Carlos Javier Renedo Estébanez

Three-phase adaptive frequency measurement based on Clarke's transformation

The utilization of Clarkes transformation in the estimation of power system frequency provides the classical single-phase methods with more robustness because the estimated frequency is computed using the information provided by the three-phase voltage. This approach is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, the proposed algorithm exhibits good behavior during dynamic conditions. The Clarke components of the voltage signals are then used to compute the frequency of the system following an iterative approach based on a proportional-integral-derivative controller. The inverse component of the voltage is also used in order to detect unbalanced conditions. The proposed algorithm has been put to the test with distorted three-phase voltage supplied by an arbitrary waveform programmable power supply and with different signals generated with an Alternative Transients Program-Electromagnetic Transients Program model.

EFECTO DE LA ADQUISICIÓN, CONSIDERANDO LA CAPITALIZACIÓN DE PÉRDIDAS, EN LA EFICIENCIA DE FLOTAS DE TRANSFORMADORES DE POTENCIA.

In the current context where the objective is the reduction of the world energy consumption, it has been published the Commission Regulation No 548 of 21 May 2014 on Implementing Directive 2009/125/EC of the European Parliament with regard to small, medium and large power transformers. This regulation establishes minimum performance values for each size and type of machine. The performance considered in this document corresponds to the maximum value developed for each transformer. This parameter is independent of the loading regime and helps to carry out performance comparisons in the operating point of minimal losses. On the other hand, some Transmission System Operators and Utilities consider the cost of losses when purchasing new transformers, this is known as capitalization of losses. This article has studied the effect of losses capitalization on the performance of power transformer fleets. For this objective, the losses of a large population of European power transformers have been considered. The machines analyzed are classified by the regulation as liquid immersed large power transformers. Moreover, the study takes into account machines with power higher than 100MVA. This European legislation proposes the same performance limits for any transformer exceeding this power. Keywords: Power Transformer, Maximum performance, Losses Capitalization, Load Index, No-load losses, Load losses

COGENERACION MEDIANTE RECUPERACION ENERGETICA DE CALOR DE GASES DE ESCAPE

In the world there are a large number of foundry factories that, thanks to their production processes, are great energy consumers. The factories are equipped with various types of furnaces such as gas, electric induction and the cupola furnace. The study carried out in this article focuses on the last type and particularly on those with a continuous casting output. The gases emitted to the outside by these facilities have a high energy content, since they remain at a high temperature and are therefore susceptible to being energy producers. Currently facilities tend to use this energy for heating the air blown into combustion. But even after that use, exhaust heat can be expelled at temperatures above 600oC and can, therefore, still be of further use.