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The article discusses an algorithm for determining the fundamental harmonics of currents and voltages in the measuring devices of relay protection at saturation of the magnetic circuits of current transformers. The aperiodic component arises due to the presence of complex resistances of generators and power lines in the parameters of the power system. Periodic components appear in microprocessor technology due to imperfection of the measuring devices. The exclusion from the short-circuit current entering the measuring devices of relay protection, non-periodic components and harmonics, except for the first one, makes it possible to increase the reliability of relay protection.

The paper addresses the problem of relay protection malfunction under the condition of saturated state of the current transformer magnetic core. The first part of the paper provides an overview on how this problem is solved in the related studies. The pros and cons of the existing approaches are highlighted and discussed. A method for reducing the influence of aperiodic components on the operation of digital relay protection is considered in detail. An algorithm for eliminating the aperiodic component in the current of the measuring element relay protection, caused by the saturation of current transformer cores, is shown and described as a simple step-by-procedure, providing the opportunity of its real-time applications. The authors focus the discussion and concluding remarks of the paper on the major advantages and the promising application spheres of the proposed approach. All the calculations provided in the case study section are based on real metering data.

In this paper, a method of samples of instantaneous currents and voltages is proposed, which allows to extract only sinusoidal information necessary for correct operation of digital relay protection and automation from information containing instantaneous values of currents containing periodic and aperiodic components. The studies were performed based on the analysis of the equations of short-circuit currents in electrical networks. The time during which the current and voltage parameters are sampled does not exceed 2 milliseconds, which is less than 1/8 of the industrial frequency period. The method made it possible to implement protections, which fix damage with a help of analog devices only for several periods of current change. At the same time, the protections implemented by analog devices are not free from errors introduced by aperiodic components. Principles for the implementation of directional protection of generators and transformers are proposed. Directional protection of generators and transformers is feasible in the presence of information about the modes of the electrical network elements that are connected with the protected ones. The proposed four-sampling method allows to implement all protections that react to periodic components of currents and voltages using only four instantaneous values of currents and voltages obtained within two milliseconds or less after the occurrence of a short circuit.

The paper presents the principles of constructing simulation models of the components of an integrated multi-energy system based on the energy hub concept. The application of the algorithms designed to develop simulation models of the components are given, the results of their implementation are verified with generally accepted theoretical approaches used to obtain the necessary characteristics depending on the set objective functions. The proposed approach offers a broad prospect for the study of many significant problems in integrated power systems with multiple carriers, including their properties, features of expansion and operation

One of the serious problems of the normal operation of power systems is a violation of efficiency of overhead power lines. Short circuits are especially dangerous. The probability of occurrence of faults is reduced, but not reduced to zero, with an increase in the quality of installation, reliability, insulators and conductive materials. The proposed method is based on the fact that the short circuit current at the beginning of the transmission line of power electric system depends on the distance (location) to the fault point. This article discusses the following topics: theoretical possibility of fault location on the time of arrival of the responses to the beginning and end of the line, the development of the algorithm processing of information, the development of the block diagram of additional devices that are not included in the phasor measurement units (PMU). The article gives an example of the application of this technique.

The presence of a great number of technical facilities that form a base of the intelligent network in the modern electric power systems requires a principally new approach to the research into the dynamic operating conditions of these systems. Currently consumers impose higher requirements for the quality of electricity and reliability of electricity supply. Therefore, the operating conditions of such power systems and their control, including that in the emergency conditions represent a challenging problem that needs to be studied. The authors use a universal approach to the mathematical modeling which is based on the input-output system represented by Volterra integro-power series. Staged training inputs were applied to identify transient characteristics. The calculation results presented in the paper demonstrate an increase in the modeling accuracy due to a more complete consideration of information on system outputs to the test inputs.

In addition to periodic components of industrial frequency, the aperiodic ones arise in windings and on the generator output leads under the conditions of shortcuts. These aperiodic components slow down the operation of the main differential protection of a generator up to ten periods of a network frequency with the application of saturated magnetic cores of current transformers as well as zero current relays and transformer differential protection [1]. This slowing down promotes accidents and can even lead to generator’s winding and steel burn-out at high-ampere currents. The present paper considers the ways to reduce the impact of aperiodic components on the operation of digital relay protection of generators and generator-transformer blocks and proposes generator’s directional digital protection.