L. Fickert

Graz University of Technology, Graz, Styria, Austria

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Publications (62)0 Total impact

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    ABSTRACT: This paper presents results of earth fault field tests in a medium voltage network using new earth fault detection methods. An interpretation of voltage and current signals measured at the area of influence is provided. The pros and cons of different algorithms in different grid constellations are elaborated. The results show that new detection algorithms can provide stable directional decisions even in combination with unconventional transducers. This information is very important for the grid operator. With reliable information of the earth fault direction, especially in rural areas, the field engineers can be deployed more efficiently. Another focus of the tests was on the earthing system. At special grid components, such as dead end poles with cable link, the earth potential rise (EPR) was measured. With the signals measured throughout the tests, results of previously taken measurements to verify the earthing system could be confirmed.
    CIRED 2013, Stockholm, Schweden; 06/2013
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    T. Wieland, F. Otto, L. Fickert
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    ABSTRACT: The effort to increase the production of renewable resources such as wind or solar power is strongly increasing especially in the distribution network. This paper deals with the question about the different characteristics (Z-, I-, S-const.) of residential loads and decentralized sources in the low voltage network. The performed simulations with a concentrated load/source at the end of the line and distributed loads/sources along the low voltage line show the effects of decentralized feed-in according to different characteristics (Z-, I-, S-const.). The use of a regulating transformer as well as reactive power management demonstrates the fundamental behavior of these measures to keep the voltage within the specified limits. Laboratory tests with a decentralized generation unit at different supply voltages illustrate the general behavior in the low voltage network. The results of the performed simulations are important for future grid planning or reconstruction measures to determine the hypothetical feed-in capacity of decentralized generation units in the low voltage network.
    Energy (IYCE), 2013 4th International Youth Conference on; 01/2013
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    ABSTRACT: Energy losses in electrical networks are usually estimated by balancing fed and delivered energy of an analyzed network area. Generally, it is not possible to derive information for loss reduction opportunities from these data. Furthermore, there is no possibility to distinguish between technical and non-technical losses. The proposed method calculates network losses in low voltage networks and takes the effect of short-time load peaks as well as unbalanced loads into consideration by using standard load profiles in connection with an obtained Loss Correction Function. The loss is calculated for each relevant line, so it provides the option to point out high-loss areas or equipment owning a high potential for loss reduction, to allow optimized investments in development and maintenance of the investigated electrical system.
    Energy (IYCE), 2013 4th International Youth Conference on; 01/2013
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    ABSTRACT: The low frequent electromagnetic mutual coupling of electric high voltage lines leads to a variety of effects in the planning and the operation of such an electrical circuit and their impact onto other line circuits (e.g. telecommunication and signal lines). The authors present a new method for calculating the interference phenomena between inductively coupled circuits. These calculations are performed with the help of the combination between the node potential method and a chain-ladder model under consideration of inductive coupled conductor arrangements. So it's possible to calculate the inductive influence, asymmetric currents (zero and negative sequence currents) of extended transmission line circuits under normal and faulty operation conditions. Calculations and results of the optimization of transposition schemes and phase configurations of a transmission line section in Austria will be presented. This method allows an optimization of the phase configuration (twisting) concerning inductive and ohmic interferences under consideration of economic and practical aspects.
    PowerTech (POWERTECH), 2013 IEEE Grenoble; 01/2013
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    ABSTRACT: In catastrophic incidents, taking critical infrastructure and equipment back into operation as quickly as possible gets more and more important. The electrical supply of information and communication technology (ICT), services of health, emergency and rescue belong to potential critical infrastructure. During outages electrical energy can be provid-ed by standby power devices such as batteries or emergency generators. However, these devices are usually limited in supply duration, are stationary or difficult to transport in cases of emergency. Thus flexible and dynamic solutions are clearly required. Such cases are considered in the project "Smart Emergency" (funded by the climate and energy fund of the Austrian government).
    Security in Critical Infrastructures Today, Proceedings of International ETG-Congress 2013; Symposium 1:; 01/2013
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    ABSTRACT: Isolated networks are common practice for operating small high voltage networks. The reason for choosing this type of network are the saving of the arc suppressing coils by coexistence of a self-healing grind in case of an earth fault During the starting up of an isolated network several unexpected voltage oscillation phenomena were detected and measured. Investigations have shown that lightning strokes in the area around the high voltage line are the sources of the voltage oscillation. Comparison between the measurement of the voltages and currents of the high voltage line and the lightning detection protocol of the Austrian Lightning and Detection System (ALDIS) show that the lightning causes the voltage oscillation. This paper describes the phenomena based on measurements, the correlation with lightning strokes and will confirm the measurements with simulation examples.
    PowerTech (POWERTECH), 2013 IEEE Grenoble; 01/2013
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  • E. Fuchs, Lothar Fickert
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    ABSTRACT: The actual valid self-extinguishing current limit of 20-kV-compensated power grids, written in the VDE 0228 is 60 A. This limit is based on trials from the years 1963 done by M. Erich und H. Heinze. In the year 1981 K. H. Koch presented results of new earth-fault trials. He concluded that the self-extinguishing current increases for larger power grids. An afresh scientific interpretation of both experiments leads to a novel proposal for a self-extinguishing current limit for compensated 20-kV-power-grids. This novel self-extinguishing current limit would allow the extension of current compensated power grids. Further the medium arc-burning time for compensated power grids is discussed.
    Electric Power Quality and Supply Reliability Conference (PQ), 2012; 01/2012
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    ABSTRACT: In the field of low voltage systems protection devices like fuses and residual current devices (RCDs) are generally implemented. Because of their high sensitivity residual current devices are very commonly used for protection against electric shock. A part for the fact that inverters may produce voltages with considerable harmonic content also RCDs deserves special attentions. Due to the increasing number of electrical equipment in the low voltage grid producing disturbing currents different RCD types (type AC, A and B) are investigated under certain conditions. For example the influence of disturbing non-sinusoidal, pulse-shaped currents or harmonics in the fault current regarding on the tripping current or on the tripping time of the RCD is analyzed.
    Electric Power Quality and Supply Reliability Conference (PQ), 2012; 01/2012
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    ABSTRACT: This paper reflects six years of managing (lecture) recording activities at Graz University of Technology (TU Graz) with a special eye on the broad experiences of the Institute of Electrical Power Systems of TU Graz (IFEA) according to podcasting as well as their advantages of using this service. Furthermore the paper analyses the history, development, and management, its increase, aspects of evaluation, and didactics as well as its future trends, facing the challenges of a university wide automated recording system. The paper too presents the latest development of an integrated search functionality offered for each single recording serviced by the Department of Social Learning (DSL) of TU Graz. This is made possible on base of OCR (Optical Character Recognition) recognition of indexed video frames. Podcasting has become an integrated part of teaching activities at IFEA and at TU Graz in general. It will be further enlarged to an automated system providing high quality multimedia lecture recordings.
    MIPRO, 2012 Proceedings of the 35th International Convention; 01/2012
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    ABSTRACT: A novel methodology for Optimal Sizing of Biomass-Fired Organic Rankine Cycle (ORC) Combined Heat and Power (CHP) System with Heat Storage is presented in this paper. The ORC technology received a lot of attention recently, especially for medium scale applications (e.g. district heating) where market potential is substantial. Another push for the technology is provided in the context of recent EU regulations to tackle the rising environmental problems, i.e. the 20-20-20 directive, which should provide another boost for the use of renewables in electric power systems. In this study, the simulation of the operation of a biomass-fired ORC CHP system is discussed first, where the dispatch of the plant is optimized to maximize the profits from electricity and heat sales. Based on the optimal dispatch values, an economic evaluation is carried out to determine the feasibility of the proposed scheme for investment purposes; this evaluation is based on calculations of modified internal rates of return for a realistic scenario. Lastly, an optimization procedure for optimal sizing of the generation architecture is convolved with the optimal operation and economic evaluation models, to achieve maximal rates of return on the ORC CHP investment. The results of the present studies demonstrate that the heat storage is not economically feasible in the assumed setup making profits from increasing the flexibility of the ORC CHP operation. Furthermore, the results show favorable economic parameters for the ORC CHP setup without the heat storage for annual heat demands higher than 5 GWh and biomass prices lower than 17 EUR/MWh.
    Renewable Energy. 01/2011;
  • Katrin Friedl, Ernst Schmautzer, Lothar Fickert
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    ABSTRACT: In December 2010 ICNIRP published new guidelines for limiting exposure to time-varying electric and magnetic fields (1 Hz to 100 kHz). There, several significant changes were made in comparison to the guidelines published in 1998. Since many national standards are based on the previous guidelines, it is obvious, that also the new guidelines will soon be incorporated in national standardizations. The proposed paper will first show the main differences between these guidelines with the focus on exposure evaluation on electrical power systems (railway systems and general electrical power supply). The specific focus will be on the change of the reference levels and - as a consequence - the different evaluation of harmonics.
    01/2011;
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    ABSTRACT: One of the major problems in determining the duration of a single-pole earth fault in compensated networks is to detect the moment of arc extinction. Currently this problem is solved by analysing the time course of the displacement voltage and identifying the moment when the amplitude is rising above or falling below a certain critical value. However, solving the issue that way leads to a high inaccuracy of the derived single-pole earth fault duration. Therefore, new ways for the determination of the earth fault duration were investigated at the Institute for Electrical Power Systems at Graz University of Technology. These new methods allow a very exact determination of the moments of fault beginning and ending. Results of these new methods will be shown. Finally, the advantage and consequences of the resulting improvement - allowing advanced protection strategies or grid operator interactions in the compensated network - will be discussed.
    01/2010;
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    ABSTRACT: In this paper the authors present an interesting method for mobile earth fault localization in resonant grounded grids. The method is based on an additional current injection with a non-grid-frequency current and detection with magnetic-field sensors in close vicinity of the line. The advantage of the presented method is that a mobile earth fault localization-unit for the operation personal is provided. Especially in medium voltage grids this method provides an interesting method for earth fault localization.
    01/2010;
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    ABSTRACT: Weltweit ist unsere moderne Industriegesellschaft von Informations- und Kommunikationstechnik (IKT) abhängig geworden, und die Versorgungssicherheit mit IKT wurde zu einem wichtigen Standortfaktor. Kommunikation ist in Zeiten immer größer werdender Anonymität und der dadurch gegebenen Abhängigkeit von öffentlichen Einrichtungen und Diensten, etwa von Notrufträgern (Blaulichtorganisationen), von besonderer Wichtigkeit. Ebenso spielt Kommunikation durch immer kürzer werdende Produktions- und Lagerhaltungszeiten für das reibungslose Funktionieren von Wirtschaft und Industrie eine überragende Rolle. In dem zur Selbstverständlichkeit gewordenen Einsatz von IKT ist jedoch eine hochgradige Abhängigkeit der modernen Gesellschaft von der öffentlichen Stromversorgung begründet. In hoch industrialisierten Ländern wie Österreich beträgt der Strombedarf des IKT-Sektors 10 % des elektrischen Energiebedarfs. Von diesen 10 % ist wiederum ca. ein Drittel für Telefonie und Übertragungstechnik zu veranschlagen (Fraunhofer-IZM & ISI, 2009). Wenngleich es in Österreich in den letzten Jahren zu keinen nennenswerten großflächigen Unterbrechungen (Blackouts) der Stromversorgung gekommen ist, sind nach Meinung von Netzsicherheitsexperten europaweite Blackouts durchaus in Erwägung zu ziehen. Solche Ereignisse hätten gravierende Auswirkungen auf das Funktionieren von IKT und auf gewerbliches und industrielles, privates und öffentliches Leben. Der Ausfall von IKT als kritische Infrastruktur stellt somit eine Bedrohung der Zivilisation dar. Da der Leistungsbedarf für IKT schon heute sehr hohe Werte annimmt und voraussichtlich weiter steigen wird, ist ein nachhaltiges und verlässliches Ersatzstromversorgungskonzept von höchster Bedeutung. Hier nehmen nach wie vor Batterien, zum Beispiel in Form einer unabhängigen Stromversorgung (USV), eine wichtige Rolle ein. Jedoch sind diese meist nicht sehr effizient und mit steigender Leistung auch wartungsintensiv und kostspielig. Im Zuge der Einführung von Smart Grid-Technologien eröffnen sich hier alternative und hoch leistungsfähige Möglichkeiten, die relativ einfach in die bestehenden Netzstrukturen integriert werden können. Beispielhaft sei hier die Kombination der Funktionalität von Smart Metern und dezentralen Erzeugungseinheiten in neuen Netzstrukturen – Smart Grids – genannt. Die dafür benötigten Erzeugungseinheiten können in diesem Zusammenhang nicht schwankungsbehaftete erneuerbare Energien wie Blockheizkraftwerke (BHKW) oder Kleinwasserkraftwerke sein; aus Zweckmäßigkeitsgründen kommen auch Dieselgeneratoren in Frage. Modern society all over the world depends on information and communication technology (ICT); and security of supply with ICT is an important location factor. In times of increasing anonymity, which makes us more and more dependent on public services such as emergency supports (emergency organizations), communication is existential. Communication also plays an important role for a good functioning of economy and industry, in the course of shorter production and storage times. The usage of ICT is taken for granted. However, the modern society's use of ICT is profoundly dependent on the public power supply. Particularly in highly industrialized countries like e.g. Austria, the ICT sector requires about 10% of the total electric energy demand. One third of these 10% is estimated to be used for telephony and transmission. (Frauenhofer-IZM & ISI, 2009). Although there have not been any significant and large scale supply interruptions (blackouts) in Austria in recent years, grid safety experts cannot exclude a pan-European blackout in future. Such an incident would have serious effects on the function of ICT, and thus, on the commercial, industrial and personal life, and is therefore a threat to our civilization. The outage of ICT as a critical infrastructure consequently constitutes a danger to the public. The electrical power demand of ICT now takes very high values and will keep rising. For this reason, a sustainable and reliable power supply concept is of paramount importance. Here, batteries still play an important role, for example in the form of an uninterrupted power supply (UPS). However, these are usually not very efficient and by increasing capacity maintenance-intensive and costly. The implementation of the smart grid technology in the public power grid opens up alternative and high-performance possibilities that can be integrated relatively easily into existing grid structures, exemplarily the combination of the functionality of smart meters and distributed generation units is called smart grids. These generation units might be non-volatile renewable energy sources such as combined heat and power (CHP) and small hydro power plants, however, for reasons of practicability there could also be used conventional gensets. SchlüsselwörterIKT-Blackouts-Smart Meter-Dezentrale Energieerzeugung-Micro Grid-Smart Grid-Kritische Infrastruktur KeywordsICT-Blackouts-Smart meter-Decentralized generation-Micro grid-Smart grid-Critical infrastructure
    e & i Elektrotechnik und Informationstechnik 01/2010; 127:303-308.
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    ABSTRACT: Earth fault distance protection with distance protection relays is common practice in solidly grounded networks. However, in compensated networks earth faults can cause big problems, because they do not extinguish themselves. To find the fault point is from high interest also in combination with network expansion [9].
    Electricity Distribution - Part 1, 2009. CIRED 2009. 20th International Conference and Exhibition on; 07/2009
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    ABSTRACT: Electrical energy must be transported from the generator to the consumer load in electrical grids. These grids consist of electrical power lines. In praxis high voltage power lines of different grids will often be situated close to each other. In this case electrical coupling effects between the lines will appear. This coupling effects leads to interference between the grids and should be investigated.
    Electricity Distribution - Part 1, 2009. CIRED 2009. 20th International Conference and Exhibition on; 07/2009
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    ABSTRACT: In earth fault compensated networks the basically capacitive earth fault current is counterbalanced by the injection of an inductive current through the arc suppression coils in such a way, that for most overhead line faults these arcs extinguish without the necessity of disconnecting the faulty grid section. Therefore these grids can be classified as self healing grids which have good power quality.
    Electricity Distribution - Part 1, 2009. CIRED 2009. 20th International Conference and Exhibition on; 07/2009
  • E. Fuchs, Lothar Fickert, C. Obkircher
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    ABSTRACT: Summary The aim of this paper is to determine the detuning of compensated networks by means of the analyses of transitory line-to-earth faults. For a suitable development of compensated networks, the limits of the standards for self-extinction have to be fulfilled. Therefore it has to be ensured that the predetermined detuning of the arc-suppression coil equals the real detuning. For this reason the problem of detuning the arc-suppression coil by raised operation voltage (saturation) will be discussed. Moreover, the problem of the influences through parallel-led power lines will be explained. Furthermore, the basics of the evaluation of the line-to-earth faults in compensated networks and how to accomplish it will be shown. Finally, a new method will be proved by means of a real transitory line-to-earth fault.
    e & i Elektrotechnik und Informationstechnik 01/2009; 126:383-388.
  • e & i Elektrotechnik und Informationstechnik 01/2009; 126(3):88-93.