Utilization of Cable Screen Earthing Current for Detection and Location of Earth Faults in Medium Voltage Networks

The paper presents issues related with detection and location of earth faults in medium voltage (MV) networks. Attention is paid on cable and cable-overhead lines. The criterion value – cable screen earthing current is presented. Afterwards, the method of utilization of the cable screen earthing current for detection and location of earth faults is described. The next part of the paper presents the results of simulation research for different variants of earth faults in cable and cable-overhead lines. The presented relations are the basis of the developed algorithm of detection and localization of earth faults. The presented considerations were confirmed by an experiment performed in the MV network.

Investigation of Turbulence Parameters Influence on Results of CFD Modeling of Flow in Ultrasonic Flowmeter

The article investigated the influence of turbulence parameters of the SolidWorks Flow Simulations CFD package on the results of flow simulation in a two-path ultrasonic flowmeter. It has been found that the main turbulence parameters of SolidWorks Flow Simulations (turbulence intensity, turbulence length, turbulence energy and turbulence dissipation) slightly affect the result of the flow simulation in a full-filled pipeline of circular profile without additional turbulous elements (turbine, rotor, other). In view of this, during the CFD modeling of the flow measurement process using ultrasonic flowmeters, it is recommended to apply turbulence parameters installed in the SolidWorks Flow Simulations CFD package by default. At the same time, the time consumed by the computer to perform CFD modeling is almost unchanged when the specified parameters of the SolidWorks Flow Simulations CFD package.

Characteristic Curves of Iridium-Rhodium Sensing Elements in High-Temperature Transducer Applications

In order to increase the capacity and efficiency factor of gas turbines and internal combustion engines while preserving their high reliability, the gas temperature and its distribution need to be measured in combustion chambers. Values of these temperatures can exceed 1800°С in an oxidizing atmosphere. Therefore, designing temperature transducers for measurements in such severe environments, special attention should be paid to the selection of thermometric materials. The requirements of the necessary accuracy and temperature range over 1800°С in an oxidizing atmosphere are fulfilled only by the temperature transducer based on iridium-rhodium alloys. The characteristic curve of such sensing elements is individual and each temperature transducer is to be calibrated. The paper discusses a technique of determining the individual characteristic curve of iridium-rhodium sensing elements of high-temperature transducers. The preparation steps to be taken prior to the calibration and the main stages of determining the characteristic curve are described. The general view of the experimental set for calibrating the sensing elements is presented. Based on the calibration results, the form of approximating polynomial of the individual characteristic curve is proposed.

Analysis of Computer Modelling Results on Fuel Rods Strength and Condition at Reduced or Absent Cooling Caused by Accident

The paper describes the phenomenology of fuel rod behaviour in severe accident. As an example, an experiment is described resulting in severe damage of 19 fuel rod assembly of VVER type; it was carried out in the CORA facility in 1993 (Research Centre, Karlsruhe, Germany). Testing conditions and results of post-test investigations of fuel assembly are given. The fuel rod code RAPTA-SFD is briefly dealt with; the code was a participant in the International Standard Problem ISP-36. The basic results are presented acquired by computer modelling CORA-W2 experiment using RAPTA-SFD code. Among the presented experimentally acquired and calculated results, the scope of the data on stainless steel component behaviour is substantial. The tested CORA-W2 fuel assembly contained a significant quantity of steel components, viz., spacer grids, a guide thimble, and a cladding of an absorber element. It is to be borne in mind that the spacer grids and a guide thimble of the updated and upgraded fuel assembly of VVER-1000 are fabricated from Zr-alloy, hence, the relative quantitative characteristics of chemical interactions between materials and stainless steel (Cr-Ni alloy) will be much lower for the up-to-date upgraded fuel assembly under identical conditions.

Enhancement of Technical and Economic Indicators of Power-Generating Units of Thermal Power Plants by Eliminating Flue Gas Recirculation

Boiler units at Ukrainian thermal power plants need to be modernized or replaced in the short run, as this is important for the national energy security. The authors determined one of possible ways to improve the efficiency indicators of coal-fired boiler units and power generating units as a whole up to the values exceeding the design ones. This variant of improvement consists in abandoning the technology of using flue gas as drying agent in pulverized coal systems and replacing it with direct discharge of the gas flow into the boiler furnace. Numerous computations were carried out to study the change of efficiency indicators and manoeuvrability of power generating units due to the replacement of the ball mill pulverizing system using flue gases for coal drying with the scheme including ball-and-race mills that use hot air as drying agent.

Enhancing safety and reliability of electric power supply to consumers through safe electricity networks of up to 1 kV

The study presents an electric network that allows both increasing the level of electrical safety and eliminating one-phase damage to the electrical network without switching off the consumer's electric energy. The application of the network does not require significant investments. The technical feasibility of implementing an electrical installation with voltage values in the emergency mode on the leading parts, which does not exceed the permissible values for normal mode, is demonstrated. An additional advantage of the proposed technical solution is the immutability of the voltage at the customer's outputs, which allows it to operate normally also in the emergency mode of the electrical installation.

Energy efficiency of modernization of translucent building envelope structures

The article focuses on determining the energy efficiency of the translucent structures of building envelope (TSBE) use with different lighting and thermal parameters. The expediency of replacing TSBE with more modern ones with higher thermal resistance and lower solar radiations relative penetration coefficient (SRRPC) is considered. The comparison was made taking into account the influence of TSBE parameters on electricity consumption in the office premises on the compensation of heat energy losses, as well as its savings due to the receipt of solar radiation during the heating period, the removal of excess heat during the cooling period and energy savings through the use of daylight during a year. It was found that despite the smaller glazing area and light-transmitting characteristics of configuration No. 3 (profile Veka Softline 82 with triple-glazed window 4Solar-16Ar-4-12Ar-4і), electricity savings when changing the configuration of TSBE No. 1 to No. 3 leads to energy savings of 31.7 kWh/yr with the TSBE area of 0.5 m2 to 419.5 kWh/yr at 6 m2, and when replacing configuration No2 by No3 – from 24.7 (STSBE = 0.5 m2) up to 397.2 (STSBE = 6 m2). This makes it possible to determine the energy and economic feasibility of TSBE modernization by installing metal-plastic structures with different lighting and thermal parameters.

Prediction of thermophysical characteristics of fuel rods based on calculations

The paper analyzes operating conditions, thermophysical characteristics were calculated as applied to WWER-1000 fuel rods in a four-year cycle for unified core. The paper gives a summary of models for calculating gas release, pressure of gases within fuel rod cladding, fuel swelling and thermal conductivity, fuel-cladding gap conductance. The thermophysical condition of fuels in a reactor core is one of the main factors that determine their serviceability. The stress-strained condition of fuel claddings under design operating conditions is closely related to fuel rod temperature, swelling, gas release from fuel pellets and the mode in which they change during the cycle and transients. Aside from this, those parameters are an independent goal of studies since their ultimate values are governed by the system of design criteria.

Simulation of pressurized water reactor to find the best control solution

Since it is impossible to simultaneously control all technological and thermal parameters of the nuclear reactor, a vertically distributed model of a power unit was developed, which allows determining the axial offset and analyzing the behavior of thermal and neutron-physical processes of individual zones in core during boron control and movement of rods, as well as regulating the power of the nuclear reactor. For ten vertically distributed zones, neutrons and thermal processes in the reactor core were analyzed, as was the change of the axial offset during the discharge of the reactor load under the influence of the movement of the rods and the increase in the boric acid concentration. The purpose of this publication is to develop a vertically distributed model of the facility and use information technology to find the best solution for the control of a pressurized water reactor.

Resources for structural optimization of gas-hydrodynamic measuring transducers

The paper presents the analysis of the resources of structural and parametric optimization of gas-hydrodynamic measuring transducers of physical and mechanical parameters of fluids. Resources such as the number of throttles and their arrangement in the diagram, type of throttle elements, measuring channels with a certain type of output signal, the supply mode of the measuring transducer can be integrated into the design process of the measuring transducer of a specific parameter. A mathematical apparatus based on set theory and combinatorial analysis is proposed for synthesizing the possible structures of throttle diagrams, graph theory – for forming a set of measuring channels. The authors have given examples demonstrating the possibilities of building different diagrams of measuring transducers using the resources for structural synthesis. The proposed resources are the means of structural and parametric optimization for synthesizing the gas-hydrodynamic measuring transducers with optimal characteristics.