Vol 52, No 1 (2018)

Abnormal/beyond-design situations during the construction of the Zaramag HPPs in 2009 to 2012 and engineering solutions that helped to overcome them are described.

The maintenance and emergency repairs of the Shavan TimberWeir in the White Sea-Baltic Canal performed in 2016 – 2017 are described.

In designing mine spillways without a profiled water drain surface that operates in the absence of contact of the water jet with the concrete within a funnel and transitional section, the problem arises of calculating the trajectory of an annular jet, taking into account the vacuum in the space under the jet. A hydraulic method for such calculation using a virtual jet is described. Calculated dependences are given. The results of calculations are compared to test results, confirming the operability of the proposed method.

Results of a survey of the technical state of the underwater sections of two bridges and a reservoir are presented. The techniques used to perform the studies are briefly described. The basic parameters of the equipment used — side-scan sonar and parametric profilograph — are presented. The advantages gained with the use of acoustic instruments in monitoring the technical state of hydraulic and traffic structures are demonstrated.

Information on technical events occurring in the course of running in operations, functional operations, and field tests and redevelopment of the process equipment of hydroelectric power plants that have occurred in Russia and abroad on domestically produced equipment and equipment produced abroad is discussed.

The change in the structure of generating capacities and the commissioning of combined-cycle power units with efficiency much higher than that of the best steam-power units motivated designing these units mainly for baseloads. However, the recent market changes in the generating capacities of Russia and other countries have required extending the normal operating range of CCPPs with HRSGs and accelerating hot start-ups after short (up to 8 – 10 hours) downtimes.

The effect of different factors on the fatigue state and fatigue strength of the low-pressure rotors of stationary steam power turbines is analyzed. Levels of variable stresses acting in the annular grooves beneath the thrust rings of the adapter disks of the low-pressure rotors are determined for the case of T-175/210-130 turbine units. Amplitudes of variable bending stresses with 50 Hz frequency in the grooves as functions of the displacements of the supports of the low-pressure rotors relative to the adjacent supports of the generator and an average-pressure rotor are obtained. It is shown that the position of the supports on the side of the generators when they turn out to be below the adjacent supports is the most unfavorable position from the standpoint of the resulting cyclic stress. With an unfavorable misalignment of the supports, the stresses produced by the intrinsic weight of the rotors together with the stresses from transverse oscillations of the shaft may exceed 20 MPa. The level of dynamic stresses in the grooves falls with a higher position of the supports of the low-pressure rotors relative to adjacent supports. Data are obtained that confirm and substantiate previously expressed theories of the influence of variable bending stresses acting in a corrosive-active medium on the formation of the fatigue cracks in the low-pressure rotors of certain types of central heating steam turbines. To reduce the formation of cracks, it necessary to achieve optimum alignment of the low-pressure rotors with adjacent rotors besides maintaining a required water and chemical regime. In selecting an optimum alignment, the influence of all the factors should be kept in mind and the variation of the support responses and operating time of the turbine unit in each of the characteristic operating modes should be taken into account.

Experimental data on measurements of isothermal relaxation current (IRC) are presented for different kinds of industrial electrical insulation: cross-linked polyethylene (XLPE) 6-kV power cables and thermosetting insulation for the stator windings of high-power rotation machinery. The ageing of and damage to electrical insulation was assessed using indicators derived from the so-called distributed charge current. An analysis of the experimental data shows that the IRC method is highly sensitive for detection of incipient defects in these insulating materials and can be used to determine the indicators of ageing in XLPE insulation and their initial and limiting values.

To detect phase wire breaks in a 6 – 10 kV overhead line, the negative-sequence voltage on the low-tension side of the 6 – 10/0.4 kV power transformer can be used. The results of studying the effect of a phase wire break in an overhead line, phase displacement groups, and phase unbalance of demand loads in a 380 V network on the negative-sequence voltage are presented. A device for signaling phase wire breaks in a 6 – 10 kV overhead line is described. The device is based on a microprocessor electricity meter installed on the low-tension side of a 6 – 10/0.4 kV power transformer.

Low-reactivity properties of anthracite, lean coals, and petroleum coke are determined by a combination of factors, including not only a low heating value of the volatile matter, but also an increase in the volatile yield and ignition temperatures, as well as decrease in reactivity properties of a non-volatile residue. The fuel preparation activities intended to increase the stability of the fuel ignition and burnout include the improvement of heat balance of the air-fuel mixture flow and favorable adjustment of the reactivity properties of the fuel supplied to the furnace.

The use of OLTC devices for supply transformers and OCTC devices on a TP is analyzed. Based on calculations performed, it is proposed to use a transformer with automatic control of secondary voltage by switching regulating windings that are located partially on the primary and partially on additional cores. The proposed model of the transformer can be considered as an alternative to transformers with OCTC device voltage 6 – 10/0.4 kV and power up to 1000 kV · A.