Том 49, № 5 (2016)

This article presents the results of analyzing the stressed state in composite reinforced concrete turbine penstocks used in high-head water dams. The analysis uses the boundary integral equation method (BIEM) for two penstock placement options: the outer surface of the downstream dam face, or within the expanse of the downstream dam face. Crack formation in concrete and thermal effects have been taken into account in this analysis.

Amathematical model is presented for two-phase flow in a pump station. The model is based on three-dimensional non-steady-state Reynolds equations. Turbulence is modeled using the standard k-ω SST model. Two-phase flow is calculated by the VOF method. Analyses of liquid behavior are presented under different initial liquid levels in the station. A optimum value for the initial liquid level is obtained. Areas of vortex formation are shown when the liquid level deviates from the recommended value. The effectiveness of the given pump station design is confirmed.

Different stepped spillway designs are presented, along with the results of model hydraulic studies of these spillways, equipped with abutments of various design.

The principles of starting up the steam power unit of the Hrazdan-5 fully fired combined-cycle power unit (Hrazdan, Armenia) are considered. This plant has neither a bypass stack for gas discharge from the gas turbine nor an external steam source for the steam-turbine gland and prestarting deaeration. Emphasis is placed on the differences between the start-up procedure followed at the plant and the procedure provided by the RD 34.25.512 Standard Instructions on Startup from Various Thermal States and Shutdown of 300-MW Boiler-Turbine Sets with K-300-240 LMZ Turbine.

The insertion of current-limiting reactors into electrical equipment operating at a voltage of 110 and 220 kV produces a change in the parameters of the transient recovery voltages at the contacts of the circuit breakers for disconnecting short circuits, which could be the reason for the increase in the duration of the short circuit, damage to the electrical equipment and losses in the power system. The results of mathematical modeling of the transients, caused by tripping of the short circuit in a reactive electric power transmission line are presented, and data are given on the negative effect of a current-limiting resistor on the rate of increase and peak value of the transient recovery voltages. Methods of ensuring the standard requirements imposed on the parameters of the transient recovery voltages when using current-limiting reactors in the high-voltage electrical equipment of power plants and substations are proposed and analyzed.

The problem of determining the instantaneous values of the electrical operating parameters for the purpose of investigating dynamic processes in nonlinear systems is considered. It is shown that existing procedures for calculating the parameters, which provide a sampling rate of the output data equal to the operating frequency period, does not enable the value of the parameters to be estimated at an arbitrary instant of time with high accuracy. A method of determining the instantaneous values of the electrical operating parameters is proposed, based on a modified Hilbert transformation. An example of the determination of the frequency, amplitude and phase of the current when there is a short circuit is presented. The results enable phenomena occurring “within” the period of the industrial current frequency to be investigated, and also enable the dynamic characteristics of power systems to be determined more accurately.

A method of detecting interturn short-circuits in the rotor winding by analyzing the magnetic field in the stator-to-rotor gap of a hydrogenerator is discussed. For the purpose of theoretical justification, the magnetic field is analyzed numerically using the finite-element method in the cases of presence and absence of short-circuited turns in the rotor winding. The numerical results are compared with experimental data for a 640 MW hydrogenerator.

The results of studying the effect of flue gas recirculation on the amount of nitrogen oxides (NO_x) formed in a TP-101 steam boiler are presented. In firing oil shale, the recirculation of flue gas to the mills makes it possible to inject the portion of the primary air replaced by this gas to the furnace above the oil-shale burners, thus providing staged firing. This measure allows reaching a NO_x concentration limit of about 170 – 190 mg/m³. During co-firing of oil shale and retort gas (60:40 of total heat input), the recirculation of flue gas to the burners reduces the NO_x concentration at the boiler outlet from 500 to 230 – 240 mg/m³.

Methods for automated creation of algorithms for operational interlocking of switchgear are examined. Algorithms are constructed on the basis of information on the main circuit of an electrical installation described in terms of IEC 61850 (Communication networks and systems in substations). The algorithms are created in the framework of a system for automated design of secondary switching circuits.