on line protection and fault location. Proper operation of the distance protection relay is also shown, and its effect on relay regions. Keywords: Distance protection relay, transmission line, zones of relay, MOV.

Ground Fault in Medium-Voltage Power Networks with an Isolated Neutral Point: Spectral and Wavelet Analysis of Selected Cases in an Example Industrial Network Modeled in the ATP-EMTP Package

The paper presents some case spectral analysis of zero-sequence voltages and currents in an example industrial power distribution network. The network layout is based on typical power delivery networks in underground coal mines. Ground fault simulations have been made using an ATP/EMTP program. Due to the high environmental risks, the reliability of the protection relay operation related to their selectivity plays an important role. This paper tries to find the reasons for nonselective operation and unnecessary tripping in extensive mine cable networks, particularly with large power sources of higher-order harmonics. It was found that in transient states—due to the decaying oscillations occurring in complex RLC circuits—the results of short time measurements of the criterion values for ground fault protective relays can be overestimated (particularly for small values of ground resistance) and lead to nonselective tripping of a healthy cable line. Therefore, it might be advisable to increase the integration time used for measuring rms values. Also, if there is a significant level of higher harmonics in the industrial network generated by high-power converters, it should be noted that the higher harmonics of the ground fault current and currents measured by ground fault protection relays assume much higher values, which may also cause nonselective tripping. In this case, it may be advisable to use higher harmonic filters in the measuring circuits and to select a sufficiently high sampling frequency in the digital protective relays.

Impacts of Distributed Generation on Power System Protection

Distributed generation (DG) offershuge benefits to the power system network to cater tothe rapidly growing demand for electric power. The integration of DG units intoexisting power networks is beneficial to both utilities and consumers. However, the installation of DG units in distribution networks might impose some operational, technical,and economic impacts. Increased short-circuitlevel and changes in load flow direction are examples of the technical issues arising from the high penetration of DG. Such issues will affect the existing protection system, mainly overcurrent relays. Thus, to ensure reliable and selective operation of protection relays, the impacts of DG should be considered. Thispaper discusses the impacts of DG on the protection systems byidentifying various protection problems.The paperis complemented by a simulation case study on the impactsof DG on fault levels, protection coordination, and distance relays.The simulatedsystem was modeledusingDIgSILENT PowerFactory®software.

Enhancing Resilience and Reliability of Active Distribution Networks through Accurate Fault Location and Novel Pilot Protection Method

The integration of distributed generation (DG) into the decentralized access of the distribution network transforms the existing structure into an active distribution network. The alteration in fault characteristics poses significant challenges to the coordinated operation of relay protection. Fault location within the distribution network plays a vital role in facilitating fault recovery and enhancing the resilience of the power system. It proves instrumental in improving the network’s ability to withstand extreme disasters, thereby enhancing the reliability of power distribution. Therefore, this paper provides a detailed analysis of the voltage fault components occurring during various fault types within an active distribution network. Building upon the identified characteristics of voltage fault components, a novel approach for the longitudinal protection of active distribution networks is proposed. This method involves comparing the calculated values of voltage fault components with their actual values. The proposed approach is applicable to various fault scenarios, including short-circuit faults, line break faults, and recurring faults. It exhibits advantages such as insensitivity to the penetration of distributed power supplies and robustness in withstanding transition resistance. The simulation results validate the effectiveness of the proposed method, affirming its applicability to diverse protection requirements within active distribution networks.

Communication-less adaptive directional overcurrent protection strategy considering islanded mode detection in active distribution networks

The integration of distributed energy resources (DERs) in electric distribution networks originates the Active Distribution Networks (ADNs). The presence of DERs introduces challenges to conventional protection schemes due to bidirectional power flows and variations in fault current magnitudes; furthermore, the connection and disconnection of DERs result in multiple ADN operating modes (OMs), deteriorating the effective operation of protective relays. Considering the above, this document presents an adaptive protection strategy to address the challenges related to the variable nature of the ADN operation. The main contribution of the proposed approach is accurate islanded mode detection without requiring communication links, enabling fault detection in all ADN operating modes. The protection strategy maintains directional overcurrent relays' coordination using local voltage and current measurements to continuously estimate the Thevenin equivalent, fault currents, and adaptive coefficients.Relay coordination is maintained through tests conducted on a modified IEEE 34-bus feeder, considering several OMs, fault types, and locations. A comparison between the proposed adaptive protection strategy and a conventional overcurrent scheme shows that relay operating time is better in 100% of the analysed cases for the former strategy. On the other hand, the maximum errors in the fault current estimation using the Thevenin equivalent parameters are between 0.05% to 2.6% for all of the analysed operating modes when compared with the true fault current magnitudes. Finally, the adequate results validate the potential of the proposed communication-less protection strategy for modern protective relaying applications.

Relay protection mirror operation technology based on digital twin

When conducting relay protection research, research costs can be significantly reduced if protection principle development, protection parameter verification and debugging can be carried out without relying on actual protection devices. The concept of ‘digital twin’ has made this possible, but the existing research has shortcomings in real-time data interaction ability, protection logic transparency, interface standardization, human–computer interaction etc., and consequently, mirror operation of relay protection in digital space has not been fully realized. Therefore, referring to the characteristics of digital twin, and combining with the practical application requirements in relay protection, this paper proposes the concept and characteristics of relay protection mirror operation based on digital twin. Key solutions are proposed to address the difficulties that may be encountered in the implementation of relay protection mirror operation in terms of protection principles, interfaces, real-time operation of the system, and human–computer interaction function simulation. Finally, an example of 110 kV double-bus and double-branch bus protection is used to verify the feasibility and progressiveness of the scheme proposed in this paper by comparing the action behavior and external characteristics of the twin protection and the actual protection device. The presented research can provide a reference for further in-depth research and application of relay protection using digital means.

State Inference and Evaluation Technology of Relay Protection Based on Digital Twinning

The problems of relay protection equipment in such aspects as the insufficient depth of data mining, not timely grasp of equipment status, and poor timeliness of fault warning restrict the development of the operation and maintenance mode of relay protection, which aims at “autonomous and controllable, safe and reliable, advanced and applicable, intensive and efficient”. This article studies the comprehensive state evaluation and action simulation deduction technology of intelligent substation relay protection equipment based on digital twins. It uses multi-source state monitoring data of relay protection equipment for state quantity correlation analysis. It constructs a key state feature index library and uses digital twin technology to model the relay protection function and software and hardware states. Through the collaborative linkage between physical devices and digital twin models, the twin can dynamically track the operational status of devices and automatically update the twin status. Finally, based on the established high-precision digital twin model, relay protection action deduction and status evaluation are carried out. Then the effectiveness of the scheme is demonstrated through example testing of the relay protection twin system.

Adaptive Directional Overcurrent Relay Coordination in Microgrid Considering Optimal Full Setting Parameters

This article proposes a novel approach for the optimal coordination of adaptive directional overcurrent relay (ADOCR) for modernized active distribution system (ADS) with microgrid (MG) functions. The goal is to keep the coordinating circumstances while reducing the protective relay operation time, as much as possible. With the proposed round-off mixed-integer particle swarm optimization (ROMI-PSO), the setting parameters are not limited to only relay time multiplier setting (TMS) and pickup current setting (PS) but can include the discrete parameter as relay characteristic curve setting (CS). In the proposed framework, The CS can be both IEC and IEEE standard curves in the proposed framework. Four buses radial system and IEC-benchmark MG system were used in a number of simulation experiments. Comparing the suggested methodology to other current methods revealed that it is more effective at determining the minimum relay operating times and ensuring the proper operation of protections under various fault allocations and operating circumstances.

Use of synchronized vector measurements technology for perform relay protection functions

RELEVANCE. Recently, along with the initial scope of synchronized vector measurements (synchrophasor) technology associated with Wide Area Measurement System (WAMS), more and more attention is paid to expanding the scope of this technology. Digital substations are one of the places for generating synchrophasor signals, at the same time, synchrophasor data are proposed to be used for the purposes of relay protection and automation at the digital substations itself, which will facilitate the construction of centralized relay protection systems at the substation. THE PURPOSE. Consider the use of synchrophasor technologies at a digital substation of the fourth type, as a replacement for Sampled Values (SV) signals. Consider additions to the standard set of synchrophasor signals necessary for the operation of various relay protections at a digital substation. Perform an analysis of the accuracy of calculating the synchrophasor when the frequency of the controlled current and voltage changes relative to the nominal value, when higher harmonics appear in the measured signal. Develop a pre-computation technique for relay protection algorithms. METHODS. When solving the problem, the method of calculating the total measurement error of the synchrophasor TVE (Total Vector Error) was used - a value that characterizes the deviation of the amplitude and phase of the measured vector from their specified values. CONCLUSION. The use of synchrophasor signals with the necessary additions for the operation of relay protection reduces the load on the digital network of the digital substation, simplifies the operation of relay protection algorithms. Calculations have shown that the measurement errors of synchrophasor do not go beyond the specified parameters. The proposed methods of precomputation allow to speed up the work of relay protection algorithms.

Simulating a Strong Magnetic Storm Impact on Russia’s Interconnected Power System of Center

Studying of a negative impact of the space weather and magnetic storms as its special case, on the performance of a critical technological infrastructure, with development of methods and means for protecting it is a relevant but difficult task. Many advanced countries, primarily the United States, are dealing with this problem. The article presents the results of elaborating a methodology for computational simulation of the impact of geomagnetically induced currents on large electric power systems. The developed methodology makes it possible to take into account the influence of changes in the reactive power and temperature of power transformer structural elements caused by magnetic biasing of their core, as well as the operation of relay protection. The impact of the geomagnetically induced currents expected during a strong magnetic storm on Russia’s Interconnected Power System of Center, including the power systems of Moscow, Leningrad and other major administrative and industrial regions of the country has been simulated for the first time. It is shown that such impact gives rise to a set of factors that can cause the development of a system-wide accident: a significant decrease in voltage at a number of power system facilities, mass-scale disconnection of power lines by their relay protections, and unacceptable heating of structural elements of some power transformers.

EXPERIMENTAL STUDY OF CURRENT SENSORS OF 0.38 KV VOLTAGE CLASS IN THREE MODES OF OPERATION OF THE ELECTRICAL GRID

The operation of existing relay protection devices is based on the measurement of electrical network parameters (voltage, frequency, current) performed using sensors installed in the electrical network. Current sensors are subject to high requirements for output data in various modes of operation of the electrical network. As current sensors in the 0.38 kV electrical grid, the following are widely used: current transformers, transreactor sensors, resistive sensors, Hall effect current sensors. (Research purpose) The research purpose is experimentally studying current sensors of various types used in electrical networks of 0.38 kilovolts. (Materials and methods) Conducted laboratory studies on a prepared laboratory stand of various current sensors in three operating modes: steady-state mode, switching mode with initial magnetic flux, switching mode without initial magnetic flux. (Results and discussion) It has been shown that not all types of current sensors can be used as a source of reference data in the construction of high-speed current protection. It was determined that transformer-type sensors can introduce a significant error in the operation of relay protection for reasons of significant angular error, pronounced processes of magnetization and enticement in switching modes. It was found that sensors based on the types of transreactor and Hall effect have the lowest angular error and resistance to switching modes. (Conclusions) It was revealed that when choosing current sensors as a source of reference data, not only passport characteristics, but also laboratory studies should be taken into account. The necessity of taking into account the operational operating time and inductance of the current sensor, the angular error and the shape of the current curve of the secondary circuit was stated.

Оценка влияния электрических станций с возобновляемыми источниками энергии на работу релейной защиты и автоматики в электроэнергетической системе

The article deals with the issue of the influence of solar power plants on the operation of relay protection and automation devices. The development of simulation models of electric power systems in the Simulink MATLAB environment has been carried out for three cases: power is supplied entirely from a solar power plant; power is supplied from the traditional source of the electric power system; the power is supplied partly from the solar power plant, partly from the traditional source of the electric power system. The description of the main parameters of the blocks of the simulation model is made. A study was also made of the influence of renewable energy sources on the sensitivity of relay protection, which directly depends on the level of short-circuit currents. Graphs of the dependence of the two-phase short circuit current on time are plotted. The conclusion is made about the decrease in the sensitivity of the relay protection in the presence of a solar power plant in the electric power system. The results obtained make it possible to calculate the parameters of various operating modes of the system, the results of which can be used to configure relay protection and automation devices.

A multi-agent based protection in distribution networks including distributed generations

This paper proposes a strategy for protection coordination in distribution networks with DGs penetration. The main objective of the present work is to employ the potential of Multi-Agent Systems (MASs), which have recently been given considerable attention in the context of smart grids. A modified scheme is proposed to minimize the number of agents while preserving the necessities of protection coordination under different contingencies. A new structure is defined for relay agent (RA) to operate in centralized or decentralized modes. Each RA contains communication and protection units, to detect an appropriate mode according to the required time to clear the fault and maintain coordination with other agents. IEC-61850 standard including GOOSE and SMV protocols used to send necessary commands and share data. The proposed protection scheme has 8 stages, which removes the fault from the network with the help of services and functions defined on the proposed structure of the relay agent. These steps include gathering network information, sending commands, and updating relay settings. In this regard, impacts of DGs are analyzed to show how they would change the operation of protective relays and their corresponding zones. Results of this research ensure the proper performance of protective devices taking into account appropriate settings and configurations.

New Procedure for Estimation of Power Fundamental Phasor Parameters in Presence of Decaying DC Components

The paper proposes a new algorithm for the estimation of the fundamental phasor in a power system, based on the removal of exponentially decaying DC components (DDCs). These components, as well as high-order harmonics and noise components, have a considerable effect on accuracy and speed of convergence in numerical and digital relays – speed of the protection relay operation. A Discrete Fourier Transform (DFT) based approach with a modified Prony method was used to calculate and remove the unwanted effect of DDCs in a time interval slightly longer than the period of the fundamental harmonics. The proposed procedure offers the possibility to estimate the parameters of unwanted DDCs in a simpler and analytically more precise way, thus facilitating its program implementation. The algorithm offers the ability to easily adjust the response speed - detection time. This flexibility of the algorithm provides a compromise in terms of response speed as well as expected reliability and security of fault detection. The developed procedure enables the monitoring of the very demanding dynamics of the current signal in short-circuit conditions, and thus the estimation of the phasor parameters of the energy signal so that the relay protection can respond to this emergency in the most adequate (adaptive) way - it becomes more precise and faster in its response. The algorithm has low numerical and computational complexity while maintaining its high performance even in conditions of a very strong noise signal. The simulation results for different test signals demonstrate high precision in the estimation of the fundamental phasor of the proposed algorithm.

CHANGES OF THE CONCEPT OF NEUTRAL POINT EARTHING OF MID-VOLTAGE GRIDS

Neutral point earthing of mid-voltage grids is implemented variously around the world, depending on the practice of individual countries with the emphasis on the technical regulations in force. Croatia is in the process of transition from star-point earthing through resistors to resonant earthing. Questions on the choice of arc suppression coil technology and the consequences for the operation of relay protection in transformer stations arise in relation to that. It is necessary to view all technical-economic aspects in order to reach an appropriate solution, while at the same time acknowledging the reliable operations of star-point earthing devices, and ensuring a satisfactory quality of electric energy supply.

Analysis of the Impact of a Modular SSSC on the Operation of Transmission Line Protection Relays using a Hardware-In-the-Loop Configuration

This paper evaluates the impact of a modular Static Synchronous Series Compensator (m-SSSC) on the operation of communication-assisted line distance and differential protection relays. The m-SSSC system incorporates an over-current protection feature to trigger the bypass mode of operation during grid faults. A case study is analyzed for a 220 kV transmission line and an m-SSSC with a reactive power rating of 80 MVAr per phase using a Hardware-In-the-Loop configuration. The obtained results show the impact of the m-SSSC system on the distance protection operation during some cases of high resistive faults. The differential protection operation was not affected by the mSSSC.

Islanding power quality detection using lighting search optimization with deep learning model on distributed generation systems

Recently, the significant penetration of distributed generations (DGs) in distribution networks has made new challenging issues in network protection. A major challenge exists in the distribution networks in the identification of islanding conditions, where a portion of the distribution network with DGs is accidentally detached from the central grid due to protection relay and circuit breaker operation. Since it results in damaging the DGs and their equipment, effective islanding condition detection model becomes essential. Besides, non-detected islanding conditions can lead to voltage and frequency deviances from the normal ranges, inappropriate operation of protection, and personnel hazards. Therefore, the recent developments in deep learning (DL) can be applied to perform island power quality detection process. In this view, this article introduces an Islanding Power Quality Detection using Lighting Search Optimization with Deep Learning (IPQD-LSODL) model. The proposed IPQD-LSODL model mainly aims to find the events in islanding power quality (IPQ) and non-islanding power quality (NIPQ). The proposed model initially applies down-sampling empirical mode decomposition (DEMD) approach which effectively filters out the basic signal from the polluted ones. In addition, deep belief network (DBN) model is used to classify the events into IPQ and NIPQ. Moreover, the hyperparameters of the DBN method were optimally chosen by the use of LSO algorithm with an intention of accomplishing maximum classification accuracy. The performance validation of the IPQD-LSODL model is carried out and validated through comparison study with existing models. The IPQD-LSODL method achieved an accuracy of 99.91 percent in the class 5. The results implied the promising performances of the IPQD-LSODL method over recent approaches.

ПАРАМЕТРИЧЕСКОЕ СОГЛАСОВАНИЕ УСТРОЙСТВ КОНТРОЛЯ ИЗОЛЯЦИИ И СОПТ

The aim of the study is to develop a method for parametric matching of insulation monitoringdevices, unearthed DC distribution systems and discrete inputs of relay protection.The use of unearthed DC distribution systems for power supply to relay protection devicesand other responsible consumers makes it possible to ensure high reliability and safety during their operation. It is necessary to ensure uninterrupted power supply to these consumerseven in the event of a ground fault in one of the DC distribution network poles. Insulationmonitoring of the network poles and the prompt execution of repair work when the insulationresistance falls below the critical level set by the response value, are a guarantee of highreliability of power supply. The article discusses the reasons leading to dangerous levels ofpole voltage unbalance and false triggering of relay protection discrete inputs during groundfaults of the signal lines connected to them. A method based on multivariate DC analysis isproposed to determine the matched insulation monitoring response value with the DC networkparameters and discrete inputs parameters, when the conditions for the occurrence ofsuch accidents are excluded. The influence of insulation monitoring devices in a DC systemon pole voltages unbalance and relay protection operation is also considered. A modificationof the insulation monitoring active method is proposed, which does not create additional polevoltage unbalance and risks of relay protection misoperation. The operating range of thestatic characteristics of the pole voltages and leakage current measuring transducers is narrowedin the grid unbalanced modes by using a modified active insulation monitoring met hod.Estimates of the increase in the insulation resistance measurement error arising in thesemodes are obtained.

Повышение электробезопасности обслуживающего персонала в условиях неполных однофазных замыканий на землю

The results are given related to the analytical studies of the causes of accidents occurrence and abnormal operating modes of electric receivers in the medium-voltage networks. It is established that the main cause of damage is the single-phase earth fault mode. It is established that the main cause of damage is a single-phase ground fault. It is found that a long single-phase ground fault increases the likelihood of transition to a more severe phase-to-phase short circuit. It is accompanied by immediate shutdown and long downtime of the equipment, large economic losses, as well as the appearance of touch and step voltages that are dangerous for people. It is identified that the earth fault current in a network with an isolated neutral will decrease in proportion to the decrease in the coefficient of the share of the transient resistance in the total earth fault current. Analysis of the operability of protection against single-phase earth faults is carried out on the example of a section of 6 kV distribution network of the coal mining enterprise JSC Polosukhinskaya Mine. Experimental studies of the efficiency of the functioning of non-directional current protection against single-phase earth faults were carried out. In the event of an incomplete single-phase earth fault, a drop in the zero-sequence current in the protected line invariably leads to a critical decrease in the sensitivity coefficient. There is a violation of the selectivity of the protection action, as a result of which the probability of electrical injury to the maintenance personnel increases. Boundary conditions for stable operation of relay protection and automation systems in case of incomplete single-phase earth faults are established. Definition of these conditions allows developing new algorithms for the operation of non-directional current protection in order to improve the electrical safety of the operating personnel.