Ground Power Research Articles

Design of universal power supply and distribution ground test system based on modularity

To solve the problems of high functional requirement, complex structure and poor versatility of manned spacecraft power supply and distribution ground test equipment, a modular universal ground power supply system (PSS) is designed. The functions of the system cover the functions of wire instruction opening, parameter measurement and state detection of the interface between the manned spacecraft and the ground equipment, and realize the universal and extensible configuration. This paper provides a general architecture design method for complex manned spacecraft power supply and distribution ground test system.

Numerical investigation on power generation performance of enhanced geothermal system with horizontal well

• Combined with thermodynamic cycle, EGS-ORC coupling model is proposed. • The optimal operation parameters of EGS-ORC are obtained. • The effect of various parameters on the performance of ORC system is probed. Enhanced geothermal system (EGS) can efficiently extract heat stored underground, while Organic Rankine Cycle (ORC) system can generate electricity with heat extracted by EGS. A combination of underground heat extraction and ground power generation systems is proposed in present work. The underground heat extraction system that consists of an EGS coupled with hydraulic-thermal horizontal wells and five disc-shaped fractures. The ground power generation system is comprised of a basic ORC system, and R245fa is used as the working fluid. The performance of combined system is numerically investigated in present work. The results indicate that with the increase of geothermal fluid mass flow rate, the geothermal fluid outlet temperature decreases rapidly, and the thermal reservoir life exhausts more earlier. In addition, the optimization of EGS is conducted as well, and the optimal case with the maximum production temperature has been obtained. It’s found that when the mass flow rate and injection temperature of geothermal fluid are 30 kg/s and 50 °C respectively, the production temperature of considered EGS drops to 441.3 K after thirty years of operation, the increase in pump power consumed by transporting geothermal fluid rises to 0.53 MW, and the net output power of ORC system drops to 895 kW. Furthermore, it’s found that the geothermal fluid mass flow rate has an obvious influence on the power generation performance. In addition, a sensitivity analysis of the three considered parameters (production pressure, fracture distance, well spacing) has been performed, which reveals that well spacing has the greatest effect on EGS power generation performance.

Design and implementation of ground power unit using a three‐level fault‐tolerant neutral point clamped inverter

AbstractDue to the widespread use of static power converters in various industries and sensitive applications such as ground power units (GPUs), it is essential that the inverters have high reliability. A failure in the inverters can cause undesirable consequences such as low performance, shutting down the system, and losing the stability of the entire system. On the other hand, in some critical industrial processes with high standstill costs and safety‐aspect concerns, such as aircraft, high reliability, and survivability of the system, are very important. Therefore, the use of fault‐tolerant (FT) inverters is inevitable in such applications. In this paper, using a three‐level fault‐tolerant neutral point clamped (FT‐NPC) inverter, the reliability of the GPUs is increased and it results in higher availability and continuous system performance. Furthermore, a simple automatic fault detection (FD) algorithm is presented by taking the inverter pole voltage as a FD parameter. The inverter is analyzed for open‐circuit fault in the switches, and the reliability of the FT‐NPC inverter is compared with the classic inverter. The simulation and experimental results of the 2‐kVA converter prototype are presented to confirm the FT inverter performance and the proposed method.

Research on the disturbance behaviour of the track chassis to the sand-gravel pavement during the steering process of the electric shovel based on DEM

To analyse and improve the disturbance behaviour of the track chassis to the sand-gravel pavement during the steering process of the electric shovel, the steering process of the electric shovel is taken as the specific analysis object, and the steering radius, the steering velocity, the grouser width, and the grouser height are regarded as influence factors. The disturbance prediction model of the electric shovel is established through the coupling method of discrete element method (DEM) and multi-body dynamics (MBD) and the Kriging model. On this basis, the steering disturbance behaviours of the track chassis to the sand-gravel pavement under different working conditions are obtained. Finally, taking variation coefficient ratio of ground pressure, power, and disturbance potential energy as the optimization goal, the multi-objective optimization based on genetic algorithm (GA) and the disturbance prediction model is implemented, and the corresponding optimization results are 6.02 m, 0.14 m/s, 19.61 mm, and 12.68 mm. The feasibility of the optimization results is then confirmed via comparison with ones of DEM-MBD coupling simulation, the results show that the variation coefficient ratio of ground pressure, power, and disturbance kinetic energy are reduced to varying degrees, and the disturbance potential energy is greatly improved. This indicates that the disturbance of the track chassis to the sand-gravel pavement has been improved, which is conducive to better steering of the electric shovel.

A novel method for trajectory recognition and working condition diagnosis of sucker rod pumping systems based on high-resolution representation learning

The pumping unit is the most important lifting equipment in the rod pumping system, which transmits ground power to the downhole pump through its sucker rod. Trajectory identification of the rod pumping system can be used to study the motion law of the pumping unit, and it is the basis for the design of the pumping parameters and the analysis of the working conditions. Most of the studies on the dynamics of the pumping unit are to discuss the simple harmonic motion of the suspension point or the motion of the crank-slider in the ideal state, which is quite different from the actual situation. In this paper, a key point detection method for oil pumping units based on high-resolution representation learning is proposed. The model adopts a multi-resolution parallel network, which connects multiple network branches with different resolutions in parallel. Then it performs multi-stage processing on the input pumping unit images and outputs the predicted Gaussian heatmaps of key points to realize the trajectory recognition of the pumping unit. Different from the traditional series convolutional network structure, which needs to recover high resolution from low resolution, the parallel structure of this model is able to maintain the high resolution of the backbone network and thus the learned representations are more accurate in spatial location. This method is also experimentally verified and compared with the latest convolutional network structure. The results show that the model accuracy of the high-resolution representation learning method is more than 6% higher than that of the comparison methods. In addition, the results of this model can be used to judge the balance of the pumping unit, automatically calculate the maximum stroke and polished rod stroke, and have guiding significance for the working condition diagnosis of the rod pumping system.

Development of an Aircraft Electric Power Architecture With Integrated Ground Power Unit

This article presents a switch-mode rectifier-based electric power architecture with an integrated ground power unit for more electric aircraft. The well-regulated high-voltage dc-bus is established from the aircraft generator. And the conventional major 270-Vdc, 28-Vdc, and 115-Vac/400-Hz buses are also preserved. In landed conditions, the ground power unit function powered by the mains is inherently possessed thanks to the proposed integrated schematic. First, the developed switch-mode rectifier using a silicon-carbide device with a wide frequency range covering utility line frequency and aircraft generated varied high frequency is presented. The allowable energy storage inductances using the embedded generator armature winding are derived. Good generator armature power quality and well-regulated dc output voltage are preserved by the designed current and voltage control schemes. Next, the utility grid-powered ground power unit established by the embedded schematic is introduced. Finally, the inverter for generating the 115-Vac/400-Hz three-phase source and the dc–dc converter for establishing the 270-Vdc bus are constructed. Normal operations, good dynamic, and steady-state performances of all the constructed power stages are verified experimentally, which can confirm the feasibility of the proposed aircraft power architecture.

Damage assessment of mobile communication facilities subjected to major earthquakes

ABSTRACT Communication systems play a critical role in emergency response during disasters. In this study, we proposed a methodology for assessing damage to mobile communication facilities subjected to major earthquakes, with consideration of both ground shaking and power outage effects. Fragility curves were employed to evaluate the damage to base stations due to ground shaking. The power transmission relationship among electrical substations was established to analyze the impact of power outage on base stations. Integration of the two evaluations yielded the total number of affected base stations and the distribution of malfunctioning base stations in a city or county. The 2016 Meinong earthquake and the 2018 Hualien earthquake were selected as case studies to verify the analytical results. The predictions exhibited acceptable agreement with disaster investigation reports from the two earthquake events. The proposed methodology enables a prompt evaluation of the seismic impact on mobile communication facilities, which could help governments in allocating rehabilitation resources during emergency response or disaster mitigation planning.

Design and Implementation of a Floating PV Model to Analyse the Power Generation

The floating photovoltaic (FPV) system is a revolutionary power production technology that has gotten a lot of interest because of its many benefits. Aside from generating electricity, the technology can also prevent the evaporation of water. The electrical and mechanical structures of FPV power stations must be studied to develop them. Much research on FPV technologies has already been undertaken, and these systems have been evaluated from many perspectives. Many problems, including environmental degradation and electricity generation, fertile soils, and water management, are currently limiting societal growth. Floating photovoltaic (PV) devices save a great of land and water resources and have a greater energy conversion efficiency than standard ground power systems. A performance investigation of photovoltaic (PV) installations set on a moving platform is carried out. The paper presents and discusses various design alternatives for boosting the profitability and efficiency of floating photovoltaic (FPV) systems. Especially, FPV systems that take advantage of increasing capabilities like monitoring, conditioning, and attention were included. Although researchers have agreed on the benefits of floating systems, there has been little in-depth research on the parameters of floating photovoltaic systems. The results of this research tests were performed, and these reveal that the beneficial monitoring and conditioning impacts result in a significant gain in performance. The effects of using flat reflections on improvements are also investigated. As a result, this research examines the evolution of photovoltaic systems, then investigates the power generation capacity of floating photovoltaic systems, and then examines the benefits and possibilities of floating PV systems in depth. The concept of developing an integrated air storage system using a floating building on waters is discussed.

A low temperature preheating strategy with optimized fuzzy controller for lithium-ion batteries

Electric vehicles (EVs) suffer from significant performance loss under low temperatures due to the limited operating temperature ranges of lithium-ion batteries. Warming up the cells before the operation is recommended by manufacturers to recover effective drive for EVs rapidly. In this paper, an optimized internal pulse preheating strategy is proposed to realize the cold start of vehicles without other ground power sources. First, an electro-thermal model of batteries is established, which can dynamically update based on the current state of charge and temperature of cells. Then the internal preheating pulse currents are obtained by using fuzzy logic control with a fixed frequency. The bidirectional pulse amplitudes are decided by the real-time state of charge and temperature in the rule-based framework. Furthermore, an offline genetic algorithm is used to optimize the fuzzy rules with the updated impedance parameters to reduce energy consumption and preheating time. Experiments are conducted with different battery initial states of charge to evaluate the superiority of the proposed strategy. Results show that the battery can achieve a temperature rise from −10 °C to 10 °C in 603 s though the state of charge is at a low level, with the temperature rise above 2 °C/min. Besides, compared with current preheating strategies, the proposed strategy can at least shorten the preheating time by 15% and save the energy loss by 10%.

Two-level model predictive control energy management strategy for hybrid power ships with hybrid energy storage system

Compared with the load power characteristics of ground power systems, the intermittent and random fluctuation of ship load power demand brings challenges to the energy management system of ship power systems. To achieve fuel economy and solve the problem of power fluctuation, the hybrid energy storage system (HESS) composed of the battery pack and ultra-capacitor is applied to the diesel-electric hybrid ship. A two-level model predictive control (MPC) strategy consisting of two optimization stages is proposed. The first stage aims to determine the power distribution solution of the diesel generator and battery at a large time-scale. In the second stage, the operation strategy of the ultracapacitor is determined at a small time-scale based on the power distribution solution of the first stage. The conventional MPC-based strategy and global optimization strategy based on dynamic programming (DP) are compared with the proposed strategy. The simulation results show that the proposed strategy has better fuel saving ability, and realizes the clear power frequency division between the supercapacitor and battery. In addition, the proposed strategy can also approach the performance of global optimization.

Research on parallel output method of DC regulated power supply

This paper describes the output characteristics of DC regulated power supply in spacecraft ground test system and proposes a scheme of DC regulated power supply parallel output with remote sampling. Then the power-on and power-off procedure as well as the characteristics of normal operation in space vehicle using ground power supply are analyzed.The transient characteristics of parallel power supply are summarized. This method with simple circuit connection is able to meet the power supply requirements of spacecraft as well as improve the reliability and security of power supply system. Experimental verification demonstrates the effectiveness of the proposed method. It solves the problem of heavy load energy requirement of spacecraft in ground test and verification stage.

Power Performance Comparison of SiC-IGBT and Si-IGBT Switches in a Three-Phase Inverter for Aircraft Applications.

The converters used to integrate the ground power station of planes with the utility grid are generally created with silicon-insulated gate bipolar transistor (Si-IGBT)-based semiconductor technologies. The Si-IGBT switch-based converters are inefficient, oversized, and have trouble achieving pure sine wave voltages requirements. The efficiency of the aircraft ground power units (AGPU) can be increased by replacing existing Si-IGBT transistors with silicon carbide (SiC) IGBTs because of the physical constraints of Si-IGBT switches. The primary purpose of this research was to prove that the efficiency increase could be obtained in the case of using SiC-IGBTs in conventional AGPU systems with the realized experimental studies. In this study, three different experimental systems were discussed for this purpose. The first system was the traditional APGU system. The other two systems were single-phase test (SPT) and three-phase inverter systems, respectively. The SPT system and three-phase inverter systems were designed and implemented to compare and make analyses of Si-IGBTs and SiC-IGBTs performance. The efficiency and detailed hard switching behavior comparison were performed between the 1200-V SiC-IGBT- and 1200-V Si-IGBT-based experimental systems. The APGU system and Si-IGBT modules were examined, the switching characteristic and efficiency of the system were obtained in the first experimental study. The second experimental study was carried out on the SPT system. The single-pulse test system was created using Si-IGBTs and SiC-IGBTs switches in the second experimental system. The third experiment included a three-phase-inverter-based test system. The system was created with Si-IGBTs and SiC-IGBTs to compare the two different switch-based inverters under RL loads. The turning off and turning on processes of the IGBT switches were examined and the results were presented. The Si-IGBT efficiency was 77% experimentally in the SPT experimental system. The efficiency of the third experimental system was increased up to 95% by replacing the old Si transistor with a SiC. The efficiency of the three-phase Si-IGBT-based system was 86% for the six-switch case. The efficiencies of the SiC-IGBT-based system were increased to around 92% in the three-phase inverter system experimentally. The findings of the experimental results demonstrated that the SiC-IGBT had a faster switching speed and a smaller loss than the classical Si-IGBT. As a result of the experimental studies, the efficiency increase that could be obtained in the case of using SiC-IGBTs in conventional AGPU systems was revealed.

Development of a screening formula for sarcopenia using ground reaction force during sit-to-stand motion

BackgroundGround reaction force during sit-to-stand motion is related to lower extremity strength, and such measurements indicating weak muscle strength, may be linked to sarcopenia. We aimed to examine and describe the relationship between sarcopenia and ground reaction force during sit-to-stand motion to develop a diagnostic tool. Research questionCan ground reaction force during sit-to-stand motion help detect sarcopenia? MethodsThis study included 627 community-dwelling older adults who were divided into non-sarcopenia and sarcopenia groups to compare ground reaction force parameters. A sit-to-stand force analyzer was used to measure the ground reaction force, power, and time between the minimum and maximum ground reaction force. We assessed the association between sarcopenia and each ground reaction force parameter. Receiver operating characteristic curve analysis was performed with sarcopenia as the dependent variable and ground reaction force-related measurements as independent variables. The probability of predicting sarcopenia was calculated using multiple logistic regression analysis, with sex and age as independent variables, and another receiver operating characteristic analysis was performed using the probability value. ResultsGround reaction force parameters related to strength and power were lower in the sarcopenia group than in the non-sarcopenia group. Furthermore, we were able to develop a formula to detect sarcopenia using the maximum ground reaction force (area under the curve; 0.906 [95% CI 0.858–0.954] for men and 0.858 [0.808–0.908] for women). The sensitivity and specificity of sarcopenia detection using this formula were 89.7% and 80.5%, respectively, for men and 95.0% and 60.9%, respectively, for women. SignificanceGround reaction force during sit-to-stand motion may reflect low skeletal muscle strength associated with sarcopenia. We were able to develop a method for sarcopenia detection by analyzing the sit-to-stand force required in only one or two sit-to-stand motions, even though it does not measure the skeletal muscle mass directly.

Разработка методики расчета перепада давления на топливном фильтре из-за появления углеродсодержащих осадков в среде жидкого углеводородного горючего (охладителя)

The paper introduces a theoretical study related to a new method for calculating the fuel filter pressure drop caused by sedimentation in a liquid hydrocarbon fuel (cooler) medium; describes some thermophysical properties of sediments in fuel systems of various heat engines; examines the inventions aimed at preventing the failure of filters and pressure drop in them. As the overview and analysis of scientific and technical literature discovered no methods for calculating the pressure drop on the filters of heat engines and power plants, we developed a new formula for calculating the fuel filter pressure drop caused by sedimentation, taking into account the thermal and electrical nature of carbon-containing sediments. Using this formula, we found a new method for calculating the pressure change, which can be used to calculate the residual life of filter elements, theoretically approbated the new method relying on the results of experimental studies by previous researchers who used aviation kerosene. As a result, we obtained the fuel filter operating time to failure in several operating modes. The method proves to be valid, as it is applicable for calculating the pressure drop in almost all ground, air, and aerospace-based heat engines and power plants under various operating conditions of the fuel system. Furthermore, the method can be used with various materials of the metal walls of filter elements, pumping speeds of hydrocarbon fuel, pressures at the fuel filters inlet, temperature conditions inside the fuel supply, and cooling channels of engines and power plants.

ЗАЛЕЖНІСТЬ ЕНЕРГЕТИЧНИХ ПРОЦЕСІВ ВИСОКОВОЛЬТНИХ ЕЛЕКТРОРОЗРЯДНИХ СВЕРДЛОВИННИХ КОМПЛЕКСІВ "СКІФ" ВІД ХАРАКТЕРИСТИК НАВАНТАЖЕННЯ

The work determines the dependences of electrical parameters of the ground and submerged parts of the charging unit of the electric-discharge borehole complex "Skif-100M" on peculiarities of changing of electrical characteristics of the active and reactive load contributed by modern geophysical cables up to 10 km long with an active resistance from 24 to 644 Ohm, capacitance from 0.2 to 1.8 μF and inductance from 2.9 to 31 mH. New dependences and conditions to increase the charging power of storage capacitor, the output power of the complex and the voltage of ground part of its power supply from load parameters were determined on the basis of analysis of transients in the charging circuit of a complex. There were realized necessary energy characteristics for creation of a universal submersible charging unit to increase energy efficiency and productivity of high-voltage borehole electric-discharge complexes of "Skif" type. The obtained results provide effective modernization of the domestic submersible electric-discharge equipment of such complexes (in particular, their ground power sources and submersible charging units). This extends the scope of their application in the oil and gas industry of Ukraine and increases the attractiveness of investment of foreign companies engaged in the processing of oil wells in different countries of the world to the Ukrainian economy. References 11, figures 4, tables 3.

An Overview of Four-Leg Converters: Topologies, Modulations, Control and Applications

In three-phase unbalanced systems, where the circulation of zero sequence current is necessary, four-leg converters provide a neutral connection for single-phase or other unbalanced loads typically utilized in three-phase distribution systems. In addition, control of the magnitude and phase of the zero-sequence voltage and/or current are also achieved using four-leg power converters. However, even when four-leg converters have become very important in several fields as for instance, four-leg microgrids and aerospace applications, a comprehensive review of the converter topologies, control methods, modulation methods and output filters have not been hitherto published. In this paper, a comprehensive overview of the state-of-the-art of four-leg converters is presented, based on the selection of over 400 papers published in journals and conferences, identifying mature and incipient topologies, modulation strategies, control schemes and applications. Each topic presented in this work is thoroughly discussed and reviewed, analyzing characteristics, implementation issues, and reported advantages and disadvantages to provide a comprehensive overview of the current research and future challenges in four-leg converters. The most important applications of four-leg converters are also discussed in this work, including stand-alone power supply, uninterruptible power supplies, grid-connected 4-leg inverters, ground power units for aerospace applications, active filtering for power quality enhancement, cooperative control of 4-leg converters for micro-grid applications, among others. Finally, future work and conclusions are highlighted in this paper.

Heat-Induced Dry Hydrolysis of Sodium Borohydride/Oxalic Acid Dihydrate Composite for Hydrogen Production.

The generation of hydrogen, free of poisonous gas, combined with a lightweight proton-exchange membrane fuel cell can expand the use of hydrogen energy from conventional ground transportation vehicles and power stations to a variety of flying vehicles and wearable devices for civilian and military purposes. Herein, a hydrogen fuel composite composed of sodium borohydride (SB) and oxalic acid dihydrate (OA·2H2O) is introduced. The SB/OA·2H2O composite was easily decomposed to generate pure hydrogen at a trigger temperature of 50 °C, at which the water molecules of the OA·2H2O component were effectively liberated, inducing hydrolysis of the SB component to produce hydrogen gas. This dry hydrolysis-based hydrogen generation using the SB/OA·2H2O composite has the merits of rapidly generating hydrogen (i.e., 0.4 g of the composite can be fully decomposed within a minute at low temperatures), free of poisonous gas, in approximately 5 wt % yield (the theoretical maximum value).

Development of Appropriate Power Distribution Design for Can-Sized satellite (canSAT)

Can-Sized satellite (canSAT) is a small satellite that is used for educational purpose. CanSAT offer student to build their satellites with their creativity which make the learning process more effective. In Malaysia, SiswaSAT is held by the Malaysia Space Agency for students in different categories to participate and build their satellites according to rules set and it should be a low-cost project. CanSAT can be divided into few parts which are communication system, onboard data acquisition, ground control station and power system. The power system is one of the important and heaviest subsystems, it needed to supply power, but weight and size are one of the main concerned as the canSAT should not exceed the required weight and selecting power supply that is matched with the overall power budget that has small size and lightweight is challenging. Therefore, the power supply selection should consider this detail. The power distribution design should be able to supply an appropriate amount of current and voltage to the components according to their specification. This study aims to develop and test the proposed prototype which is named ScoreSAT able to provide data and have enough power supply for the whole operation. Therefore, an initiative to develop the appropriate power distribution design for canSAT is taken to overcome the problem of the power system. Moreover, each subsystem needs to be tested by obtaining the results from the onboard data acquisition and transmit the data using the communication system before integrating into the power system. ScoreSAT prototype needs to carry the system that is mounted inside, thus the space inside the prototype needs to be fully utilized for the whole system to fit in. ScoreSAT completes the mission by obtaining data acquisition during the operation.

Электромагнитное загрязнение околоземного космического пространства излучением ЛЭП

We present an overview, based on satellite observations at low Earth orbits, on electromagnetic radiation from ground power transmission lines at an industrial frequency 50–60 Hz. Particular attention has been given to Chibis-M and DEMETER satellite observations. The electric 40-cm antenna of the micro-satellite often recorded 50–60 Hz radiation (known as Power Line Emission (PLE)) when it flew over industrialized areas of the planet. The PLE spectral amplitude varied from 1.2 to 18 (μV/m)/Hz0.5, which corresponds to the electric field amplitude E~1 μV/m. We report results of numerical calculations of the electromagnetic response of the atmosphere and ionosphere to a large-scale surface emitter at a frequency of 50 Hz. According to simulation results, PLE with an intensity of ~1 μV/m observed on satellites in the nightside ionosphere at midlatitudes can be excited by an unbalanced current 8–10 A in a power transmission line above the earth's crust with conductivity of 10–3 S/m. At middle and low latitudes with an inclined geomagnetic field, the maximum response in the upper ionosphere to the transmission line radiation should be seen shifted equatorward, although this shift is less than that upon guidance by the geomagnetic field. The maximum amplitude of the electromagnetic response of the ionosphere to the power transmission line emission decreases for an inclined geomagnetic field, but insignificantly. To date, the PLE intensity in near-Earth space has turned out to be higher than the intensity of natural radiation in this range (Schumann resonances and ion whistlers), and continues to grow with the technological development of mankind.

Electromagnetic pollution of near-Earth space by power line emission

We present an overview, based on satellite observations at low Earth orbits, on electromagnetic radiation from ground power transmission lines at an industrial frequency 50–60 Hz. Particular attention has been given to Chibis-M and DEMETER satellite observations. The electric 40-cm antenna of the micro-satellite often recorded 50–60 Hz radiation (known as Power Line Emission (PLE)) when it flew over industrialized areas of the planet. The PLE spectral amplitude varied from 1.2 to 18 (μV/m)/Hz0.5, which corresponds to the electric field amplitude E~1 μV/m. We report results of numerical calculations of the electromagnetic response of the atmosphere and ionosphere to a large-scale surface emitter at a frequency of 50 Hz. According to simulation results, PLE with an intensity of ~1 μV/m observed on satellites in the nightside ionosphere at midlatitudes can be excited by an unbalanced current 8–10 A in a power transmission line above the earth's crust with conductivity of 10–3 S/m. At middle and low latitudes with an inclined geomagnetic field, the maximum response in the upper ionosphere to the transmission line radiation should be seen shifted equatorward, although this shift is less than that upon guidance by the geomagnetic field. The maximum amplitude of the electromagnetic response of the ionosphere to the power transmission line emission decreases for an inclined geomagnetic field, but insignificantly. To date, the PLE intensity in near-Earth space has turned out to be higher than the intensity of natural radiation in this range (Schumann resonances and ion whistlers), and continues to grow with the technological development of mankind.