Zdobysław FLISOWSKI, Konrad SOBOLEWSKI, Przemysław SUL
Factors influencing occurrence of lightning losses in electrical installations of building facilities
It is not only the intensity of lightning discharges as well as structural and environmental factors of an endangered system that influence lightning hazard to a facility equipment but also the structural and environmental factors of power supply systems and external connections. Characterised are here some of these factors and an assessment is made of their influence on the threat to electrical equipment of buildings. Also, when making the assessment of a lightning hazard to electrical equipment in a building facility one must definitely distinguish between the number of the expected severe events and overvoltages caused by them and the value of their importance as their number comprises all event occurrences but the values that matter are connected only with direct lightning strikes into a building object – but if there are no such events, only with the strikes into power supply lines entering a building or into other objects or trees in the very close vicinity.
Keywords: electrical installations of buildings, lightning losses, assessment of lightning hazards in a building
Laboratory testing of conductive and non-conductive roof covering samples resistance to lightning currents
Thunderstorms, occurring in nature, with their lightnings causing overvoltages have direct impact on the safety of building facilities. Conducted were tests, in cooperation with a design and execution company, concerning results of a lightning current flow through various types of roof coverings. Investigations described here reflect the situation in which a direct lightning strike hits a roof covering unprotected against lightning discharges or protected in an improper way. Laboratory tests were conducted with the use of an impact current of 100 kA peak value and with a 10/350 µs waveform reflecting the current of a real lightning discharge to the ground.
Keywords: safety level of building facilities, roof coverings, investigations on results of a lightning current flow through various types of roof coverings
Maria KASKA, Andrzej SŁAWIŃSKI, Aneta ŚWIERCZ
Material tests for power industry in the light of EU program documents and European initiatives
Materials science is the synthesis of many branches of basic sciences like chemistry, physics, biology as well as the engineering ones like metallurgy, ceramics, biotechnologies and nanotechnologies. The main challenge of material technologies is the cognition of complex bonds between atoms and molecules creating a material microstructure and their influence on its macroscopic technical properties. The key to match the material properties to the expected functional applications is understanding how a microstructure influences physical and chemical parameters of a material and its behaviour in various conditions and applications. An analysis is made of research directions in the scope of advanced materials for power industry applications in the perspective of the coming years – until 2020 and 2050 – in the light of program documents and European initiatives.
Keywords: material science, material technologies, analysis of research directions until the years 2020 and 2050, EU program documents
Marcin BIERNACKI, Przemysław MAJEWSKI
The impact of a public transport electric bus traffic cycle on the operation of a supply battery
Presented are road tests used, among other things, for research of newly designed drive systems of city buses. Developed was the authors’ own model of a bus test route basing on one of the standardized bus ride cycles in urban conditions and on real data collected during multiple rides between end stops on one of the public transport routes in one of the largest cities in Poland. Analysed is the electric energy storages operation taking into account requirements concerning the vehicle range (according to the needs of the public transport company and taking into account the current technical capabilities), durability and mass of the energy source as well as the time needed to charge the source after one cycle or many driving cycles. Considered is application of batteries made with technologies different from the most popular now Li-Ion or Li-Po ones.
Keywords: city bus, battery, power supply source
Janusz BADUR, Tomasz KOWALCZYK, Mateusz BRYK, Kamil BANAŚ, Michał STAJNKE, Bartosz KRASZEWSKI, Paweł ZIÓŁKOWSKI, Piotr Józef ZIÓŁKOWSKI
Maximum operational flexibility of steam power units
Presented is a proposal to accelerate steam turbines start-ups by proper steam supply during the turbines non-stationary states. Examined were the most stressed places of the device taking due account of both the traditional Huber-Misses-Hencky hypothesis and the Burzyński’s one. In case of frequent start-ups the increasingly crucial role play thermal stresses for which the stress normal components are the most important ones in contrary to conventional tangential components being the basis for equivalent stresses calculations on the foundation of the Huber-Misses-Hencky hypothesis. Calculations aimed at achieving maximum flexibility were carried out using the numerical thermal-FSI tool that simultaneously analyses fluid and structure in order to fully integrate temperature fields and thus more accurately determine stresses in a structure.
Keywords: steam power units, operational flexibility of units, acceleration of steam turbines start-ups
Hanna WOJTUSZEK-SZEWCZYK, Marcin SZEGA
Analysis of electric energy supply to critical infrastructure end-users on the example of selected hospitals
Presented is here the hospital power supply system, hazards to this supply and an analysis of power supply to hospital facilities in one of the Polish counties. Analysed problems referring to securing the energy safety of the selected hospitals work show that there is a need of further and enhanced cooperation between science and technology communities as well as decisive persons and institutions connected with the power, IT, medical and legal sectors and also the crisis management.
Keywords: hospital power supply system, hazards to electric power supply to hospitals, analysis of hospital facilities power supply reliability
Electrical and magnetic properties of rocks
Rocks magnetic properties are contingent upon rock-forming minerals contained in them. Important role is played here by magnetic properties of chemical elements that the rocks are made of as well as the type of bonds and crystals structures. Magnetic properties of rocks are characterized by a value called magnetic susceptibility that determines ability of a given substance to change its magnetization under the influence of an external magnetic field. From among magma rocks it is the alkaline ones that show higher magnetic susceptibility than the acidic ones. The main rock-forming minerals are bad electric conductors. Given are electrical properties of some rocks. Another electrical properties that distinguish rocks are phenomena of pyroelectricity and piezoelectricity.
Keywords: rocks, electrical and magnetic properties of rocks, pyroelectricity, piezoelectricity