Category Archives: Fără categorie

Fuzzy Model for Estimating the Power Consumed in a Transformer Station

Fără categorie

Abstract

The paper studies the implementation of a new transformer station in a network designed to take over some of the existing consumers, to provide the necessary energy
for a number of new consumers and a reserve for future new connections to the electricity grid. By creating a fuzzy model, a number of rules have been created to highlight the power consumtion regimes, manifested at the level of the transformer station. Also, the possibility of optimizing and taking over from existing clients was created so that a balance and an optimization can be created regarding the disposition of the consumers on each station.		 images

Current Issues Regarding the Analysis of the Physico-Chemical and Electrical Properties of Transformer Oil

Fără categorie

Abstract

Researchers and practitioners interested in the operation, monitoring and diagnosis of electrical equipment (such as: transformers, motors and generators, circuit
breakers, etc.) know that in order to ensure a safe operation of such equipment it is necessary to know, among other things, the condition of the insulation system. This is one of the essential information to know because about 40% of failures which occur in the operation of the electrical equipment are due to insulation breakdown; in some cases
they can reach even close to 100%. In this context this paper proposes the presentation of several modern methods and equipment for the study and analysis of physical and chemical properties (namely: analysis of water content, density and interfacial tension, dissolved gas analysis and furan components determination) and electrical parameters
(namely: determination of loss factor and relative permittivity) of transformer oil. Samples of transformer oil type MOL TO 30.01 (uninhibited electrical insulator, nonadditive), new StaSo Transformer Oil I (high quality inhibited insulating oil) and TR 30 oil were studied. Two samples were collected directly from the original barrel, two samples were collected from the transformer tank after dielectric tests at the transformer’s manufacturer and also two samples of used TR 30 oil were collected from two transformers. The tests were carried out in an accredited laboratory with calibrated equipment. The results highlighted the properties of each analyzed sampled. The interpretation of the results emphasized the qualities and defects of each analyzed oil
sample and whether or not they fit the standards in the field.		 images

Modeling of Thermal Transfer Parameters by Transparent Construction Elements

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Abstract

The article presents a case study on the modeling of heat transfer parameters through transparent construction elements. Conducting experimental studies on the scale of an entire building is very complex, on the one hand due to the size and geometric  complexity of the studied objectives and, on the other hand, due to numerous random
factors (climatic conditions or how the buildings are operated). In order to be able to carry out a study on the real behavior of the buildings, models are made for them, taking
into account the real mode of operation of the installations related to these  constructions. The present article consists in making a modeling for a simple exterior window, with a single sheet of glass that separates the interior space of an enclosure (rooms) from the exterior environment. The modeling will be performed both for the case of a building located inside a locality and for the case of the location of the building outside the locality.		 images

Exhaustive Optimization Method Applied on Electromagnetic Device

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Abstract

This paper presents the application of an exhaustive optimization method based on the design of experiments (DOE) and the finite element method (FEM), with the aim of improving the actuation force developed by a DC electromagnet. The optimization of this device has been the subject of several previous works, allowing comparisons between the optimization methods applied in terms of the obtained precision and the workload.
According to previous studies, two geometric parameters (the angle ratio of the support tip and the coil shape ratio) are very influential on the force developed at the maximum
air gap. Thus, the exhaustive optimization method took into account these two  parameters for its maximization, having as constraints the maintenance of the global dimensions of the device (external radius, the height of carcass, height of the plunger with support) and of the cross-section of the winding. The optimization algorithm used the results of 2-D FEM numerical experiments carried out with the FEMM program in combination with the LUA language and is based on the response surface methodology (RSM) and analysis of variance (ANOVA). Second-order polynomial models of the objective function were calculated using full factorial designs with three levels per factor. After three iterations, a very good result was obtained, comparable to those obtained by other methods, but with a significant cost in terms of workload, the optimum obtained being a global one.		 images

Automatic Sorting System for Educational Training

Fără categorie

Abstract

At the same time as the introduction of automated equipment in industry, production operators and maintenance workers servicing automated stations require professional training courses depending on the category and job. Depending on the particularity of the production process, these training courses can be done internally at the production unit, at external industrial partners or at universities. The paper presents an automatic tire sorting system made on a small scale. The sorting system is composed of an input stock and two output stocks of sorted tires. Tire storage in the two output stocks is done with an electro-pneumatic manipulator robot. The sorting is done according to the tire bead width, for which the system is equipped with the appropriate sensors. The structure is
controlled by an Arduino Mega2560 microcontroller development system. The sorting station can also be controlled manually by the operator via a joystick and some buttons. In comparison to other sorting systems, the robot structure is simpler. It performs the transfer of the tires by only two movements, thus reducing the handling time. Also,
the automatic sorting system realized corresponds to the requirements imposed on flexible production systems. The automatic system can be used both for training students
from technical faculties and industrial operators in the field.		 images

Reactive Energy Compensation Equipment Used in High Power Laboratories

Fără categorie

Abstract

The power quality covers the means to conserve energy resources, such means consist in improving the power factor and judiciously managing the reactive energy in the power system. Electric grids do not have an unlimited energy transmission capacity, therefore any load on the grid with reactive energy is measured by the energy distributor/supplier and billed to the consumer. On the premise that for industrial consumers, the main consumers of reactive energy are the low-load induction motors and transformers, this paper presents a synchronization equipment for a wound-rotor induction motor with a power of 2000 kW, nominal voltage 6kV, nominal current 210A, which allows the increase of the power factor, significantly reducing the reactive energy consumption. The equipment presented was designed, built, tested and validated by tests carried out in
the high-power laboratory.		 images

Comparative Analysis in the Case of Indirect Current Control in a Shunt Active Filtering System

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Abstract

In this paper, the performance of a three-phase four wire shunt active power filter (APF) using indirect current control with active load current calculation was compared with that corresponding to using indirect current control with prescribed current calculation from the voltage controller. It is clear that, under balanced and sinusoidal voltage conditions, these two methods give similar results. The variant of the indirect current control with prescribed current calculation from the voltage controller has the  advantage of simplicity, but exhibits increased sensitivity to voltage ripples on the compensation capacitor, as they are reflected in the output of the voltage controller. The whole system was modeled using MATLAB-SIMULINK software. The simulation results demonstrate the applicability of both methods for APF control. images

Application of Electrical Substation, Ring Topology versus Star Topology

Fără categorie

Abstract

In order to solve the problem of analyzing network performance of SCADA (Supervisory Control And Data Acquisition) system communication of power grid in effective and practical way, this paper proposes to change the star topology with ring topology, specifically method rapid spanning tree protocol (RSTP), in an electrical substation.
The paper discusses about SCADA architecture, main equipment like remote terminal unit, intelligent electronic device, server, server network time protocol, HMI (human
machine interface), router and their role in the electrical substation. Also, the levels of the command hierarchy in the SCADA system are discussed. Each level has certain tasks
set for the optimization and reliability of the electrical substation. The data flow describes the types of information that are transmitted between hierarchical levels. In the last
part the paper the topologies of the system are described.		 images

Analyzing the Influence of Harmonic Parameters on Accuracy Indices When Applying Wavelet Transform

Fără categorie

Abstract

The paper deals with the evaluation of root mean square deviations and maximum absolute relative errors associated to the decomposition followed by recomposition
based on Wavelet Packet Transform (WPT) of signals polluted with harmonics. Subtrees associated to sets of harmonics presenting practical interest for industrial applications
are addressed. The study uses artificial signals generated through the superposition of perfect sinusoids with pairs of harmonics which proved to be related in an almost exclusive manner to pairs of nodes from the bottom level of a WPT tree. 4 parameters had to be considered when determining the maximum and minimum values of errors for each set: the clustered harmonics’ magnitudes and their phase-shifts relative to the  omponent of fundamental frequency. The decomposition/recomposition are time-efficient due to an
original system of flags labeling each node from the WPT tree. For each analyzed set of harmonics, 3d graphical representation of minimum and maximum errors along with
the associated 3d graphical representation of the phaseshifts are provided. At the same time, per set limits of errors ranges were established and discussed while specific patterns
were deduced for the context in which extreme errors appear (phase-shifts and harmonic magnitudes). The results were commented, and conclusions were drawn.		 images

Two Numerical Studies for Longitudinal Movement of a Canard UAV with Vectored Thrust

Fără categorie

Abstract

This work presents a study concerning the possibilities to improve the longitudinal dynamic of a canard UAV using vectored thrust. It is followed to harness the advantages of canard configuration of UAV and to obtain further a better longitudinal dynamic, able to fulfil more complex missions than canard UAV without vectored thrust. There are tested two methods. The first uses the UAV polars obtained in XFLR 5 and extended, using literature experience, a little bit over the stall angle. By this method is determined the necessary gain between the elevator steering angle and thrust deflection angle in order to maintain the UAV in landing configuration (flaps down) to the optimum angle of attack for landing. Using this method is studied also the effect of vectored thrust in maneuver, in cruise configuration. Step signal on the elevator, thrust and both commands simultaneously are applied on the UAV without and with vectored thrust and are identified the advantages of vectored thrust in this situation. The second method uses the polars of the UAV components obtained in XFLR5, extended independently up to a little bit above each stall angle. By this way is studied the effect of the vectored thrust on the atack angle in horizontal flight for the UAV in cruise configuration. There are obtained horizontal flight parameters (speed, elevator steering, angle of attack and thrust), when vectored thrust is used. It is followed to obtain results for attack angle as high as possible. Both methods are limited by the results obtained in XFLR 5, that can’t determine polars at atttack angles near stall, and for the second method, by the aerodynamic interferences between UAV components. images