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Renewable energy sources are indigenous, and can therefore contribute to reducing dependency on energy imports and increasing security of supply. Development of renewable energy sources can actively contribute to job creation, predominantly among the small and medium sized enterprises, which are so central to the Community economic fabric, and indeed themselves form the majority in the various renewable...
This paper considers development trends and perspectives for widespread implementation of distributed generation, based on renewable energy sources (RES) in the Baltic States. The main issue of the research is integration of RES into the power grid and electricity markets. Paper provides an overview of legislative statements and main rules, which regulates formal relationships between power producers...
The paper presents a comprehensive methodology for stochastic assessment of customer financial losses due to voltage sags over a specified period of time. Modern automated process controls are very sensitive to voltage sags. Therefore, for accurate economic assessment of power quality the exact and precise counting of expected process trips due to voltage sags is very essential. This paper proposes...
The world climate changing is driving the electric power production towards renewable energy sources. The development of wind turbines has reached the power level of 5 MW and wind farms up to 1000 MW are planned. Investigations have shown that the cost for production of wind energy is in the same level as coal and gas. The large amount of hydro power in the Nordic countries can be used to compensate...
Protective relays play an important role in today's complex power generation, transmission and distribution systems. Consequently, this process has given rise to the need for more broad-based dynamic automated testing. For this, a PC-based real-time simulator for relay testing was developed in the last years, including the capability of automated closed loop testing. The simulation program NETOMAC...
In oil-filled power equipment such as power transformers, partial discharge or local overheating will precede a final shutdown. Accompanied with such problems is a decomposition of insulating material into gases, which are dissolved into the transformer oil. The gases dissolved in oil can be separated with some membranes based on the differences in permeability of membranes to different gases. This...
Simulation results relevant to realistic configurations of medium-voltage (MV) and low-voltage (LV) distribution systems provide useful information to evaluate both the expected level of power quality problems on LV networks due to lightning and the benefits achievable by a proper installation of protection devices. The paper describes a procedure to evaluate lightning overvoltages induced on MV lines...
The effects - better expressed, the threats - of Geomagnetically Induced Currents (GICs) are now reasonably well known. GICs are supposed to be caused by electrically charged particles ejected from the Sun. These particles create ionospheric currents that ";mirror"; into Geomagnetically Induced Currents in the ground. It is believed that only high latitudes are vulnerable to these phenomena,...
This paper presents and discusses the results of several measurements carried out on photovoltaic systems connected to LV-grid, from the harmonic distortion viewpoint. The PV-system inverters are characterised by different ratings, in the range of 850 W up to 3 kW, and different structures, including low-frequency and high-frequency transformers. The harmonics emission and the total harmonic distortion...
This paper present a coordinated allocation and control of Step voltage regulators (SVRs) and Static Var Compensators (SVCs) for voltage deviations in case distributed generations are installed in distribution networks. In the proposed method, the reactive tabu search (RTS) with multiple structures and functions has been applied to the coordination. Firstly, the locations of SVRs are selected optimally...
Modern distribution systems include the presence of generation units, namely Embedded Generation (EG), that can affect the Power Quality (PQ) levels inside the systems. This paper concerns with the analysis of PQ effects linked to the installation of fuel cell based production systems. Site and system indices are proposed to quantify these effects in terms of slow voltage variations, harmonic pollution...
This paper analyzes the market price discovery process in an auction market structure. The market clearing price determines the market equilibrium, price and quantity. Once price discovery occurs, the bids are committed, and contracts are written Single and double-side auction market structures are analyzed. Numerical examples are provided to illustrate the market clearing prices discovery.
This paper introduces an simple background about common mode current and the associated effects, like electromagnetic interference (EMI) in power leads and the overvoltage on motor terminals, that are also studied and showed when the static converter are separated by considerable distance. The simplified method to design EMI filters to input and output converter is included. The simulations are running...
This paper deals with the fault location on high voltage series compensated lines. A new approach to evaluate the fault distance is proposed. The distributed-parameter line equations are preferred to describe the overhead lines. The algorithm uses two-terminal measurements, but those data do not require synchronization. No information on the fault resistance value and on the fault type is necessary...
In power system transient stability assessment, direct methods have been used to estimate the critical clearing time on real-time applications. Direct methods that use the controlling unstable equilibrium point concept are accepted as efficient to first swing transient stability analysis. However, some difficulties are observed in the computation of the PEBS exit point and the controlling unstable...
This paper presents part of a more extensive work to solve the equilibrium point between the spinning reserve margin and the load shedding scheme as a consequence of generation failure so as to compensate economical transfers between generators and consumers. This paper analyses the effect of generation failures for different reserve levels considering a full dynamic representation. To this purpose,...
This paper presents an approach to the allocation of transmission losses to the agents of a power system operating under pool conditions, which consider all the operational constraints of the system. The approach belongs to the family of incremental methods of allocation. The technique is based on the perturbation of optimum theorem, which works with a Lagrangian function associated with the perturbed...
This article discusses about networks designers and operators drawing more attention to thermal stability of cable metallic cover (shield) assuring about it both in the process of maintenance of the existing oil paper insulation cables (lead-covered) and in selecting new cables with plastic insulation (copper cover); In the result of cooperation of Riga Technical University and Latvenergo specialists...
This paper focuses on the restructuring process of electricity distribution business that is currently taking place in many countries, including Finland. The driving forces of the process include, for instance, the regulatory reforms of the sector and the efficiency incentives set by the regulators, the owners' increased profit expectations, technological developments, and the legislative requirements...
In the paper, the intermittent earth faults and their detection have been discussed. The intermittent fault belong to the most difficult detectable one due to its low and unstable measuring signals. The discussion has been carried out on the true fault recorded in the typical MV distribution network. It is shown that the criterion values applied, up to now, to the ground-fault protections can be ineffective...
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