The methods of determining the kind of phase-to-phase short circuit (SC) on the lines of 6–35 kV for improvement the technical perfection of their current protections are surveyed. Preference is given to the method of determining damages according to the relative unbalance the operating currents. The possibility of using the phase currents or their differences for this purpose is demonstrated. The method of computational experiment was used to investigate the influence of the DC load line and transition resistance at the failure site on the relative asymmetry of the currents that ultimately determines the reliability of the establishment of the kind of SC. It is discovered that when the phase currents are used to determine the type of the failure higher sensitivity to remote two-phase SC is achieved. However, in this case, the accuracy of determining the type of failure is more affected by currents of the line load. Determination of failure with the use of differences of phase currents is less sensitive to remote two-phase SC. However, this provides less impact on the accuracy of determining the type of failure of load line currents. Transition resistance at the failure site shifts the relative unbalance of the currents to the area of twophase SC. It is established that despite the kind of a remote SC in parallel lines the proposed methods provide accurate determination of types of failure that simultaneously occurs on the monitored line. When failures are superpositioned, one of which is on one of the parallel lines near the common bus and the other second on the monitored bus, the kind of the SC, determined by any of the proposed methods may differ from the actual one. It depends on the types of resulting failures, the combinations of shutting phases, the steady-state current distribution in the network and other factors. The proposed methods make it possible to determine the kind of phase-to-phase SC, in the worst case, for a time not exceeding the period of industrial frequency.

Assessments of the relevance of the kinds of attributes regulated by classifiers, evaluation of parameters of individual reliability, of parameters of reliability of multivariate data clusters relate to the primary problems the decision of which would make it possible to reduce operational expenses of electric power system objects. The lack of specialized software systems, the knowledge-intensiveness of algorithms of calculation needed for the solution of operational tasks determine the predominant application of the intuitive approach. Some factors, such as lack of operating experience and subjectivity of the intuitive approach lead to the essential risk of making the incorrect decision. The article presents analytical methods that make it possible to consider the expediency of classification of multivariate statistical data, to identify the relevant types of signs, to rank the objects in power systems and to form clusters of homogeneous data. The methods function with the aid of calculations of indicators of reliability. The originality of methods consists in application of an fiducial approach. Experimental data are compared to boundary values of a fiducial interval. Statistical functions of fiducial distributions are obtained by imitating modeling of samples of random variables for a series of numbers of random variables samples. The analysis of dependency of boundary values on a number of realizations made it possible to obtain a fairly simple equation of regress with the accuracy of no less than 0.995. Formation of a set of relevant kinds of attributes is demonstrated on behalf of an estimation of average duration of idle time during emergency repair made for the analysis of the law of alterations by months of year when the calculation of a parameter of individual reliability for the third power unit in case of failure of boiler facility, representation of set of realizations of duration of idle time in emergency repair clusters. As a result of the repairs, the aging of equipment and devices, alterations of important types of signs that cause the change of the results of the ranking of objects of power system and their technical condition, are observed.

The most important features of outdoor lighting lines are of considerable length and the use of a large number of light sources of an average power. Under such conditions, in order to determine and maintain the optimal modes of operation of outdoor lighting networks with a bilateral supply it is necessary to choose the wire section of the line. This section should provide the required voltage levels to the light sources in all modes, but it should not be too high, in order not to increase the cost of the grid. This article demonstrates an example of the choice of the optimum conductor cross-section of the lighting line when it is working in a normal mode (bilateral power supply) with voltage levels at the power items of 230 V, as well as in the mode of unilateral power (at voltage loss in the second power item) with a value of the voltage of 230 V in the first item of the power supply. The method of calculation of the mode of such a line that had been presented in part 1 of the article was used. The calculation is performed with the of MathCad software. The diagrams of the voltage distribution at items of the lighting line with bilateral power under conditions of different modes of functioning are plotted for various sections of aluminum conductors. The choice of the optimal values of the cross sections of the lighting network was based on the mentioned diagrams. The specific features of different modes of operation of the lighting line with the chosen conductor cross section were analyzed. Operating parameters for each phase of the line (i.e. voltage at the items of the circuit, power, currents, power loss and voltage drop in all sections) were determined. The presented data make one possible to estimate the power consumption of the lighting line taking the daily schedule of enabling and disabling of outdoor lighting networks into account. The most economical modes were determined.

The traction characteristic of an electric vehicle is the main characteristic of mechanical system that reflects its key performance indicators. Implementation of the traction characteristic is based on controlling angular speed and torque of electric traction motor in an automatic control system. The static mechanical characteristic of an electric traction motor in an automatic control system is the most important characteristic that determines weight, size and operating characteristics of an electric traction motor and serves as the basis for design. The most common variants of constructive implementation of a traction electric drive are analyzed, and a scheme is chosen for further design. Lagrange’s equation for electric mechanical system with one degree of freedom is written in generalized coordinates. In order to determine the generalized forces, elementary operation of all moments influencing on a moving car has been calculated. The resulting equation of motion of the electric vehicle corresponding to the design scheme, as well as the expressions for calculation of characteristic points of static mechanical characteristics of traction motor (i.e. the maximum and minimum time, minimum power) are obtained. In order to determine the nominal values of the angular velocity and the power of electric traction motor, a method based on ensuring the movement of the vehicle in the standard cycle has been developed. The method makes it possible to calculate characteristic points of the mechanical characteristic with the lowest possible power rating. The algorithm for calculation of mechanical characteristics of the motor is presented. The method was applied to calculate static mechanical characteristic of an electric traction motor for a small urban electric truck.

Booster pumping plants, equipped with a group of pump units operating in parallel, are typical objects of the city water supply system. Improving its power efficiency is a very urgent topical objective, because its power consumption is a significant part in the structure of power consumption of water utilities. The aim of the present study is to identify opportunities of improving the power efficiency of pumping stations due to the automatic control of the pump group. The paper presents results of the study of the instantaneous efficiency changes of booster pumping stations under the conditions of variable water consumption. The basic reasons of the reducing pumping plant efficiency are reported in the article. Among them, there is a sharp decline in the effectiveness of the regulated pump units, when they functioning for the hydraulic network with a significant static component of the pressure. The main factors affecting the duration of the adjustable pumping unit in inefficient area are determined. The method of controlling a group of pumping units, taking into account the instantaneous efficiency of each of them was suggested. The approbation of this method at the local booster pumping stations was fulfilled. The effects of disabling the controlled pump unit which is in the ineffective area, on the overall efficiency of the pumping station and on alteration of its output pressure immediately after the pump is switched off are studied. It was shown that the timely shutdown of an inefficiently controlled pump unit can reduce the power consumption of the pumping plant by 8–10 % as compared to the traditional control methods. The range of variation of the instantaneous efficiency of the pumping station can serve as a criterion of correct selection of pumping equipment as well it can be the rationale of the necessity for its replacement.

The possibilities of operation of electric generators based on internal combustion engines with air cooling under conditions of cogeneration, when, along with the electricity, heat release in different embodiments is provided. Such facilities are usually realized on the basis of gasoline internal combustion engines (i.e. gasoline is used as a fuel). They can be used in the household, by professional builders, geologists, the military and rescuers in the area of emergencies and in areas with a lack of infrastructure. The basis of the facility is the gasoline generator Hitachi-2400 with an air-cooled power of 2.4 kW. The basic methodology for the study of microthermal power plants based on an air-cooled internal combustion engine which is based on balance equations is presented. The facility operation ensures the measurement of all temperatures and expenses of operating environments for determining heat flow in accordance with the proposed methodology. The specifications of heat exchangers for utilizing the heat of exhaust flue gases are presented. The energy diagram illustrating the useful effect of the application of various heat exchangers are plotted. Cogeneration possibilities of the facility are provided, firstly, by the release of heat with the air that cools a cylinder of the internal combustion engine, and, secondly, by the release of heat of hot water heated by utilizing the heat of the leaving flue gases, and, thirdly, in the calculated version, by the release of heat with air that is sequentially heated due to the cooling of the cylinder head and then by utilizing the heat of exhaust gases. It is demonstrated that the fuel heat utilization factor can be increased from 0.22 to 0.50–0.60, depending on the adopted technical solutions.

A large proportion of consumption of different types of energy by the residential sector, especially in the heating period, makes the energy efficiency of buildings without considering the loss of fuel with a significant reduction in hourly load on the generators, especially at night, already insufficient for real energy savings. Therefore in Belarus, in order to attract the consumer, electricity tariff for heating at night hours (from 11 p.m. to 6.00 a.m.) is three times cheaper than at any other time. Significant increase of the electricity consumption of at night could be achieved by using heat accumulators for heating and hot water supply to the residential sector. Particularly effective are water accumulators of heat and accumulators of underfloor heating that enable to use a coolant with a temperature of 40 оC and to increase the useful supply of heat. The use of heat accumulators for daily heating, ventilation and hot water supply of buildings significantly reduces the cost of creating the infrastructure of the territory under construction by eliminating the necessity of running the distribution network of heat or gas supply. The use of the heat accumulators is necessary due to the increase of the time-weighted average outdoor temperature. The mentioned increase in the City of Minsk in the heating season is of about 0.1 °C per year in average, and as for the last 20 years, the increase has led to a reduction of the required heat load on the premises by about 10 %. Research and project work on choosing the most effective options for the arrangement and use the heat accumulators in buildings of the various functions ought to be fulfilled in order to make the application of heat accumulators successful. In this respect civil and power engineers as well as operators should work together so to determine the chronological, technical and economic conditions of charging and use of heat accumulators.