Showing papers by "V. Fernao Pires published in 2007"
12 Apr 2007
TL;DR: In this paper, Park transformation of the differential currents is used to detect magnetic inrush from an internal fault in a power transformer differential relay, which does not require a very high computational effort.
Abstract: Discrimination between an internal fault and a magnetizing inrush current has been recognized as a power transformer protection problem, since can cause malfunction of a differential relay. To overcome this problem the paper proposes a new approach for transformer differential protection. This approach is based on the Park transformation of the differential currents. Using this technique each harmonic that must be used for the protection will be converted in a dc component. So, one of the advantages of this approach is that the proposed algorithm does not require a very high computational effort. The evaluation of this technique is performed by a Matlab/Simulink-based simulator. From the obtained results it is possible to verify that the relay can correctly discriminates magnetic inrush from an internal fault.
10 citations
12 Apr 2007
TL;DR: In this article, a new algorithm for the detection of a three-phase induction motor stator fault is presented, which is based on the identification of a specified current pattern obtained from the transformation of the three phase stator currents to an equivalent two-phase system.
Abstract: In this paper a new algorithm for the detection of a three-phase induction motor stator fault is presented. Several fault detection methods are based on the analysis of the input current Park's vector. This diagnostic technique is based on the identification of a specified current pattern obtained from the transformation of the three-phase stator currents to an equivalent two-phase system. This new algorithm proposes a pattern recognition method to identify induction motor stator faults. The proposed fault diagnosis system is based on the statistic moment method, and also indicates the extension of the stator fault. Simulation and experimental results are presented in order to verify the effectiveness of the proposed method.
6 citations
01 Nov 2007
TL;DR: In this article, a single-stage flyback pfc converter is used as a power supply of a testing distance relay system and a fast and robust sliding mode controller enables also high power factor and nearly sinusoidal input current.
Abstract: In this paper, a single stage flyback pfc converter is used as a power supply of a testing distance relay system. The flyback pfc converter topology, operation and control are presented. A fast and robust sliding mode control of the input current is also presented. The sliding mode controller enables also high power factor and nearly sinusoidal input current. The dc output voltage of the converter is controlled by a proportional integral (PI) controller. Simulation and experimental results from a laboratory prototype are presented and discussed.
5 citations
12 Apr 2007
TL;DR: In this article, the authors describe the development of a battery charger system for the autonomy of lead-acid batteries assessment in real time, which is implemented an algorithm that models the dynamic behavior of the battery under different charge and discharge profiles.
Abstract: This paper describes the development of a battery charger system for the autonomy of lead-acid batteries assessment in real time. In the monitoring system it is implemented an algorithm that models the dynamic behavior of the battery under different charge and discharge profiles. This will allow evaluating in real time, the available electrical energy storage in the battery. For the implementation of the proposed monitoring system the most important parameters that influence the autonomy of the battery have been identified. These parameters are: the electrical current, the voltage, the temperature and how the batteries are used in their charges and discharges regimes (historic of the battery). It was also developed the power supply and their system control which is used to assure that the electrical charge current of the batteries stays inside of the values recommended by the manufacturer. The ac/dc power converter is based on a single-phase power factor corrector buck topology. Extensive tests were made on the system for different charge and discharge profiles. This shows the right operation of the monitoring system as well as the accuracy of the proposed model for the batteries autonomy assessment that have showed a margin of error less than 6%.
2 citations
01 Jan 2007
TL;DR: In this article, a fault detection method for a three-phase induction motorstator fault is presented, which is based on the analysis of the Park's vector of the input current.
Abstract: Inthis paperanewalgorithm forthedetection of a three-phase induction motorstator fault ispresented. Several fault detection methods arebasedontheanalysis of theinput current Park's vector. Thisdiagnostic technique is basedontheidentification ofa specified current pattern obtained fromthetransformation ofthethree-phase stator currents toan equivalent two-phase system. Thisnew algorithm proposes apattern recognition methodtoidentify induction motorstator faults. Theproposed fault diagnosis systemisbasedonthestatistic momentmethod, andalso indicates theextension ofthestator fault. Simulation and experimental results arepresented inordertoverify the effectiveness oftheproposed method.