Frantisek Janicek

The cause of false operating of the rotor ground fault protection based on the AC injection method

In this paper we tackle the issues of the protection of a synchronous generator field winding in the case of the first ground fault. We analyze the reasons of false operation of the rotor ground fault protection based on the AC injection method on the synchronous machine with a static excitation system. This paper presents the results of the measurements on a ground rotor fault protection of a synchronous generator. These measurements were aimed primarily on harmonic analysis of the field voltage and the current flow through the insulation system of the rotor and also through the rotor ground fault protection during a failure-free steady state of the generator. This submission includes also our results of computer simulations that prove the causes of incorrect operation of the rotor ground fault protection based on the AC method.

RECOVERY OF WASTE USING THE GASIFICATION AND OXIDATION OF SCRAP TIRES

The investigation of the use of microwave gasification as a method that allows to obtain energy from end-of-life (ELTs) tires was subject of this study. The gasification of the waste was carried out within the laboratory microwave reactor HR – Lab, followed by the microwave-assisted oxidation of synthesis gas (syngas) which took place in a small microwave reactor – Microwave Oxidation System (MOS). Details of the experiment, such as power and temperature profile as a function of time and material charges distribution, are listed and explained. Analysis of gasification produced syngas in terms of composition and energy values was done also.

Microwave Supported Treatment of Sewage Sludge

Abstract This work is focused on microwave treatment of sewage sludge. The aim of our experiments was to investigate the impact of microwave radiation upon different sewage sludge parameters such as concentration of nitrates and nitrites, phosphates, COD (Chemical Oxygen Demand), SVI (Sludge Volume Index) and the microscopic structure of sludge. The experiments with microwave irradiation of sewage sludge indicate that moderate microwave power causes visible effects on the chemical, physical and biological properties of the sludge. The calculation of profitability and energy efficiency is also presented.

Dynamic Analysis of Overhead Power Lines after Ice–Shedding Using Finite Element Method

Abstract In this paper, the analysis of ice-shedding from ACSR conductors to its swing up height and vibration using Finite Element Method (FEM) is presented. For the numerical simulations the effective material properties of the ACSR conductor are calculated using the homogenisation method. Numerical analysis concerning vibration of one and triple-bundle conductors with icing for a whole range or on their certain parts are performed. The impact of ice-shedding to the mechanical tension in the conductors at the points of attachment is investigated and evaluated. Identification of the impact of ice-shedding from the ACSR conductors on its mechanical state may contribute to increasing the safety and quality of an electrical transmission system.

Applications of superconducting quantum interference devices

A superconducting quantum interference device (SQUID) is a very sensitive magnetometer used to measure extremely subtle magnetic fields based on superconducting loops containing Josephson junctions. SQUID represents the most accurate sensor to measure the magnetic field and voltage. Overview of the potential applications and possible improvements of SQUID are the aims of this work. In general, the transducers of physical quantities on voltage and magnetic field allow wide range of other applications. Such converters may lead to an improved universality of SQUIDs. Potential improvements was verified by simulation of series and parallel multiple quantum interference devices. It provides opportunities to improve their sensitivity.

Roadmap for Smart Metering in the Slovak Republic

The Slovak Republic (SR) is an inland country in the middle of Europe with a total area of 49 035 km2 and population 5.45 million people. The capital is Bratislava and the country is member of the European Union. The annual electric energy consumption is 28 862 GWh and production is 28 135 GWh (2011). The average electricity consumption in the household sector is 2.5 MWh per year and the average price is 140 EUR/MWh. The electric energy distribution in Slovakia is assured by 3 regional distribution companies covering 2.35 million points of supply. The annual volume of supplied electric energy by distribution companies via HV and LV networks has reached the level of 18 000 GWh. The area of electric energy distribution is regulated by the independent authority Regulatory Office for Network Industries. The Slovak Republic has approved the Concept of Energy Efficiency, having the primary target to achieve gradual lowering of energy demands to the level of European Union. In the years 2001 – 2010, the total volume of final electric energy consumption was reduced by 6%, i.e. by 7 TWh. Construction of intelligent metering systems is another step to achieve a higher energy efficiency, according to the Concept of Energy Efficiency of SR and according to the Directive of the European Parliament and Council 2009/72/EC of July 13, 2009. The intelligent metering systems are perceived as a part of a smart grid construction, conducted already for several years by main manufacturers, operators of the transmission and distribution systems. Automated meter reading (AMR) based solutions have covered all significant points of supply in the wholesale category, in a total number of 50 000 with consumption monitoring reaching the total volume of approximately 50% of consumed electric energy. At the LV voltage level, most of the points of supply have an electromechanical or static meter installed. The Regulatory Office for Network Industries in cooperation with the Ministry of Economy assessed the analysis of deploying intelligent metering systems for the LV level positively, and joined other European countries, such as Germany, Poland, Hungary, Slovenia, Romania, Bulgaria, Greece, Latvia, Portugal and Belgium. The economic assessment of the AMI deployment project in Slovakia and implementation of intelligent metering systems is assumed within the years 2013 to 2020. The project covers the points of supply with annual consumption above 4 MWh, representing approximately 23% of all assumed points of supply at the LV voltage level. The target number of points of supply, expected to have the intelligent meters installed by 2020, is approximately 600 000, with consumption representing approximately 53% of the total annual consumption of electric energy at the LV voltage level. The rollout scope could be affected by the planned revaluation of CBA. The implementation is based on several types of intelligent 1 and 3 phase meters, according to the supply point type, which are differentiated by their functional specification in basic, advanced and special ones. The total assumed annual economic benefits following the implementation of intelligent metering system and installation of intelligent meters at the LV level are expected to be around EUR 36.16 per one point of supply. The biggest benefit will belong to the end customer. The CAPEX figures per one point of supply should be around EUR 131.00 and the operating costs OPEX should be EUR 8.23 per annum. Most of the problems in specification and architecture design are caused the current extent of standardization, legislation and return of investment. In order to verify the technical and economic assumptions, a pilot project will be launched in the years 2013 – 2014 covering 1% of the total final volume, i.e. approximately 6 000 points of supply. The rollout itself is planned in the years to follow. Until the end of 2016, it will cover the consumers having the annual consumption more than 15 MWh with a maximum reserve capacity in the point of supply at least 30 kW, or at least 45 A and until the end of 2020 the consumers having the annual consumption more than 4 MWh with maximum reserve capacity in the point of supply less than 30 kW or 45 A.

Awareness System Implemented in the European Network

Abstract Transmission system in Slovakia is part of a synchronously interconnected system of continental Europe. Besides indisputable technical and economical benefits of cooperation many hazardous factors exist of fault condition spreading with impact on our system. Even today a system break-up escalated into a vast blackout is a real danger. European transmission system operators continually work on preventive measures and develop systems with a goal to handle critical situations. The ambition of the European Awareness System is to signalize the rise of these situations and also assist with system restoration

Overheating of primary and secondary coils of voltage instrument transformers

We deal with the numerical model of overheating of primary and secondary coils of voltage instrument transformer. Calculated values are compared with two different measuring methods — measuring with thermal sensors and calculation of heating from measured resistance. All calculations are solved in three operating conditions by rated voltage, thermal limiting output and rated voltage factor 1.9 Un according to IEC 61869-3 standard. In the paper is studied dependence between overheating and thermal transmittance. The article also deals with simple design of core, primary and secondary coil of voltage transformer with two secondary windings.

Prediction and production of small PV power plant

The aim of this work is the evaluation of the data obtained from experimental PV solar system performance. 500 Wp PV system is installed on the roof of Faculty of Electrical Engineering and Information Technology of Slovak University of Technology in Bratislava, Slovakia. In addition the obtained results are compared with the PVGIS simulation. A brief summary of components and construction parts of photovoltaic system, description of the individual elements forming the system (photovoltaic modules, the inverters and the equipment of measuring and data processing) is given. The electrical parameters of PV system and irradiation intensity which allows the calculation of efficiency during the operation of PV grid connected systems are measured. Moreover, the measurements of weather and environmental factors like temperature and other (humidity and air pressure, wind speed) have been continuously done. Detailed analyses under different operating conditions, performing some monthly and daily analysis and comparing them with solar radiation database from climatologic data homogenized for Europe (PVGIS) were performed.

Use of microwave for energy recovery from different types of waste

Progressive processing method which uses microwave assisted gasification of selected types of waste is discussed in this work. A brief summary of waste management in the EU and processing capabilities are given in the introduction. The next section discusses the legislative aspects of waste management. Substantial part presents the research results achieved when microwave assisted gasification was applied for energy recovery of sewage sludge, waste tires, sawdust and wood pellets.