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Power and instrument transformers represent important components of electric power transmission and distribution stations. An important indicator of the condition of the insulation of such equipment is the evolution of the partial discharge (PD) level, since an increase of this level usually indicates the development of a fault affecting the insulation quality. Detection of partial discharges in the...
The Conservative Power Theory (CPT) is one of the latest approaches to definitions of powers and compensation in systems with nonsinusoidal voltages and currents. It is shown in this paper that the CPT misinterprets power phenomena in electrical systems, however, and it does not create right fundamentals for the power factor improvement by reactive compensation. In particular, capacitive compensation...
This paper presents the principle of a load flow algorithm adjusted to asymmetrical operation of the three-phase distribution networks. The algorithm is based on an iterative procedure, which is independently applied on three equivalent sequence networks and uses a phase-to-phase equivalent model for unbalanced loads connected to the analyzed network.
Nowadays great efforts are done in order to improve the performance of soft magnetic materials due to their wide use in industrial applications. This paper deals with a comparative analysis of the influence of the alloying elements on magnetic properties of several grades of electrical steels. The magnetic characteristics are obtained in the sinusoidal magnetization regime at low frequency, of 1 Hz,...
This paper describes the magnetic field measurements performed in a public access area — a market place, situated in the close vicinity of a transformer substation part of the Romanian national power grid. The measurement results were compared to the limits, regarding the human exposure to electromagnetic fields, imposed by normative documents. An analytical simplified estimation was performed too...
Achieving mathematical model and simulation is essential in the design of complex installations. This allows analysis of different operating modes and behavior evaluation system. This enables notification of possible errors and their correction, avoiding additional costs involved in achieving and testing facility in real conditions. Some operating modes may be degraded modes would be very difficult...
This paper is concerned with the study of electrical contacts between the components used in building key parts of high temperature superconducting (HTS) electromagnets, e.g., HTS coils, HTS current leads, etc. Some preliminary tests on two types of junctions are presented, Cu — HTS and HTS — HTS, and some details of their manufacturing process are shown. Experimental and numerical results on the...
This work deals with the numerical analysis of the electromagnetic field problem for one proposed Ferrite — Cored Eddy Current Sensor, using the Quick Field software; this sensor can be used in the waste management for metal separation. Using this software, many specific cases are analysed, namely, when sensor probe coil is placed on different types of metallic samples (ferromagnetic and non ferromagnetic);...
This paper presents a case study for monitoring the quality of electric energy in an industrial consumer. The measurements were carried in the power supply point and the data processing was achieved using LabVIEW software. It was made an interface to allow reading of files and processing them (creation of data tables and charts). Based on the data obtained from the measurements and using the interface...
This paper is concerned with the implementation of the Fryze-Buchholz-Depenbrock theory in the control of an active DC-traction substation. The active DC-traction substation taken into consideration is obtained by adding a specific system for active filtering and regeneration to a classical DC-traction substation with twelve-pulse uncontrolled rectifier. The main component is a voltage source inverter-based...
The article presents an industrial application from a plant regarding the automatic movement of some trucks transporting building materials from one sector to another. It presents an alternative solution to conventional control installation of trucks (with electromechanical relays, timers) with a modern control installation made with PLC, static frequency converter, and touch panel.
Nowadays the development of electric and electronic equipment with applications in industry, medicine, and telecommunications or in outer space imposes the new requirements regarding the reduction of the risk of the electrostatic discharges occurrence. New researches have been developed to obtain polymeric compounds as answer to this demand and new multifunctional polymeric compounds with antistatic...
The paper presents the energetic performances of a system used for drying of current transformer from 110 kV Ciungetu power station. In fact, the drying process is based on an induction heating system that contains a half-controlled rectifier and a voltage source inverter that operates with resonant load. Two frequencies are taken into consideration for the inverter control. The former is the resonance...
This paper reflects the evolution from the 2D to the 3D finite element analysis of the squirrel-cage induction motors related to the evaluation on the influence of the broken bar fault and the investigation of methods for the efficient fault detection. Based on the scalar 3D formulation of the electromagnetic field and through the step by step in time domain finite element solution, the time dependence...
Presently, the concept of renewable energy is gaining ground, because power, and especially electrical power or electrical applications, are tending towards renewable sources, and as a consequence the use of renewable energy increased over the past years. This paper presents a review of multiport converters, different multiport converters are to be discussed, and a comparison between a transformer...
The direct torque control (DTC) is the preferred control technique of the induction motor in electric traction applications. It has advantages, as it is a sensorless control technique, but also disadvantages. The main disadvantage is related to the switching frequency which is the same with the sampling frequency of the entire control loop. This determines high requirements for the control system...
With the development of Distributed Energy Systems the dynamic support of Microgrids Energy Quality is of great importance an optimized operating scheme for a grid-connected based photovoltaic (PV) system is analyzed. The proposed model comprises of a PV plant with lead acid batteries (LABs) Energy Storage coupled to the grid by means of a three-phase inverter (VSI). The PV plant and the battery storage...
This paper presents a torque ripple control approach which can be applied to a surface permanent magnet synchronous motor in a faulty case. The fault considered is an asymmetry created by unbalance number of turns in the three phases of the motor stator winding. Proposed control strategy provides the current reference in order to decrease the motor torque ripple. This torque control has been implemented...
This article presents a method for the computerized diagnosis of entry lighting signals in a CFR1 railway station. The railway station is controlled by a Electrodynamic Centralized type 4 block-and-interlocking installation. The work presented here deals with interrupted glowing wire signals of the red light and with the inability to command the call signal. The proposed method substantially shortens...
The paper deals with the analysis using Wavelet Packet Transform (WPT) and Fast Fourier Transform (FFT) of synthetically generated signals. The signals are initially sine waves of 10 periods with linearly decreasing/increasing magnitude M. M varies according to a constant slope G. The studied absolute difference between the final and initial values of M belongs to the set {2,5, 5, 7.5 and 10}% from...
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