This page has only limited features, please log in for full access.

Prof. Dr. Nikos Mastorakis
Department of Industrial Engineering, Technical University of Sofia, Bulevard Sveti Kliment Ohridski 8, 1000 Sofia, Bulgaria

Basic Info

Basic Info is private.

Research Keywords & Expertise

0 Algorithms
0 Artificial Intelligence
0 Network Security
0 Robotics
0 Simulation

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Conference paper
Published: 05 October 2018 in MATEC Web of Conferences
Reads 0
Downloads 0

The electrodynamic strength, as forces acting between the current-carrying electric circuits are exerted as long as the currents exist, and have the tendency of deformation and displacement of the circuits. In short-circuit regimes the strength in electrical equipment becomes severe. For instance, short-circuits highly affect power transformers connected to power transmission lines. The effects are also strong because of mechanical deformations occurring in the power transformer connection part. In line with this idea, in this paper it is made an analytical study upon the a.c. single-phase and a.c. three-phase electric circuits, taking into account the current instantaneous maximum value. The paper also entails numerical simulations of electrodynamic strength in power transformer busbars under short-circuit conditions. MATLAB software, with its specific extensions, enable simulation models to generate the charts of the electrodynamic forces in the power transformer connection bars.

ACS Style

Cornelia A. Bulucea; Constantin Brindusa; Doru A. Nicola; Nikos E. Mastorakis; Carmen A. Bulucea; Philippe Dondon. Evaluating through mathematical modelling the power equipment busbars electrodynamic strength under sudden short-circuit conditions. MATEC Web of Conferences 2018, 210, 02004 .

AMA Style

Cornelia A. Bulucea, Constantin Brindusa, Doru A. Nicola, Nikos E. Mastorakis, Carmen A. Bulucea, Philippe Dondon. Evaluating through mathematical modelling the power equipment busbars electrodynamic strength under sudden short-circuit conditions. MATEC Web of Conferences. 2018; 210 ():02004.

Chicago/Turabian Style

Cornelia A. Bulucea; Constantin Brindusa; Doru A. Nicola; Nikos E. Mastorakis; Carmen A. Bulucea; Philippe Dondon. 2018. "Evaluating through mathematical modelling the power equipment busbars electrodynamic strength under sudden short-circuit conditions." MATEC Web of Conferences 210, no. : 02004.

Conference paper
Published: 31 October 2013 in Proceedings of The 3rd World Sustainability Forum
Reads 0
Downloads 0

This paper is a sequel to a study by the authors of the electric power systems comprising the generator circuit-breakers (GCBs) at power plant generator terminals. A sustainable assessment of the current interruption requirements of a GCB addresses the main stresses on the generator circuit breaker, revealing that the GCB current interruption requirements are significantly higher than for the distribution network circuit breakers. Hence, generator circuit-breakers are subject to unique demanding conditions caused my specific stresses, namely: high asymmetrical fault currents resulting from high d.c. components of the fault current; greater electrical, thermal and mechanical stresses when interrupting longer arcing time faults; and important dielectric stress after the electric arc extinction caused by the transient recovery voltage (TRV). This paper extends other studies of the authors of the energetic and exergetic transformation chain at the interruption current transient process in an electric power system that comprises the generator circuit-breaker, as well as the transient recovery voltage (TRV) which appears after the interruption of a short-circuit fed by the synchronous generator or by the main step-up transformer. For achieving the TRV equivalent configuration the authors applied the method of operational symmetrical components (o.s.c.), and utilized the operational impedances of synchronous generator and of main transformer, depending on the fault location. Modeling the transient recovery voltage of circuits emphasizes aspects with direct implications on commutation equipment. Thus, the o.s.c. method can be applied at the poles of any breaker, for any eliminated fault type, if the network configuration and elements are known. The TRV, which appears after the interruption of a short-circuit fed by the generator, may be considered like an oscillation, where the oscillation factor and the rising rate (RR) of the TRV are established by the electrical machine parameters: resistance, inductance and capacitance. Consequently, modeling of concentrated equivalent parameters of the synchronous generator at perturbations caused by current interruption transient processes is achieved in this study through an approach based on sustainability concepts. These findings allow for simulations of the transient recovery voltage and comparisons with experimental results.

ACS Style

Cornelia Bulucea; Marc Rosen; Doru Nicola; Nikos Mastorakis; Carmen Bulucea. Some Aspects of Sustainable Energy Conversion During Transient Processes in Electric Power Systems Comprising Generator Circuit Breakers. Proceedings of The 3rd World Sustainability Forum 2013, 1 .

AMA Style

Cornelia Bulucea, Marc Rosen, Doru Nicola, Nikos Mastorakis, Carmen Bulucea. Some Aspects of Sustainable Energy Conversion During Transient Processes in Electric Power Systems Comprising Generator Circuit Breakers. Proceedings of The 3rd World Sustainability Forum. 2013; ():1.

Chicago/Turabian Style

Cornelia Bulucea; Marc Rosen; Doru Nicola; Nikos Mastorakis; Carmen Bulucea. 2013. "Some Aspects of Sustainable Energy Conversion During Transient Processes in Electric Power Systems Comprising Generator Circuit Breakers." Proceedings of The 3rd World Sustainability Forum , no. : 1.

Conference paper
Published: 29 October 2012 in Proceedings of The 2nd World Sustainability Forum
Reads 0
Downloads 0

The concepts of science, including concepts related to sustainability including exergy and embodied energy, were developed to describe our knowledge about aspects of the universe. A convincing example of the usefulness of embodied energy and exergy for analyzing systems which transform energy is the generator circuit-breaker (GCB) disconnection process. Nowadays, the electric connection circuits of power plants (based on fossil fuels as well as renewable sources) entail GCBs at the generator terminals, since the presence of that electric equipment offers many advantages related to the sustainability of a power plant. A classic circuit-breaker is an automatically electrical switch designed to protect against inherent operation faults, such as overload or short-circuit. A generator circuit-breaker is located between the generator and the main step-up transformer, this location influencing the operating conditions since GCBs are significantly more difficult to apply to some operating regimes than classical network circuit-breakers. Consequently, the electrical and mechanical performance required of a GCB exceeds the requirements of a standard distribution circuit-breaker. Generally, a circuit-breaker must detect a fault condition, and once a fault is detected, electric contacts within the circuit-breaker must open to interrupt the circuit. In an alternating current (a.c.) circuit the interruption of a short-circuit is performed by the circuit-breaker at the natural passing through zero of the short-circuit current. During the current interruption, an electric arc is generated between the opened contacts of the circuit-breaker. This arc must be cooled and extinguished in a controlled way. Since the synchronous generator stator can flow via high asymmetrical short-circuit currents, which will not pass through zero (at least on one phase) many time periods after the fault appearance, the phenomena which occur in the case of short-circuit currents interruption determine the main stresses of the generator circuit-breaker; the current interruption requirements of a GCB are significantly higher than for the distribution network circuit breakers. Although the phenomena produced in the electric arc at the terminals of the circuit-breaker are complicated and not completely explained, the concept of exergy is useful in understanding the physical phenomena. The electric arc study can prove that the limits between the microscopic and macroscopic phenomena are fragile and certain phenomena could be studied in related frames of work. The electric arc that occurs during the interruption processes in a circuit-breaker can be studied as a very high temperature continuous plasma discharge, and thermodynamic parameters must be taken into consideration; alternatively it could be seen as an electric conductor by a resistance depending on the current intensity (under a constant low voltage) and studied within the Faraday's macroscopic theory. Electric arc interruption is of great importance, because an uncontrolled electrical arc in the apparatus could become destructive since, once initiated, an arc will draw more and more current from a fixed voltage supply until the apparatus is destroyed. However, the appearance of an electric arc at the terminals of the circuit-breaker should not be necessarily seen as a damaging phenomenon since if the electric arc would not appear the network embedded magnetic energy would be converted to electric energy, leading further to high over-voltages. Consequently, during the conversion process of the system magnetic energy in the arc thermal energy, the exergy is not destroyed, and it must be taken into consideration as embodied energy, used further on in the interrupting process. Just after the short-circuit current interruption by the generator circuit-breaker (when the GCB has been subjected to a 50,000 degree plasma arc), between its opened contacts arises the transient recovery voltage (TRV) which constitutes the most important dielectric stress after the electric arc extinction. If the rising rate of TRV exceeds the rising rate of dielectric strength across the open gap within the extinction chamber of the GCB, the electric arc will rekindle (re-strike) and this time the electric arc exergy will be entirely used in a mechanical destructive process determined by the electrodynamics forces. Since the magnitude and shape of the TRV occurring across the generator circuit-breaker are critical parameters in the recovering gap after the current zero, in this paper, we model, for the case of the faults fed by the main step-up transformer, the equivalent configurations, with operational impedances, for the TRV calculation, taking into account the main transformer parameters, on the basis of the symmetrical components method. This study focuses on this fault location because the transformer-fed-fault currents can be very high since the full energy of the power system feeds the faults.

ACS Style

Cornelia Bulucea; Marc Rosen; Doru Nicola; Nikos Mastorakis; Carmen Bulucea. Analyzing the Interruption Processes in the Generator Circuit Breaker through Sustainability Concepts. Proceedings of The 2nd World Sustainability Forum 2012, 1 .

AMA Style

Cornelia Bulucea, Marc Rosen, Doru Nicola, Nikos Mastorakis, Carmen Bulucea. Analyzing the Interruption Processes in the Generator Circuit Breaker through Sustainability Concepts. Proceedings of The 2nd World Sustainability Forum. 2012; ():1.

Chicago/Turabian Style

Cornelia Bulucea; Marc Rosen; Doru Nicola; Nikos Mastorakis; Carmen Bulucea. 2012. "Analyzing the Interruption Processes in the Generator Circuit Breaker through Sustainability Concepts." Proceedings of The 2nd World Sustainability Forum , no. : 1.

Journal article
Published: 11 October 2012 in Entropy
Reads 0
Downloads 0

Theoretically, the concepts of energy, entropy, exergy and embodied energy are founded in the fields of thermodynamics and physics. Yet, over decades these concepts have been applied in numerous fields of science and engineering, playing a key role in the analysis of processes, systems and devices in which energy transfers and energy transformations occur. The research reported here aims to demonstrate, in terms of sustainability, the usefulness of the embodied energy and exergy concepts for analyzing electric devices which convert energy, particularly the electromagnet. This study relies on a dualist view, incorporating technical and environmental dimensions. The information provided by energy assessments is shown to be less useful than that provided by exergy and prone to be misleading. The electromagnet force and torque (representing the driving force of output exergy), accepted as both environmental and technical quantities, are expressed as a function of the electric current and the magnetic field, supporting the view of the necessity of discerning interrelations between science and the environment. This research suggests that a useful step in assessing the viability of electric devices in concert with ecological systems might be to view the magnetic flux density B and the electric current intensity I as environmental parameters. In line with this idea the study encompasses an overview of potential human health risks and effects of extremely low frequency electromagnetic fields (ELF EMFs) caused by the operation of electric systems. It is concluded that exergy has a significant role to play in evaluating and increasing the efficiencies of electrical technologies and systems. This article also aims to demonstrate the need for joint efforts by researchers in electric and environmental engineering, and in medicine and health fields, for enhancing knowledge of the impacts of environmental ELF EMFs on humans and other life forms.

ACS Style

Cornelia A. Bulucea; Marc A. Rosen; Doru A. Nicola; Nikos E. Mastorakis; Carmen A. Bulucea. Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems. Entropy 2012, 14, 1894 -1914.

AMA Style

Cornelia A. Bulucea, Marc A. Rosen, Doru A. Nicola, Nikos E. Mastorakis, Carmen A. Bulucea. Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems. Entropy. 2012; 14 (10):1894-1914.

Chicago/Turabian Style

Cornelia A. Bulucea; Marc A. Rosen; Doru A. Nicola; Nikos E. Mastorakis; Carmen A. Bulucea. 2012. "Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems." Entropy 14, no. 10: 1894-1914.

Journal article
Published: 30 March 2012 in Sustainability
Reads 0
Downloads 0

Over the last several decades, it has become increasingly accepted that the term xenobiotic relates to environmental impact, since environmental xenobiotics are understood to be substances foreign to a biological system, which did not exist in nature before their synthesis by humans. In this context, xenobiotics are persistent pollutants such as dioxins and polychlorinated biphenyls, as well as plastics and pesticides. Dangerous and unstable situations can result from the presence of environmental xenobiotics since their harmful effects on humans and ecosystems are often unpredictable. For instance, the immune system is extremely vulnerable and sensitive to modulation by environmental xenobitics. Various experimental assays could be performed to ascertain the immunotoxic potential of environmental xenobiotics, taking into account genetic factors, the route of xenobiotic penetration, and the amount and duration of exposure, as well as the wave shape of the xenobiotic. In this paper, we propose an approach for the analysis of xenobiotic metabolism using mathematical models and corresponding methods. This study focuses on a pattern depicting mathematically modeled processes of resonant absorption of a xenobiotic harmonic oscillation by an organism modulated as an absorbing oscillator structure. We represent the xenobiotic concentration degree through a spatial concentration vector, and we model and simulate the oscillating regime of environmental xenobiotic absorption. It is anticipated that the results could be used to facilitate the assessment of the processes of environmental xenobiotic absorption, distribution, biotransformation and removal within the framework of compartmental analysis, by establishing appropriate mathematical models and simulations.

ACS Style

Cornelia A. Bulucea; Marc A. Rosen; Nikos E. Mastorakis; Carmen A. Bulucea; Corina C. Brindusa. Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures. Sustainability 2012, 4, 561 -573.

AMA Style

Cornelia A. Bulucea, Marc A. Rosen, Nikos E. Mastorakis, Carmen A. Bulucea, Corina C. Brindusa. Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures. Sustainability. 2012; 4 (4):561-573.

Chicago/Turabian Style

Cornelia A. Bulucea; Marc A. Rosen; Nikos E. Mastorakis; Carmen A. Bulucea; Corina C. Brindusa. 2012. "Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures." Sustainability 4, no. 4: 561-573.

Conference paper
Published: 02 November 2011 in Proceedings of The 1st World Sustainability Forum
Reads 0
Downloads 0

Over the last several decades, it has become increasingly accepted that the term xenobiotic relates to environmental impact, since environmental xenobiotics are understood to be substances foreign to a biological system, which did not exist in nature before their synthesis by humans. In this context, xenobiotics are persistent pollutants such as dioxins and polychlorinated biphenyls, as well as plastics and pesticides. Dangerous and unstable situations can result from the presence of environmental xenobiotics since their harmful effects on humans and ecosystems are often unpredictable. For instance, the immune system is extremely vulnerable and sensitive to modulation by environmental xenobitics. Various experimental assays could be performed to ascertain the immunotoxic potential of environmental xenobiotics, taking into account genetic factors, the route of xenobiotic penetration, and the amount and duration of exposure, as well as the wave shape of the xenobiotic. In this paper, we propose an approach for the analysis of xenobiotic metabolism using mathematical model and corresponding methods. This study focuses on a pattern depicting mathematically modelled processes of resonant absorption of a xenobiotic harmonic oscillation by an organism modulated as an absorbing oscillator structure. We represent the xenobiotic concentration degree through a spatial concentration vector, and we model and simulate the oscillating regime of environmental xenobiotic absorption. It is anticipated that the results could be used to facilitate the assessment of the processes of environmental xenobiotic absorption, distribution, biotransformation and removal within the framework of compartmental analysis, by establishing appropriate mathematical models and simulations.

ACS Style

Marc Rosen; Cornelia Bulucea; Corina Brindusa; Nikos Mastorakis. Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures. Proceedings of The 1st World Sustainability Forum 2011, 1 .

AMA Style

Marc Rosen, Cornelia Bulucea, Corina Brindusa, Nikos Mastorakis. Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures. Proceedings of The 1st World Sustainability Forum. 2011; ():1.

Chicago/Turabian Style

Marc Rosen; Cornelia Bulucea; Corina Brindusa; Nikos Mastorakis. 2011. "Approaching Resonant Absorption of Environmental Xenobiotics Harmonic Oscillation by Linear Structures." Proceedings of The 1st World Sustainability Forum , no. : 1.