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In conditions of complicated structure of modern power grids, a special emphasis is given to the issues of ECA failure-free operation. This article is concerned with the problems of increasing sensitivity and selectivity of line power unloading automatics because its correct operation plays an important role in ensuring energy security and survivability of power systems. Within the framework of this paper, the full cycle of development of ECA algorithm is considered. ECA is performing the functions of line power unloading automatics. The development cycle includes the tasks of tentative assessment of electrical equipment operating modes, rationale for choosing the automatics tripping characteristics, algorithm design and programmable logic controller (PLC) based implementations. It also includes the laboratory testing with the use of real-time hardware and software complex. The calculation data of steady-state and transient operating modes of power electrical equipment presented in the article were carried out in software complexes RastrWin, Rustab. The power facilities of the interconnected power systems of Urals, Siberia and Kazakhstan were considered as modeled objects of power systems. In accordance with the obtained results, the tripping characteristics of device being developed were determined. Based on the results of mathematical simulation of electrical equipment transient operating modes, the major disadvantages of device algorithm, which controls the active-power flow through the line, were determined. Besides, methods focused on increasing the sensitivity and selectivity of such automatics are proposed. The developed algorithm controls the active-power flow over a given cross section. Measurements of electrical parameters are carried out at one of the lines in cross section. The total value of active-power flow over the cross section is calculated according to the equivalent circuit. To increase the sensitivity and selectivity of automatics, the algorithm uses the action time adjustment. It is determined depending on the previous operating mode of transmission line. The algorithm for line power unloading automatics described in this article was implemented on a PLC system in accordance with the IEC 61131 standard. The obtained device was successfully tested on the real-time hardware and software complex. This paper presents the results of the carried out device performance tests, and the characteristics of the used mathematical simulation.

The research is devoted to the problem of electromagnetic compatibility of toroidal chokes with microprocessor elements of printed circuit boards. The scientific novelty of the work lies in the determination of the most favorable option for the location of the chokes through the minimization function. The analysis of target vector functions and the most effective option is carried out. The purpose of the study is to determine the permissible location of the chokes, at which the electromagnetic interference, they create for the microprocessor elements of the printed circuit board, will be minimal. The object of the study is a printed circuit board of a microprocessor-based device for measuring the grounding resistance of supports of high-voltage power lines, in the power circuit of which toroidal chokes are used. The subject of this work is the electrophysical properties of toroidal chokes, which are sources of electromagnetic interference for microprocessor elements of control and measuring instruments. The research methodology consists in carrying out numerical experiments to calculate the electromagnetic field with subsequent analysis of the obtained vector functions of the magnetic field strength H on the board surface. The assessment of the influence of interference caused by chokes is carried out using the developed mathematical model and numerical methods for calculating the electromagnetic field. For computational calculations, the authors have developed a software algorithm implemented using the Delphi programming language. The choice of the mutual arrangement of the chokes on the microprocessor integrated circuit is carried out as a result of solving the optimization problem by the gradient method, taking into account the given restrictions on the condition of electromagnetic compatibility. To assess electromagnetic compatibility, a design model of a printed circuit board of a microprocessor device with toroidal chokes was developed. As a result of a numerical experiment, a method for automated determination of the location of toroidal chokes within an integrated microcircuit of resistance devices of the proposed control of electrodes of overhead power transmission line supports was tested. As a result of research, it was found that for electromagnetic compatibility of microelectronic devices, it is sufficient to place the toroidal chokes of power circuits closer to the corners of the printed circuit board. In other design cases, the EMC class 1 requirement is not met.

The article deals with questions of researching and analysis of voltages induced in protective shields of three-phase shielded conductor in modes of asymmetric short circuits external to generators of power station. The development of recommendations and measures to ensure electromagnetic compatibility of measuring circuits of microprocessor devices is an urgent research task, since it is generally determined by the electrophysical properties of the interference source and the analog-digital element base of the measuring part of the devices. The scientific novelty of the work consists in the development of measures to eliminate the induced electromagnetic influence on control and measuring cables switched to current and voltage measuring transformers. The purpose of the study is to assess the electromagnetic effect of the industrial frequency field on control and measuring cables laid near a phase-shielded current pipeline, as well as to develop measures to ensure their electromagnetic compatibility. The paper presents a method for calculating the distribution of the intensity modulus H of a magnetic field induced by an industrial frequency current from a generator at an electric power station. For the modes of single-phase, two-phase and two-phase short circuits to the ground, patterns of the distribution of the magnetic field intensity modulus H are constructed, a stiffness class is assigned according to the magnetic field effect on control and measuring cables in accordance with the classification. Recommendations to reduce the level of exposure to the magnetic field intensity H are given. In case of using the screen, a repeated calculation was performed to compare and determine the effectiveness of this event. As a result of numerical experiments, the effectiveness of the use of an additional screen as one of the measures to ensure electromagnetic compatibility is justified. The use of an additional steel shield makes it possible to reduce the magnetic field strength on the surface of control and measuring cables to acceptable values and, as a result, ensure reliable operation of microprocessor control, protection and automation devices.