Toader Cornel

Universitatea Națională de Știință și Tehnologie Politehnica București | UPB · Department of Electric Power Systems

Electromagnetic shielding is one of the most important concerns of operators from high and very high voltage field, especially those carrying out live work. The electromagnetic field generated by high-voltage overhead power lines and high-voltage equipment may be harmful, especially to those operating these installations. Taking into account the ex...

This paper deals with the identification of balance, unbalance and distortion components in unbalanced three-phase systems with distorted waveforms containing harmonics and interharmonics. The analysis starts from the harmonic distortion and unbalance components found through the symmetrical component-based (SCB) approach previously defined by the...

The paper presents a study of electric field distribution on insulator strings, which are used for suspension of overhead transmission lines of 400kV and are stressed by power frequency voltage. The investigated insulator strings are used on transmission networks of National grid of Romania. The simulation uses the Finite Element Method (FEM) and C...

In low voltage distribution electricity grids is important to examine how to protect against hazardous voltages and currents that can occur with insulation degradation. It was found that the treatment of neutral defect is important in those regimes, the present paper aim to analyze the networks with isolated neutral. Describing phenomena circuitry...

In modern society, the quality of energy is very important for users. So, the transmission and distribution operators have to ensure continuity in energy supply. In this respect, is almost mandatory that the maintenance of the network to be done working in live conditions. These operations are very dangerous for the safety of workers, not only beca...

This paper presents a mathematical model used to calculate the symmetrical components depending on load current (actual values and phases) in low voltage electrical distribution networks. Based on the mathematical model proposed, transformer losses were evaluated for two windings transformers. Case studies dealt with non-symmetric mode due to load...

This paper presents a mathematical model used to calculate the symmetrical components of the load current in electrical distribution networks of low voltage. Based on the mathematical model proposed power lines were calculated tasks under sinusoidal. Case studies dealt with non-symmetric mode due to load imbalance on the distribution network of low...

History in use electromagnetic radiation in treating people various health conditions have a long history. Top questions about electromagnetic field effects occurred around the 40's in the same with the development of radar tracking systems. This paper aims to make an analysis of the studies and current research on the effects of electromagnetic fi...

Electric domestic appliances are part of our daily life; they improve the quality of life. Concerning energy consumption of domestic appliances, great improvements was achieved these last years. The modern energy-efficient electric domestic appliances are electronically controlled. Generally, in a three-phase system, they constitute an unbalanced a...

Thirty two per cent of all injury risks identified at work are risks arising from work equipment. In this sense, the use of protective equipment, respectively earthing devices during interventions / works in electrical installations are the main protective measure against these risks. Short-circuit current calculation is necessary to determine the...

This work aims at resolving the issue of a model that uses symmetrical mathematical components, dedicated to longitudinal simple unbalance for three phase radial transmission electrical lines of an electricity distribution system. The symmetrical component of both current and voltage are obtained, as well as values of the electric distribution syst...

Current structure of the main electric distribution utility in Romania consists in three areas, which cover the center and north areas of Country. Starting from the analysis of small users and users on the distribution utility subsidiaries and ways of building load profiles used in other countries and presented in the literature, are proposed follo...

This paper reviews concepts and methods for electricity customers classification in competitive electricity markets. We present an overview of classification techniques, including classical approaches (applications of statistics and deterministic clustering techniques), as well as methods based on artificial intelligence (neural networks, fuzzy sys...

In a symmetrical and balanced three-phase system with distorted waveforms, a well-known rule states that each harmonic order corresponds to a specified sequence (positive, negative or zero). In this ideal case, the current in the neutral conductor (or more generally in the return path) contains only triplen harmonics. However, this rule is no longe...

This paper deals with the problem of assessing the impact of Distributed Generation on the existing electrical distribution systems from the reliability point of view. A main point in the reliability analysis performed in this work is the probabilistic characterization of the random variables involved in the reliability calculations, as time to fai...

The basic concepts for assessing the characteristics of unbalance and harmonic distortion in the general case of a distribution system operating in unbalanced conditions and with distorted waveforms have been introduced by the authors in a specific symmetrical component-based (SCB) framework. The adoption of the indicators defined in the SCB framew...

Voltage dips are usually followed by the most important damages due to, for example, the lack of input for minimum voltage relays, leading to short-term interruptions. A great deal of attention must be paid for the consumers which cannot sustain supply interruption. Therefore, it is necessary to adopt special schemes in order to ensure power supply...

The proper evaluation of the distribution systems behavior is a particularly difficult task, due to the complexity of the distribution system response to failures. The issues concerning system islanding, which have a major impact on reliability results, are overviewed and included in the overall reliability model. Results of reliability analysis ar...

The aim of the study presented within this paper is the monitoring and analysis of electric power quality supplied to a tri-generation plant. The measurements were made before commissioning the plant, while investment work was still in progress. The main objective of the study was to certify that the voltage values are kept within the limits impose...

This paper deals with the use of a set of indicators defined within a symmetrical component-based framework to study the characteristics of the Steinmetz compensation circuit in the presence of waveform distortion. The Steinmetz circuit is applied to obtain balanced currents in a three-phase system supplying a single-phase load. The circuit is anal...

With a view to the integration in national power system of new power plants based on renewable energy sources, such as wind energy, this paper presents the technical requirements related to the connection of the wind power plants to the main grid. Grid connected wind turbines may cause power quality problems, such as voltage variation and flicker,...

NORMATIV PENTRU PROIECTAREA Şl EXECUTAREA REŢELELOR DE CABLURI ELECTRICE NTE 007/08/00

The characterization of three-phase systems with neutral under unbalanced operation in the presence of waveform distortion is a key aspect in the power quality studies. This paper presents the application to a number of real cases of a unified framework providing a set of synthetic indicators capable to explain the individual effects of unbalance a...

This paper introduces an original and rigorous formulation for computing the unbalance and distortion components of phase and neutral currents in the framework of the symmetrical component transformation. The proposed formulation extends recent literature results, in which different matrices were used for unbalance characterization in the presence...

Customer classification is aimed at providing to the electricity suppliers a sound information on the electricity consumption, to be used for formulating dedicated tariff structures. Different clustering methods can be adopted for assisting the process of electricity customer classification. Previous studies have identified two methods - hierarchic...

This paper illustrates the application of different methods for classifying the electricity customers on the basis of their electrical behaviour. All the aspects ranging from the feature definition to the clustering techniques and related clustering validity indicators are discussed by using a real case study composed of over 200 non-residential cu...

Phenomena usually associated to neutral conductor interruption in low voltage networks touch a sensitive aspect of distribution business clients: the safety of utilisation devices. Therefore a tool to allow assessments of risks associated to this behaviour is needed. This papers aims to propose a mathematical model to realistically describe the beh...

Various techniques for electricity customer classification are presented and discussed, with the focus on highlighting the behaviour of electricity customers. The surveyed techniques include classical approaches (applications of statistics and deterministic clustering algorithms), as well as methods based on artificial intelligence (neural networks...

This paper addresses the optimization of voltage control in distribution systems in the presence of distributed generation. The objective is minimizing the voltage deviations at the load nodes with respect to specified reference values. The optimization is solved by means of a new approach based on nested evolutionary programming. Results are shown...

Accurate knowledge of the customers' consumption patterns represents a worthwhile asset for electricity providers in competitive electricity markets. Various approaches can be used for grouping customers that exhibit similar electrical behavior into customer classes. In this paper, we focus on two approaches for customer classification-a modified f...

The significant penetration of electronically controlled devices and equipment in low voltage distribution networks represents a primary source of concern due to proven 'ability' to worsen power quality problems that affect to an ever increasing extent these networks. Due to established practice with bureau buildings designs single-phased customer...

The massive penetration of electronically controlled devices and equipment in low voltage distribution networks is hold responsible for the worsening power quality problems that affect to a greater extent these networks. Combinations of such customers may result in serious non- symmetrical loading of distribution networks with direct effect in the...

This paper deals with the classification of electricity customers on the basis of their electrical behavior. Starting from an extensive field-measurementbased database of customer daily load diagrams, we searched for the most appropriate indices or sets of indices to be used for customer classification. We propose two original measures to quantify...

This paper deals with the classification of the electricity customers for building up dedicated tariff structures based on their electrical behaviour. Starting from the results of field measurements, the load patterns are characterised by a set of indices representing the shape of the load curves. An automatic clustering algorithm is used to form t...

Reactive power circulation in distribution networks represents a major source for the technological consumption, component of a larger package of performance indices of distribution operators. Tackling the compensation issue, given the current co-existence of various perturbation requires good knowledge of phenomena and this paper tries to summaris...

This paper deals with the presentation of an approach that can be used to decide whether load data gathered by measurements over a limited period of time can be used to produce probabilistic distributions associated to load models. The key issue of this modelling conduct relies with the random nature of load behaviour and the association of stochas...

Objective needs for the determination of electric energy losses for two-windings transformers from transformer posts (TP) and transformer substations (TS) are presented in this work. The paper proposes an original mathematical model to determine the energy losses of TP or TS, valid for the general case of one or several transformers (identical or d...

The Curvature Carpathians (between the Trotus and Dâmbovita river valleys) are the most complex sector of the Subcarpathians. They developed in the Carpathian foreland depression during the Miocene and Pliocene. The paper deals with the various influences on present-day slope evolution: rocks, geological structure, slope parameters, drainage and hu...