Directions for improving the quality of electrical energy

At industrial enterprises, powerful electrical installations and power receivers with a specific nature of power consumption (nonlinear, asymmetric, rapidly changing load) are becoming more widespread, which has led to an increase in the distortion of current and voltage curves in the nodes of general-purpose power supply systems. On the other hand, for the control of technological processes, computer technology and electronic automation, means of control, measurement and signaling are increasingly used, which, as a rule, are connected to the same general-purpose power supply systems and experience negative effects from energy-intensive power consumers. Power equipment (motors, transformers, capacitors) is also subject to the negative effects of distortion, resulting in increased heating and reduced equipment life. Electromagnetic interference is understood as electromagnetic, electrical and magnetic phenomena created by any source and which undesirably affect the useful signal - the transmission of electricity from the power source to the consumer. Accordingly, the propagation paths of electromagnetic interference in power supply circuits are distinguished. Galvanic paths are created by directly connecting sources of electromagnetic interference to the corresponding circuits. Electrostatic paths are due to the electrical component of the electromagnetic field and arise due to the existence of parasitic capacitances between the individual elements of the circuit. Magnetic paths are due to the magnetic component of the electromagnetic field and arise due to the existence of parasitic mutual inductances between individual elements of the circuit. Electromagnetic paths - radiation interference. Consider specific examples of the propagation of electromagnetic interference. Electrical installations generate radiation interference and conduction interference. The propagation medium of radiation interference is the space surrounding these installations. The conducted studies have shown that there are known methods for protecting electrical networks and control systems from these interferences by shielding and grounding screens and housings of electrical installations. Therefore, these types of interference do not have a significant impact on the construction of power supply systems. The greatest influence on electrical receivers and control systems is exerted by conduction electromagnetic interference, the propagation medium of which is wires, cables, bus ducts, current ducts, reactors. Since all electrical receivers have electrical connections with each other through galvanic paths, these interferences can affect any electrical receiver of a given power supply system. Electromagnetic interference created by electrotechnological installations can be divided into the following: - technological, created due to a sharply variable mode of operation (these include fluctuations and voltage dips); - electrical, determined by the type of installations, their control and switching systems (these include non-sinusoidality and asymmetry of currents and voltages, impulse overvoltages, aperiodic and constant components in currents); - structural and technological, depending on the composition of the load in groups of electrical receivers and their switching; - structural-composite electrotechnical, characterized by the mutual influence of interference on each other. Electromagnetic interference is not intentional as it occurs during the normal operation of these installations. By their nature, electromagnetic interference is divided into two types: deterministic and random. The electromagnetic compatibility of electrical receivers is understood as their ability to function without deteriorating quality indicators when they are powered jointly from a common network. The study of the electromagnetic compatibility of electrical receivers is of great technical importance, especially in connection with the rapid introduction of elements of microelectronics and microprocessor technology into the control systems of electrical receivers. This problem needs to be solved in the following directions: – consideration of the causes, effects and methods of reducing unintentional electromagnetic interference; – determination of the susceptibility of electrical receivers to electromagnetic interference and their control systems; – prediction of electromagnetic compatibility to electromagnetic interference; – development of effective measures to protect electrical receivers and their control systems from electromagnetic interference; – construction of power supply systems for industrial enterprises, taking into account the electromagnetic compatibility of different power receivers. Power engineers of industrial enterprises, developers of electrical equipment and designers need to know the permissible norms of electromagnetic interference introduced by electrical receivers into power supply systems. Power supply systems of industrial enterprises, where there are sources of electromagnetic interference, must be built taking into account the electromagnetic compatibility of power receivers, i.e., all power receivers must function normally in this power supply system. In order to meet the conditions of electromagnetic compatibility, it is necessary either to reduce the level of electromagnetic interference created by electrical receivers to acceptable values or to separate the power supply of electrical receivers that create electromagnetic interference and are sensitive to them. Reducing the level of electromagnetic interference is carried out using various functional devices or by increasing the power of power supplies. To date, there is no consensus on the most optimal methods for reducing electromagnetic interference. The greatest reduction in electromagnetic interference is achieved by using various functional devices (higher harmonic filters, balancing devices, static compensators, longitudinal compensation installations, etc.), as well as multifunctional devices (filter-balancing, symmetrical-compensating, symmetrical-filter-compensating, etc.). However, reducing electromagnetic interference to zero is neither technically nor economically feasible. In the economic comparison of various electrical receivers, it is necessary to take into account the cost of not only the electrical receivers themselves, but also devices for bringing electromagnetic interference to normalized values. When choosing the types of electrical receivers, one should also focus on electrical receivers that are less sensitive to electromagnetic interference. For example, the sensitivity of gas-discharge light sources to voltage fluctuations is about 2 times less than incandescent lamps. Therefore, in the presence of sources of voltage fluctuations, only gas-discharge lamps should be used, which in many cases will make it possible to dispense with special devices to reduce voltage fluctuations. Of great importance for solving the problems of electromagnetic compatibility of electrical receivers is the correct choice of their type. It is known that the same technological process can be performed by different types of electrical receivers. For example, the smelting of cast iron can be carried out in induction furnaces, AC and DC arc furnaces. These three types of power receivers create different types of electromagnetic interference, so when choosing a type, you should focus on power receivers that create lower levels of electromagnetic interference for a given industrial enterprise. Indicators of the quality of electrical energy are not levels of electromagnetic compatibility. For each electrical receiver connected to a common connection point, its own permissible values of power quality indicators for interference introduced into the general-purpose power supply system (permissible individual contribution of the electrical consumer to the overall level of interference) must be set. When developing and manufacturing electrical receivers that create interference, it is necessary to provide them with special technical devices that would reduce the levels of interference introduced into the supply network.