doc. Ing. Jan Mikeš, Ph.D.

The complementary radio navigation system based on the Very Low Frequency signals produced by lightning is an alternative to today's Global Navigation Satellite Systems. The system operates on different principles and uses different radio frequency bands. The signals have higher availability in problematic places. The analyses based on the historical data of Word Wide Lightning Location Network demonstrated the good availability of the service, sufficient number of lightning strokes and good geometry calculated for a 10-second time window for positioning based on the Time of Arrival principle. The geometry was evaluated with the help of the Geometric Dilution of Precision coefficient. The Geometric Dilution of Precision median for the reception of the lightning signal from a range of 10,000 km moves around one except at the southern polar regions and the probability of the service availability exceeds 80%.

The goal of this paper is to demonstrate the capability of the 1U CubeSat to study the radiation spectra on LEO. The research was realized by the Lucky-7 mission with the primary goal of testing electronics such as a power supply, piNAV L1 GPS receiver, UHF communication system, and other subsystems in the natural space environment, and the secondary goal of testing the possibility of using 1U CubSat class satellites for scientific tasks. The satellite is equipped with a piNAV GPS receiver and piDOSE radiation detector, silicon diode radiation spectrometer, camera, and other sensors. The on-board computer enables storage of 34 h of measurements of the radiation spectrum. These measurements can be downloaded by the UHF communication system during four satellite passes over the monitoring ground station. We successfully verified all necessary instruments and their cooperation and measurement procedure. The UHF communication was identified as the most critical subsystem because of its low capacity, which slowed down the satellite operation. We needed four zenith passes to upload 34 h of measurement.

Safely conducting flowing lightning current into the grounding system via air-terminals and down-conductors constitutes a key method of protecting objects being struck by lightning discharge. At present, there is no other safer method of protection than capturing and conducting lightning current and its dispersion in the ground. By having to conduct powerful lightning current, the protection systems are exposed to excessive thermic and electrical stress. When such protection systems are correctly designed, installed and regularly checked, the threat to objects is considerably reduced as the systems are dimensioned for such purposes. An opposite case occurs when a protection system is damaged, most frequently due to the thermic effects of lightning current. Then, there are only two possibilities of detecting damage: either by providing regular and timely inspections or by means of controls based on the information supplied by a lightning strike counter. The key requirement of the first method is that the relevant object has not been repeatedly struck by lightning current during a period of at least 5 years. The other method provides instant information, in real time, and inspection of the protection system may be carried out immediately. Hence, sooner than another lightning stroke discharge could be repeated. This paper examines the method of detecting lightning current in down-conductor and the possibility of providing real-time information.

Lightning poses a risk to buildings, people, and technical facilities. The lightning air-terminal and down-conductor are the basic protection against direct lightning discharge. In terms of the reliable functioning of the lightning conductor, the key is to monitor the passage of the lightning current through the lightning conductors and to brief the facility manager in real time of the need to carry out appropriate checks. We hereby present a system for contactless monitoring of lightning attacks, and experimental results of testing by means of a lightning impulse current generator (LICG). Finally, we introduce an IoT system for large-scale monitoring.

This paper deals with the measurement of ionising radiation emitted in the vertical field of electric discharge generated between the tip and the grounded plate electrode. The generator set-up was for 400 consecutive negative discharges with voltage amplitude 0.9 MV, waveform shape 1.2/50 mu s, discharge energy 80 kJ and electrodes 1 m apart. Thermoluminescent, passive detectors were used to avoid electromagnetic interference from the discharge. The detectors were placed at the electrodes and three vertical positions 1 m from the discharge axis. This work extends a previous study focused on dosimetry in the plane parallel to the ground. This experiment confirmed the presence of a photon/electron component at the electrode tip and 0.5 m vertical position at a distance of 1 m from the discharge axis. In addition, the presence of neutrons was found for new positions in the vertical axis and the ground electrode.

We investigated the air supply mode effects on ozone production of the surface dielectric barrier discharge in the cylindrical configuration. The air into the discharge volume between two coaxial cylinders was supplied through four nozzles axially or tangentially. Using tangential air supply, the vortex flow in the part of the discharge chamber was created. Because the active electrode was in the form of interconnected rings on the outer surface of the glass tube, we changed the airflow orientation concerning this electrode. The existence of vortex airflow affects the plasmachemical processes taking part in the discharge, and therefore, it affects discharge ozone production. We also paid attention to ozone concentration and temperature of output air measurements as a function of the duration of the experiment for both tangential and axial air supply modes. We found that the time required for the stabilization of generated ozone concentration depends on the discharge power, and for our experimental conditions, it smaller than approximately 70 s. Besides, in the case of tangential air supply into the discharge chamber, the concentration of ozone produced by the discharge is for higher discharge power increased in comparison with the concentration for the axial air supply mode.

Power grids are the arteries of national and transnational integration. They increase the security of supply and ensure economic synergy effects. Whenever the master-minds of European unification presented plans for pan-European power grids in the 1920s, Czechoslovakia was always involved. However, the division of Europe after the Second World War led to Czechoslovakia's integration into grid of the Comecon countries, which was largely decoupled from Western Europe. Since 1995, the Czech network of transmission lines has been an integral part of the European power generation and distribution grid, and the Czech Republic plays an important role in the power supply in Central Europe.

In this study, we focus our attention on the impact of ozone (O3) and ultraviolet radiation (UV) on materials usable for three‐dimensional (3D) printing. Specifically, we have studied the potential degradative effect on the most commonly used filaments, such as polylactic acid (PLA) and acrylonitrile–butadiene–styrene (ABS). The effect has been examined on objects printed on a 3D printer and on the materials of discharge chambers of O3 generators from which they were printed. For the purpose of adequate assessment of the actual impact of O3 and UV, samples were monitored for a period of 18‐hr of exposure. The methods of Raman spectroscopy, optical and scanning electron microscopy and Fourier‐transform infrared spectroscopy (FTIR) have been employed for an objective evaluation of potential modifications. A generator equipped with a chamber printed from a new PLA filament and an active electrode system in the form of a stripes electrode, or more precisely, in the second case, a honeycomb‐active electrode, both cut out of a thin copper foil, was used for the generation of O3 and UV radiation. The tested materials showed substantial resistance to O3 exposure under the test conditions. The result of measurements suggested that these materials could be used for chambers for the O3 as well as for active particle generation. In this study, we focus our attention on the impact of ozone (O3) and ultraviolet radiation on materials usable for three‐dimensional printing.

Článek představuje cesty odborného charakteru českých elektrotechniků a zejména konstrukčního elektrotechnika Vladimíra Lista zejména od 90. let 19. století do roku 1939 a jejich vliv na rozvoj tehdejšího technického školství, průmyslu, komunikačních možností nebo vědecké mezinárodní činnosti a spolupráce. Jeho cesty se vztahovaly nejen k jeho vlastnímu studiu (Ústav Montefiore v belgickém Liège v letech 1900-1902), k důležitým politicko-ekonomicko-technickým záležitostem českých zemí a Československa (jako např. jeho úspěšná účast na jednání k mírové smlouvě ve Versailles v letech 1919-1920), ale zejména se týkaly Listovy práce na elektrifikaci Československa a technicko-normalizačního hnutí (do Francie, Švýcarska, Německa aj.) nebo vědeckých konferencí (v podstatě do celého světa včetně USA, Japonska aj.). Listovy cesty ukázaly nutnost pro odborníky získávat zkušenosti prostřednictvím mezinárodní kontaktů, které zhodnocují nejen osobní život a odbornost jedince, ale významně přispívají i k rozvoji celé společnosti.

We studied the effect of the driving voltage of frequencies 4, 7, and 10 kHz and two different active electrode setups on electrical properties, ozone production, and UV radiation of wavelengths 320-420 nm of the dielectric barrier discharge in air. The first active electrode setup comprised the strip electrode made from the copper foil. The second setup comprised the stainless steel wire mesh electrode with square cells. The ozone concentration, as well as the ozone production yield, is higher for the discharge with the strip active electrode setup than for the discharge with the mesh active electrode set up. The increased frequency decreases the voltage required to obtain maximum ozone concentration. The intensity of UV radiation is higher for the discharge with the mesh active electrode setup than for the discharge with the strip active electrode setup for all investigated frequencies. The intensity of UV radiation at a particular voltage depending on the frequency and active electrode setup sharply increases. The high concentrations of ozone produced by the discharge with the strip active electrode setup are accompanied by lower intensities of generated UV radiation. For the discharge with the mesh active electrode setup, the situation is reversed.

We investigated the effect of a non-doped diamond layer deposition on the active electrode of the dielectric barrier discharge in the air on its electrical characteristics and ozone generation. We found that this new non-traditional application of diamond layers affects electrical parameters of the discharge and increases not only the concentration of ozone produced by the discharge but also ozone production yield by similar to 70%. Considering obtained results together with the high corrosion resistivity and chemical inertness of the diamond layers, the application of these layers on the dielectric barrier discharge electrode can be an interesting alternative to the usage of photocatalysts for the enhancement of ozone generation by electrical discharges.

Terrestrial gamma and neutron flashes can result in considerable radiation exposure of aircraft crew and passengers in their close vicinity. Lightning impulse voltage generators imitate selected stages of natural lightning processes and can serve as a test environment for the development and calibration of detector systems for such short term radiation events. This work presents the results of measurements of absorbed dose using thermoluminescent dosimeters for 400 negative discharges at the lightning impulse voltage generator. The thermoluminescent dosimeter CaSO4:Dy and the combination of lithium-fluoride detectors MTS-6, MTS-7, and MTS-N were used to quantify the photon and neutron components of the radiation field. The detectors were placed in four positions near the generator spark gap. The results confirm the presence of thermal neutrons and photon radiation in two positions at the lightning impulse voltage generator.

The authors have rearranged an optimal method for signal processing of interferometric measurements, based on the angle-of-arrival estimation approach, and have analyzed errors of estimating the direction of arrival of intercloud pulse signals. The method was then implemented in the performance of optimized interferometer hardware. This article presents application of an array of plate antennas matched by the 50 omega parallel resistor that are directly connected to 50-omega high-frequency low-noise amplifiers for each channel. The important contribution of the authors is to cover the plate antenna capacitance to the input bandpass filter. The proposed compensation enables to reduce linear distortion of the received signal, which is one of the main sources of errors of the time-of-arrival estimation, and to optimize the antenna impulse response. The novelty of this article can be seen in the application of the artificial intercloud pulse generator for testing, precision calibration of the proposed system, and fixing of potential imperfections and losses in both hardware and processing software. The practical application of the proposed interferometer is demonstrated on the processing of real lightning events. As the interferometer operates in the frequency bands that are dedicated to other radio communication services, this article provides results for measurements of interference that were realized with the aim of finding an optimal installation location.

Příspěvek popisuje vybrané výstupy a zaměření aplikovaného výzkumu společnosti CHEMCOMEX, a.s., které cílí na následující oblasti: systém záchytu polutantů srážkových vod; zamezení negativního vlivu hydrogeologických vrtů na podzemní vody; mobilní úpravu decentralizovaně produkovaných obtížně zpracovatelných odpadních vod; pokročilé oxidační technologie pro vodárenské a environmentální aplikace; zpracování a zhodnocení čistírenských kalů; komplexní vodíkovou technologii pro nápravu ekologických škod.

Numerous scientific disciplines such as hydrology, meteorology, oceanography or geology take advantage of remote measuring and monitoring. Data measurement in remote locations and the transmission of measured data is an essential part of these disciplines. The critical element of remote measurement and monitoring systems is a remote station. When designing such a device, it is necessary to solve issues of the construction, power system, data transfer or autonomous operation systems. This paper introduces the Autonomous Groundwater Monitoring Station with Wireless Communication which has been designed and installed in a field application. The individual parts of the station such as construction, software, hardware, wireless communication system or systems for autonomous operation are presented.

VHF interferometer serves for the registration and localization of lightning radio pulses for further analyses of the inter-cloud processes that are connected with charge transfer and emission of radio pulses. As the bandwidth, of the VHF interferometer, is very wide due to the precise measurement of the time difference of arrival, the interferometer generates a large volume of data that must be processed and stored. The triggering system of the VHF lightning interferometer enables to select scientifically valuable data from the data stream. The ideal triggering unit synchronizes data acquisition with the return stroke event. The basic requirements placed on the triggering circuits are a low false alarm rate and a high probability of lightning discharge detection. The unit consists of a whip antenna that is sensitive in the electrical field, an amplifier and a matched filter that is tuned to the return stroke wave. The usage of the correctly designed matched filter increases detection probability of the lightning discharge and reduces false alarm rate. The key problem is laboratory testing of the triggering unit in a near-realistic environment. The paper proposes a method based on the generation of the return stroke wave by a lightning current generator. As the gain of the common electrically short whip antenna cannot be determined with sufficient precision, the electric field of the generator is properly calibrated by an electromagnetic field probe based on a plate radiator. This approach facilitates accurate control of the amplitude of the return stroke radio wave and study of the sensitivity of the triggering circuits on nonstandard waves.

As a technical and scientific branch, electrical engineering (and later also informatics or information science) began to be shaped and developed approximately since the last third of the 19th century, notably since 1881, the year of the convention of the First International Electrotechnical Congress and Exhibition in Paris, a gathering that defined basic electrotechnical units. Greater accent on the development of electrical engineering (and informatics) came at the time of the two World Wars, when—after WWI—all the major countries in the world had started building their national grids which were consequently interconnected primarily for technical and economic reasons. The period after WWII saw the emergence of cybernetics, electronics, electrical engineering and electronic miniaturization and informatics, disciplines fully dependent on a well-functioning and well-proportioned (and in most cases already internationally intertwined) electrification system.

Článek se zabývá vývojem elektromobility v českých zemích v historických perspektivách.

This article discusses an alternative possibility of detecting lightning discharge strike at a lightning protection system, as compared with the classical sensors based on the inductive principle (using a coil) or the principles requiring external feed, such as the application of the Faraday optical transformer. The key advantage offered by our proposed system is its indirect method of evaluating the impacted lightning protection system, which is based on the piezoelectric principle. Other advantages of the proposed system include direct independence on the lightning current passing through the downconductor and thus a lower risk of damage to the sensor by the lightning current, and absolute independence of the inner installation and, therefore, elimination of any risks for its operators and users, as well as a lower risk of an electric discharge flashover and outbreak of fire in a given structure.

The paper presents design and application of a telemetry system for stratospheric balloon based on Internet of Things System of SigFox. The purpose of the telemetry system is balloon tracking during the stratospheric flight. It was tested on experimental flight of FIK III stratospheric balloon equipped with SigFox as main transmitter and UHF transmitter for backup. The payload consisted of ADS-B receiver, and two independent dosimeters for radiation measurement. The paper presents verification of operation of telemetry system on results obtained during experiment. The end of paper covers also some considerations about advantages and drawbacks of such solution.

Der Artikel konzentriert sich auf die Entwicklung der Beleuchtung in tschechischen Ländern. Die Autoren basieren auf primitiver Leuchtbeleuchtung und entwickeln die Geschichte der Gasbeleuchtung insbesondere in größeren Industriestädten weiter. Der Schwerpunkt liegt auf dem Vergleich der elektrischen Beleuchtung in den tschechischen Ländern und in Europa mit dem Schwerpunkt auf dem Beitrag eines der ersten tschechischen Elektrotechniker, František Křižík, und der Anwendung seines differentiellen Bogenlampencontrollers.

The authors of the article have devised a lightning monitoring system whose positive features can be divided into two interconnected groups. The first major advantage is greater safety of people and animals living in the buildings hit by lightning discharge. This is the most important goal in terms of safety. With online diagnostication it is possible immediately to set up an evacuation regime for the object, and a rescue operation may be launched in the object well before any undesirable destructive effects of the lightning discharge have time to develop. The second major advantage is unquestionable evidence proving that an object has really been hit by lightning discharge – this particular factor can be used for insurance events, insurance policies and the work of insurance companies themselves.

The Czech (Czechoslovak) technical standardization was institutionalized soon after the disintegration of Austro-Hungary and after the establishment of its successor states, i.e. independent Czechoslovakia on October 28, 1918. The first Czechoslovak standardization institution was founded on December 28, 1922 as the Czechoslovak Standardization Society (Czech acronym ČSN). Enjoying the status of a generally beneficial, non-profit organization, the Society was made up of manufacturing plants, professional unions, commercial organizations, universities etc. Members paid membership fees and participated in the institution’s activities according to their interest and at their own costs. Draft technical standards were drawn up by experts from industrial plants, research institutes, universities etc. The International Association of Standardization Organizations (ISA) was established in Prague six years later, in 1928, initiated by Czech professor Vladimír List (1877-1971) within a group of European technicians. In the years 1932-1934 Vladimír List also served as the ISA President, a post that was accorded to him not only in recognition of his technical achievements and erudition; it also had a great impact on the development of Czechoslovak standardization in general and in the electrical engineering sector in particular.

The paper presents telemetry system for stratospheric balloon mission based on the UHF transceivers designed for Internet of Things. The system operates in 869.5 MHz frequency band. The system uses very short packet without channel coding that can be successfully received and decoded under low signal to noise ratio. The modem sensitivity −124 dBm and the transmission power 25 dBm can ensure reliable communication for distances longer than 100 km with omnidirectional antennas and 200 km with 10 dBi ground station directional antenna. The telemetry system uses GFSK modulation of bit rate 1200 Bd and is designed for a transmission of the balloon position and status.

Během let 1870–1880 začala být elektrotechnika významnou součástí industrializačních procesů v druhé etapě průmyslové revoluce. Elektrotechnika jako samostatná vědní a technická disciplína se ukázala být jednou z hlavních větví druhé průmyslové revoluce a založila tak i průmyslové podnikání v tomto oboru. Elektrotechnický průmysl začal ovlivňovat další výrobní obory a zpětně svůj vlastní výzkum. K takovémuto výzkumu se na prvním místě řadily elektrické točivé (dynamo-elektrické) stroje. Umožňovaly více praktických aplikací v průmyslu a začaly konkurovat univerzálním parním strojům. Změnu přinesl W. Siemens v uplatnění dvojité T kotvy v dynamoelektrických strojích, jejichž 160. výročí v tomto roce vzpomeneme.

En juin 2016, l ´assemblée générale de l´ICOM (conseil international des musées) dans sa réunion a Milan propose de réfléchir dans le cadre de la charte de Sienne au theme "Musées et paysages culturel". Impliquer les musées dans la gestion et l´entretien du paysage culturel signifie développer leur vocation naturelle, en élergissant leur responsabilités depuis les collections jusqu´au patrimoine et territoire.

For surface dielectric barrier discharge in air, we examined the effect of titanium dioxide on various regions of the active electrode on the electrical parameters of discharge, on its emission spectra, and for demonstration of the obtained results also on the concentration of ozone produced by the discharge. We used the active electrode in the form of nine interconnected parallel strips and a square counter electrode. The TiO2 layer covered either only the strips, the region between the strips, or all active electrode. As reference discharge we used the discharge without any layer of TiO2. We found that direct application potential has a version when the strips of the active electrode are covered with a layer of TiO2, because the concentration of ozone produced by the discharge is the highest in all investigated cases. This finding could therefore be used for construction of more efficient ozone generators.

This study examines the effect of airflow orientation with respect to the strip active electrode on concentration of ozone and nitrogen dioxide produced in a planar generator based on the surface dielectric barrier discharge. The orientation of the airflow was tested in parallel and perpendicular with respect to the strips. It was found that in the investigated range of average discharge power, the ozone concentration increases approximately by 25% when airflow was oriented in parallel with respect to the strips in comparison with perpendicular orientation of the airflow. Similarly the increase of nitrogen dioxide concentration was observed for parallel orientation of the airflow with respect to the strips in comparison with the perpendicular orientation of the airflow. Within the range of wavelengths from 250 to 1100 nm, the changes of intensities of spectral lines associated with airflow orientation have been observed. A 3D numerical model describing ion trajectories and airflow patterns have also been developed.

Dans le large éventail des disciplines techniques enseignées dans les écoles secondaires et supérieures des pays tchèques durant la seconde moitié du XIXe siècle, ce texte se concentre sur l’analyse historique de l’enseignement de la science de l’électricité et de l’électrotechnique, ainsi que de leurs manuels, dans les pays tchèques.

Pour la période de l’entre-deux-guerres et au début de la guerre froide dans le domaine de l’industrie électrotechnique tchécoslovaque, il faut parler de lobbying positif lorsque le domaine industriel de la nouvelle Tchécoslovaquie chercha le soutien des sociétés étrangères qui créèrent d’importantes filiales ou instaurèrent la coopération dans la production sur le territoire tchécoslovaque (parmi les sociétés françaises par ex. Schneider et Cie, Creusot, Chaudoir), et des groupes financiers tels que par ex. l’Union européenne industrielle et financière. Ce lobbying positif des États étrangers fut soutenu en Tchécoslovaquie par les différents représentants de l’Union électrotechnique tchécoslovaque (ESČ) et notamment en France avec son aide à la conclusion du contrat pour l’exploitation des brevets et licences étrangers, pour l’utilisation des pièces pour la production électrotechnique sur le territoire de la Tchécoslovaquie, pour l’obtention des débouchées pour les produits électrotechniques tchécoslovaques, etc.

Článek se zabývá legislativou instalace a provozování alternativních jímačů ESE v ochraně před bleskem.

We examined the possibility of finding an alternative to the photocatalyst titanium dioxide for enhancement of ozone generation by electrical discharges. As a rough indicator of the photocatalytic activity of the catalysts, we took the concentration of the ozone produced by the surface dielectric barrier electrical discharge in air. This discharge is, apart from the source of the charged and excited species, also the source of ultraviolet radiation, which could be used for the activation of photocatalysts. From various photocatalysts we have chosen zinc oxide. We compared the effect of ZnO and TiO2 on the enhancement of discharge ozone production and we found that for this application ZnO shows almost the same effect as TiO2 photocatalyst.

Developments in the electronics industry and the growing availability of appliances, equipped with electronic components, are two factors contributing annually to the mounting interference risk and surge damages resulting from direct or indirect effect of atmospheric discharges into conductive structures of building. The authors of this study focused on electromagnetic models of buildings that can be verified for specific external (basic) ways to protect buildings through an air termination system (lightning conductor), down conductors (both usually metallic, hence high-voltage cables). The protection system cannot be checked only by a design controlling according to the applicable standards IEC 62305, but on the basis of numerical calculation as well, which definitely provides more accurate and comprehensive results. These make it possible to get an immediate overview of the risks that may occur in buildings. This method is presented in this study. The authors carried out a comparison of the effects of new commercially available construction materials (Polyvinyl chloride – PVC, Polyethylene – PE) materials, which have been found in many architectural and building designs recently. As a reference parameter, the authors monitored separation distance /s/ for each construction material.

Tento příspěvek nabízí odbornou reakci na sérii článků, které byly uveřejněny v časopise Elektrointalatér (4/2015) Účinná vnější ochrana pomoci jímacího systému NIMBUS a (5/2015) Technický popis aktivních a pasivních hromosvodů. Čtenáři časopisu Elektroinstalatér se obraceli na vedení subkomise Ochrana před bleskem při TNK 22 s žádostí, aby byly na stránkách tohoto časopisu uvedeny zásadní skutečnosti, které jsou v souladu s legislativou ČR v oblasti ochrany před bleskem, a čtenáři měli tak možnost vytvořit si ucelený pohled na problematiku vnější ochrany před bleskem.

The authors of the article accentuate the significance of symmetrical placement of lightning conductors on the position of lightning current in them. The aim of the article is to prove the instructions described in the standard IEC 62305 and confirm the conclusion that buildings should be protected not only by a lightning rod but also by lightning conductors that constitute an irreplaceable component of a comprehensive protection system. If lightning rod influences the safe placement of lightning discharge above a building, then individual lightning conductor determines its safe grounding. Lightning conductors have a major impact on the induction of lightning current in structures. Unfortunately, many buildings whose height is much bigger than their width (towers, lookout towers, high-rise buildings, factory tacks) contain only one lightning conductor, which does not ensure their protection. The authors prove this fact on examples of protection of structures such as lookout towers and wind power plants.

The authors verify the separation distance coefficient /s/ setting of the distance according to the International standards IEC 62305, ed. 2, based on mathematical modeling. The coefficient of the separation distance is established in standards according to the empirical relationships. The authors wants to point out the possibility of more precise verification provided by real model experiments on building materials that are commonly used worldwide. For this purpose, mathematical models were carried out in collaboration with the Czech Technical University in Prague and the company DEHN + SÖHNE and compiled several artificial wall materials (air, concrete, PE and PVC). Behind them, object wiring (installation loop) was adjusted. In front of the wall, down-conductor was established. The assembly was tested by current impulse of 10/350 s; 0.25/100 s; 1/200 s. The result is a set of adjustments that could be accepted by the international standardization committees for the revision of the standards IEC 62305 and the national standards STN 34 1398 and NF C 17-102.

For the surface dielectric barrier discharge in air we investigated the effect of temperature and various arrangements of the input and output of the feeding gas of the discharge chamber together with related changes of electrical parameters on the discharge ozone production for the temperatures in which commercial ozone generators function. The obtained results are useful for the construction of commercial ozone generators because they show the importance of temperature as well as airflow patterns in the discharge chamber on the electrical parameters of the discharge and on its ozone production.

Automated heating, lighting and irrigation systems are nowadays standard features of industrial and commercial buildings, and are also increasingly found in ordinary housing. In addition to the benefits of user comfort, automated technology for buildings saves energy and, above all, it provides enhanced protection against leakage of water and hazardous gases, and against fire hazards. Lightning strikes are a natural phenomenon that poses a significant threat to the safety of buildings. The statistics of the Fire and Rescue Service of the Czech Republic show that buildings are in many cases inadequately protected against lightning strikes, or that systems have been damaged by previous strikes. A subsequent strike can occur within the period between regular inspections, which are normally made at intervals of 2–4 years. Over the whole of Europe, thousands of buildings are subjected to the effects of direct lightning strikes each year. This paper presents ways to carry out wireless monitoring of lightning strikes on buildings and to deal with their impact on lightning conductors. By intervening promptly (disconnecting the power supply, disconnecting the gas supply, sending an engineer to inspect the structure, submitting a report to ARC, etc.) we can prevent many downstream effects of direct lightning strikes on buildings (fires, electric shocks, etc.) This paper introduces a way to enhance contemporary home automation systems for monitoring lightning strikes based on wireless sensor networks technology.

Danger and stress posed to transformer winding through overvoltage still represent a hotly debated and hitherto unresolved technical issue the designers and operators of high-performance equipment have been grappling with. The actual impossibility of accepting all the real parameters of a transformer in its substitute model leaves considerable space for its constant improvement and modifications. Accepting the surrounding phenomena and properties of the transformers gives rise to complex situations and difficulties in the process of solving the model. Models tackling some of the issues pertaining to circuit models or electromagnetic field models have been developed on a long-term basis. Another issue in hand is the very complexity of the process of solving a model. This study introduces a model accepting solely the capacitance influences of transformer components, using the methods derived from the theory of LaxeWendroff’s and LaxeFriedrich’s approximation of differential equations of the hyperbolic type for the solution of the respective equations. It does not represent solutions for all the parameters of a transformer, but provides an overview of the size of the initial impulse stress of transformer winding, doing so with adequate accuracy.

The article offers not only a comparison of the efficiency and size of the protective zone of the first lightning rod by means of a computer model and contemporary mathematical and computing methods (method of the rolling sphere and the apex angle method), but it also highlights the unique social milieu in which Diviš developed his initial idea. It was an interplay of dogmatic religious scholastics and rational enlightenment in physics and natural sciences that was eventually conducive to the construction of one of the first devices for the protection against direct lightning impact. In their article, the authors also examine the transfer of knowledge on the protection against lightning impact from and to the Czech lands. A key approach to the protection against lightning was correct understanding and assessment of lightning charge, an analysis of the contact tip phenomenon and many issues relating to electrostatic phenomena. Seen in a historical perspective, the Czech lands had established an efficient platform of scientific centres, which linked up to and developed the pioneering work of Prokop Diviš several decades later. Also in terms of standardization, the Czech Republic has been active on a long-term basis, while espousing the European standards with its own ČSN EN 62 305 standard. In many other respects, this country has been loyal to traditions; after all, the very first decree on the protection of gunpowder depots against lightning in the Habsburg monarchy came from Empress Maria Theresa and was published shortly after 1778. The lightning protection standard, issued by the Czechoslovak Electrical Engineering Union in the 1950s, had introduced a fundamentally new concept that served for the implementation of most protective systems in this branch until 2006.

Článek představuje možné způsoby návrhu ochrany před bleskem ve specifickém prostředí - konkrétně fotovoltaické elektrárny. S liberalizací trhu elektrické energie, s rozvojem rozptýlené výroby elektrické energie nejrůznějšími nekonvenčními metodami především fotovoltaickými panely, větrnými elektrárnami a bioplynovými stanicemi narůstá počet selhání těchto elektráren v případě přímého zásahu blesku do jejich elektrických i neelektrických částí. Mnohdy stavby za desítky milionů korun jsou vystavovány nebezpečí přímého i nepřímého zásahu blesku. Riziko způsobuje absentující nebo špatně navržená a provedená ochrana. Autoři představují a kriticky hodnotí možné způsoby ochrany v konkrétním případě fotovoltaické elektrárny postavené v roce 2008 v obci Rodvínov v Jihočeském kraji severovýchodně od Jindřichova Hradce v nadmořské výšce 490 metrů a dokazují, jak špatně zvolená ochrana (kdy převládlo finanční hledisko) může způsobit mnohatisícovou škodu.

V článku se pojednává o nově zrestaurované stroje malé vodní elektrárny v Čachrově na říčce Ostružné v rodném domě významného českého elektrotechnika Františka Křižíka.

Článek hodnotí jednu z dalších ze série selhání nevhodně instalovaných moderních prostředků pro ochranu objektů před přímým úderem blesku založených na principu, který je v literatuře označovaný jako ESE (Early Streamer Emission). Obtížná prokazatelnost zvýšené účinnosti ESE a nesprávná interpretace laboratorních výzkumů ESE vede k tomu, že se v České republice instalují aktivní jímače ESE mimo platné české normy. V důsledku selhání funkce ESE se objekty stávají nechráněnými. Objekt v památkové péči o rozměrech 130 x 73 x 15 metrů byl chráněn pouze jedním jímačem ESE a jedním svodem. Ve vnitřních elektrických rozvodech byly instalovány přepěťové ochrany SPD typu 1, 2 a 3. Po úderu blesku do střešní konstrukce objektu o vrcholové hodnotě bleskového proudu 7 kA (vlny 10/350) byly zničeny elektronické systémy (EPS, EZS, CCTV a dalších) v celkové hodnotě cca 3 000 000 korun. Proto po určitou dobu nebyl objekt zabezpečen proti: a) vniknutí cizích osob (odcizení cenných sbírek), b) požáru cenných sbírek a c) poškození samotného památníku.

Historie ČKD je poměrně pestrá, složená z vývoje jednotlivých menších strojírenských podniků, zakládaných postupně na území českých zemí a vyvíjejících se v rámci industrializace ve větší továrny. ČKD se utvářelo dlouhodobě, zejména na základě dvojí fúze v letech 1921 a 1927, kdy vznikl jeden z největších výrobních celků prvorepublikového Československa. Ten především stál u zrodu celosvětově známé značky Made in Czechoslovakia.

This paper summarizes the developmental conditions for the emergence of protection against lightning. It reviews the legislation especially in the Czech Republic over the last 15 years, and its application for active lightning conductors. The paper presents examples of the damage caused by lightning strikes on buildings protected by ESE lightning rods constructed using the French national standard NFC 17-102 [1] and STN 34 1391 [2]. Installation of lightning conductors based on these standards is not, however, in accordance with the valid legislation in the Czech Republic and Hungary. In response to a growing number of ESE installations in the Czech Republic, it is vital to inform both the broader professional publc and the lay public of cases involving failures of this type of lightning conductor.

Článek charakterizuje vývoji elektromobility v české společnosti od počátku 19. století do roku 1945. Snaží se vystihnout význam elektromobilů pro českou průmyslovou a společenskou praxi prostřednictvím tří hlavních elektrotechnických podnikatelů (Křižík, Kolben, Sousedík), kteří měli o elektromobily vážný zájem a kteří myšlenku elektromobilu rozvíjeli a i ji uvedli v život.

This study introduces a transformer model accepting solely the capacitance influences of transformer components, using the methods derived from the theory of Lax Wendroff´s and Lax-Friedrich´s approximation of differential equations of the hyperbolic type for the solution of the respective equations. It does not represent solutions for all the parameters of a transformer, but provides an overview of the size of the initial impulse stress of transformer winding, doing so with adequate accuracy.

Before World War I, Austro-Hungary was a state that covered a vast territory, comprised many nationalities and inhabitants and was, to a large extent, economically independent. For its part, the newly established Czechoslovak Republic in 1918, a successor state to Austro-Hungary, faced completely different conditions. Yet, almost three quarters of the former monarchy's industries remained in its territory, primarily in the Czech lands. That is why in the years 1918-1938 Czechoslovakia focused on the manufacture and export of goods, but had to import raw materials. The country had to seek new markets and cope with foreign competitors. It was far from easy to win recognition for a new unknown brand Made in Czechoslovakia. And yet, the country succeeded thanks to the quality of its products made by such emerging companies as the complex of Baťa plants in Zlín, the Škoda companies in Pilsen and Českomoravská-Kolben Daněk (Bohemian-Moravian-Kolben-Daněk or ČKD for short) in Prague, companies known all over Europe and throughout the world. As early as in 1898 the architect of the ČKD complex was Emil Kolben (1862-1943), who had just returned from a study visit to Edison in the United States and from Oerlikon in Switzerland. This man figured not only among outstanding theoreticians and experts in heavy-current electrical engineering but was an accomplished manager in his time. The ČKD brand products soon went beyond the local framework of the Czechoslovak Republic, representing the designation Made in Czechoslovakia all over the world throughout the period between the two world wars. During the totalitarian regimes in the country, Kolben´s name, possibly also due to its Jewish origin, was destined to be forgotten forever, but the current Czech Republic has linked up to and been developing his unappreciated entrepreneurial heritage.

Článek ukazuje na možná rizika související s instalací aktivních hromosvodů a celkovou nevhodnou volbu ochrany před přímým zásahem blesku. Po úderu blesku o vrcholové hodnotě proudu 111 kA do aktivního jímače ESE, který byl umístěn na střeše hotelu, blesk přeskočil z jednoho svodu na vnitřní instalaci objektu. Bezprostředně poté se vzňala střešní konstrukce hotelu. Hotel byl těsně před kolaudací, a tedy nebyl obsazen lidmi. Celkové škody činily asi 300 000 korun. Hromosvod měl platnou zprávu o revizi....?!

Článek se zabývá nejenom právními, ale i technickými aspekty při volbě vhodné ochrany objektů před přímými i nepřímými účinky bleskového výboje. Na základě technických fakt ukazuje, jak nevhodná volba ochrany, ovlivněná finanční úsporou, může způsobit několikatisícové škody.

Příspěvek reflektuje životní pouť jednoho z nevýznamnějších a nejosobitějších techniků - elektrotechniků první Československé republiky - Vladimíra Lista (1877-1971). Autor se zaměřuje na dokumentování Listova odborného a lidského formování v intelektuálně českém rodinném prostředí a v Praze na akademickém gymnáziu a později na technice. Zachycuje Listův výběr povolání, jeho lidské vlastnosti, touhu po vzdělání a po uplatnění svých znalostí. Dokumentuje zrod jednoho z příslušníků prvorepublikové technické elity, osobnosti, která sehrála důležitou roli nejen při koncipování a rozvoji československého technického školství, ale především v rámci Elektrotechnického svazu československého (ESČ) a v československém průmyslu (působení ve firmě Františka Křižíka a v odborných skupinách při koncipování elektrifikačního zákona). Ukazuje Listovu energii při řešení technických a praktických problémů, jeho smysl pro humor i pro rozhodné a odpovědné odborné vystupování a pevné a morální životní postoje. Listův život a odborné působení představuje jako studnici poučení a námětů i pro současného technika, tím dokládá i historickou významnost této nevšední osobnosti.

L´article traite de la reconstruction de la maison natale de l'inventeur František Křižík dans Plánice pres de Klatovy. Il décrit ré-ajustement de l'exposition sur la vie Křižík et l'exposition interactive de l'énergie électrique au début du 20eme siecle.

Analýza výbuchu vzniklého přímým zásahem blesku do bioplynové stanice v Malšicích chráněné před bleskem podle francouzské normy NF C 17-102 a ESE jímačem.

Article deals with historical development of Nuclear Energy in Czechoslovakia. It describes uranium mining, analyzes the development of the Faculty of Nuclear Sciences and Physical Engineering CTU in Prague and the Institute for Nuclear Research in Rež. It also deals with decisions about the construction of nuclear power plants in Jaslovske Bohunice, Mochovce and Temelin. Contribution characterizes the approach of Czechoslovakia forming the world's nuclear power industry since 1945.

This paper focuses on the calculation of the deformation forces when short-circuit occurs in chokes. The aim was to describe the mechanism generating deformation forces and determine the possible resistance of the equipment. The computer program for rapid and accurate calculation of this problem was presented.

Studie se zabývá nekonvenčními metodami návrhu hromosvodní ochrany objektů. Prostřednictvím sestaveného fyzikálního modelu úderu blesku do budovy autoři zpřesňují stávající intuitivní metody návrhů ochrany stanovené na základě empirických odhadů (metoda valivé koule, metoda vrcholových úhlů). V rámci normotvorné podpory (ČSN EN 62 305) analyzují relativní přesnost teoretického výpočtu vůči prakticky užívaným návrhům. Cílem příspěvku je rešeršní báze metod orientovaných na snížení nechráněných míst budov. Na základě elektromagnetického modelu úderu blesku do objektu je komparována na jedné straně přesnost a na druhé náročnost výpočtu v rámci možné elektrotechnické praxe. Řešení je ověřeno s výstupy výzkumu, které byly publikovány v zahraniční literatuře.

New technologies of operated risk has been arising which allow the direct management and safe getting down into the areas free of persons, animals, and buildings. However, all these arrangements are based only on the theoretical preconditions. This contribution is aimed to open the discussion about the active lightning protection.

Electrical Engineering, Its Terminology and Its Reflection In Czech Literature. Overview of presented contributions in the Czech literature is presented.

Historie elektrotechniky v českých zemích. Příspěvek se zaměřuje na klíčové milníky vývoje elektrotechniky.

This paper deals with the fast processes and their consequences which occur in the coils of HV transformers (high-voltage transformers). The study is based on the comparison of computer simulation and mathematical model in the case of the one-position coil. The aim of this contribution is to verify the validity of this model and its numerical solution for the practical usage in the construction of transformers. Authors compare the experimentally received data with the discrete mathematical and computer models in order to reach the applicability of their results for real conditions of transformer operation.

Příspěvek porovnáná rychlé přepěťové jevy probíhající u jednovrstvé a vícevrstvé cívky vysokonapěťového transformátoru. Studie se zabývá možnostmi řešení rozšířeného náhradního schématu vícevrtstvé cívky prostřednictvím jejího diskrétního modelu. Cílem práce je sledovat teoretické chování mnohavrstvého vinutí transformátoru při příchodu impulzní vlny na vstupní zavity cívky a komparovat dosažené průběhy s modelem cívky jednoduché (válcové). Rozložení poteniálu přepěťové vlny uvnitř systému vinutí cívek může způsobit v oslabeném místě destrukci izolace. Každé zmenšení zemní kapacity (paralelní náhrada) a současné zvětšení podélné (seriová náhrada) linearizuje počáteční průběh impulzního napětí působícího na vstupní svorce transformátoru. Hlavním předmětem studia je význam nastavení těchto parametrů prostřednictvím vícepolohových cívek, resp. prokládaných vinutí, resp. kapacitních štítů.