Abstract. The apparent power and the derived power factor are two of the quantities of the biggest use and application inside the Electric Engineering. However, nowadays it continues staying the controversy on their definitions and more appropriate meaning in the most general situations in unbalance and distortion, and unequal resistances in the distribution lines. In the last years they have been distinguished two focuses concerning the functional definitions of apparent power: the European approach, more theoretical and better developed, and the American approach, more practical focus but with smaller rigor. Although from the point of view of their practical application, the use of a definition or another doesn't suppose important numeric differences, if present differ from the conceptual point of view. This is made notice in applications that suppose the use of modern equipments of static compensation. The apparent power of the European approach in its conception only permits parallel compensation, while the apparent power of the American approach admits the seriesparallel compensation. This paper introduces the definitions of apparent power of both approaches and it establishes a discussion on its application in the three-phases loads compensation.

One of the most common strategies used in the Active Power Filters (APFs) control is the derived from the instantaneous reactive power theory. Since its publication, a lot of others formulations have been developed in order to achieve compensation objectives different of the proposed in the original one. Nevertheless, all those formulations present a common characteristic: none of them can be applied to n wire systems where n>4. This paper presents a new approach which can be applied to n wire systems. The control strategy proposed in this new formulation can obtain any compensation objective. Besides, the control derived from the other formulations can be obtained by means of this new one.

Changes in the regulation of electrical systems have meant a reorganisation of the firms in the sector, subdividing them into different areas of action. Distribution firms, in addition to supplying energy, are now responsible for monitoring the "service quality" with which the product reaches the client and for communicating to the Ministry of Economics (Minister for Energy Policy and Mines) and to the corresponding Administrations information as to service quality established in the decree-law. The first of its contents refers to continuity of the service, for which measurement and control procedures have already been passed, such that we now have the first published data at community level. As regards product quality, the aforementioned Royal Decree indicates that the characteristics of the wave must be those specified in norm UNE-EN 50160, while the corresponding measurement and control procedures, for which there are already some draft versions, are still pending approval. The paper focuses on the quality of the product and aims to harmonise the steps established in some of the draft versions to delimit margins, establish measurement periods and suggest a format for the presentation and interchange of data. In collaboration with the electricity company IBERDROLA, we have begun to acquire measurements, to carry out a "precompliance" study in the province of Burgos.

Under the conditions prevalent in the late Pleistocene (small huntergatherer groups and frequent inter-group conflicts), coevolution of gene-related behavior and culturally transmitted group-level institutions provides a plausible explanation for the parochial altruistic and reciprocator traits of most modern humans. When, with the agricultural revolution, societies became larger and more complex, the collective nature of the monitoring and punishment of norm violators was no longer effective. This led to the emergence of new institutions of governance and social hierarchies. Likely, the smooth acceptance of the new institutions was possible only because, in the majority of the population, the reciprocator trait had become an internalized norm. However the new ruling class has its own dynamics which in turn may lead to new social crisis. Using a simple model, inspired on previous work by Bowles and Gintis, these effects are studied here.

Abstract. In this paper, a hybrid passive-active power filter is proposed to compensate the non-linear loads in electrical power systems. The main compensation target is to mitigate the load current harmonics. An active power filter can be used to eliminate the load current harmonics, but it is a high cost solution. The use of passive filters are a more economical solution, but the main problem is that these filters cause resonance currents in the system. In this case, two shunt passive LC filters are designed to eliminate the more significant load harmonics. An active power filter, in series with them, is used to improve the filtering characteristics. Besides, it avoids the resonance between the source impedance and the passive filter impedance. This hybrid shunt conditioner is more effective than only a shunt passive filter, and it is a cheaper solution than a shunt active power line conditioner alone. A practical case is presented to check the proposed hybrid conditioner: the compensation of a three-phase diode rectifier.