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In this paper, the possibility of increasing the transmission capacity of power transmission lines 35 to 220 is considered. The methods of phase convergence and splitting are considered as known methods for increasing the capacity of power transmission lines, The use of insulating cross-arms and spacer blocks mounted between the wires of different phases, allows to bring the phases of power transmission lines together, thereby reducing the longitudinal reactance of the line and increasing the transverse capacitance. Similarly, by splitting the wires, it is possible to get the same results. The studies were carried out on the basis of an analysis of the equations determining the parameters of power transmission lines. The use of insulating cross-arms and spacer blocks allows not only to increase the transmitted power, but also to reduce the dimensions of power transmission lines and the alienation of land under it, to reduce the environmental impact. Increasing the capacity of power transmission lines will reduce the electric power network, thereby increasing its reliability and manageability.

This paper describes the method of determining a location of short circuit on transmission lines when saturation of current transformers magnetic cores and aperiodic components in measured currents are there. The method is based on measuring ratio of the reverse sequence current on one side of a line to the current on the other side. It is shown how to exclude the aperiodic component in measured currents. It is shown that four samples of currents in the initial short-circuit period are sufficient to determine all the parameters of mode necessary for the implementation of relay protection and determination of short-circuit locations.

The authors propose the algorithms to calculate the actual values of currents and their derivatives. The algorithms allow a sharp reduction in the aperiodic components of currents in the calculated actual values and their derivatives. The algorithms are developed to calculate the instantaneous values of positive- and negative-sequence currents when the information obtained during a time interval equal to two milliseconds or less is used. An algorithm is devised to calculate the sinusoidal components of the currents in the presence of aperiodic components in the samples. To eliminate the disoperation of digital relay protection and improve the accuracy of fault location, it is necessary to eliminate the influence of aperiodic components in the currents drawn to the measuring devices of relay protection. The algorithm completely eliminates the aperiodic component at any time constants and is implemented by four samples of currents. The four samples of currents separated by three sampling intervals are sufficient for calculating all the parameters of currents, including the positive and negative-sequence currents, in particular in the case when the magnetic cores of current transformers reach saturation. The proposed methods for setting the industrial frequency parameters to avoid the aperiodic components in short-circuit currents are based on the algorithms that process the data from three and four samples of currents.

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.

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 methods of determining fault locations on transmission lines in networks with earthed neutral using the instantaneous values of industrial frequency parameters are considered. The algorithm of a one-way method of determining the location of one-phase open fault in transmission line is proposed based on processing of instantaneous currents and voltages. For sampling intervals of 0.5 to 0.625 ms, the measurement time will not exceed 2.5 ms. During this time, there will be no saturation of the coil flux guide of the current transformers, i.e., the relay protection receives undistorted information. The algorithm is applicable for cases when phase discontinuities are accompanied by a short-circuit.

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.

The introduction of microprocessor technology in the management of energy objects, including diagnostics, into relay protection and automation, allows combining and unifying relay protection of individual objects into a single system. One of the methods of unified relay protection may be directional protection. It is possible to develop and offer directional protection for generators, transformers, which are currently not used. An obstacle to the use of directional protection of generators and transformers is the presence of aperiodic components in the short-circuit currents, that introduce distortions in determining the angle between the short-circuit currents and voltages. At the “Power Supply” Department of the North-Eastern Federal University named after M.K. Ammosov a method that excludes aperiodic components in the secondary currents of current transformers of power system objects was developed, which made it possible to exclude incorrect actions of directional protections, including when saturating the current transformer magnetic cores. The method is based on processing four instantaneous samples of currents separated by identical sampling intervals.