Existing Relay Protection Research Articles

Analysis of a nuclear power plant’s responses to the open-phase fault of preferred power supply

This paper explores the phenomenon of open-phase fault of nuclear power plants for preferred power supply, focusing on three distinct scenarios, normal operation, start, and overhaul. For each scenario, the paper discusses the responses of existing relay protection devices, which are crucial for detecting and mitigating open-phase faults. These responses vary depending on the impedance at the fault location and the load rate of the plant. This paper highlights that open-phase faults can lead to three-phase imbalances in the power system, but their impact on voltage levels is not always straightforward due to the transformer and motor compensation effects. Additionally, the paper identifies blind zones in open-phase fault detection, where existing relays may fail to respond effectively, leading the plant to enter a station blackout state. In conclusion, the research underscores the importance of open-phase fault detection and protection in nuclear power plants. It reveals potential vulnerabilities in existing relay configurations and emphasizes the need for enhanced monitoring and safety measures to prevent extended plant operation under open-phase fault conditions.

Principle of predicting the reduction of insulation properties of electric motor windings

The simplicity of the design of the asynchronous electric motors (AM) allows them to be widely used in industry. The AM fleet sometimes reaches 80% of the total load of the enterprise. According to statistics, more than 60% of AM failures are observed due to damage to the insulation of the AM stator winding. The reason is premature dynamic and thermal aging of the insulation, which leads to the failure of the conductive and grooved parts of the AM winding. As a result of a decrease in the dielectric properties of the insulation, damage occurs in the stator windings of AM, such as turn, phase-to-phase short circuits, which tend to develop into a short circuit. Short circuits in the stator windings of the AM are emergency and lead to a sudden disconnection of the AM from the power supply network by existing relay protection means, for example, current cut-off or thermal protection. Sudden, non-sanctioned disconnection of the electric motor from the power supply leads to the shutdown of technological equipment, damage to equipment, raw materials and economic losses. The aim of the work is to develop the principles of timely monitoring and prediction of the state of housing and interphrase insulation of stator windings of AM using the energy of capacitors with local compensation of reactive power. To achieve this goal, research was carried out at a laboratory institution with AM, in which branches of turns were made. The transient processes of capacitor discharge are considered and new methods for monitoring and predicting the residual insulation life are proposed. The new method is based on monitoring the condition of the insulation after each disconnection of the AM from the power supply, while using the energy that remains in the capacitors. The use of a change in the velocity characteristic of the constant discharge time of the capacitor made it possible to predict the residual service life of the AM. The personality of the study is that under the conditions of local compensation of reactive power, it is possible to use the energy remaining in the capacitors to diagnose and predict the state of insulation, as well as the change in the velocity characteristic of the capacitor discharge time constant, which is a criterion parameter for predicting the residual service life of the AM. The carried out studies confirmed the development of test diagnostics in conditions of reactive voltage compensation, which is a new direction in systems non-poisonous diagnostics, which requires continued research and applications in industry.

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).

Research on Power System Performance Evaluation Based on Machine Learning Technology

Power systems often suffer from various large disturbances during operation, especially grounding and short-circuit faults of operating lines, which may lead to transient instability of the system. In view of the fact that the existing relay protection is difficult to be fully applied to the power system with high permeability distributed energy, the machine learning algorithm is applied to the relay protection of the power system. Enhance the robustness of the model to noise; In the training, more weight is given to the unstable samples to balance the influence caused by the difference in the number of samples. In addition, a regular term is introduced into the loss function to control the complexity of the model and reduce over-fitting, thus adapting to various operating conditions of the power system. By comparing the difference between measured data and estimated data to detect bad data, the machine learning method is more intelligent than the traditional method. The research results show that the transient stability evaluation method based on incremental learning of support vector machine greatly reduces the learning time while maintaining the evaluation performance, and is a promising online learning algorithm for transient stability evaluation.

Fault Modeling of IIDG Considering Inverter’s Detailed Characteristics

As more and more inverter interfaced distributed generators (IIDGs) such as PV are connected to the distribution network (DN), the existing relay protection system may malfunction due to the impact of the IIDGs. In order to evaluate that impact, the fault analysis of the DN with IIDGs is needed and the fault modelling of IIDG is of great significant for the fault analysis and the protection system validation and improvement. This paper proposes a new fault modelling method of IIDG that could consider the detailed characteristics of the inverter in different situations including the limitation of the modulation. The symmetrical fault model of PQ controlled IIDG is deduced by the proposed method, based on which the symmetrical fault analysis of the DN with IIDGs is carried out. The proposed model depicts IIDG as a voltage-controlled current source or a voltage-controlled voltage source according to whether the modulation is limited, therefore covers the full characteristics of the inverter under different conditions, improving the modelling accuracy. The case study based on the modified IEEE 13 nodes system shows that the fault analysis results obtained from the proposed model are more consistent with electromagnetic transient simulation than that of the state-of-art fault model, verifying its effectiveness.

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.

Методика выбора параметров противоаварийных команд на отключение потребителей в сетях 0,4 кВ

Conventionally, when accidents entailing active power imbalance occur in a power system, the underfrequency load shedding devices disconnect the necessary and sufficient amount of loads at the 10 kV voltage level. These load shedding operations are carried out without the possibility of taking into account the importance of certain consumers at the 0.4 kV voltage level. What is more, in view of using loads highly sensitive to power supply continuity, recent years have seen more stringent requirements being imposed on the reliability of their power supply. On the other hand, the availability of new computerized facilities opens the possibility of improving the reliability of supplying power to them even in the emergency load limitation mode. Specifically, this can be achieved by integrating the existing relay protection and automatic control systems with the automated electricity consumption monitoring and control system in such a way that consumers at the 0.4 kV level are selectively disconnected by commands of the underfrequency shedding control devices installed at the 10 kV voltage level. The article considers issues concerned with elaborating a procedure for selecting the values of the information parameter specifying the duration of command signals for disconnecting 0.4 kV loads produced by the automatic underfrequency load shedding devices at the 10 kV voltage level. It is proposed to perform load shedding operations by using a new method developed at the Moscow Power Engineering Institute National Research University. According to the proposed method, loads operating at the 0.4 kV voltage level are selectively disconnected through artificially creating a voltage sag (interruption) and using it as the underfrequency shedding command signal for disconnecting less critical loads. The article presents the principle of tuning-out from possible events and phenomena in the power supply network internal and external parts taking into account the existing setpoints of the relay protection and automatic control devices, and the influence of motor loads in generating and transmitting the command signal for short-term interruption of voltage via the 10 and 0.4 kV power network. A procedure for selecting the timing tuning parameters of the emergency control command generating and receiving devices.

Особенности релейной защиты и автоматики вдольтрассовых линий электропередачи

The article presents acomprehensive analysis of existing relay protection and automatic control systems of 6(10) kV overhead power lines laid along the pipeline route, including the basic circuits of sectioning and 10/0.4 kV substations. A procedure for selecting current cut off protection stages for power line linear parts with a single-side power supply is presented, and the choice of current protection parameters for sectioning substations on the basis of modern reclosers is substantiated in a detailed manner. The principles for designing modern systems supplying power to consumers situated along the trunk gas transmission lineroute areconsidered. The specific feature spertinent to application of relay protection equipment and operation algorithms of power line automatic controls are presented.

Micro-Grid Fault Transient Characteristics and Relay Protection

Micro grid can minish the impact from fluctuation of distributed generator by control and management system as a new type of power system. But micro-grid also brings disadvantages on power attemperation, function and relay protection. Firstly the inverter’s electric model is built and the fault transient is simulated. Inverter interfaced distributed generator shows evident non-linear characteristic for the limits on power and current from control system. In this paper, according to the fault transient simulation results, analysis of the problems faced by the existing relay protection and corresponding solutions is given respectively.