Cuestiones teóricas de Fundamentos de Ingeniería Eléctrica (III)

Trifásica

Magnitudes de fase

La tensión de fase es la tensión en una de las impedancias de una carga trifásica. En el caso de un generador, es la tensión de uno de los generadores monofásicos que conforman el equivalente de un generador trifásico.

La intensidad de fase es la intensidad que circula por una de las impedancias de una carga trifásica. En el caso de un generador, es la intensidad que circula por uno de los generadores monofásicos del generador trifásico equivalente.

Como se puede observar en la siguiente figura, las magnitudes de fase se definen en función del tipo de conexión de la carga o generador trifásico. No son las mismas en una configuración en estrella que en una conexión en triángulo.

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Survey on the Performance of Source Localization Algorithms

1 Department of Electrical Engineering, Universidad Carlos III de Madrid, Avda. Universidad, 30, Leganés, 28911 Madrid, Spain
2 Department of Electronic and Electrical Engineering, University of Strathclyde, 204 George Street, Glasgow G1 1XW, UK

Fresno, J.M.; Robles, G.; Martínez-Tarifa, J.M.; Stewart, B.G. Survey on the Performance of Source Localization Algorithms. Sensors 2017, 17(11), 2666.

  • 2017 Impact Factor: 2.475
  • 16/62 (Q2) in ‘Instruments & Instrumentation’
  • Journal Impact Factor Percentile: 74.59

This paper is Open Access and can be downloaded here.

http://dx.doi.org/10.3390/s17112666

http://www.mdpi.com/1424-8220/17/11/2666

Abstract— The localization of emitters using an array of sensors or antennas is a prevalent issue approached in several applications. There exist different techniques for source localization, which can be classified into multilateration, received signal strength (RSS) and proximity methods. The performance of multilateration techniques relies on measured time variables: the time of flight (ToF) of the emission from the emitter to the sensor, the time differences of arrival (TDoA) of the emission between sensors and the pseudo-time of flight (pToF) of the emission to the sensors. The multilateration algorithms presented and compared in this paper can be classified as iterative and non-iterative methods. Both standard least squares (SLS) and hyperbolic least squares (HLS) are iterative and based on the Newton–Raphson technique to solve the non-linear equation system. The metaheuristic technique particle swarm optimization (PSO) used for source localisation is also studied. This optimization technique estimates the source position as the optimum of an objective function based on HLS and is also iterative in nature. Three non-iterative algorithms, namely the hyperbolic positioning algorithms (HPA), the maximum likelihood estimator (MLE) and Bancroft algorithm, are also presented. A non-iterative combined algorithm, MLE-HLS, based on MLE and HLS, is further proposed in this paper. The performance of all algorithms is analysed and compared in terms of accuracy in the localization of the position of the emitter and in terms of computational time. The analysis is also undertaken with three different sensor layouts since the positions of the sensors affect the localization; several source positions are also evaluated to make the comparison more robust. The analysis is carried out using theoretical time differences, as well as including errors due to the effect of digital sampling of the time variables. It is shown that the most balanced algorithm, yielding better results than the other algorithms in terms of accuracy and short computational time, is the combined MLE-HLS algorithm.

Detection of Partial Discharge Sources Using UHF Sensors and Blind Signal Separation

This paper is open access and can be dowloaded here.

Boya, C.; Robles, G.; Parrado-Hernández, E.; Ruiz-Llata, M. Detection of Partial Discharge Sources Using UHF Sensors and Blind Signal Separation. Sensors 2017, 17(11), 2625.

  • 2017 Impact Factor: 2.475
  • 16/62 (Q2) in ‘Instruments & Instrumentation’
  • Journal Impact Factor Percentile: 74.59

http://dx.doi.org/10.3390/s17112625

http://www.mdpi.com/1424-8220/17/11/2625

Abstract— The measurement of the emitted electromagnetic energy in the UHF region of the spectrum allows the detection of partial discharges and, thus, the on-line monitoring of the condition of the insulation of electrical equipment. Unfortunately, determining the affected asset is difficult when there are several simultaneous insulation defects. This paper proposes the use of an independent component analysis (ICA) algorithm to separate the signals coming from different partial discharge (PD) sources. The performance of the algorithm has been tested using UHF signals generated by test objects. The results are validated by two automatic classification techniques: support vector machines and similarity with class mean. Both methods corroborate the suitability of the algorithm to separate the signals emitted by each PD source even when they are generated by the same type of insulation defect.
Keywords— blind source separation; electric insulation; partial discharges; UHF detection

Planar localization of radio-frequency or acoustic sources with two receivers

Department of Electrical Engineering. Universidad Carlos III de Madrid. Avda. Universidad, 30. 28911 Leganes. Madrid. Spain

* Author to whom correspondence should be addressed

The paper is open access and can be dowloaded here.

Fresno, J.; Robles, G.; Martínez-Tarifa, J. Planar localization of radio-frequency or acoustic sources with two receivers. In Proceedings of the 4th Int. Electron. Conf. Sens. Appl., 15–30 November 2017; ; doi:10.3390/ecsa-4-04892

Abstract— In the localization of electromagnetic or acoustic emitters, generally, when a pulse is radiated from a source, the wave will arrive to two receivers at different times. One of the advantages of measuring these time differences of arrival or TDOA is that it is not required a common clock as in other localization techniques based on the time of arrival of the pulse to the receiver. With only two sensors, all the possible points in the plane that would give the same TDOA describe a hyperbola. Using an independent third receiver and calculating the intersection of the three hyperbolas will give the position of the source. Therefore, planar localization of emitters using multilateration techniques can be solved at least with three receivers. This paper presents a method to locate sources in a plane with only two receivers reducing the number of acquisition channels and hence, the cost of the equipment. One of the receivers is in a fixed position and the other describes a circumference around the first one. The TDOA are measured at different angles completing a total turn and obtaining a periodic function, angle versus TDOA, that has all the geometric information needed to locate the source. The paper will show how to derive this function analytically with the distance from the fixed receiver to the source and a bearing angle as parameters. Then, it will be demonstrated that it is possible to fit the curve with experimental measurements to obtain the parameters of the position of the source.

Keywords— Time differences of arrival, localization techniques, radio frequency, ultra high frequency, antennas