References of "Sachau, Jürgen 50002967"
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See detailTopology and Parameter Estimation in Power Systems through Inverter Based Broadband Stimulations
Neshvad, Surena UL; Margossian, Harag UL; Sachau, Jürgen UL

in IET Generation, Transmission & Distribution (2016)

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly ... [more ▼]

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly complicated the powerflows on the power network, requiring advanced and intelligent parameter knowledge to optimize the efficiency, quality and reliability of the system. This paper describes a method for identifying parameters associated with the power system model. In particular, the proposed algorithm in this paper addresses the line parameter and topology identification task in the scope of state estimation. The goal is to reduce the a priori knowledge for state estimation, and to obtain online information on the power system network. The proposed parameter estimation method relies on injected stimulations in the network. Broadband stimulation signals are injected from distributed generators and their effects measured at various locations in the grid. To process and evaluate this data, a novel aggregation method based on weighed least-squares will be proposed in this paper. It combines and correlates various measurements in order to obtain an accurate snapshot of the power network parameters. In order to test its capabilities, the performance of this algorithm is evaluated on a small-scale test system. [less ▲]

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See detail11,8-100% Rural Renewable Energy and Power Supply and its Influence on the Luxembourgish Power System
Norta, David Peter Benjamin UL; Winkler, Christoph; Allelein, Hans-Josef et al

in Energy Procedia (2015), 73

Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively small ... [more ▼]

Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively small Luxembourgish electricity system is analysed (0.55 Mio Inhabitants). Current power-system-models mainly focus on larger systems, due to the unavailability of specific consumption-data. Prices and effects on the Luxembourgish power system of different supply scenarios for rural-private households are analysed. A linear optimisation for the minimum-cost of the power-supply of a village with the following renewable energy resources: wind- (max.100 kW), solar-PV- and hydrokinetic-power is made. The electricity-demand scales with the number of inhabitants and agricultural-consumers. The wind-power-potential differs with the location of the village. The solar-radiation is assumed to be the equal over the country, due to the small size of approximately 80 by 50 km. The hydrokinetic turbines complete the supply where a village is located close to a river. The minimum cost of the specific village power-supply is the result of the optimization. The installation- and maintenance-cost of each renewable technology are considered. The whole number of a rural Luxembourgish model villages private households is considered and their electricity contribution to the system is estimated for different renewable energy supply scenarios, namely from 20% to 100% renewable-energy-scenarios. For each scenario the power exchanged from the village to the grid is calculated in 15-min-steps for 9-years, the amount differs widely with the number of applied generation technologies. Due to the high share of imported electricity of about 80% in the recent years, every consideration of national power generation does not harm the supply security. Luxembourg is a good model country to analyse the high share of distributed, renewable generators, due to its structure of rural and civic regions and their effects on a central European region with a high electricity-consumption. [less ▲]

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See detailHydrokinetic Micro-Power Generation in Small Rivers - a New Approach
Norta, David Peter Benjamin UL; Ramanathan, Sriram; Sachau, Jürgen UL et al

in Renewable Energy and Power Quality Journal (2015)

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third ... [more ▼]

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third renewable energy resource, the hydropower has been already developed within the last decades and grew not significantly in the last years. Since some years the development of smaller hydrokinetic turbines increased. The smaller size of some hydrokinetic turbines enables new, unused sites to be harnessed in smaller rivers. The paper deals with the key specifications of hydrokinetic turbines and their influence on a villages’ energy supply. It introduces the concept of a turbine with variable immersion depths to exploit also locations with a varying water level. Based on historical hydrological data a propeller and oscillating hydrofoil type of hydrokinetic turbine are compared, it was found that the variable immersion depths increases the energy harvest. Furthermore, it is shown that in a generation portfolio of hydrokinetic and solar power plants an average Luxembourgish household theoretically renewable supplied has to exchange less energy with the power grid, the higher its share of hydrokinetic generation is. [less ▲]

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See detailDistribution Network Protection Considering Grid Code Requirements for Distributed Generation
Margossian, Harag UL; Deconinck, Geert; Sachau, Jürgen UL

in IET Generation, Transmission & Distribution (2015), 9(12), 1377-1381

The amount of inverter based distributed generation (DG) connected to the low and medium voltage levels is increasing rapidly. Their growing impact on the power system has already driven some distribution ... [more ▼]

The amount of inverter based distributed generation (DG) connected to the low and medium voltage levels is increasing rapidly. Their growing impact on the power system has already driven some distribution network operators to start imposing requirements on their operation similar to those described in transmission grid codes. This paper studies how different grid code requirements can affect the fault current levels in the distribution network and explores the possibility of using the grid code requirements to ensure the reliability and selectivity of the protection of distribution feeders. [less ▲]

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See detailVerification and Implementation of Pseudo-Random-Binary-Sequences for Online Determination of Grid Impedance Spectrum
Tewari, Udit; Neshvad, Surena UL; Sachau, Jürgen UL

in The Renewable Energy & Power Quality Journal (2015, March 25)

The number of inverter based distributed power generators connected to the power network has rapidly grown in recent years. The consequence of this phenomenon is an increasingly complex distribution grid ... [more ▼]

The number of inverter based distributed power generators connected to the power network has rapidly grown in recent years. The consequence of this phenomenon is an increasingly complex distribution grid, requiring advanced and intelligent monitoring and observation tools in order to guarantee satisfactory power quality and reliability. This paper describes a novel power line impedance estimation method, implementing an innovative technique based on modifications of the Pulse Width Modulator’s pulse pattern on the inverters, in order to generate Pseudo-Random Binary Sequence based pilot signals. The stimuli are generated at different locations in the distribution grid, and detected at the transformer sub-station through cross correlation between the received distorted signal and the sequence, the parameters of the propagation channel can be estimated. Simulations in typical grid situations verify that the proposed algorithm is robust to a realistic environment and would [less ▲]

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See detailHydrokinetic Micro-Power Generation in Small Rivers - a New Approach
Norta, David Peter Benjamin UL; Ramanathan, Sriram; Sachau, Jürgen UL et al

Poster (2015, March 25)

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third ... [more ▼]

The so called German electrical “Energiewende” is mainly based on the installation of solar photovoltaic and wind energy converters as the main new renewable European generation resources. The third renewable energy resource, the hydropower has been already developed within the last decades and grew not significantly in the last years. Since some years the development of smaller hydrokinetic turbines increased. The smaller size of some hydrokinetic turbines enables new, unused sites to be harnessed in smaller rivers. The paper deals with the key specifications of hydrokinetic turbines and their influence on a villages’ energy supply. It introduces the concept of a turbine with variable immersion depths to exploit also locations with a varying water level. Based on historical hydrological data a propeller and oscillating hydrofoil type of hydrokinetic turbine are compared, it was found that the variable immersion depths increases the energy harvest. Furthermore, it is shown that in a generation portfolio of hydrokinetic and solar power plants an average Luxembourgish household theoretically renewable supplied has to exchange less energy with the power grid, the higher its share of hydrokinetic generation is. [less ▲]

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See detail11,8-100% Rural Renewable Energy and Power Supply and its Influence on the Luxembourgish Power System
Norta, David Peter Benjamin UL; Winkler, Christoph; Sachau, Jürgen UL et al

Poster (2015, March 10)

Introduction; Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively ... [more ▼]

Introduction; Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively small Luxembourgish electricity system is analysed (0.55 Mio Inhabitants). Current power-system-models mainly focus on larger systems, due to the unavailability of specific consumption-data. Prices and effects on the Luxembourgish power system of different supply scenarios for rural-private households are analysed. Methodology; A linear optimisation for the minimum-cost of the power-supply of all villages with the following renewable energy resources: wind- (max.100kW), solar-PV- and hydrokinetic-power is made. The electricity-demand scales with the number of inhabitants and agricultural-consumers. The wind-power-potential differs with the location of the village. The solar-radiation is assumed to be the equal over the country, due to the small size of approximately 80 by 50 km. The hydrokinetic turbines complete the supply where a village is located close to a river. Results; The minimum cost of the specific village power-supply is the result of the optimization. The installation- and maintenance-cost of each renewable technology are considered. The whole number of rural Luxembourgish private households is considered and their power contribution to the system is estimated for different renewable energy supply scenarios, namely from 11,8% to 100% renewable-energy-scenarios. For each scenario the power exchanged from the village to the grid is calculated in 15-min-steps for 9-years, the amount differs widely with the amount of applied technologies. Discussion; Due to the high share of imported electricity of about 80% in the recent years, every consideration of national power generation does not harm the supply security. Conclusion; Luxembourg is a good model country to analyse the high share of distributed, renewable generators, due to its structure of rural and civic regions and their effects on a central European region with a high electricity consumption. [less ▲]

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See detailWideband Identification of Power Network Parameters Using Pseudo-Random Binary Sequences on Power Inverters
Neshvad, Surena UL; Chatzinotas, Symeon UL; Sachau, Jürgen UL

in IEEE Transactions on Smart Grid (2015)

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large ... [more ▼]

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large portion of the electricity demand is fed in through the distribution grid, whose good health and operational status will be important for guaranteeing grid stability. In Luxembourg, the distribution network is sparsely monitored and controlled, thus instabilities arising due to line overvoltage or DG malfunctioning are not rapidly detected and resolved. This research discusses a novel and low infrastructure methodology for online monitoring of the distribution grid. Such a tool will be increasingly necessary in order to guarantee the stability, reliability and security of the power network, as a larger and larger portion of the energy demand will be satisfied by DG in future years. In this research, advanced system identification techniques utilized in communications, such as Pseudo-Random Binary Sequences, Successive Interference Cancellation are applied to estimate the transfer function of power network propagation paths. The developed method proposes an online monitoring tool that computes grid parameters in real time during operation, without extensive infrastructure addition, by utilizing the PWM based inverters on the grid for active system identification. [less ▲]

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See detailUsing Polyurethane to Reduce the Production Cost of Hydrokinetic Turbine Foils
Norta, David Peter Benjamin UL; Lanser, Christoph; Sachau, Jürgen UL et al

in Proceedings International Conference on Hydropower for Sustainable Development (2015, February 05)

Polyurethane made profiles can be used for hydrokinetic oscillating foil micro turbines to reduce their production cost. For this purpose, a NACA 0015 profile is designed with a computer aided design ... [more ▼]

Polyurethane made profiles can be used for hydrokinetic oscillating foil micro turbines to reduce their production cost. For this purpose, a NACA 0015 profile is designed with a computer aided design software and milled from aluminium. From this sample a negative mould of silicone is produced. This negative was used to produce finally polyurethane foils. Holes and grooves can be simply implemented in the negative by placing corresponding shapes made of metal within the silicone form. A massive reduction of the production cost of about 1600 Euro for a polyurethane (PUR) foil of 1000 mm length compared to an aluminium foil of the same shape is accomplished. [less ▲]

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See detailAnalysis of local grid stability by Hydrokinetic Turbines around a Hydropower Plant in India
Tewari, Udit UL; Sachau, Jürgen UL; Norta, David Peter Benjamin UL et al

Poster (2014, September 08)

Indian proverb, “the utmost darkness is under the oil lamp”, is indeed true in relation to present scenario in places under local distribution grids in India, situated around the Hydropower plants. These ... [more ▼]

Indian proverb, “the utmost darkness is under the oil lamp”, is indeed true in relation to present scenario in places under local distribution grids in India, situated around the Hydropower plants. These conventional hydropower plants use hydrostatic energy for power generation with a conversion efficiency of 85-95%, whereas the energy possessed by available body of moving water around the plant, known as “Hydrokinetic energy”, is difficult to extract due to low flow rates. This poster, prepared in collaboration with Smart Hydro Power GmbH, Germany presents the impact of “ Combined Cycle Hydroelectric Power System”- a combination of hydropower plant and hydrokinetic turbines, to provide additional power to the local grid situated around an existing hydropower plant. It intends to show that, for water rich areas, hydrokinetic turbines are an inexpensive option and offer a viable solution for securing reliable power and stabilizing the local grid situated around a hydropower plant. [less ▲]

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See detailIntegration of Distributed Renewable Generators in the Luxembourgish Power System
Norta, David Peter Benjamin UL; Sachau, Jürgen UL; Allelein, Hans-Josef

Poster (2014, September 08)

The amount of renewable generators increases worldwide. With the higher share of renewable resources in a system, simultaneously the alternating power generation increases. To understand the intermittent ... [more ▼]

The amount of renewable generators increases worldwide. With the higher share of renewable resources in a system, simultaneously the alternating power generation increases. To understand the intermittent influence of the three main renewable technologies, namely windpower, solarpower and hydropower, energy balances of larger regions and the corresponding renewable, distributed generation has to be estimated to understand their generators’ influence on a system. In the following Luxembourg is considered. [less ▲]

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See detailShort Circuit Calculation in Networks with a High Share of Inverter Based Distributed Generation
Margossian, Harag UL; Deconinck, Geert; Sachau, Jürgen UL

Scientific Conference (2014, June 24)

Conventional short circuit calculation programs do not consider the actual behavior of inverter based distributed generation (DG). Several techniques to consider them have been suggested in literature and ... [more ▼]

Conventional short circuit calculation programs do not consider the actual behavior of inverter based distributed generation (DG). Several techniques to consider them have been suggested in literature and are briefly described in this paper. A tool is developed with the combination of these techniques. The approach uses standard short circuit calculation tools and accommodates inverter based DG with different fault responses. The approach is evaluated and compared against other techniques using a realistic test distribution network model. [less ▲]

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See detailHorizontally Oscillating Hydrofoil-River-Turbine with Variable Immersion Depth
Norta, David Peter Benjamin UL; Sachau, Jürgen UL; Hans-Josef, Allelein

Scientific Conference (2014, May 22)

Motivated by the unused hydrokinetic potential of smaller European rivers and creeks we develop a horizontally oscillating hydrofoil turbine to exploit those resources. Based on the work of T. Kinsey and ... [more ▼]

Motivated by the unused hydrokinetic potential of smaller European rivers and creeks we develop a horizontally oscillating hydrofoil turbine to exploit those resources. Based on the work of T. Kinsey and Prof. G. Dumas of the Laval University, Canada, on vertically oscillating hydrofoils we adapt and improve the technology to the resources especially given in the country of Luxembourg in inner Europe. Currently, the energy of rivers is mainly harnessed and transformed in electricity by the well-known barrage type of hydropower plants. This type of hydropower plant becomes harder to implement, since the protection of the natural river flow and the protection of fishes and other animals becomes more important in Europe (see also Recovery of the European Eel Stock). The passage through an ordinary barrage turbine can lead to “very high mortality, notably on migrating silver eels”. Therefore other technologies have to be used to harness the still available rivers energy, namely hydrokinetic turbines. The field of hydrokinetic river turbines is in the beginning to evolve and first projects were implemented in the United States and Europe, harnessing large rivers and tidal currents. But there are fewer approaches available for smaller rivers with varying flow conditions, since the current propeller based concepts need a certain river depths and speed to generate electricity. Furthermore, it could be useful to implement controllable turbines, so that they serve the consumers need but do not lead to peaks in an energy systems balance, which have to be damped with other technologies, for example storages or throttle processes in thermal power plants. The hydrokinetic turbine, presented in this paper is fully controllable; its angle of incidence and its oscillation frequency can be controlled. The advantage of the full control of the motion of the moving hydrofoil is an improved efficiency of the power extraction from the seasonal but also daily varying flow conditions of smaller creeks. Furthermore we can answer with a varying power output to the altering consumers need. We can generate the power needed, once the dependence between oscillation frequencies, variation of the angle of incidence and the power output is derived. Operating the system, fixed to a raft, hold at a position floating on a river, we can also answer to the varying depth of the hydro resource. A simple mechanism can vary the immersion depth of the hydrofoil and adapt the harnessed flow cross-section to the current river conditions. This mechanism enables the new turbine concept to harness currently not useable hydro resources, which were limited by their minimum water depth. Furthermore the system can be protected from dangerous flood conditions with this lifting and lowering mechanism. We expect that we can contribute with this horizontally oscillating hydrofoil-river turbine to a higher share of hydropower generation in the field of micro generation. We are aiming on a concept which is modular (consisting of low kW range single modules) and can be adapted to the rivers size and the consumers’ needs. We will present the specifications of our idea which is currently on the way to be setup in our lab, to prove the controllability and want to present the physical restrictions and potentials for several flow conditions. [less ▲]

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See detailDistribution Grid Monitoring through Pilot Injection and Successive Interference Cancellation
Neshvad, Surena UL; Chatzinotas, Symeon UL; Sachau, Jürgen UL

in IAEE Conference Proceedings (2014)

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large ... [more ▼]

Due to the push for renewable energy in the last decades, European countries have witnessed an exponential growth of Distributed Generation (DG) on the Medium Voltage (MV) network. An increasingly large portion of the electricity demand is fed in through the distribution grid, whose good health and operational status will be important for guaranteeing grid stability. In Luxembourg, the distribution network is sparsely monitored and controlled, thus instabilities arising due to line overvoltage or DG malfunctioning are not rapidly detected and resolved. This research discusses a novel and low infrastructure methodology for online monitoring of the distribution grid. Such a tool will be increasingly necessary in order to guarantee the stability, reliability and security of the power network, as a larger and larger portion of the energy demand will be satisfied by DG in future years. In this research, advanced system identification techniques utilized in communications, such as Pseudo-Random Binary Sequences, Successive Interference Cancellation are applied to estimate the transfer function of power network propagation paths. The developed method proposes an online monitoring tool that computes grid parameters in real time during operation, without extensive infrastructure addition, by utilizing the PWM based inverters on the grid for active system identification. [less ▲]

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See detailOnline Determination of Grid Impedance Spectrum through Pseudo-Random Excitation of a Pulse Width Modulator
Neshvad, Surena UL; Chatzinotas, Symeon UL; Sachau, Jürgen UL

in Renewable Energy & Power Quality Journal (2014)

The last decade has seen a dramatic rise in renewable energy converters connected to the grid, consisting mostly of intermittent distributed generators on the medium or low voltage grid. Due to this ... [more ▼]

The last decade has seen a dramatic rise in renewable energy converters connected to the grid, consisting mostly of intermittent distributed generators on the medium or low voltage grid. Due to this evolution in energy transmission, improved monitoring and control of the distribution grid is becoming mandatory in order to efficiently integrate the new power sources and guarantee power quality, efficiency and reliability. Our paper describes a reliable and precise power grid impedance estimation method using an innovative scheme to control the Pulse Width Modulator’s pulse pattern on the inverters, in order to inject broad spectrum identification patterns. The generated harmonics and inter-harmonics will allow the online computation of the complete spectrum of the grid impedance at the Point of Common Coupling during normal operation. Simulations in typical grid situations verify that the proposed algorithm is robust to a realistic environment and can be used for automated feedback control. [less ▲]

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See detailLTI Modell arbiträrer wechselrichtergeführter Inselnetze
Jostock, Markus UL; Sachau, Jürgen UL; Tuttas, Christian

in Automatisierungstechnik (2013), 61(12), 818-830

This paper presents the development of a control model for inverter driven island grids. The herein presented structured approach creates a multi voltage source inverter model from a single inverter state ... [more ▼]

This paper presents the development of a control model for inverter driven island grids. The herein presented structured approach creates a multi voltage source inverter model from a single inverter state space model and combines this with the node incidence matrix of a network into a compound model of an island grid. The presented approach allows to analyse arbitrary grid structures and different inverter models and it incorporates a large number of inverters. The model can be particularly used for ohmic-inductive low voltage lines. At the end of the article, a stability analysis of a sample network is presented. [less ▲]

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See detailHydrokinetic and Solar Energy Contribution to a Reliable Energy Supply
Norta, David Peter Benjamin UL; Sachau, Jürgen UL; Allelein, Hans-Josef

Poster (2013, November 18)

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See detailStructured Analysis of Arbitrary Island Grids
Jostock, Markus UL; Sachau, Jürgen UL; Hadji-Minaglou, Jean-Régis UL et al

Scientific Conference (2013, October 08)

This paper recapitulates an analytic control model for arbitrary island grids and presents findings on the dynamic behaviour of purely inverter driven island grids. Pole zero plots of different grid ... [more ▼]

This paper recapitulates an analytic control model for arbitrary island grids and presents findings on the dynamic behaviour of purely inverter driven island grids. Pole zero plots of different grid structures are presented and the influence of several inverter parameters on the grid stability is analysed. Findings show that for improved grid stability the inverter’s time constants should also relate to their rated power. Further it is shown how P-Q rotation in the droop control can improve the integration density of renewable power sources in the distribution grid. [less ▲]

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See detailModular Hydrokinetic Micro Generation
Norta, David Peter Benjamin UL; Sachau, Jürgen UL; Allelein, Hans-Josef

Poster (2013, October 07)

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See detailFeeder Protection Challenges with High Penetration of Inverter Based Distributed Generation
Margossian, Harag UL; Capitanescu, Florin UL; Sachau, Jürgen UL

in Proceedings of the EUROCON 2013 conference (2013, July)

The increasing proportion of inverter based distributed generation (DG) in the power system may limit the short circuit power available at distribution substations and consequently cause significant ... [more ▼]

The increasing proportion of inverter based distributed generation (DG) in the power system may limit the short circuit power available at distribution substations and consequently cause significant troubles for the protection of distribution feeders where DG are connected. In this paper, the current practices of distribution network operators in dealing with higher penetration levels of DG are investigated and evaluated using a realistic 31-node distribution network model with limited short circuit supply. The paper discusses the challenges for the protection system related to the integration of increasingly significant amounts of DG and highlights the need for more sophisticated protection systems. [less ▲]

Detailed reference viewed: 109 (31 UL)