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Power engineering: research, equipment, technology

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Vol 22, No 3 (2020)
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POWER ENGINEERING

3-13 711
Abstract
Heat exchange capacity increase is one of the main concerns in the process of manufacturing modern heat exchange equipment. Constructing heat exchangers with porous metals is an advanced technique of heat exchange increase. A construction of heat exchangers with porous aluminum is described in this paper. The first heat transfer agent (hot water) flows through thin copper tubes installed within the porous aluminum. The second heat transfer agent (freon) flows through the pores of aluminum. Laboratory facility was created to study such a heat exchanger. Series of experiments were carried out. The purpose of the research presented here is to create a mathematical model of heat exchangers with porous metals, to perform analytical calculation of the heat exchangers and to confirm the results with the experimental data. In this case, one can`t use the standard methods of heat exchangers calculation because the pores inner surface area is indeterminate. The developed mathematical model is based on the equation describing the process of cooling the porous plate. A special mathematical technique is used to take into account the effect of tubes with water. The model is approximate but its solution is analytic. It is convenient. One can differentiate it or integrate it, which is very important. Comparison of calculated and experimental data is performed. Divergence of results is within the limits of experimental error. If freon volatilizes inside the heat exchanger, the heat of phase transition has to be taken into account alongside with heat capacity. The structure of the mathematical model makes it possible. The results presented in this paper prove the practicability of using porous materials in heat exchange equipment.
14-22 474
Abstract
So far rather large number of torches for chamber combustion of gaseous fuel differing among themselves on the nature of gas-distribution for mixture of fuel with air is known. For domestic oil-gas torches of power coppers their unification as combustion of fuels is characteristic, that is heat of combustion of the burned fuel can change in quite wide limits. Moreover, directly in use on thermal power plant their reconstruction is made for reduction of length of a torch, achievement of uniform radiation of a torch, change of local values of temperatures of a torch or reduction of their maximum values. As a rule, the detailed researches received after reconstruction of these torches are not conducted. Foreign torches are designed and made on combustion of fuel of a concrete type with the set heat of combustion. At the same time the main role for increase in efficiency is assigned to computer regulation of a ratio of fuel and air, gas-distribution - central tubular. Except high cost, the difficulty of application of foreign torches for domestic power coppers is connected with adaptation of automatic equipment of these torches to the system of automation of domestic coppers. Therefore for domestic coppers one of the directions them modernization for the purpose of increase in efficiency is reconstruction of schemes of gas-distribution in the existing torches. In this article the efficiency of application of peripheral tubular gas-distribution in comparison with the combined peripheral tubular gas-distribution combined with conic central gas-distribution when using as the main tagentsialny peripheral twist of air is investigated. These schemes of gas-distribution are applied in coppers of TGM-84A of the Kazan TES-3 and the Nizhnekamsk TES-1 on which experiments on identification of efficiency of these types of gas-distribution for combustion of natural gas of the Urengoy field are made.
23-35 533
Abstract
Detection of defects at an early stage of their occurrence, especially for power transformers that have worked out the standard term, is an acute problem. This article discusses the possibility of using the system of monitoring, control and diagnosis of transformer equipment (SMUID) electrical systems in conjunction with the automated control system of electrical equipment (ASU ETO) and automated information-measuring system of commercial electricity metering (AIIS KUE) with the use of QR-code, as well as using TeamViewer for the operational elimination of accidents and identify abnormal operation of transformer equipment. Transformer monitoring system is designed for monitoring isolation, recording and analysis of partial discharges, monitoring of technical condition ensuring maximum fault-free service life of transformers. In addition, the introduction of automated diagnostics and electrical equipment is a necessary condition for the introduction of SmartGrid technology in industrial electric networks, contributes to the reduction of capital investments in the renewal of the equipment fleet. The methods currently used do not detect dangerous insulation degradation, are not sensitive to its aging, and in some cases mistakenly assess the isolation condition. The work analyses the operability and quality of the systems under consideration, shows the hierarchical structure of SMUID. By applying the proposed idea with the QR-code, it is possible to speed up the process of searching for information about the current technical state of electrical equipment.
36-43 597
Abstract
To supply small cities with electric and thermal energy it is proposed to create selfcontained energy complex based on gas turbine plants (GTP), wind generators and electric storage cell. A scheme for the joint operation of these plants is offered, a methodology for calculating the quantitative characteristics of a wind power plant, gas turbines and electric storage cell is developed. Electric storage cell provide coverage the peak portion of the daily electrical load curve. The heat load is ensured by the operation of the waste-heat boiler and the peak boiler. Using the example of a power complex with an electric load of 5 MW and a heat load of 17.5 MW, the generation of electric energy by wind driven power plant and gas turbine plants, the supply of electric energy from electric storage cell, the heat loads of the waste-heat boiler and peak boiler by months of the year are calculated. When the power share of the wind power plant is 0.2, the electric storage cell provide for an annual period from 5.2 to 10.7 % of the daily demand of the electric load schedule. The electric power of the gas turbine plant in winter is reduced to 70 % of the maximum load of the consumer, in summer - up to 55 %. An increase in the relative share of the power of a WDPP reduces the electric capacity of a gas turbine plants, its cost, while the cost of electric storage cell increases.
44-50 471
Abstract
It is known that the thermal and mechanical characteristics of the air flow in the output channel of the turbocharger compressor largely determine the efficiency and quality of the gas exchange processes of the piston engine. The research was carried out on an experimental installation containing a turbocharger, output channels of different configurations, a measurement database and a data collection system. It was found that the stabilization of the flow in the output channel of the compressor leads to a significant increase in the heat transfer intensity (up to 25 %) compared to the base pipeline, while reducing the degree of turbulence by up to 30 %. In the output channel of the compressor with grooves, there is an even more significant increase in the heat transfer intensity (up to 30 %) with an increase in the degree of turbulence by up to 12% compared to the base channel. The proposed configurations of the compressor output channels can be used to intensify heat exchange in order to naturally cool the air during the intake process, as well as to stabilize the gas dynamic parameters of the flow in order to reduce the hydraulic resistance of the intake system of the turbocharged engine.
51-59 518
Abstract
Reliability of power supply to consumers and the efficient use of energy resources are priority tasks in the process of operational dispatch control of the energy system. Limitations of the throughput capacity of the electric network increases the value of the non-released power reserve, which in case of violation of the normal mode at one electric power facility can lead to a system accident. The aim of the work is to develop an algorithm for assessing the throughput of the electric network. In this study of the steady-state operating modes of the power system, a method is proposed for online modeling of the parameters of the electric power regime and its verification in a real scheme for determining the throughput of the electric grid. To solve the tasks posed in the work, we used: the theory of multivariate experiment, the theory of systems of linear equations, methods of mathematical modeling, software and computer systems Cosmos. The regression function is used to simulate the power flow over a network element. The methods based on the linearized and complete models with the measured values are compared and estimated using the correlation coefficient. The method can be used in the practice of supervisory control and research organizations in solving problems of improving the characteristics of the regimes, planning and operating the power system in real time, as well as the development of electric networks and power systems. The efficiency of the proposed method was verified during the experiment.
60-67 611
Abstract
Object. The article presents the results of computer research, the purpose of which was to develop dynamic models of low-power twin-shaft gas turbine units (GTU) equipped with automatic excitation and speed regulators with predictive links. Methods. Setting up the regulators of the commissioned gas turbine requires complex calculations. The use of algorithms that make it possible to improve the classical regulators with minimal costs allows us to effectively solve the problems of their settings. These include prognostic algorithms that allow you to configure the automatic control system using one parameter - forecast time. The models presented in the article are implemented using the Simulink package of the MATLAB system. Results. The influence of prognostic algorithms on the quality of controlling the voltage and rotor speed of a gas turbine generator in the modes of connecting and dumping loads is studied. Studies have shown that increasing the coefficient of the amplifier of the auto-predictive speed regulator can significantly reduce overshoot and the transition process, and also has a positive effect on voltage regulation. Conclusions. The results made it possible to formulate the following conclusions: the use of prognostic regulators when connecting an additional load to the gas turbine allows you to remove the oscillation, reduce voltage dips, reduce the transient time by 2.5 s; with a sharp load shedding due to the use of prognostic algorithms, it is possible to completely remove the oscillation, reduce the overshoot of the rotor speed and overvoltage at the generator terminals, and also significantly reduce the transient time for speed compared to classical regulators; the use of prognostic algorithms allows us to obtain acceptable quality indicators of transients without the use of complex regulator tuning procedures.

ELECTRICAL ENGINEERING

68-77 413
Abstract
A new method for diagnosing power and switching electromagnetic mechanisms containing a control electromagnet and a movable armature is proposed. The movable element of the diagnosed electromagnetic mechanism (EMM) is irradiated with a high-frequency probing electromagnetic field and the reradiated electromagnetic field from it is recorded. The source of the probing field and the receiver of the re-radiated field is the EMM electromagnet winding. The probing electromagnetic field is formed by imposing on the low-frequency high-voltage operating voltage of the supply winding of the electromagnet EMM an additional high-frequency low-voltage voltage. The diagnostic parameter is determined by algorithmic processing of the measurement results of the magnitude of the voltage increment on the EMM winding, caused by exposure to a reradiated electromagnetic field, and the technical condition of the diagnosed electromagnetic mechanism is determined by the absolute value of the di-agnostic parameter. The method allows to diagnose the current state of the main functional units of the EMM and to control its operating modes as a whole.
78-89 439
Abstract

Idle voltages proportional to corresponding magnetic flows of three-phase transformer of general purpose are measured using differential methods aimed at detection of inter turn faultin windings of three-leg transformers.

The standard method of determining the inter turn fault in the transformer windings is based on measuring idling current and measuring loss power. In addition, differential methods well known in relay protection are proposed to determine the presence of inter turn faultin three-phase linear transformers. The methods are based on the fact that the inter turn fault increases the magnetic resistance of the phase rod of the transformer core, in the phase winding of which there is a inter turn fault. When one-phase voltage is applied to the winding of phase B in the windings of side phases A and C of the linear three-phase transformer, the same voltage phase and amplitude shall be induced. When phase A and C windings are connected in opposition and differential signal is measured, voltage difference of phases A and C is as follows. If, in the original, intact state, the differential signal was close to zero, the inter turn faultin one of the side phases A or C introduces an imbalance and the differential signal increases. The differential signal is easily measured against the background of the near zero differential signal in the intact state of the transformer, which causes a high sensitivity of the differential method to the presence of inter turn fault. In case of a inter turn faulton the winding of the central phase B, it is necessary to take into account the differential signal in the intact state of the transformer.

INSTRUMENT-MAKING, METROLOGY AND INFORMATION-MEASURING INSTRUMENTS AND SYSTEMS

90-96 565
Abstract
Described the generator of resonance radiofrequency with the step of change 50 kHz in the range 520 MHz and pulse programmer of the pulse sequences for relaxometer of proton magnetic resonance (PMR). Using algorithm of direct digital synthesis (DSP), the RF generator has the ability to produce RF signal with a short switching time and high resolution in frequency and phase. To facilitate the generation of RF pulses, used the pulse programmer implemented in the FPGA directed by the auxiliary controller DSP to generate RF pulses with required sequences and parameters. Realized the testing of the generato r by method of computer modelling in the program Quartus II 12.1 and was shown the opportunities of synthesis of RF-pulses sequences with the phases 0, π/2, π, 3π/2 with resonance frequency tuning.
97-106 676
Abstract
The article substantiates the relevance of the inspection of overhead power lines by determining the mechanical loads of the conductors. The conductor sways under the action of external loads and variable internal mechanical loads. The conductor behaves in span like a pendulum. Using the inclinometric method, it is possible to determine the deviations of the conductor in space from its equilibrium position. Having restored the geometry of the conductor in the span of an overhead power line, mechanical loads can be determined. A model of the harmonic oscillations of the conductor in flight is derived to assess the mechanical loads of the conductor overhead power lines. This mathematical model is based on mathematical models of a flexible thread and a model of a physical pendulum. A conductor is a physical pendulum, where the conductor acts as the body, and in the role of the fixed axis of rotation, a straight line passing through the suspension points of the conductor. The developed model allows you to determine the arrow of its sag from the period of oscillations of the conductor in the span. The article considers algorithms for calculating the conductor sag arrows for two cases: the conductor suspension points are at the same height; conductor suspension points are at different heights. A theoretical calculation is given for a model of a span overhead power line with an estimate of the sensitivity of the developed model and its error in determining the sag of the conductor. Using the arrow of the conductor sag, you can restore its geometry, and hence the mechanical load of the conductor. Therefore, knowing the initial geometric parameters of the span of the overhead power line and the current period of the conductor’s oscillations, it is possible to examine its current state.


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ISSN 1998-9903 (Print)
ISSN 2658-5456 (Online)