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Geomagnetically induced currents (GICs) are a consequence of space weather activity that can affect power grid operation and stability worldwide. GICs manifest as quasi-direct currents flowing between the power grids and the conductive earth, and are often measured with a Hall sensor placed at the transformer neutral. Globally, the number of power grid substations with GIC measurements has grown quickly in recent years, but Austria remains one of the few countries with a dataset of long-term GIC observations. GIC measurements in substations in the Austrian power grid have been carried out since 2016, with a maximum of seven concurrent substation measurements, providing a unique opportunity for GIC measurement analysis.In this study, we present an analysis of the last six years of GIC measurements in Austria. Seven custom-built stand-alone GIC measurement systems have been installed in the 220 and 380 kV transmission levels, measuring currents up to 25 A. We identify recurrent geomagnetic activity in the measurements, and also find man-made sources of low frequency currents using frequency analysis. We focus on two geomagnetic storms from September 2017 and May 2021 to discuss the effects of GICs on a mid-latitude power transmission grid. In conclusion, we find that there is a daily level of noise in the data and that, even during the largest events when 14 A were measured, transformer heating remains unlikely.

Low-frequency currents (LFC) or quasi-DC (QDC) in the electrical power transmission network, and especially in power transformers, are causing negative effects such as an increase in noise level, in reactive power consumption and in power losses. Currently, no classification of LFC is available to identify a possible source. In order to identify the origin of undesired LFC, classifications of LFC in current and audio measurements are defined. They are based on a spectrum analysis of current and audio measurements. These classifications are successfully tested in laboratory and field measurements. Consequently, LFC sources are identified by field and laboratory measurements and analytical approaches. For power transformer operators, a user-friendly and fast method is presented to identify LFC in the transformers. The method is based on audible measurements and serves as a first estimator for low-frequency currents in power transformers.

The drastic increase of renewable energy sources in combination with the fade-out of big thermal units leads to an increase in the amount of flexibilities for the European electricity system. Since a huge amount of flexibilities are located in the distribution system area, the potential and proper amount for modelling is challenging to catch. Transmission system operators (TSOs) need to establish a way to retrieve this data to carry out analysis to determine their level of security of supply. Probabilistic resource adequacy assessments serve as a basis to terminate those levels and try to answer the question of sufficient generation can be provided every hour of the year to cover future demand. Within this study, some general introduction to Resource Adequacy Assessments within Europe is provided. Special focus is drawn to the implementation of flexibilities by the use of a new database supporting future flexibilities. Since probabilistic resource adequacy assessments constantly develop, an assessment of adding stepwise amounts of demand-side response (DSR) to the Austrian system is performed. DSR aims to increase or decrease demand by shifting peak values to time intervals when this would be beneficial to system operation using stimulation through market pricing signals.

Due to today´s increased demands on grid operation management, new methods for earth fault localization and detection are needed. The fault localization should be performed as quickly as possible and under the condition, that the fault current at the fault location will not be significantly increased. The pros and cons of Distance Protection in solid grounded networks are well known. In case of a single-line earthfault, the current via the fault location in solid grounded networks is in the range of some kA. In compensated networks the residual current $I_{\mathrm{res}}$ via the fault location is, in case of a single line fault, only few ampere. Very often this current is much smaller than the load current of the feeder. A distinction between load current, circulating currents in meshed networks and fault current is more or less not possible. Therefore, the Earthfault-Distance-Protection in compensated networks is usually switched off. With the new transient relays, based on the qu2-algorithm, it is possible to detect in the substation very reliable the faulty feeder and the direction of the fault. This statement is also correct for meshed networks. In a 110-kV-network the distance between two substations is in the range of 50 km to 200 km. Also if the feeder is identified correctly, it is still a challenge to locate the exact fault position on this feeder. The results of field-test in a 110-kV-network with different fault impedances will be presented.

Transmission system operators are responsible for security and reliability of their grid. An important topic is the analysis of possible risks for the transmission system network. The paper presents actual results about geomagnetically induced currents (GIC) in the Austrian transmission system. Because of problems with unexpected noise at some transformers, investigations were started, which gave an indication that DC could be the source of this noise. Due to the particular geological structure of the country, the influence of GIC in Austria is higher than for the most other countries in Central Europe. A simulation model to compute GIC was set up and compared to the measured DC transformer neutral current. The comparison of the simulated and measured currents shows a good correlation. High geomagnetic disturbances, which lead to high currents according the simulation model, can be confirmed by the measurement. Differences between measurement and simulation can be seen in the region of “fast” fluctuation within seconds. By detailed analysis of the times of occurrence it was shown, that currents from underground railway, which are operating with DC, flow through the transmission grid, too.

The rapid change of power generation within Europe followed by upcoming tasks resulting from the electricity regulation guideline forces Transmission System Operators (TSOs) to establish and improve existing generation adequacy calculations on a national and pan-European level. With these processes, TSOs shall be able to forecast their installed production units within a defined time-period and assess if installed generation and import capabilities can cover forecasted demand.Over the past, the European Network of Transmission System Operators for Electricity (ENTSO-E) set up a couple of processes, which serve the European TSOs to assess generation adequacy. The current existing processes cover time horizons from one week until 20 years ahead. This paper provides an overview of the current existing adequacy processes in Europe, followed by the distinction of probabilistic and deterministic assessments.As there are several upcoming challenges for TSOs resulting from the new electricity regulation guidelines [10], TSOs need to establish their national adequacy assessments. Also current existing European assessments need to be further developed and fine-tuned. Various activities in regards of model development are currently ongoing throughout Europe. As a starting point for future work, this paper serves as an introduction into this important and current topic and will be followed by future research activity.

Conductive grounded electrical power transmission networks offer a low resistance path for currents induced in the ground. High latitude regions or those with low earth conductivity are especially affected by geomagnetically induced currents (GICs), which are caused by space weather events. Induced currents can cause damages of assets or system outages. Austria, as part of the European Alps with low conductive areas, tends to have a higher risk of induced currents in the electrical power transmission network, therefore, the effect of space weather in the power system has been investigated. Two independent models of GICs in Austria were set up and verified through comparison to ongoing transformer neutral point current measurements. Further research fields, such as space weather prediction, power transformers under dc bias and countermeasures for system operation are outlined.

Geomagnetically induced currents (GICs) in power systems, which can lead to transformer damage over the short and the long term, are a result of space weather events and geomagnetic variations. For a long time, only high-latitude areas were considered to be at risk from these currents, but recent studies show that considerable GICs also appear in midlatitude and equatorial countries. In this paper, we present initial results from a GIC model using a thin-sheet approach with detailed surface and subsurface conductivity models to compute the induced geoelectric field. The results are compared to measurements of direct currents in a transformer neutral and show very good agreement for short-period variations such as geomagnetic storms. Long-period signals such as quiet-day diurnal variations are not represented accurately, and we examine the cause of this misfit. The modelling of GICs from regionally varying geoelectric fields is discussed and shown to be an important factor contributing to overall model accuracy. We demonstrate that the Austrian power grid is susceptible to large GICs in the range of tens of amperes, particularly from strong geomagnetic variations in the east–west direction.

Transient measurements in several substations in the Austrian transmission system were performed in the last years. Based on these measurements it was possible to detect signal sequences which show direct and nearby lightning discharges as well as the coupling effects between phases and ground wire after lightning strikes. These transient voltages were measured by using resistive-capacitive voltage dividers (RC-divider) to generate a high quality dataset. The high bandwidth of the RC-divider and its resulting frequency stability is needed to analyzed such transient events. A correlation between the measurements and the data of the Austrian Lightning Location System was performed. In this paper, three different representative measurements of atmospheric discharges to or close to transmission lines will be presented.

Transmission system operators are responsible for secure and reliable operation of their grids. An important topic is the analysis of possible risks for the transmission system network and the system equipment.

Dezentrale Anlagen, die in ein Netz einspeisen, stellen bei Einhaltung der geltenden Vorschriften und Normen besondere Herausforderungen an die Schutztechnik. Aus Krisenuberlegungen und Energieeffizienzbestrebungen werden derzeit autonome Inseln zur Versorgung mit elektrischer Energie als Option zur Versorgung der Allgemeinbevolkerung uberlegt. Die Autoren zeigen in dieser Veroffentlichung, wie derzeit die schutztechnischen Aufgaben in dezentralen Energieversorgungssystemen gelost sind. Sie beschreiben mogliche Umsetzungsmoglichkeiten fur autonome Inseln und zeigen die Herausforderungen in technischer und rechtlicher Hinsicht zur Realisierung dieser Inseln auf.

Im vorliegenden Beitrag wird eine Methode zur Berechnung der Kabelreserve in oberschwingungsbehafteten geloschten Netzen entwickelt. Durch Netzerweiterungen und vermehrten Einsatz von Kabeln steigen die Erdschlussstrome, so dass Probleme mit der Einhaltung der zulassigen Grenzen des Erdschlussreststroms entstehen. Die auftretenden Oberschwingungsspannungen und die daraus resultierenden Oberschwingungserdschlussstrome sind die masgeblichen betriebs- und ausbaubeschrankenden Parameter. Resonanzen konnen zusatzliche Einschrankungen bedingen. Abschliesend werden die derzeit moglichen Masnahmen zur Erweiterung des Netzausbaus im Falle des Erreichens der Loschgrenze aufgezahlt.

Die Erfassung der Leitungsimpedanzen in Form der symmetrischen Komponenten Mit-, Gegen- und Nullimpedanz war schon immer eine wichtige Voraussetzung fur die richtige Einstellung der Leitungsschutzgerate sowie zur korrekten Lastflussberechnung. In der vorliegenden Arbeit werden die mathematischen Grundlagen zur Impedanzmessung dargelegt. Weiters werden mogliche Fehler bei der Impedanzbestimmung beschrieben, es sind dies einerseits Fehler, die durch ausere Einflusse (Storfelder) bei der Messung der Impedanzen auftreten konnen, andererseits Fehler, die durch Anwendung unrichtiger oder zu stark vereinfachter mathematischer Formeln entstehen konnen. In einem praktischen Beispiel wird die herkommliche Messmethode mit der frequenzselektiven Methode verglichen.

Omeprazole is a proton pump inhibitor, which is used for the treatment of peptic ulcers, reflux esophagitis and Zollinger-Ellison syndrome. It is a poorly soluble, chemically labile drug with a high degradation rate in aqueous media. The aim of this study was to show the feasibility of omeprazole stabilization using the DissoCubes technology and to find optimal production parameters for a stable, highly concentrated omeprazole nanosuspension. The high performance liquid chromatography analysis has proved the predominance of the nanosuspension produced by high pressure homogenization in comparison to an aqueous solution. Even 1 month after production no discoloration or drug loss was recognizable when the nanosuspension was produced at 0 degree C. As a result it can be stated that the production of nanosuspensions by high pressure homogenization is suitable for preventing degradation of labile drugs.

Neutral point treatment is a very important topic for protection and network operation. For different reasons 400-kV AC-power networks are operated with direct grounding of the neutral point. One major part of electrical networks are transformers. In transmission systems, usually at least one transformer per substation is operated with direct grounded neutral point, thus allowing earth currents to enter the transformer. New transformers are designed for very low noise emissions. During commissioning of a new transformer, unexpected noise was noticed and saturation due to DC currents respectively very low frequency currents (below 1 Hz) was assumed to be the reason. In a current research project of Austrian Power Grid and Graz University of Technology measurements of the neutral point current were performed. Analyses of these measurements revealed several frequency components in the spectrum, including DC, slow variations below 1 Hz, 16.7 Hz from railway system, 50 Hz mains, harmonics and interharmonics. This paper gives a description of the measurement setup, highlighting the problem of recording small DC currents in the presence of high AC currents. Furthermore results from a neutral point current measurement in the Austrian 400-kV-grid are presented and discussed.

Large parts of the endoplasmic reticulum of the yeast, Saccharomyces cerevisiae, are located close to intracellular organelles, i.e. mitochondria and the plasma membrane, as shown by fluorescence and electron microscopy. Here we report the isolation and characterization of the subfraction of the endoplasmic reticulum that is closely associated with the plasma membrane. This plasma membrane associated membrane (PAM) is characterized by its high capacity to synthesize phosphatidylserine and phosphatidylinositol. As such, PAM is reminiscent of MAM, a mitochondria associated membrane fraction of the yeast [Gaigg, B., Simbeni, R., Hrastnik, C., Paltauf, F. & Daum, G. (1995) Biochim. Biophys. Acta1234, 214–220], although the specific activity of phosphatidylserine synthase and phosphatidylinositol synthase in PAM exceeds several-fold the activity in MAM and also in the bulk endoplasmic reticulum. In addition, several enzymes involved in ergosterol biosynthesis, namely squalene synthase (Erg9p), squalene epoxidase (Erg1p) and sterolδ24-methyltransferase (Erg6p), are highly enriched in PAM. A possible role of PAM in the supply of lipids to the plasma membrane is discussed.

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.

In this paper the authors present measurements, calculations and results of the optimization of transposition schemes and phase configurations of transmission lines in a region in Austria regarding inductively coupled transmission lines. Different development states of the power circuit and variants under economic and realizable practical conditions are presented. The calculations were performed with a new calculation method combining the node potential method and a chain-ladder model for coupled line conductors to calculate the inductive influence and unbalance currents (zero-sequence currents) of extended transmission line circuits in normal operation mode. The presented method allows the calculation of unbalance currents and the effects of inductive coupling for a given network scenario with a coupled transmission line model. The investigation of these disturbance currents lead to an optimized transposition scheme considering economic aspects (reduced number of transposition towers at predefined places, small zero-sequence currents, etc.). With this method existing grids can be optimized by reducing circulating currents. Also extension strategies and decisions for the integration of new transformer substations and different grid configurations can be provided. (4 pages)

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.

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.

In recent years power system companies are trying to save money and improve their capabilities or convenience by using consumer network technology in their ICT networks for maintaining and monitoring power systems. These new ICT technologies bring new challenges to the organization and communication structures inside power companies. Furthermore there are efforts to transmit sensitive measurement and control data over public networks. However, issues like real-time, reliability, availability, and data integrity cannot automatically be presumed any more in the Internet. The cost advantages are in contrast to the possibly decreased security. In this paper, the authors will discuss the problems mentioned above and provide exemplary approaches to a solution that is feasible in reality. Also the authors would like to raise awareness among the power system owners for security topics in conjunction with ICT networks. Examples to illustrate the challenges are given, and an interdisciplinary approach to ensure comprehensive information security is suggested.

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. In previous investigations the authors found that the classic algorithm of these distance protection relays principally can be used also for compensated networks, - however the accuracy of the distance calculation strongly depends on the network conditions. In this paper a new improved algorithm is developed. The simulations show, that this improved distance calculation provides very good accuracy up to earth fault transitions impedances of 1 kohm. Furtheron it is shown in the paper that the same algorithm can be used in 2-phase networks as well. With the implemented improvements the algorithm again allows earth fault transitions impedances of up to 1 kohm. Finally, the simulation results are validated by real test data to verify the usability of this improved algorithm.

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. Especially in resonant grounded grids the earth fault compensation coils (so called Petersen-coils) have to be adjusted to operation limits like the residual earth fault current (IRES) and the maximum allowed displacement voltage (UNE). In capacitive influenced resonant or isolated grounded grids displacement voltages caused by capacitive coupling effects exist. In this case the allowed operating sector depending on the before mentioned limits of the grid have to be determined to provide a secure grid operation. In this paper the authors present the effects of the capacitive and inductive interference between parallel high voltage power lines depending on the neutral point treatment of these grids. Especially the effects (displacement voltages) in resonant grounded grids like the earth fault compensated network will be shown. Examples were given, practical investigations and an approach for optimization in a typical 220/110 kV grid is shown.

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. Due to the fact of sometime prolonged earth fault current flow special safety precautions must be met. When present-day grids are extended by the installation of additional cables, their operation is subjected to limitations concerning the effects of the earth fault current. The current can exceed the admissible limits and an innovative neutral point treatment is necessary. This effect leads to costly modifications of either the grounding systems or modifications in the protection schemes or both. As far as standardization is concerned, the present standards in central Europe may undergo changes which will lead to modifying the design and operation mode of these networks. This network operation implicates problems in localization of earth faults, especially concerning the in-depth localization. Under these aspects the operation mode of principally continuing the regime of resonance grounded networks with a change to transient middle ohmic earth fault compensated networks in case of a persisting earth fault appears to be in many cases an attractive solution.

In this paper the calculation of neutral to earth voltages in compensated high voltage networks influenced by cross coupling is shown. Especially itpsilas shown how to calculate the line parameters (line to line and line to earth capacitances) which are necessary for further investigations in the network analyses. Furthermore the optimization (decrease) of the neutral to earth voltage by varying the phase configurations with the help of calculation software is shown.

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]. In previous investigations the authors found that the classic algorithm of these distance protection relays principally can be used also for compensated networks, - however the accuracy of the distance calculation strongly depends on the network conditions [1],[2]. In this paper a new improved algorithm is developed. For this purpose an exact 3-phase mathematical simulation model of the investigated network is used to check the results of the improved algorithm. The simulations show, that this improved distance calculation provides very good accuracy up to earth fault transitions impedances of 1 kohm. Furtheron it is shown in the paper that the same algorithm can be used in 2-phase networks as well. With the implemented improvements the algorithm again allows earth fault transitions impedances of up to 1 kOhm. Finally, the simulation results are validated by real test data to verify the usability of this improved algorithm.

Substantial gaps in the used electrical protection concepts which lead to expensive damages are often causes for major failures. A majority of the failures are caused by earth faults, which can not only damage the decentralized wind power plant but also harm people. An effective electrical protection concept is an effective instrument to risk avoidance, and a suitable electrical earth fault protection concept does not necessarily cause large financial expenses and additional components. A consistent protection concept can be provided at small expenses by suitable component choice and integration when planning the decentralized power plant. Knowledge of the earth faults and network configurations is necessary, as well as a net-spreading aspect and experience in the functions and possibilities of modern protection technology. This paper presents different possibilities for earth fault protection in decentralized power plants.

For loss reduction In distributed networks a multiplicity of possibilities exist. The use of cables instead of overhead lines as well as larger diameters of the lines lower the arising losses in distribution networks. Likewise a more even load profile leads to a reduction of losses, so that in the consequence primary energy, costs and CO2-emissions can be saved. Unbalances through asymmetrical loads arise particularly within the low-voltage grids and they are responsible for substantial losses compared with the situation of symmetrical load conditions. In this paper investigations are presented, which show that considerable loss reductions can be obtained by decentralized compensation. For the computation of the losses in urban distribution networks a model is developed. The parameters (standardised load profiles, number and kind of typical consumers, line data etc..) can be varied. Results of model computations are presented.

Forced use of cables in earth fault compensated networks increases the capacitances to ground in the grid so that the capacitive ground fault current ICE increases, which causes problems concerning arc extinction. The ground fault current (limited to 132 A due to standards in Austria) depends on detuning, damping, unbalance, harmonics, saturation, operating voltage, harmonic resonances, and the distribution of the line inductances and capacitances (within the grid). A new grid calculation program was developed by TU Graz which allows to calculate the expansion limits of earth fault compensated networks under consideration of the harmonic contents in the fault current. Concerning the determination of these limits existing formulae are adequately adapted. The calculated results have been verified in real network experiments. Technical measures for further operation of the grids are investigated

The following paper reviews the previous and current progresses in the field of e-learning at the Institute of Electrical Power Systems (IFEA) of the University of Technology Graz/Austria (TU Graz). A brand new e-learning course system - the ABC-system that follows international experiences in the field of e-Learning - is presented. It recommends a way of generating online and offline courses from the very beginning of collecting multimedia content like a sound file of a load profile made heard by the method of sonification up to the final classroom session. Therefore helpful tools like the IFEA viewer and the ABC-layout have been developed. Furthermore a short abstract about the national and international cooperation IFEA holds in this specific subject is presented

The unassigned open reading frame YDL142c was identified to code for cardiolipin synthase, Cls1p. A cls1 deletion strain is viable on glucose, galactose, ethanol, glycerol and lactate containing media, although the growth rate on non-fermentable carbon sources is decreased. Mitochondria of the cls1 mutant are devoid of cardiolipin but accumulate the cardiolipin precursor phosphatidylglycerol when grown on non-fermentable carbon sources. Specific activity of phosphatidylglycerolphosphate synthase in cls1 is reduced to 30–75% of the wild-type level. Amounts of mitochondrial cytochromes and activity of cytochrome c oxidase, however, are not affected in the cls1 deletion strain. Collectively, these data indicate that cardiolipin is not essential for aerobic growth of Saccharomyces cerevisiae.

The sequence of biosynthetic steps from phosphatidylserine to phosphatidylethanolamine (via decarboxylation) and then phosphatidylcholine (via methylation) is linked to the intracellular transport of these aminoglycerophospholipids. Using a [3H]serine precursor and permeabilized yeast cells, it is possible to follow the synthesis of each of the aminoglycerophospholipids and examine the requirements for their interorganelle transport. This experimental approach reveals that in permeabilized cells newly synthesized phosphatidyl-serine is readily translocated to the locus of phosphatidylserine decarboxylase 1 in the mitochondria but not to the locus of phosphatidylserine decarboxylase 2 in the Golgi and vacuoles. Phosphatidylserine transport to the mitochondria is ATP independent and exhibits no requirements for cytosolic factors. The phosphatidylethanolamine formed in the mitochondria is exported to the locus of the methyltransferases (principally the endoplasmic reticulum) and converted to phosphatidylcholine. The export of phosphatidylethanolamine requires ATP but not any other cytosolic factors and is not obligately coupled to methyltransferase activity. The above described lipid transport reactions also occur in permeabilized cells that have been disrupted by homogenization, indicating that the processes are extremely efficient and may be dependent upon stable structural elements between organelles.