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Explosions of high voltage oil-filled electrical equipment (OFEE) lead to a significant material damage. These explosions occur under action of an arc discharge (AD) which arises after internal short circuit. Modernization of OFEE design and protection systems is the possible way to achieve significant reduction of potential explosion and substantial reduction of material losses. Examination of perspective explosion-proof OFEE designs and new explosion protection systems demands the effective test methods. In present work results of development and application of an arcless source of pulse pressure (ASPP) are described. In ASPP the testing impulse is produced by the jet of powder gases (JPG) which arises at the combustion of explosive materials. In this work results of experimental researches of AD in transformer oil (TO) at conditions typical for AD initial stage have been presented: current rise time was 3-5 ms, the maximum arc current was up to 30 kA, AD burning time was 3-20 ms. The energy released in AD amounted to 0.1 MJ. It was established, that electric field strength in AD column was about 0.2 kV/сm, gas producing factor in AD was 110 l/MJ, growth rate of pressure in TO was about 0.3 MPa/ms. These results allowed to create an ASPP with demanded parameters. Experiments proved that TO flow under action of AD and JPG are similar given that the same influence duration of the energy released in AD is equalled enthalpy of JPG at liquid inlet. In this work the transformer fracturing behavior after explosion has been analyzed; and the requirements for protection systems have been formulated. By means of ASPP the breadboard model tests of two well-known OFEE explosion protection methods were carried out. In the first method it is assumed that the protection is reached due to fast dump of pressure inside of OFEE case when special membranes are opened. In the second protection method it is offered to establish porous coverings on internal surfaces of OFEE cases. Experiments were carried out on OFEE model with the characteristic size of 1 m at action energy up to 1.5 MJ. It was shown, that these systems cannot protect the transformer body from significant damages. The dynamic protection system of transformer (DPS) has been described. The efficiency of this new system using ASPP has been verified in experiments with autotransformer of 25 MW. It was shown that DPS protects the transformer from considerable damages at least at dynamic impulse of about 3 MJ.

This paper describes an air gap that switches one of the sections of capacitive storage, which consists of 234 K41I-7 capacitors (5 kV, 23.4 mF). The arrester is launched from a special plasma initiator. The design of the arrester used elements that allow a large electric charge to pass with the ability for subsequent rapid replacement. The response time delay of the arrester is ~20 μs with instability of the response time of the order of 10 μs. This air gap was used to switch a capacitive storage device consisting of 160 K75-100 capacitors (176 mF, 6 kV).

A current collector with a solid-state discharger for 268 input and the same number of outgoing RK-50-9 RF cables from a high-voltage capacitive storage to the load is described. The spark discharger is started using a special initiator. The discharger design has a number of elements that reduce the self-inductance of the spark gap to 50 nH and increases the reliability of its operation via partitioning of cables (switching is performed by forming plasma contacts simultaneously at six points). The delay time of the discharger response is ~5.5 μs with an operation-time instability of approximately 500 ns.

The results of experiments with an initiator of lithium and graphite, whose mass was 10% of the mass of the projectile, are presented. Similar initiators produce plasma with a high speed of sound and provide the initial speed of the projectile of ∼0.5 km/s. The droplet-shaped damage on the insulating wall of the accelerator channel are described. The link between the appearance of these damages and the sharp deceleration of the plasma piston (PP) is noted. A hypothesis relating the occurrence of damages to the resonant deformation of the channel under the action of a moving high-pressure front is discussed. It is shown that the hypothesis about the resonant deformation of the channel qualitatively explains the known features of the accelerator operation.

An autonomous multichannel generator of optical sync pulses is described. The interval between sync pulses of this generator can be set with a step of 250 ns. The maximum delay between sync pulses is 262 ms. Programming of the delay can be carried out both from the control panel located on the generator and from a personal computer. The generator is completely autonomous. The estimated operating time without replacement of batteries is 20 years.

A model of a high-power current pulse generator based on an explosive magneto-cumulative generator with electrically exploded copper-conductor breakers capable of generating a powerful electromagnetic pulse impact in a limited space of 16 m3 is described. An experimental setup has been constructed that contains tools for diagnostics of the parameters of the electromagnetic pulse impact. The results of experimental studies in the form of measured pulse values of the current in and voltage across the load are presented. An electric field intensity of ~0.5 MW/m has been achieved. The rate of the increase in the magnetic field density reached 0.12 T/μs.

The report presents the results of the development and field testing of a mobile test facility based on a helical magnetic cumulative generator (MCGTF). The system is designed for full-scale modeling of lightning currents to study the safety of power plants of any type, including nuclear power plants. Advanced technologies of high-energy physics for solving both engineering and applied problems underlie this pilot project. The energy from the magnetic cumulative generator (MCG) is transferred to a high-impedance load with high efficiency of more than 50% using pulse transformer coupling. Modeling of the dynamics of the MEG that operates in a circuit with lumped parameters allows one to apply the law of inductance output during operation of the MCG, thus providing the required front of the current pulse in the load without using any switches. The results of field testing of the MCGTF are presented for both the ground loop and the model load. The ground loop generates a load resistance of 2–4 Ω. In the tests, the ohmic resistance of the model load is 10 Ω. It is shown that the current pulse parameters recorded in the resistive-inductive load are close to the calculated values.

This paper demonstrates the practical application of the explosive magnetic generator (EMG) as a source of high-power pulses for mobile testing complex EMG (MTC EMG). Hereinafter, the name of explosion generator is used on a par with the name of helical explosion-magnetic generator. Laboratory sample was brought to a level of modern complex, which is able to solve the applied problems in the grid power systems. MTC EMG is able to reproduce the output currents, similar to lightning currents, so it can be used to simulate a pulse impact on the energy system. The report contains: a description of the basic physical and electrical solutions underlying the construction of the generator of lightning currents, output characteristics, and results of MTC EMG field testing. Optimization of schemes including the different impedances of EMG and inductive resistive load with the use of transformer coupling allowed the effective energy transfer from the EMG to the load. Pulse currents and voltages on the load and also the response of soil between ground loops under the action of lightning currents, generated by MTC EMG, were registered in the testing. Autonomous measuring instruments included in the complex were protected from electromagnetic interference.

Explosive-magnetic generators (EMGs) unlike capacitive storages (CSs), as a rule, have growing power. The effective operation of pulsed plasma loads, such as pulsed plasma accelerators (PPAs), plasma foci, plasma breakers, etc, can be provided at realization of the mentioned advantage of EMG as a power source. A technique of laboratory experiments with PPA is presented in this paper. The experiments with PPA powered by CS precede the explosive experiment with EMG. The dependencies of the load operation modes on the start parameters are determined by the analysis of the experimental data. They included the dynamics of the inductance and the position of the current shell inside the PPA. The technique allows reducing the number of expensive explosive experiments and supplements the database of nonlinear dependencies of the load parameters under various amplitudes of the current pulse that is important for mathematical modeling. The technique based on experiments together with the estimations allowed solving the problem of matching of non-linear loads type PPA with EMG. Thus, the productivity of experiments with EMG increases greatly. The developed technique can be adapted to a wide class of nonlinear loads.

A mobile testing complex prototype on the basis of an explosive magnetic generator (MTC EMG) is developed to simulate a lightning current pulse. The main element of this complex is a current pulse generator comprising a EMG with a pulse transformer for energy release into the load. The electric chain of the MTC EMG is theoretically analyzed taking into consideration energy losses in active resistances in the primary circuit of the transformer and the inductive-resistive nature of the load, which resulted in the minimization of energy losses in the primary circuit depending on the electric chain parameters. It was found that, if the energy losses are minimized, the efficiency of transferring the EMG energy into the load exceeds 50%. As a result of the field tests of the MTC EMG, its basic characteristics were determined and the waveforms of the current pulses and voltages in the load were obtained. It is shown that the results of the mathematical simulation of current pulses in the load are in good agreement with the experimental data.

This paper includes the results of an investigation of high-voltage pulse effects on insulators of a 10-kV power line. Experiments have been performed by means of equipment that simulates the simultaneous effect of a pulse disturbance and a power line operating voltage. Critical levels of insulator flashover have been determined. These levels are dependent on the pulse disturbance duration, and a number of other effects. The electric characteristics of insulators degrade when high-voltage pulses are injected on an insulator with power ON. As a result, some insulators have been destroyed. The possible reason of destruction is the presence of latent defects.

The present paper reports the results of experimental investigations of an arc discharge in the transformer oil under typical conditions of discharge occurring after internal fault in high-voltage oil-filled electric equipment. The flow of the transformer oil under the action of the jet of powder gases has been investigated. It has been shown that the actions of the arc discharge and the jet of powder gases are equivalent provided that energy and the time of action are the same. A new method of explosion safety tests is described in which the dynamic impact of the arc on high-voltage equipment is simulated by means of the dynamic energy stored in explosives. The suitability of the method has been demonstrated on trials of instrument transformers of the 110 kV and 330 kV class.

The resource of associated petroleum gas (APG) in crude oil production in the Russian Federation is estimated on the basis of statistical data from oil-extracting companies on oil production and associated petroleum gas, as well as the structure of gas utilization. The absolute value of the APG resource across the Russian Federation is estimated on the basis of the annual weighted average value of the gas-oil ratio at the deposits.

Results are given of theoretical and experimental investigations of schemes of matching of magnetocumulative generator (MCG) and load, which include a helical MCG, storage inductance coils, solid-state switch, and explosive current breaker. Magnetocumulative generators in combination with constant and variable storage inductances are developed and investigated. The results of numerical studies are checked in experimental runs under a model load with inductance of 100 nH and under a load with variable inductance. The possibility is demonstrated of using the MCG developed as the effective power supply for a pulsed plasma accelerator (PPA).

The objective of our study was to evaluate the levels of natriuretic peptides in patients (pts) with heart failure with preserved ejection fraction (HFpEF) in 12 month after ST elevation myocardial infarction (STEMI) with a focus on the function of left atrium (LA) and left ventricular (LV) filling pressure. 55 pts were included in the study. 6-minute walk test was performed. Echo exam was performed by the diagnostic system VIVID 7. BNP in whole blood was determined using the Triage ® Meter BNP test. The serum levels of NT-pro BNP, NT-pro ANP («Biomedica», Austria) were determined in blood samples by enzyme-linked immune-sorbent assay (ELISA). LA volume index were differences (16.03±3.39 ml/m2; 25.36±8.26 ml/m2; 29.41±9.46 ml/m2 accordingly I, II, III class) depending on severity of HF. Well as E/E’ ratio were differences (7.5±1.4; 9.8±5.1; 13.5±7.6 accordingly I, II, III class) depending on severity of HF. The LA volume index correlated with levels of NT-pro ANP (R=0.29; p=0.04), levels of NT-pro BNP (R=0.37; p=0.01), levels of BNP (R=0.51; p=0.0001). The LV filling pressure correlated with levels of NT-pro ANP (R=0.45; p=0.002), levels of NT-pro BNP (R=0.49; p=0.001), levels of BNP (R=0.37; p=0.01).

Results of hypervelocity impact tests at an electromagnetic launcher with plasma armature are described. The tests were performed with a thick duralumin disk of 80–100 mm diameter and of 40 mm height impacted by a lexan cylinder of 1.5–3 g mass. The projectile velocity amounted to 4–5.5 km/s. The launcher operational characteristics are described. In the tests, various configurations of the target fracture were obtained including cratering and spall cracks, disks and cones. The computer simulations were accomplished by means of a 2D axisymmetrical SPH code using interparticle contact algorithms. In these algorithms, stresses and velocity at the contact points of Lagrangian particles are computed by the linear Riemann solver. For description of material failure, a model based on a threshold stress criterion was used. The main features of material distribution and target fracture are reproduced in simulations.

This paper considers the possibility of creating on new physical principles a highspeed current-limiting device (CLD) for the networks with voltage of 110 kV, namely, on the basis of the explosive switching elements. The device is designed to limit the steady short-circuit current to acceptable values for the time does not exceed 3 ms at electric power facilities. The paper presents an analysis of the electrical circuit of CLD. The main features of the scheme are: a new high-speed switching element with high regenerating voltage; fusible switching element that enables to limit the overvoltage after sudden breakage of network of the explosive switch; non-inductive resistor with a high heat capacity and a special reactor with operating time less than 1 s. We analyzed the work of the CLD with help of special software PSPICE, which is based on the equivalent circuit of single-phase short circuit to ground in 110 kV network. Analysis of the equivalent circuit operation CLD shows its efficiency and determines the CLD as a perspective direction of the current-limiting devices of new generation.

Pyrolysis temperature, concentration of the feeding hydrocarbon, and the gas residence time in the pyrolytic system are the principal factors that govern particulate carbon (soot) formation during pyrolysis of a particular hydrocarbon. Benzene acetylene, carbon tetrachloride, and methane diluted in helium have been pyrolyzed in a jet-flow reactor under near-isothermal conditions at 1373–1673 K and with gas residence times up to 125 ms. The influence of temperature and initial concentration of the hydrocarbon on the onset of dispersed carbon formation as well as on the particle number density of soot produced have been studied. The empirical equations to simulate the induction periods of soot formation, τind (s), during isothermal pyrolysis of benzene, acetylene, carbon tetrachloride, and methane as functions of concentration of the feeding hydrocarbons and the pyrolysis temperature were obtained as follows: τ ind = ( 6.3 ± 0.8 ) × 10 − 12 [ C 6 H 6 ] − 0.8 exp ⁡ ( 26 , 700 / T ) τ ind = ( 3.2 ± 0.5 ) × 10 − 9 [ C 2 H 2 ] − 0.9 exp ⁡ ( 19 , 000 / T ) τ ind = ( 4.3 ± 0.7 ) × 10 − 9 [ CCl 4 ] − 0.9 exp ⁡ ( 18 , 700 / T ) τ ind = ( 9.0 ± 1.5 ) × 10 − 10 [ CH 4 ] − 0.9 exp ⁡ ( 21 , 600 / T ) where [CnHm] is the hydrocarbon concentration in a feeding gas (mole fraction) and T is the temperature (K). Differences in the induction periods of soot nucleation for various hydrocarbons might account for the inhibition effect of soot particle formation observed during pyrolysis of hydrocarbon mixtures. The particle number density of soot produced during pyrolysis of hydrocarbons diluted in helium under near isothermal conditions was demonstrated to be constant in the gas residence times interval which ranged from 10 to 125 ms.

The formation of soot during pyrolysis of tetrachloride carbon in the temperature interval 1423–1623 K and its mixtures with methane at 1573 K is studied under conditions close to the isothermal ones. The induction periods of soot formation from CCl4 are measured. The equations to calculate the induction period of soot formation, the concentration of soot particles, and its specific surface as a function of the temperature and concentration of CCl4 are derived. The inhibition of soot formation is observed in the isothermal pyrolysis of a CCl4−CH4 mixture. It is shown that the particle nuclei are formed only from Cl4, and the CH4 molecules are spent only for the heterogeneous growth of the formed particles.

This short communication deals with the surface area and the yield of soot formed during pyrolysis of benzene and p-xylene

Soot formation under isothermal conditions during pyrolysis was investigated for the following hydrocarbons: methane, acetylene, benzene, toluene and p-xylene. Over the temperature range 1150- 1400°C the soot particle number density was shown to depend linearly on the hydrocarbon concentration for all hydrocarbons investigated. Activation energies of soot particles aerosol formation were demonstrated to be within the limits 313—340 kJ/mol. Expressions to calculate the particle number density and the soot surface area were obtained. The particle number density and the soot surface area are the parameters applicable for a quantitative estimation of hydrocarbons tendency to soot formation during pyrolysis. Relative to methane this tendency of hydrocarbons investigated is arranged as follows: acetylene: benzene: toluene: p-xylene: methane, 8.8:8.2:6.6:4.5:1.0.

The results of experimental study of two-stage explosive magnetic generator with magnetic flux trapping (EMG MFT) and opening switch in the primary circuit are presented. It was shown that this type of generator demands less than 3 μs to achieve the maximum of current derivative (30 - 100 kA/μs) and maximum of the output voltage. The generators with such parameters are necessary for a number of loads, for example, for the plasma accelerator with growing inductance. At the same time the problem of emerging surge in the secondary circuit of the generator was solved through the introduction of a separate single-turn closing switch with high breakdown voltage. The comparison of the performance of two types of EMG MFT is described. The first type generator was with opening switch in the primary circuit, the second one was without breaking of the primary circuit. They had approximately the same initial input parameters (inductances of the primary and the secondary circuits and the coupling coefficients) and the same inductance of model load - 1.16 μH.

High-pressure region accelerating a projectile in plasma-dynamic launchers may induce a resonant deformation of barrel. A projectile interaction with dynamic asperities, arising on a barrel surface, causes degradation performance of these launchers. This paper represents the analysis of the famous experimental results, which confirm the essential influence of resonant deformation on the characteristics of EM launchers with plasma armature.

Soot formation upon the pyrolysis of binary and ternary mixtures of various hydrocarbons is studied. The experimental values of the specific surface areas Ssp of soot particles are compared to the calculated values obtained assuming that any of the hydrocarbons in the mixture are inhibitors. Analysis of the results obtained for the mixtures containing acetylene shows that, when the acetylene concentration is higher than a certain value, the nuclei of soot particles are formed from acetylene, whereas other hydrocarbons participate in

The dielectric body in a channel of electromagnetic launcher (EML) accelerates under action of pressure of plasma. There are severe enough basis to consider that in a channel of constant cross section the velocity of plasma flow can not surpass a velocity of sound in plasma. Accordingly, the maximum accessible velocity of throwing projectiles in EML is limited to a velocity of sound. The velocity of sound in plasma is determined by its composition and temperature. The plasma in a channel of EML is usually produced due to erosion of walls of the channel. Under typical conditions of EML operation the velocity of sound in plasma is 5-7 km/s that coincides with values of throwing velocity obtained experimentally. The increase of a velocity of throwing can be reached only at increase of the velocity of sound in plasma. The probable solutions permitting to raise the velocity of sound till 10-12 km/s are discussed. Probably, it is impossible to receive values of sound velocity above 15-20 km/s for the working conditions of EML, therefore the velocity of throwing at a level 12-15 km/s is limiting for EML. One of methods of increase of a sound velocity in EML is the using of the massive initiators from lithium and graphite. The results of experimental study of the EML characteristics with such initiators have been presented. It has been shown, that at usage of such initiators erosion of walls of a channel essentially decreases, and the high values of conversion of electromagnetic energy brought to a channel, in a kinetic energy of projectile (about 20 %) have been reached.

Submerged twin-arc separate-bath welding process variables for the steel thick-walled bridge structures of 40 mm thick and the positive results of the mechanical test are discussed. In this process, welding rate increases by 2.45 times and welding material consumption reduces.

The purpose of this Short Communication is to compare the calculation results of particle number densities obtained both during combustion and pyrolysis of acetylene

Several types of multi-stage flux-trapping helical flux compression generators for high impedance loads are considered. Short-pulse two-stage helical generators with diameter 100 mm and initial energy of 0.5-3 kJ have supplied energy up to 40 kJ into a 5-/spl mu/H inductive load in a time of about 15 /spl mu/s. Long-pulse two-stage generators with final helix diameter of 110 mm initial energy of 0.8-2.7 kJ have supplied energy up to 350 kJ into a 0.3-/spl mu/H inductive load. Long-pulse three-stage generators with final helix diameter of 160 mm and initial energy of approximately 5 kJ have supplied up to 700 kJ into a 0.5-/spl mu/H inductive load. Model generators without flux trapping and with final helix diameter of 160 mm and initial energy of approximately 20 kJ have supplied energy up to 1.0 MJ into a 0.5 /spl mu/H inductive load. Long-pulse two-stage generators with final helix diameter of 160 mm and initial energy of approximately 30 kJ produce energy up to 1.6 MJ in a load of 0.5 /spl mu/H.