Relay Protection Algorithms Research Articles

Анализ частотных характеристик токовых датчиков цифрового трансформатора тока и напряжения

Digital measuring current and voltage transformers (DCVT), which incorporate various current and voltage sensors are the key sources of information about processes at modern digital substations. Classic small-sized current transformers, Rogowski coils, magnetotransistor sensors, Hall effect sensors, fiber-optic Faraday effect sensors, as well as shunts can be used as current sensors in DCVTs. For redundancy purposes, current channels are performed in several copies and on different sensors. Sensors that are different in nature have their own set of advantages, which together makes it possible to obtain the effect of eliminating the shortcomings of specific sensors. For example, they may not have a saturation effect or transmit the direct current component quite accurately, which is a significant advantage over classic current transformers. At the mains frequency, the behavior of these sensors is predictable, but their behavior is not well studied at higher and lower frequencies. Thus, it is decided to study the frequency response and phase response of these sensors in a wide frequency range. To solve the problems within the framework of this study, physical experiment, analytical and empirical solution methods have been used. As a result of the study, the frequency response and phase response of current sensors of DCVT in a wide frequency range have been obtained. Analog filter has been designed to correct the signal of the magnetotransistor sensor. The results obtained coincide with theoretical data and can be considered when developing digital relay protection and automation algorithms.

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.

A Method and an Algorithm for Implementing Relay Protection of 6(20)/0.4 kV Step-down Transformer Substations

The article discusses a method and an algorithm for implementing the protection system for a 6(20)/0.4 kV transformer substation, using which its reliable operation is secured regardless of the grid configuration and operation mode and the operation parameters of higher-level electrical installations. The proposed method makes it possible to clear any fault in the 0.4 kV network with minimal time delays. To this end, it is necessary to supplement the 0.4 kV network with current transformers (if they are not available) and forward the algorithm control output to the circuit breaker tripping coils. To ensure short-range backup protection, the circuit breakers protective functions remain in operation. Based on the existing electrical network, the approximate pickup parameters of the proposed method are pointed out, and recommendations for their optimization are given. Various contingencies in the 0.4 kV electrical network are considered to verify the correct functioning of the proposed relay protection method and algorithm.

АЛГОРИТМ ВЫЧИСЛЕНИЯ ЕМКОСТНЫХ ТОКОВ ПРИ ОДНОФАЗНОМ ЗАМЫКАНИИ НА ЗЕМЛЮ, ИСПОЛЬЗУЮЩИЙ ПАРАМЕТРЫ АВАРИЙНОГО И ДОАВАРИЙНОГО РЕЖИМОВ

Relevance Single-phase earth faults are the most common type of damage in networks with an isolated neutral. At the same time, there are no universal solutions for localization and search of single-phase circuits. The availability of information on the capacitive currents of a damaged line can become the basis for the development of new relay protection and automation algorithms for the localization and elimination of single-phase short circuits in networks with an isolated neutral. The current trend in 6–35 kV distribution networks is the development and implementation of intelligent power grid technologies that allow for high-precision measurements and data transmission. The article presents, developed by the authors, an algorithm for calculating capacitive currents in single-phase earth faults using technologies of intelligent electrical networks. Aim of research Development of an algorithm for calculating capacitive line currents in single-phase earth fault using the parameters of emergency and preemergency modes. Creation of a simulation model of a device implementing the developed algorithm, and subsequent evaluation of the algorithm based on the results of simulation modeling. Research methods The study of the developed method was performed in the Matlab Simulink software package. Results An algorithm for calculating capacitive currents in a single-phase earth fault using the parameters of emergency and pre-emergency modes is presented and described in detail. The conducted studies of the developed algorithm using simulation modeling have shown high accuracy in calculating capacitive currents in the single-phase earth fault mode.

Enhancing power system stability with AI-based relaying algorithms – A review

Artificial Intelligence (AI) and Machine Learning (ML) are emerging technologies that are increasingly being used to improve various aspects of power systems. In particular, AI-based relaying algorithms have the potential to revolutionize the way power systems are protected from faults and failures. Relaying algorithms play a critical role in ensuring the stability and reliability of power systems. However, traditional relay protection algorithms face several challenges, including difficulty handling complex and dynamic systems, limited fault detection accuracy, and slow response times to changing conditions. AI-based relaying algorithms can address these challenges by leveraging the power of Artificial Intelligence and Machine Learning. This paper presents an overview of AI-based relaying algorithms and their potential applications in power systems. It explores the use of AI techniques such as Artificial Neural Networks (ANN), Decision Trees (DT), and expert systems for improving the accuracy and reliability of relay protection. It also discuss the steps involved in AI-based relaying algorithms, including feature extraction, classification, and result output. This paper highlights the importance of further research and development in this field to fully realize the benefits of AI-based relaying algorithms.

Relay Protection and Automation Algorithms of Electrical Networks Based on Simulation and Machine Learning Methods

The tendencies and perspective directions of development of modern digital devices of relay protection and automation (RPA) are considered. One of the promising ways to develop protection and control systems is the development of fundamentally new algorithms for recognizing emergency modes. They work in accordance with the triggering rule, which is formed after processing the results of model experiments. These algorithms are able to simultaneously control a large number of features or mode parameters (current, voltage, resistance, phase, etc.). Thus, the algorithms are multidimensional. This approach in RPA becomes available since the computing power of modern processors is quite enough to process the required amount of statistical data on the parameters of possible normal and emergency operation modes of electrical network sections. The application of classical machine learning algorithms in RPA tasks is analyzed, in particular, methods of k-nearest neighbors, logistic regression, and support vectors. The use of specialized trainable triggering elements is studied both for building new protections and for improving the sophistication of traditional types of relay protection devices. The developed triggering elements of the multi-parameter RPA contribute to an increase in the sensitivity and recognition of accidents. The proposed methods for recognizing emergency modes are appropriate for implementation in intelligent electronic devices (IEDs) of digital substations.

Development of an Intelligent System for Distance Relay Protection with Adaptive Algorithms for Determining the Operation Setpoints

The drastic consequences of emergencies force us to look for ways to increase the stability of the device operation at overhead power transmission lines (OHPTL). It can be achieved by developing new algorithms for determining the protection operation setpoints and detecting the damage location. Fault detection at OHPTL of 10 kV and above is mainly carried out by the devices based on the measurement of emergency mode parameters. For fault detecting one should analyze the parameters of not only current and voltage at the accident time, but also of the overhead power line. Specific active resistance, specific reactance, specific active conductivity and specific reactive conductivity are used to characterize the overhead power transmission lines. As a rule, these parameters are normalized to the unit of length of the overhead line (OHL) and linear values are used in the calculations. When analyzing power lines, tabular approximate values of longitudinal and transversal parameters in equivalent circuits are used, although solving problems in an unsimplified form leads to significant refinements of the known solutions, since OHLs are influenced by external atmospheric factors (ambient temperature, soil moisture, wind force, ice formation, etc.). The paper analyzes these characteristics and evaluates the influence of the listed factors on the linear longitudinal and transversal parameters of overhead lines. A functional dependence of external factors on the distance protection actuation setpoint was obtained. A method for automatic correction of the setpoint of the intelligent protection complex and an adaptive relay protection algorithm was developed, taking into account changes in climatic factors, enabling to reduce the “dead zone” length and increase the protection sensitivity. The use of line parameters obtained from the sensors in the calculations give rise to a more accurate fault detection based on the use of remote sensing methods.

Distributed automated control and protection system for power lines with any degree of longitudinal compensation

With longitudinal compensation of the reactance of the line, the problem of its protection against overcurrents arises from the point of view of relay protection. The problem is relevant with a greater degree of compensation. When compensating more than 50% of the reactance of the line, the protection of the power transmission line becomes practically impossible due to the failure or false operation of all existing types and forms of protection [1, 2]. Therefore, at present, the compensation of the line reactance is, as a rule, no more than 50% [3, 4], which does not allow the full potential of the line in terms of its transmission capacity to be revealed. The purpose of this study was to develop and test a new relay protection algorithm to be able to solve the above problem. The studies were carried out using modeling techniques in the PS CAD package, where a power transmission line with longitudinal compensation and an algorithm to protect it from internal damage were built. When carrying out the research, the work was carried out on the protection algorithm of the power transmission line with longitudinal compensation in the static mode without transferring electricity between substations and without the transmission mode along the active power line in both directions. It is shown that in order to determine the location of the damage, it is possible to use the criterion of the angle of the active component of the short-circuit current, which depends exclusively on the voltage angle and does not depend on the reactive parameters of the electrical network. The simulation result showed correct operation in all investigated modes. The algorithm described in the article showed quite satisfactory results, which makes it possible to protect the power transmission line with any degree of longitudinal compensation.

Application of linear discriminant analysis for classification of electrical grid emergency states

The approach of development of relay protection algorithms based on statistical data analysis suggests a transition from traditional protections to innovative multidimensional algorithms of recognition which are able to use the available information for emergency states identification more efficiently. The state parameters used for recognition are usually combined into a single multidimensional space. This results in computational complexity of the recognition algorithm. Thus, it is advisable to implement relay protection algorithms based on generalized features. This decision will make it possible to decrease the dimension of the feature space and increase response time of the protection. The linear discriminant analysis is used to reduce the feature space dimension when recognizing the states of an electrical grid section. The training sampling for statistical analysis is formed using a simulation model of the analyzed network section. The error matrix obtained as a result of the application of k-nearest neighbors algorithm for the state classification in the developed feature space was taken as a criterion for the feature space efficiency. A method of feature space dimension reduction for the task of multidimensional relay protection was proposed. It involves generalized features of response obtained via linear discriminant analysis. The method allowed formation of a setting plane which is the most effective for different types of short-circuit classification. This setting plane provides an error-free state classification while the setting planes obtained by pairs of initial features demonstrate an error of up to 50 %. The set goal of the feature space dimension reduction was achieved. Linear discriminant analysis is advisable to use by relay protection manufacturers for reduction of the feature space dimension in multidimensional relay protection problems, including multiple classification problems.

Support Vector Machines for Providing Selectivity of Distance Protection Backup Zone

The development of present-day power systems is associated with the wide use of digital technologies and intelligent algorithms in control and protection systems. It opens up new opportunities to improve relay protection and automation hardware and develop its design principles. Simulation modeling becomes a new tool not only for studying power systems operation but also for designing new relay protection methods. The use of simulation modeling in combination with machine learning algorithms makes it possible to create fundamentally new types of digital relay protections adaptable to a specific protected facility and able to use all the available current and voltage measurements to the fullest extent possible. Machine learning also allows developing auxiliary selective elements for improving the basic characteristics of existing relay protection algorithms such as selectivity, sensitivity, and speed of operation. The paper considers an example of designing an auxiliary element to provide selectivity in the backup zone of distance protection. The problem is solved using one of the most widely known machine learning techniques, i.e., the method of support vector machines (SVM).

Recognizing Ability of Local Currents During Two-Side Observation of Transmission Line

The article is aimed at analyzing the various information and parameters involved in diagnosing the fault location on the power line and identifying the damaged branch if there are several branches. Relay protection algorithms widely use the separation of the short-circuit current into the previous and emergency components. The latter carries the basic information of the fault location. Recently, it was found that the emergency component can also be divided into two components, namely normal and local. The local component is particularly very important because the ratio of local currents shows a strong dependence on the fault location or on the damaged branch, but does not depend on the fault current and, most importantly, does not on the part of the electrical system external to the observed line. The influence of unobserved branches on the accuracy of determining the damaged location by the proposed measurement is analyzed. Attention is drawn to the correlation between local currents algorithm and the emerging trends in merging or unifying the characteristics of relay protection and automation.

Распознающая способность локальных токов при двухстороннем наблюдении линии электропередачи

The article is devoted to information factors contributing to the recognition of the fault location in the power line, and if there are several branches, it is possible to identify the damaged branch. Relay protection algorithms widely use the separation of short-circuit current into the previous and emergency components. The latter carries basic information of the fault location. Recently, it was found that the emergency component, in turn, can be divided into two components, which are called normal and local. The local component is of particular information value, since the ratio of local currents shows a strong dependence on the fault location or on the damaged branch, but does not depend on the fault current and, most important, on the part of the electrical system external to the observed line. The influence of unobserved branches on the accuracy of determining the location of damage by the proposed measurement is analyzed. Attention is drawn to the correspondence of the local currents algorithm to the emerging tendency to unify the characteristics of relay protection and automation.

Algorithm for phasor estimation during current transformer saturation and/or DC component presence: definition and application in arc detection on overhead lines

During the current transformer (CT) saturation, the secondary current waveform of a CT is notably different from the primary current's waveform. When the discrete Fourier transform (DFT) is applied to such a distorted secondary current of a CT, the obtained root mean square (RMS) value is significantly lower than it actually is, which can lead to the malfunctioning of the relay protection devices. The operation of some relay protection algorithms (such as certain algorithms for electric arc detection on overhead lines) is conditioned by higher fault current harmonics. Obviously, due to the secondary current's distortion, the higher current harmonics cannot be accurately estimated. On the other hand, even when there is no CT saturation, the RMS value can be incorrectly estimated under DFT due to the fault current's direct component. This study presents a new algorithm which enables an accurate RMS value estimation regardless of the CT saturation and/or presence of the direct fault current component. What is more, the algorithm also enables the estimation of higher fault current harmonics under CT saturation. Various tests have indicated a high precision and robustness of the proposed algorithm and the possibility of combining this algorithm with the algorithm for electric arc detection on overhead lines.

Principles of Organization of Relay Protection in Microgrids with Distributed Power Generation Sources1

New relay protection algorithms have become necessary because of the special features of microgrid regimes with distributed power generation sources. The approach proposed in the present article assures compatibility of different relay protection devices, the capacity to freely choose different devices on each level and in each protection zone, and the potential for the use of new and different relay protection algorithms implemented in a centralized, decentralized, or mixed variant.

New and traditional relay protection algorithms integration in 6-35 kV distribution network

We conducted an applicability analysis of both modern and prospective relay protection types in future 6-35 kV field circuits. We demonstrated the advantages of using new differential-logic and multi-parameter relay protection algorithms, as well as the methods for relay protection tripping parameters calculation. We developed an integration scheme for existing and prospective relay protections types to increase the sensitivity and speed of the relay protection system for SmartGrid. We suggested the main stages of implementing new relay protection types.

K-Nearest Neighbors Algorithm Application in the Electrical Grid States Recognition Problems

One of the ways to improve the reliability of electrical grids is associated with the introduction of complex and resource-intensive algorithms in intelligent electronic devices (IED) that perform the functions of relay protection and automation at substations. Simulation modelling is used to study the features of the protected object functioning and its application makes it possible to take into account the variability of electrical grid states in the formation of IED algorithms, which are characteristic of the analyzed electrical grid section. In addition, this approach makes it possible to use for short circuits detection only those information features that have a high information value in a specific problem of states recognition. Machine learning methods are advisable to use for modern relay protection algorithms implementation. One of such methods is the k-nearest neighbours method. The article substantiates the effectiveness of the method application in comparison with the conventional algorithms on the example of protection of an electrical grid section with a distributed generation source. The reported study was funded by RFBR, project number 19-38-90144.

Research on Power System Relay Protection Method Based on Machine Learning Algorithm

With the development of power industry, there are gradually high permeability distributed energy systems. However, the existing relay protection is difficult to be effectively applied in this type of power system. To solve this problem, this paper applies machine learning algorithm to power system relay protection. Firstly, the structure of power system with high permeability and distributed energy is analyzed, and the challenges which current relay protection algorithms faced are introduced in detail. Then, the artificial intelligence algorithm is introduced, and the machine learning algorithm in artificial intelligence algorithm and its application in power system are mainly studied. Finally, the power system relay protection based on machine learning algorithm is deeply studied, and the specific implementation method and implementation flow are designed. The machine learning algorithm studied in this paper is helpful to the development of technology in the field of power system relay protection.

Identification of interturn faults in power transformers by means of generalized symmetrical components analysis

The paper deals with experimental identification of transformer internal faults, an important factor in reliability and sustainability of power supply systems. Task of identification of transformer internal faults requires increasing sensitivity of relay protection by calculation of components most sensitive to interwire faults from transformer current. In order to study internal faults in transformer, the model in Simulink MATLAB was developed on the basis of transformer constitutive equations. Transformer with short circuited wires was simulated as a multiwinding transformer. We provide the calculation of transformer parameters. Model was applied for analysis of transients in power transformers, such as interwire fault, transformer inrush, and fault in transformer connections. Analysis of power transformer internal faults by means of time-dependent symmetrical components of currents is provided. These symmetrical components were calculated for the first harmonic of current by means of discrimination of firs harmonic by low-pass filter and compensating elements implementing phase shift. Described method allows calculation of symmetrical components during transient and under non-sinusoidal conditions. Simulation results showed the advantage of instantaneous symmetrical components of other direct values. Those components were implemented in relay protection algorithms for identification of internal faults in transformers.

Improved algorithm of wide‐area current differential protection based on non‐uniform quantisation

Current differential protection characterised by whole-line quick action has now become the main concept in the research of the wide-area relay protection algorithm. However, strict requirements on broadband and real-time capability are difficult to meet in actual projects. Aiming at reducing the system traffic while not compromising the protection performance, the study proposes an improved algorithm of wide-area current differential protection based on non-uniform quantisation. The algorithm is proposed based on the information theory and in view of the non-uniform distribution of information redundancy of current signal in different width intervals. Comparing with traditional current differential protections, the improved algorithm is able to retain the sensitivity and reliability of the protection while reducing at least 44% of the system traffic whenever internal or external faults occur. It facilitates the realisation of wide-area differential protection in practice. Through digital simulation and dynamic simulation, the study demonstrates that the algorithm can distinguish fault places correctly and features a relatively high degree of sensitivity.

On the Coordination of Current Transformers and Relay Protection and Automation Operation of Electric-Power Systems in Transient Short-Circuit States

Due to the increasing number of incorrect actions of relay protection in transient processes accompanied by saturation of current-transformer (CT) cores, there is a need for developing a domestic standard for protective CTs designed to operate in transient states. The following ways to provide proper relay protection operation in transient states accompanied by saturation of CTs in operation are considered: (a) CT shedding that includes an increase in control cables’ cross sections, (b) development of relay-protection and automation algorithms based on the recognition of crash conditions in an appropriate CT transformation time interval of 2–3 ms, (c) development of relay-protection and automation algorithms with virtual CT error compensation, and (d) development and introduction of new primary-current converters. It is concluded that, for existing large power plants with installed TPX current transformers, it is advisable to use improved digital relay-protection algorithms for information processing obtained from CTs, for example, by methods (b) and/or (c).