Neagu Bogdan | Technical University of Iasi (original) (raw)

Papers by Neagu Bogdan

2017 9th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2017

An important requirement of a distribution network is that the voltage variations at the end user... more An important requirement of a distribution network is that the voltage variations at the end user terminals should be as low as possible. This paper investigates a particular approach that highlights the influences which the connection of shunt capacitors may have over the solutions for voltage control in distribution networks. The problem of optimal capacitor allocation for the minimization of bus voltage deviation was solved using an intelligent computation approach, the so-called Whale Optimization Algorithm (WOA), in order to find the near-optimal solutions for the capacitor allocation problem in electric distribution systems. For validating the feasibility of the algorithm, a real distribution network was used and the results were compared with those obtained using the well-known Particle Swarm Optimization algorithm.

2017 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM) & 2017 Intl Aegean Conference on Electrical Machines and Power Electronics (ACEMP), 2017

The hydropower plants have been one of the most important points in the secure operation of the s... more The hydropower plants have been one of the most important points in the secure operation of the system in the last period. The massive introduction of the renewable energy sources with a variable production, determined the hydropower plants to become a major player in the power system control, helping stabilize fluctuations between demand and supply. The availability, flexibility and reliability of power production and also the quality of energy in hydropower plants determine an appropriate control of the system behavior in normal operating conditions, and in the ones improper. An expert system for optimal power allocation into a dispatchable unit which include three hydropower plants is proposed in the paper. The obtained results have shown that the expert system can be used with success for a proper power allocation between plants inside of a hydropower dispatchable unit for the next day.

In present, technological condition, the distorting (nonsinusoidal) state appearance in public di... more In present, technological condition, the distorting (nonsinusoidal) state appearance in public distribution networks is inevitable, because any non-linear or parametric circuit element represents a harmonic source, and the decrease of negative effects produced by this state is an essential issue. Under these circumstances, the paper presents distorted state parameters computation methodology and software application for complete and complex analyses. On the strength of recorded measurements with different monitoring systems based on Alpha-meters and harmonic analysers, the distorting state parameters for some substation from Iaşi County, was computed. The results can be used by the specialists to adopting important decisions for public distribution network planning, development and operation.

2018 International Conference and Exposition on Electrical And Power Engineering (EPE), 2018

Energy efficiency is a major concern for utilities. For electricity transmission and distribution... more Energy efficiency is a major concern for utilities. For electricity transmission and distribution companies, while efficiency can be achieved by replacing old equipment from the networks with newer devices, or incorporating into the existing infrastructure additional components, such as FACTS solutions, all these measures are costly and require major changes in the network, with added time and financial costs. These measures should be applied only after all other options, which do not incur additional costs, are exhausted. One of these measures is Phase Load Balancing (PLB). This paper proposes a PLB approach built using the Particle Swarm optimization (PSO) algorithm. The PSO-PLB algorithm is tested on a real low voltage (LV) electricity distribution network (EDN), and the results, measured in electricity savings though loss reduction, prove its efficiency.

Brain and language, Jan 7, 2017

Response control in the forms of stopping and slowing responses is thought to be implemented by a... more Response control in the forms of stopping and slowing responses is thought to be implemented by a frontal-subcortical network, which includes the subthalamic nucleus (STN). For manual control, stopping is linked to STN beta (13-30 Hz) and slowing responses are linked to lower frequencies (<12 Hz). Whether similar STN oscillatory activities are associated with the control of spoken responses is not clear. We studied 16 patients with STN LFP recordings during manual and vocal stop signal tasks in two experiments. We found increased beta activities for stopping spoken responses, similar to manual stopping. However, unlike manual stopping, stopping spoken responses elicited a right-lateralized beta power increase, which may be related to previously reported hyperactivity of right-sided motor control regions in stuttering. We additionally studied STN power changes associated with slowing responses in the same stop-signal tasks by comparing slower vs. faster go trials. Now, rather than...

2017 11th IEEE International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), 2017

The paper presents a comprehensive approach using clustering based data mining for load curves ch... more The paper presents a comprehensive approach using clustering based data mining for load curves characterization in real distribution networks. The load curves characterized by their main indicators is made using information provided by Smart Meters. The proposed method was tested using a real database with 60 rural substations. The results demonstrate the ability of the methodology to be efficiently used by distribution operators in patterns discovery of the load curves characteristics with the help of which an energy losses estimation in transformers from the distribution substations could be made.

2017 11th IEEE International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), 2017

The paper aims to realize the micro-grid control in presence of distributed generation (DG) sourc... more The paper aims to realize the micro-grid control in presence of distributed generation (DG) sources and the automatic voltage regulators (AVR). The provided analysis had into account highlighting the influence of the hybrid energy systems with consideration of the automatic voltage regulators on the power losses and the voltage level into micro-grids. The obtained results with the highest power/energy saving were obtained when there was a strong correlation between the DG sources and automatic voltage regulators.

2016 8th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2016

The paper investigates the power losses for real distribution networks in harmonic polluted state... more The paper investigates the power losses for real distribution networks in harmonic polluted state. Actually, the low voltage (LV) distribution networks supply a significant number of nonlinear consumers which causes a distorted and unbalanced state. A negative effect of these states is represented by the increase of power losses in distribution network elements. Even if the symmetrical sinusoidal state is initially considered for the power losses, in reality this often leads to power lines overloading, especially for the neutral. The method for power losses estimation in LV distribution network in harmonic polluted environment is very difficult to use. The aim of this paper is to present a reasonably accurate approach to evaluate the effects of harmonic currents on power losses for LV distribution networks using fuzzy techniques. Moreover, to highlight the proposed methodology, a study case for a real low voltage distribution network in order to compute the additional power losses due to the distorted state is provided.

2016 8th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2016

This paper presents a decision making methodology based on fuzzy logic for an optimal location of... more This paper presents a decision making methodology based on fuzzy logic for an optimal location of distributed generation (DG) sources into an electrical distribution system to reduce the losses and improve the voltage profile. The methodology has two stages: at first is determined the preferential zone where can be located the DG based on the operational characteristics (modelled in paper as fuzzy variables) and the second stage determines the optimal location for DG using Hurwitz criterion. The methodology is verified on a 20 kV real rural distribution network.

2016 International Conference and Exposition on Electrical and Power Engineering (EPE), 2016

The power distribution networks supply nonlinear consumers which causes a distorted and unbalance... more The power distribution networks supply nonlinear consumers which causes a distorted and unbalanced state. A repercussion of these states is represented by the increase of active power losses. Even if the symmetrical sinusoidal state is initially considered for the power losses, in reality this often leads to power lines overloading, especially for the neutral. The existing method for power losses computation in distribution networks with distorted operating state is very difficult to use. The paper investigates the additional power losses for a real distribution network, considering three representative scenarios, close to real operation states. The aim is to present an accurate approach for evaluating the effects of harmonic current flows on the feeder power losses. In order to validate the proposed methodology, a study case is provided. The additional power losses due to the distorted state, for all conductor cross section of the Romanian low voltage power networks are computed.

2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016

The paper presents a fuzzy approach for evaluation of the power/energy losses in transformers fro... more The paper presents a fuzzy approach for evaluation of the power/energy losses in transformers from the electrical distribution networks considering three input variables: the loading factor, the voltage on low side, and the performance standard. These are modelled as linguistic variables and fuzzy numbers. The obtained results on a real distribution network have shown that the developed approach can be used as an alternative tool to estimate the power/energy losses in transformers in uncertainty conditions when there is few information about the network state and performance standard.

Scientific reports, Oct 11, 2016

We are interested in characterizing how brain networks interact and communicate with each other d... more We are interested in characterizing how brain networks interact and communicate with each other during voluntary movements. We recorded electrical activities from the globus pallidus pars interna (GPi), subthalamic nucleus (STN) and the motor cortex during voluntary wrist movements. Seven patients with dystonia and six patients with Parkinson's disease underwent bilateral deep brain stimulation (DBS) electrode placement. Local field potentials from the DBS electrodes and scalp EEG from the electrodes placed over the motor cortices were recorded while the patients performed externally triggered and self-initiated movements. The coherence calculated between the motor cortex and STN or GPi was found to be coupled to its power in both the beta and the gamma bands. The association of coherence with power suggests that a coupling in neural activity between the basal ganglia and the motor cortex is required for the execution of voluntary movements. Finally, we propose a mathematical mo...

2015 7th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2015

In the last years, the fuzzy techniques started to be used to model the uncertainties from distri... more In the last years, the fuzzy techniques started to be used to model the uncertainties from distribution systems. The qualitative assessments for power quality indices can be mathematically translated into membership functions and thus integrated in several methodologies used for planning or operation purposes. This paper focuses on the voltage quality assessment of distribution system under uncertain conditions and proposes an approach based on fuzzy techniques. Thus, the indices for evaluation of slow voltage variations (mean value of voltage and mean square deviation voltage) and mean daily load are expressed in linguistic terms and fuzzy numbers. The linguistic terms characterize categories of electric substations, obtained with Ward clustering method. The algorithm was tested using an electric distribution system with 117 substations (20/0.4 kV) that supplies the rural consumers. The results are comparable to the real values.

ABSTRACT The rational structures or configurations setting are one of the most complex levels in ... more ABSTRACT The rational structures or configurations setting are one of the most complex levels in the distribution networks design and operation. The evolution of computing technology at remarkable performances directly influenced the mathematical methods and algorithms for electric energy distribution systems design and operation. Thus, taking into account the distribution networks topology or structure, the paper proposes a methodology for the radial distribution network route optimization. In this regard it is proposed an algorithm that, starting from the set of nodes defined by loads, allows the optimal route construction based on a successive search method and the introduction of additional nodes branch. Finally, to highlight en the usefulness of proposed methodology, a real rural distribution network from our country was analysed.

2012 13th International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), 2012

ABSTRACT The important changes that occurred during the last years regarding the shifting of the ... more ABSTRACT The important changes that occurred during the last years regarding the shifting of the consumption share from high voltage (HV) to medium voltage (MV) and low voltage (LV), the diversification and the increase of the number of non-linear and/or non-symmetrical consumers, the removal of the reactive power sources (shunt capacitor banks - SCB) that contained polychlorinated biphenyl compounds (PBC) placed in the electricity repartition and distribution systems (ERDS), etc., led to the appearance of some complex problems related to the maintaining of the quality of electricity delivered to the consumers through ERDS. Using multi-criteria optimization processes, the paper presents mathematical models, algorithms and computation software intended for the best management of the reactive power sources, both in the nodes of the electricity repartition systems (ERS) and the electricity distribution systems (EDS). Thus, either traditional algorithms or algorithms based on possibilities offered by artificial intelligence are used.

2014 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), 2014

ABSTRACT A fundamental component of a smart grid is transmission and distribution system monitori... more ABSTRACT A fundamental component of a smart grid is transmission and distribution system monitoring and control. Accurate load, power flow and voltage estimation is required for real time generation capacity dispatching and congestion management in wide area power systems or in networks with distributed generation. In electrical networks, bus voltage levels, load, generation and branch power flows are interdependent, and ones can be determined if others are known. This is a problem that can be solved using the approximation capabilities of artificial neural networks (ANNs). This paper explores the possibility of replacing the classic estimation algorithms in voltage and power flow estimation with ANN approaches, using available data from the Romanian power system.

Materials Science Forum, 2012

ABSTRACT Information about the spatial distribution of the electric field can be obtained by meas... more ABSTRACT Information about the spatial distribution of the electric field can be obtained by measuring the electrode impedance as a function of the diameter of the electrolyte surrounding the electrode. The non-uniform distribution of the electric field around the electrode is supported by the variation of the geometry factor (GF) with the electrical conductivity and geometry of the volume conductor. A comparison of the values obtained for the GF from experimental data, from model calculations and simulations help to understand the non-uniform distribution of the electric field. The GF calculated from four-electrode-measurements is significantly higher. GF should be used with caution in calculations of the deep brain stimulation (DBS) electrode impedance.

2014 16th International Conference on Harmonics and Quality of Power (ICHQP), 2014

The paper is focused on slow voltage variations in the nodes of an electric distribution system. ... more The paper is focused on slow voltage variations in the nodes of an electric distribution system. A clustering based approach to classify the nodes (substations) in categories described by linguistic terms from viewpoint of slow voltage variations is proposed. The linguistic terms are defined in function by the daily average load of nodes and the voltage quality indices (average value and mean square deviation of voltage). The approach was applied to a zone of a distribution system with 117 substations (20/0.4 kV) that supplies mostly the residential consumers, but it can also be applied to substations operating at other voltage levels and supplies another consumers' categories.

Neuroscience Letters, 2005

In a hippocampal mouse brain slice the CA1 stratum radiatum field potential evoked by electrical ... more In a hippocampal mouse brain slice the CA1 stratum radiatum field potential evoked by electrical stimulation of the Schaffer collaterals was used to analyze the very early responses. Parallel bipolar electrodes were utilized to lower the voltage induced by the stimulating current in the recording electrode, and to keep the induced voltage within the linear range of the headstage preamplifier and the recording amplifiers. When the stimulating and recording electrodes are in saline in the same plane and same depth, the shapes of the recorded voltage and stimulating current are similar. The shape of the recorded voltage significantly changes when the recording electrode is in the stratum radiatum of CA1. The signal recorded in the first 2 ms, before the presynaptic volley, indicates the existence of a fast response shown as a positive deflection. For times slightly longer than the stimulating pulse width, the fast response overlaps with the voltage induced by the discharging of the polarization charge accumulated in the double layer capacitance at the interface between metal and saline. For times longer than about 1.4 ms the fast response and presynaptic volley are superimposed. The fast response is about 0.5 mV when the stimulating charge is 15-25 nC. The demonstration that the fast response disappears upon bath perfusion of tetrodotoxin is convincing support for its axonal origin. We postulate that this fast response represents the current source corresponding to the Schaffer collaterals excitatory sink. An undistorted recording of the first 2 ms of the sweep gives useful information about the fast neuronal activity measured extracellularly, and cannot be regarded as a simple stimulus artifact.

Journal of the renin-angiotensin-aldosterone system : JRAAS, 2003

Using isolated rat aortic rings perfused with Krebs-Henseleit saline, the vascular effects of ang... more Using isolated rat aortic rings perfused with Krebs-Henseleit saline, the vascular effects of angiotensin (1-7) (Ang [1-7]) and its interactions with angiotensin II (Ang II) were investigated. Ang (1-7) induced endothelium-dependent relaxation and vasodilating effects in preparations precontracted with phenylephrine. Without preconstriction, Ang (1-7) at high doses (10-6-10-5 M) produced either a significant inhibition of Ang IIinduced vasoconstriction or a non-tachyphylactic vasopressor response. While losartan inhibited the vasoconstriction induced by Ang (1-7), A779 blocked only its relaxation. Unlike losartan, blockade of AT 2-receptors with PD 123319 had no effect. Taking into account the biphasic effects of angiotensin (1-7), we propose that it is one of the active components of the renin-angiotensin system, which is involved as a modulator both in the counter-regulatory actions of Ang II and in the self-regulation of its own vasodilating effects.

2017 9th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2017

An important requirement of a distribution network is that the voltage variations at the end user... more An important requirement of a distribution network is that the voltage variations at the end user terminals should be as low as possible. This paper investigates a particular approach that highlights the influences which the connection of shunt capacitors may have over the solutions for voltage control in distribution networks. The problem of optimal capacitor allocation for the minimization of bus voltage deviation was solved using an intelligent computation approach, the so-called Whale Optimization Algorithm (WOA), in order to find the near-optimal solutions for the capacitor allocation problem in electric distribution systems. For validating the feasibility of the algorithm, a real distribution network was used and the results were compared with those obtained using the well-known Particle Swarm Optimization algorithm.

2017 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM) & 2017 Intl Aegean Conference on Electrical Machines and Power Electronics (ACEMP), 2017

The hydropower plants have been one of the most important points in the secure operation of the s... more The hydropower plants have been one of the most important points in the secure operation of the system in the last period. The massive introduction of the renewable energy sources with a variable production, determined the hydropower plants to become a major player in the power system control, helping stabilize fluctuations between demand and supply. The availability, flexibility and reliability of power production and also the quality of energy in hydropower plants determine an appropriate control of the system behavior in normal operating conditions, and in the ones improper. An expert system for optimal power allocation into a dispatchable unit which include three hydropower plants is proposed in the paper. The obtained results have shown that the expert system can be used with success for a proper power allocation between plants inside of a hydropower dispatchable unit for the next day.

In present, technological condition, the distorting (nonsinusoidal) state appearance in public di... more In present, technological condition, the distorting (nonsinusoidal) state appearance in public distribution networks is inevitable, because any non-linear or parametric circuit element represents a harmonic source, and the decrease of negative effects produced by this state is an essential issue. Under these circumstances, the paper presents distorted state parameters computation methodology and software application for complete and complex analyses. On the strength of recorded measurements with different monitoring systems based on Alpha-meters and harmonic analysers, the distorting state parameters for some substation from Iaşi County, was computed. The results can be used by the specialists to adopting important decisions for public distribution network planning, development and operation.

2018 International Conference and Exposition on Electrical And Power Engineering (EPE), 2018

Energy efficiency is a major concern for utilities. For electricity transmission and distribution... more Energy efficiency is a major concern for utilities. For electricity transmission and distribution companies, while efficiency can be achieved by replacing old equipment from the networks with newer devices, or incorporating into the existing infrastructure additional components, such as FACTS solutions, all these measures are costly and require major changes in the network, with added time and financial costs. These measures should be applied only after all other options, which do not incur additional costs, are exhausted. One of these measures is Phase Load Balancing (PLB). This paper proposes a PLB approach built using the Particle Swarm optimization (PSO) algorithm. The PSO-PLB algorithm is tested on a real low voltage (LV) electricity distribution network (EDN), and the results, measured in electricity savings though loss reduction, prove its efficiency.

Brain and language, Jan 7, 2017

Response control in the forms of stopping and slowing responses is thought to be implemented by a... more Response control in the forms of stopping and slowing responses is thought to be implemented by a frontal-subcortical network, which includes the subthalamic nucleus (STN). For manual control, stopping is linked to STN beta (13-30 Hz) and slowing responses are linked to lower frequencies (<12 Hz). Whether similar STN oscillatory activities are associated with the control of spoken responses is not clear. We studied 16 patients with STN LFP recordings during manual and vocal stop signal tasks in two experiments. We found increased beta activities for stopping spoken responses, similar to manual stopping. However, unlike manual stopping, stopping spoken responses elicited a right-lateralized beta power increase, which may be related to previously reported hyperactivity of right-sided motor control regions in stuttering. We additionally studied STN power changes associated with slowing responses in the same stop-signal tasks by comparing slower vs. faster go trials. Now, rather than...

2017 11th IEEE International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), 2017

The paper presents a comprehensive approach using clustering based data mining for load curves ch... more The paper presents a comprehensive approach using clustering based data mining for load curves characterization in real distribution networks. The load curves characterized by their main indicators is made using information provided by Smart Meters. The proposed method was tested using a real database with 60 rural substations. The results demonstrate the ability of the methodology to be efficiently used by distribution operators in patterns discovery of the load curves characteristics with the help of which an energy losses estimation in transformers from the distribution substations could be made.

2017 11th IEEE International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), 2017

The paper aims to realize the micro-grid control in presence of distributed generation (DG) sourc... more The paper aims to realize the micro-grid control in presence of distributed generation (DG) sources and the automatic voltage regulators (AVR). The provided analysis had into account highlighting the influence of the hybrid energy systems with consideration of the automatic voltage regulators on the power losses and the voltage level into micro-grids. The obtained results with the highest power/energy saving were obtained when there was a strong correlation between the DG sources and automatic voltage regulators.

2016 8th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2016

The paper investigates the power losses for real distribution networks in harmonic polluted state... more The paper investigates the power losses for real distribution networks in harmonic polluted state. Actually, the low voltage (LV) distribution networks supply a significant number of nonlinear consumers which causes a distorted and unbalanced state. A negative effect of these states is represented by the increase of power losses in distribution network elements. Even if the symmetrical sinusoidal state is initially considered for the power losses, in reality this often leads to power lines overloading, especially for the neutral. The method for power losses estimation in LV distribution network in harmonic polluted environment is very difficult to use. The aim of this paper is to present a reasonably accurate approach to evaluate the effects of harmonic currents on power losses for LV distribution networks using fuzzy techniques. Moreover, to highlight the proposed methodology, a study case for a real low voltage distribution network in order to compute the additional power losses due to the distorted state is provided.

2016 8th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2016

This paper presents a decision making methodology based on fuzzy logic for an optimal location of... more This paper presents a decision making methodology based on fuzzy logic for an optimal location of distributed generation (DG) sources into an electrical distribution system to reduce the losses and improve the voltage profile. The methodology has two stages: at first is determined the preferential zone where can be located the DG based on the operational characteristics (modelled in paper as fuzzy variables) and the second stage determines the optimal location for DG using Hurwitz criterion. The methodology is verified on a 20 kV real rural distribution network.

2016 International Conference and Exposition on Electrical and Power Engineering (EPE), 2016

The power distribution networks supply nonlinear consumers which causes a distorted and unbalance... more The power distribution networks supply nonlinear consumers which causes a distorted and unbalanced state. A repercussion of these states is represented by the increase of active power losses. Even if the symmetrical sinusoidal state is initially considered for the power losses, in reality this often leads to power lines overloading, especially for the neutral. The existing method for power losses computation in distribution networks with distorted operating state is very difficult to use. The paper investigates the additional power losses for a real distribution network, considering three representative scenarios, close to real operation states. The aim is to present an accurate approach for evaluating the effects of harmonic current flows on the feeder power losses. In order to validate the proposed methodology, a study case is provided. The additional power losses due to the distorted state, for all conductor cross section of the Romanian low voltage power networks are computed.

2016 International Symposium on Fundamentals of Electrical Engineering (ISFEE), 2016

The paper presents a fuzzy approach for evaluation of the power/energy losses in transformers fro... more The paper presents a fuzzy approach for evaluation of the power/energy losses in transformers from the electrical distribution networks considering three input variables: the loading factor, the voltage on low side, and the performance standard. These are modelled as linguistic variables and fuzzy numbers. The obtained results on a real distribution network have shown that the developed approach can be used as an alternative tool to estimate the power/energy losses in transformers in uncertainty conditions when there is few information about the network state and performance standard.

Scientific reports, Oct 11, 2016

We are interested in characterizing how brain networks interact and communicate with each other d... more We are interested in characterizing how brain networks interact and communicate with each other during voluntary movements. We recorded electrical activities from the globus pallidus pars interna (GPi), subthalamic nucleus (STN) and the motor cortex during voluntary wrist movements. Seven patients with dystonia and six patients with Parkinson's disease underwent bilateral deep brain stimulation (DBS) electrode placement. Local field potentials from the DBS electrodes and scalp EEG from the electrodes placed over the motor cortices were recorded while the patients performed externally triggered and self-initiated movements. The coherence calculated between the motor cortex and STN or GPi was found to be coupled to its power in both the beta and the gamma bands. The association of coherence with power suggests that a coupling in neural activity between the basal ganglia and the motor cortex is required for the execution of voluntary movements. Finally, we propose a mathematical mo...

2015 7th International Conference on Electronics, Computers and Artificial Intelligence (ECAI), 2015

In the last years, the fuzzy techniques started to be used to model the uncertainties from distri... more In the last years, the fuzzy techniques started to be used to model the uncertainties from distribution systems. The qualitative assessments for power quality indices can be mathematically translated into membership functions and thus integrated in several methodologies used for planning or operation purposes. This paper focuses on the voltage quality assessment of distribution system under uncertain conditions and proposes an approach based on fuzzy techniques. Thus, the indices for evaluation of slow voltage variations (mean value of voltage and mean square deviation voltage) and mean daily load are expressed in linguistic terms and fuzzy numbers. The linguistic terms characterize categories of electric substations, obtained with Ward clustering method. The algorithm was tested using an electric distribution system with 117 substations (20/0.4 kV) that supplies the rural consumers. The results are comparable to the real values.

ABSTRACT The rational structures or configurations setting are one of the most complex levels in ... more ABSTRACT The rational structures or configurations setting are one of the most complex levels in the distribution networks design and operation. The evolution of computing technology at remarkable performances directly influenced the mathematical methods and algorithms for electric energy distribution systems design and operation. Thus, taking into account the distribution networks topology or structure, the paper proposes a methodology for the radial distribution network route optimization. In this regard it is proposed an algorithm that, starting from the set of nodes defined by loads, allows the optimal route construction based on a successive search method and the introduction of additional nodes branch. Finally, to highlight en the usefulness of proposed methodology, a real rural distribution network from our country was analysed.

2012 13th International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), 2012

ABSTRACT The important changes that occurred during the last years regarding the shifting of the ... more ABSTRACT The important changes that occurred during the last years regarding the shifting of the consumption share from high voltage (HV) to medium voltage (MV) and low voltage (LV), the diversification and the increase of the number of non-linear and/or non-symmetrical consumers, the removal of the reactive power sources (shunt capacitor banks - SCB) that contained polychlorinated biphenyl compounds (PBC) placed in the electricity repartition and distribution systems (ERDS), etc., led to the appearance of some complex problems related to the maintaining of the quality of electricity delivered to the consumers through ERDS. Using multi-criteria optimization processes, the paper presents mathematical models, algorithms and computation software intended for the best management of the reactive power sources, both in the nodes of the electricity repartition systems (ERS) and the electricity distribution systems (EDS). Thus, either traditional algorithms or algorithms based on possibilities offered by artificial intelligence are used.

2014 International Conference on Optimization of Electrical and Electronic Equipment (OPTIM), 2014

ABSTRACT A fundamental component of a smart grid is transmission and distribution system monitori... more ABSTRACT A fundamental component of a smart grid is transmission and distribution system monitoring and control. Accurate load, power flow and voltage estimation is required for real time generation capacity dispatching and congestion management in wide area power systems or in networks with distributed generation. In electrical networks, bus voltage levels, load, generation and branch power flows are interdependent, and ones can be determined if others are known. This is a problem that can be solved using the approximation capabilities of artificial neural networks (ANNs). This paper explores the possibility of replacing the classic estimation algorithms in voltage and power flow estimation with ANN approaches, using available data from the Romanian power system.

Materials Science Forum, 2012

ABSTRACT Information about the spatial distribution of the electric field can be obtained by meas... more ABSTRACT Information about the spatial distribution of the electric field can be obtained by measuring the electrode impedance as a function of the diameter of the electrolyte surrounding the electrode. The non-uniform distribution of the electric field around the electrode is supported by the variation of the geometry factor (GF) with the electrical conductivity and geometry of the volume conductor. A comparison of the values obtained for the GF from experimental data, from model calculations and simulations help to understand the non-uniform distribution of the electric field. The GF calculated from four-electrode-measurements is significantly higher. GF should be used with caution in calculations of the deep brain stimulation (DBS) electrode impedance.

2014 16th International Conference on Harmonics and Quality of Power (ICHQP), 2014

The paper is focused on slow voltage variations in the nodes of an electric distribution system. ... more The paper is focused on slow voltage variations in the nodes of an electric distribution system. A clustering based approach to classify the nodes (substations) in categories described by linguistic terms from viewpoint of slow voltage variations is proposed. The linguistic terms are defined in function by the daily average load of nodes and the voltage quality indices (average value and mean square deviation of voltage). The approach was applied to a zone of a distribution system with 117 substations (20/0.4 kV) that supplies mostly the residential consumers, but it can also be applied to substations operating at other voltage levels and supplies another consumers' categories.

Neuroscience Letters, 2005

In a hippocampal mouse brain slice the CA1 stratum radiatum field potential evoked by electrical ... more In a hippocampal mouse brain slice the CA1 stratum radiatum field potential evoked by electrical stimulation of the Schaffer collaterals was used to analyze the very early responses. Parallel bipolar electrodes were utilized to lower the voltage induced by the stimulating current in the recording electrode, and to keep the induced voltage within the linear range of the headstage preamplifier and the recording amplifiers. When the stimulating and recording electrodes are in saline in the same plane and same depth, the shapes of the recorded voltage and stimulating current are similar. The shape of the recorded voltage significantly changes when the recording electrode is in the stratum radiatum of CA1. The signal recorded in the first 2 ms, before the presynaptic volley, indicates the existence of a fast response shown as a positive deflection. For times slightly longer than the stimulating pulse width, the fast response overlaps with the voltage induced by the discharging of the polarization charge accumulated in the double layer capacitance at the interface between metal and saline. For times longer than about 1.4 ms the fast response and presynaptic volley are superimposed. The fast response is about 0.5 mV when the stimulating charge is 15-25 nC. The demonstration that the fast response disappears upon bath perfusion of tetrodotoxin is convincing support for its axonal origin. We postulate that this fast response represents the current source corresponding to the Schaffer collaterals excitatory sink. An undistorted recording of the first 2 ms of the sweep gives useful information about the fast neuronal activity measured extracellularly, and cannot be regarded as a simple stimulus artifact.

Journal of the renin-angiotensin-aldosterone system : JRAAS, 2003

Using isolated rat aortic rings perfused with Krebs-Henseleit saline, the vascular effects of ang... more Using isolated rat aortic rings perfused with Krebs-Henseleit saline, the vascular effects of angiotensin (1-7) (Ang [1-7]) and its interactions with angiotensin II (Ang II) were investigated. Ang (1-7) induced endothelium-dependent relaxation and vasodilating effects in preparations precontracted with phenylephrine. Without preconstriction, Ang (1-7) at high doses (10-6-10-5 M) produced either a significant inhibition of Ang IIinduced vasoconstriction or a non-tachyphylactic vasopressor response. While losartan inhibited the vasoconstriction induced by Ang (1-7), A779 blocked only its relaxation. Unlike losartan, blockade of AT 2-receptors with PD 123319 had no effect. Taking into account the biphasic effects of angiotensin (1-7), we propose that it is one of the active components of the renin-angiotensin system, which is involved as a modulator both in the counter-regulatory actions of Ang II and in the self-regulation of its own vasodilating effects.