• RED ACTIVA: Innovation on Isolated Neutral Distribution Grid Automation

• ICT for Energy Efficiency

• Aportaciones al Modelado del Transformador en Alta Frecuencia

• Power Quality Impact of a Small Wind Energy Conversion System Connected to the LV Grid

• A Comparison of Transformer HF Models and their Application to PQ Analysis

• Aportaciones al Modelado del Transformador en Alta Frecuencia

Electricity generation is changing as new, renewable and smaller generation facilities are created, and classic topologies have to accommodate this distributed generation. These changes lead to the creation of smart grids in which advanced generation, information and communication technologies are needed.

Information metering is important, and one of the most important grid parameters to be measured and controlled is the temperature of overhead conductors due to their relation to the maximum allowable sag of the line.

The temperature and current of an overhead conductor and the weather conditions surrounding the cable are measured every 8 min for more than a year. With these data, the accuracies of the different algorithms presented in the standards (CIGRE TB601 and IEEE 738) are studied by implementing them in MATLAB®.

The use of precise measurements of solar radiation and low wind speeds with ultrasonic anemometers, improves the accuracy of the estimated temperature compared with the real measured conductor temperature. Additionally, using dynamic algorithms instead of assuming a steady state analysis increases the accuracy. However, an equilibrium between the accuracy and mathematical complexity should be obtained depending on the specific needs.

Together with the impurities, the thermal fluxes are one of the major sources of uncertainty during the realization of the International Temperature Scale of 1990 (ITS-90) defining fixed points. The use of computational fluid dynamics (CFD) is a valuable tool to develop models that describe the time evolution of the phase transformation (essentially the evolution of the solid–liquid interface) as a function of given theoretical assumptions and given parameters (furnace thermal gradients, freezing initiation, ambient temperature and insulation). The models can be validated by observing the impact of the selected parameters on the observed corresponding melting curves and used to achieve a full understanding of these thermal effects and their impact on uncertainty. This paper proposes an ITS-90 metallic fixed points CFD model together with some results about the influence of the furnace thermal gradients and the freezing initiation techniques.

This paper presents the steady and dynamic thermal balances of an overhead power line proposed by CIGRE (Technical Brochure 601, 2014) and IEEE (Std.738, 2012) standards. The estimated temperatures calculated by the standards are compared with the averaged conductor temperature obtained every 8 min during a year. The conductor is a LA 280 Hawk type, used in a 132-kV overhead line. The steady and dynamic state comparison shows that the number of cases with deviations to conductor temperatures higher than 5ºC decreases from around 20% to 15% when the dynamic analysis is used. As some of the most critical variables are magnitude and direction of the wind speed, ambient temperature and solar radiation, their influence on the conductor temperature is studied. Both standards give similar results with slight differences due to the different way to calculate the solar radiation and convection. Considering the wind, both standards provide better results for the estimated conductor temperature as the wind speed increases and the angle with the line is closer to 90º. In addition, if the theoretical radiation is replaced by that measured with the pyranometer, the number of samples with deviations higher than 5ºC is reduced from around 15% to 5%.

The transformers lifespan depends importantly on its refrigeration. Mineral oils perform this work in the majority of the power transformers. However, this type of coolant has two main drawbacks: low biodegradability and low ignition point. Several alternative liquids are being developed in order to overcome these drawbacks. This paper compares their thermal-fluid behavior with a mineral oil by means of several parameters, such as temperature, flow rate, fluids velocity, convective heat transfer coefficient (h) and the cooling criterion (P). These are calculated using the numerical results of the simulation of a 3D-model of a Low Voltage Winding that belongs to a power transformer with ONAN cooling. The software COMSOL Multiphysics has allowed the simulation of the geometry using a physical model in which buoyancies and viscous forces are the only considered establishing the natural convection. As a result of the comparison, it is clear that the mineral oil is the best coolant liquid. Among the alternative liquids, silicone oil would be the second best coolant fluid, followed by the synthetic and natural esters, respectively. On the other hand, it seems to be clear that the 3D simulations can be used to compare properly the cooling capacities of the liquids.

The paper discusses the effect of two-front melting on the liquidus temperature of the eutectic Pt–C and the eutectic temperature of the system in its pure state. This influence factor has not been considered thus far in the uncertainty budget associated with the assignment of thermodynamic temperatures to the eutectics Co–C (1597.15 K), Pt–C (2011.05 K), and Re–C (2747.35 K), selected in the European Metrology Research Programme project Implementing the New Kelvin. For Pt–C, simulation of the effect of two-front melting on the melting process has been done before in a 1D analytical model, and this formed the starting point to the present study. In this study the melting process is analyzed by means of a 2D axisymmetrical finite-volume model. In the model, freezing and melting are considered for an impure ingot and for a pure ingot. As to the impure ingot, the impurity concentrations are the concentrations met in current practice of the realization of the high-temperature reference fixed point, but formulated in terms of an effective concentration and associated effective distribution coefficient k<1k<1 , related to a Scheil fit to the melting curve at given melting conditions as measured for the eutectic Pt–C. Heat injection rates for melting varied from 15 000 Wm^(−2) down to 3000 Wm^(−2). In any case for the impure system, two melting fronts are showing up. For the pure system, only one melting front is generated, traveling from the outside of the ingot toward its inside.

This study forms part of the European Metrology Research Programme project implementing the New Kelvin to assign thermodynamic temperatures to a selected set of high-temperature fixed points (HTFPs), Cu, Co–C, Pt–C, and Re–C. A realistic thermal model of these HTFPs, developed in finite volume software ANSYS FLUENT, was constructed to quantify the uncertainty associated with the temperature drop across the back wall of the cell. In addition, the widely applied software package, STEEP3 was used to investigate the influence of cell emissivity. The temperature drop, ΔTΔT , relates to the temperature difference due to the net loss of heat from the aperture of the cavity between the back wall of the cavity, viewed by the thermometer, defining the radiance temperature, and the solid–liquid interface of the alloy, defining the transition temperature of the HTFP. The actual value of ΔTΔT can be used either as a correction (with associated uncertainty) to thermodynamic temperature evaluations of HTFPs, or as an uncertainty contribution to the overall estimated uncertainty. In addition, the effect of a range of furnace temperature profiles on the temperature drop was calculated and found to be negligible for Cu, Co–C, and Pt–C and small only for Re–C. The effective isothermal emissivity (εeff)(εeff) is calculated over the wavelength range from 450 nm to 850 nm for different assumed values of surface emissivity. Even when furnace temperature profiles are taken into account, the estimated emissivities change only slightly from the effective isothermal emissivity of the bare cell. These emissivity calculations are used to estimate the uncertainty in the temperature assignment due to the uncertainty in the emissivity of the blackbody.

This paper presents a comparative study of the electricity consumption (EC) in an urban low-voltage substation before and during the economic crisis (2008–2013). This low-voltage substation supplies electric power to near 400 users. The EC was measured for an 11-year period (2002–2012) with a sampling time of 1 minute. The study described in the paper consists of detecting the changes produced in the load curves of this substation along the time due to changes in the behaviour of consumers. The EC was compared using representative curves per time period (precrisis and crisis). These representative curves were obtained after a computational process, which was based on a search for days with similar curves to the curve of a determined (base) date. This similitude was assessed by the proximity on the calendar, day of the week, daylight time, and outdoor temperature. The last selection parameter was the error between the nearest neighbour curves and the base date curve. The obtained representative curves were linearized to determine changes in their structure (maximum and minimum consumption values, duration of the daily time slot, etc.). The results primarily indicate an increase in the EC in the night slot during the summer months in the crisis period.

When characterizing high-temperature fixed points, the fraction of the melting time of the regular part of the plateau with respect to the total melting time, is critical. Maximizing the melting duration minimizes the uncertainty associated with the determination of the fixed-point temperature. One factor that affects this quality is the effect of the thermal bridging between the external and internal surfaces of the ingot enclosed by the cell. This paper presents the results of simulations for the eutectic Pt-C, investigating the effects of different ingot shapes on the duration of the melt plateau. It was found that the formation of a thermal bridge from the rear of the blackbody cavity toward the outer surface of the ingot was critical and that its formation could be delayed or suppressed through a proper choice of the ingot shape. The shapes considered included, firstly, the shape of the rear of the cavity, in contact with the ingot, either cone-shaped or dome-shaped, and secondly, the inside rear surface of the cell, in contact with the ingot, being a cone, a convex dome, or flat. The presence of impurities in the alloy was taken into consideration, and its influence in the evolution of the liquid–solid interface compared with that for the pure alloy. The effect of changing the thermal isolation of the cell, at its front side, was also considered. A dome-shaped surface for the rear of the cavity was found to be more favorable for the development of a regular melting front, in conjunction with the segregation of impurities during melting. At the rear of the cell, a flat surface ensures the back wall is the last to experience thermal bridging, resulting in more extended melting plateaus.

This paper reports thermal modelling that aims to establish if the measurement method – either by a radiation thermometer or by a thermocouple – significantly influences the measured temperature of the high temperature fixed points Co-C, Pd-C and Ru-C. It is clear that both measurement techniques have specific physical characteristics which may affect the temperature measured during the melting plateau. With the radiation thermometer, the radiation heat transfer is directly influenced by the environment because the back-wall is effectively viewing the cold outside environment. In the case of a thermocouple direct viewing of the outside world is blocked so radiation transport is significantly reduced; however, in the case of the thermocouple there is a different component of heat transfer, namely conduction from the thermowell walls in contact with the thermocouple along the thermocouple stem itself.

We explore the evolution of the Spanish power system vulnerability over the next two decades and its dependency on fossil fuel prices and CO2 allowances costs. Also, the influence of different generation technologies (clean coal, nuclear and solar technologies) on this vulnerability has been considered. The diversity of primary energy resources has been evaluated to carry out the above analysis by means of two indexes: the Shannon index (H) and an adapted biodiversity index (Δ). These indexes have been applied to the power results of the period 2013–2032 that are obtained from a stochastic linear model of the Spanish generating system. As a main conclusion, the vulnerability calculated with Δ is bigger than that deduced from H and showing a negative trend throughout the period. In order to reverse this tendency, the future Spanish generating system should be composed of all the available technologies, considering all the primary energy resources.

The increasing use of small wind energy has made it necessary to develop new methods to improve the efficiency of this technology. This improvement is best achieved considering the interaction between the various components, such as the wind rotors, the electrical generators, the rectifiers and the inverters, as opposed to studying the individual components in isolation. This paper describes a methodology to increase the efficiency of Small Wind Turbines (SWTs) equipped with a Permanent Magnet Synchronous Machine (PMSM). To achieve this objective, capacitor banks will be connected between the PMSM and the rectifier. This methodology is motivated by two clear aims. The first one is to operate the SWT with its maximum power coefficient Cp. The second one is to select the most suitable capacitor bank for each wind speed to optimise the energy supplied to the grid. The methodology will be tested on a commercial 3.5 kW SWT, and the results will be studied to determine its feasibility.

The implementation of batch processing has increased due to its intrinsic flexibility and adaptability. These are essential characteristics when it comes to producing high-value added materials such as agrochemicals, pharmaceuticals, specialty chemicals…the demand for which has grown in recent decades.

Although industrial processes are highly diverse, a common feature to all is that they utilize fossil fuels as the energy source. The reliance on fossil fuels as a primary source of energy generates a negative impact on the environment. The implantation of renewable energies and efficient usage of energy has thus become crucial. Improving energy use could be achieved through advancements in plant machinery and the use of methodologies such as ‘process integration’.

Process integration can be described as system oriented methods that could be used during the design and retrofit of industrial processes in order to obtain an optimal utilization of resources. The methods have traditionally focused on an efficient energy use, although recently process integration techniques cover other areas such as efficient use of raw materials, emission reduction and process operations. Energy integration tries to reach the optimization of heat, power, fuel and utilities.
The consideration of energy integration complicates the process design and the generation of batch process design alternatives, so what is now required is the proposal and development of different approaches and methods oriented towards recovering energy in this kind of industrial process. Improving energy end-use efficiency will make it possible to reduce dependence on energy imports and bring about innovation and competitiveness.

The aim of this work is report the main contributions that have been carried out in order to attain energy integration in batch processes, as well as different examples of applications that have shown the possibilities offered by the developed tools.

This paper takes us a step forward with respect to previous definitions for the measurement of electric power quantities under non-sinusoidal conditions.A new decomposition of voltage, current and power is presented in order to determine the extent to which the distribution company and the electrical energy consumer are each responsible for the harmonic distortion measured at the point of common coupling, PCC.This gives us three different quantities: fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with consumer distortion. These magnitudes can also be measured in relation to power factor compensation and harmonic elimination problems in power distribution systems.In addition to this, the power factors resulting from the new decomposition are also analyzed and the decomposition algorithm implemented on a measurement platform based on a digital signal processor, DSP.Finally, the general structure of the system, focusing on both hardware and software, is also discussed.

The utilization of LED technology in lighting applications has been increasing during the last several years. Parameters like efficiency, reliability, chromatic response and cost are important to consider this technology as a competitive one. LED technology involves power converters so overall Power Quality performance has to be analyzed in terms of emission and susceptibility. This paper reviews the Power Quality behavior of some commercial grade LED lamps and establishes a comparison with the long established incandescent lamp.

This article is the result of an analysis into the behavior of several forest species that could be used as energy crops in Cantabria. The species studied belong to several botanical genera. The study was conducted in several stages: firstly, the species was introduced to explore growth data and discard those species of slower growth. Once the genus maximising the biomass production was determined, several species of it were studied from the energy perspective. This combination of both allows the energy density for each species to be obtained, therefore making it possible to determine how big a cultivation area is required for a specific thermal power plant. Thus, for a power plant of 10 MWe, between 15,451 and 24,578 ha of Eucalyptus would be necessary, depending on the species chosen, at an approximate age of 4 years.

The eutectics Co–C, Pt–C, and Re–C, with phase transition temperatures of 1597 K, 2011 K, and 2747 K, respectively, are presently investigated for their suitability to serve as reference points for dissemination of T (and T90) within the context of the “Mise en pratique of the definition of the Kelvin” (MeP-K) at high temperature. Temperatures are to be measured by means of radiation thermometry of cavity radiators embedded in the associated eutectic. This paper deals with the determination of the cavity spectral effective emissivities, which are influenced by the reflective properties of the graphite constituting the cavity on the one hand, and by the temperature distribution within the cavity and over the radiation-shield structure in front of the cavity, on the other. We have begun a comprehensive effort to determine the cavity effective spectral emissivities at 405 nm and 650 nm. The overall program involves diverse measurements on representative graphite samples, furnace-temperature profile measurements, calculations of temperature distributions, and, finally, based upon this information, calculation of effective emissivity dependencies for cavity radiators. Here we report the current status of the study, including cavity temperature distributions and Monte Carlo modeling results, associated with appropriate steps of the envisaged overall project. For the time being, the modeling assumes current estimates of the graphite emissivity and the bi-directional reflectance distribution function (BRDF), which will be updated as experimental data become available.

This article shows that lamp aging has a significant correlation with flicker generation. In this research work, a test system and a methodology able to measure optical fluctuation produced by different types of lamps and ballast are presented. This experimental platform provides a correlation between voltage flicker levels and optical flicker perception. This platform can be considered as a first step in the definition of new lamp models. The limits of the severity of flicker caused by voltage fluctuations are defined in Europe by the standard CENELEC EN 50160.

The evolution of the vulnerability of the Spanish power generation system with respect to the primary energy resources hasbeen assessed by three new indexes developed from biodiversity analysis. The first of these indexes measures, in percentage, the uniformity of the primary energy resources in the system. The second one quantifies the diversity by means of the equivalent number of primary energy resources that are present in similar proportions in the system. The third one allows the calculation of the diversity reduction in the system with the non-evenness of these primary energy resources. They have been applied to the energy results of a stochastic linear model, developed with
the software GAMS, in order to demonstrate their usefulness. In this model several generation technologies have been considered (nuclear, clean coal technologies, etc), and also several scenarios
of fossil fuel costs. The number of primary energy resources that have to be used depends on the degree of uniformity of the system and on their influence on diversity. In the Spanish case, if nuclear generation is not considered as an energy source, the diversity of the system will diminish significantly in the future, making the system more vulnerable.

High-temperature fixed points (HTFPs) based on eutectic and peritectic reactions of metals and carbon are likely to become, in the near term, reference standards at high temperatures. Typically for radiation thermometry applications, these HTFPs are generally formed of a graphite crucible, with a reentrant well, an included 120° cone, and a nominal aperture of 3 mm. It is important to quantify the temperature drop at the back wall of the cavity, and to understand the influence of the crucible configuration and furnace conditions on this drop. In order to study these influences, three different situations have been modeled by means of the finite volume method for numerical analysis. The first investigates the influence of the furnace temperature profile on the temperature drop by simulating four different furnace conditions. The other two study variations in the crucible configuration, namely, the thickness of the graphite back wall and the length of the blackbody tube.

En el mundo existe un número importante de factorías de fundición que, por su proceso productivo, son grandes consumidoras de energía. Las factorías trabajan con diversos tipos de hornos como son los de gas, de inducción eléctrica, y de cubilote. El estudio de este artículo se centra en los de cubilote y más concretamente en aquellos que tienen una producción de colada continua. Los gases que estas instalaciones emiten al exterior tienen un gran contenido energético, ya que se encuentran a alta temperatura y por lo tanto son susceptibles de aprovechar energéticamente. Actualmente las instalaciones suelen tener un aprovechamiento energético para el calentamiento del aire soplado a la combustión. Pero incluso después de este aprovechamiento térmico los gases de escape se pueden expulsar a temperaturas superiores a 600ºC y por lo tanto aún son susceptibles de aprovechar energéticamente. La recuperación de calor de estos gases se puede destinar a producir electricidad, siendo ésta una alternativa que conduce a: incrementar la eficiencia del proceso, disminuir las emisiones de contaminantes gaseosos (la generación eléctrica no emite nada que no se emitiera anteriormente), y reducir los costes de operación de la planta.
En este trabajo se han analizado dos alternativas de aprovechamiento energético del calor residual de estos gases mediante cogeneración. La primera consiste el empleo de módulos prefabricados, y la segunda en una instalación clásica de cogeneración con caldera de recuperación y turbina de vapor. Para cada alternativa se han realizado dos análisis: uno económico (considerando inversión, ingresos por electricidad y los costes de operación) y otro técnico (considerando la viabilidad técnica de su instalación, presentando ventajas y desventajas de cada una de las alternativas). Esto nos ha permitido establecer una serie de conclusiones generales que se aportan al final del artículo.

This paper presents the influence of a nuclear generation option on CO2 emissions and on the cost of the Spanish long-term generation system by means of the development of a stochastic linear model, based on the software GAMS, where multiple aspects have been contemplated: the uncertainty regards fossil fuel and CO2 emission allowance prices by analysing different scenarios, the stability and supply security of the system by considering different restrictions, the maximum grade of penetration of the different technologies by means of commissioning plans, etc. Only two of the conclusions drawn are focused on here. First, it is possible to get a clean system without nuclear power generation but the cost would be higher than in the case where the existing nuclear power plants continue to operate. Second, the development of clean coal technologies could be affected negatively by the development of nuclear generation.

This paper investigates, through thermal modeling the effect on the radiance temperature of imperfectly filled thermometric fixed points. A two dimensional axisymmetric thermal model was established and the effect on the radiance temperature of various ingot imperfections such as voids and cracks in different places and of different dimensions in the ingot structure was calculated. It was found that the radiance temperature of the fixed point is quite tolerant to even relatively large flaws in the ingot structure. Only when flaws of significant dimensions near the radiating back wall were introduced was the overall radiance temperature significantly affected.

Quality assessment during DC motor manufacturing should involve quality controls designed to detect various fault conditions associated with the components included in the machine.

Some defects, however, can be produced by the automatic manufacturing process during the assembly of the individual components. Inter-turn short-circuits, turn to earth short-circuits and open winding, among other fault conditions, can result from the field poles manufacturing and insertion inside the stator. The main problem with these kinds of faults is that though the motor is likely to be operational, there is a high probability of motor breakdown in the near future.

In this paper, the above fault conditions are analyzed and a thermal model and an infrared monitoring test method for manufacturing quality control is proposed.

En los últimos años, el diseño de máquinas eléctricas se ha ido apoyando, cada vez más, en herramientas informáticas de pre-dimensionamiento, diseño y simulación, en los ámbitos eléctrico, magnético y térmico.

In this paper we evaluate ΔT, the temperature drop across the cavity’s backwall, and its standard uncertainty u(ΔT) for the high-temperature eutectic fixed points Co-C, Pt-C and Re-C with eutectic temperatures TE of 1597 K, 2011 K and 2747 K, respectively; the evaluation involves a variety of cavity-furnace geometries. For the derivation of u(ΔT) the partial uncertainties in ΔT associated with the uncertainties in the thermal conductivity Kg of graphite, in the cavity-wall emissivity Eg and in the furnace-temperature profile ahead of the cavity are evaluated and quantified. ΔT is shown to vary with TE4 for a given cell-furnace configuration, with typical values of 12 mK, 25 mK and 92 mK at the Co-C, Pt-C and Re-C fixed-point temperatures, respectively. For the uncertainty in the temperature drop we find globally u(ΔT) ≈ 0.1·ΔT.

This paper presents a step forward respect to the previous definitions for the measurement of electric power quantities under non-sinusoidal conditions. A new decomposition of voltage, current and power is presented in order to determine the responsibility of the distribution company and the electrical energy consumer for the harmonic distortion measured at the point of common coupling, PCC. This way, three types of variables should be managed, namely fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with the consumer distortion. These magnitudes can be also measured in relation to power factor compensation and harmonic elimination problems in power distribution systems. Moreover, the power factors resulting from the new decomposition are also analyzed. The algorithm of the decomposition will be implemented on a measurement platform based on a digital signal processor, DSP. The general structure of the system, hardware and software, are also discussed.

Quality assessment during dc motor manufacturing should be accomplished by quality controls in order to detect the different fault conditions associated to the components included in the machine. However, some defects can be produced by the automatic manufacturing process during the assembly of the individual components. Among others, inter-turns short-circuit, turn to earth short-circuit and open-winding can result from the rotor insertion inside the stator. The main problem with these kind of faults is that the motor can operate but there is a high probability of motor breakdown in the near future.

Energy recovery in the industry is one of the most important parameters with which the companies have to play to be competitive and respectful with the environment, because it helps to improve the energy efficiency. In that way, the use of energy recovery systems plays an important role. This gets a special relevance in batch Processes, where the needs of heating and cooling are not produced at the same time. Therefore, the study and optimization of heat recovery systems with thermal storages can play an essential part.
In this paper, it is analyzed the heat recovery system made by a heat exchange network and thermal storages which will optimize the heat recovery in batch industrial processes.

In this work, the waste from 10 forest species of Cantabria have been characterized from the point of view of energy. The studied species were the waste of: Eucalyptus globulus, Eucalyptus nitens, the hybrid E. globulus × E. nitens, Eucalyptus viminalis, Eucalyptus smithii, Eucalyptus regnans, Eucalyptus gunni, Fagus sylvatica, Quercus robur and Pinus radiata. The leaves were the tree part with the greatest NCV (net calorific value) in all the species. The best results were obtained for the leaves of E. smithii (24.5 MJ/kg), F. sylvatica (22.8 MJ/kg) and E. nitens (22.5 MJ/kg), at minimum moisture. Values around 65,000 MJ per hectare and year were obtained for the Eucalyptus spp., and 47,000 MJ per hectare and year for the P. radiata. The economic-environmental analysis revealed that the use of the forest waste for energy production would mean an approximate annual income of 8 M€ and would fix the annual CO2 emitted by the Cantabrian industries at 78%.

In this article, a new design for reversible air–air heat pumps is proposed. This design is not based on the refrigerant changeover, as is proposed by ASHRAE, but rather is based on the inversion of the air flow on the ducts. Thanks to this modification it is possible to use any air–air refrigeration machine for air conditioning as a reversible heat pump.

The new design is more efficient, especially when the building requires greater air quality and therefore a larger amount of outdoor air. It also increases its efficiency as the outdoor temperatures become more extreme.

This improvement will make it possible to use heat pumps, with acceptable performances, in more rigorous climates than those in which they are used today.

Is it advisable to replace ferraris based meters with electronic meters? The permanence of the electromechanical meters currently in use is often justified on the grounds of their long working life and low price. However, it is well known that they are highly sensitive to external conditions and that many factors can lead to miscalibration. This work attempts to clarify some key points in order to answer the previous question. It reviews the operating principles of energy meters. The behavior of watt-hour meters under nonsinusoidal conditions is also studied. The disturbances considered were harmonics, unbalance and main frequency variations.

This work studied the potential use of the waste from Eucalyptus globulus and Eucalyptus nitens as energy crops, evaluating young and adult stages of both in all four seasons of the year with different moisture contents. The study was carried out made in Cantabria (North coast of Spain), located at latitude 43°28′N, and longitude 3°48′W. In this region, 29,513 ha are dedicated to the growth of Eucalyptus, with about 80% E. globulus, and 20% E. nitens. Six different plantations have been analyzed and their bioclimatic diagrams determined. After the collection of samples the potential energy of every sample was obtained, they were weighed, analyzed and burned, giving a mean net calorific value of 17,384 and 17,927 kJ/kg in the adult stage of E. globulus and E. nitens, respectively. The results for the young stage of both species were 17,708 and 18,670 kJ/kg. Moisture content in the samples has a great influence on power production. Finally, the economic and environmental consequences of these crop species for the region of Cantabria were analyzed.

The optimum energy consumption in an air conditioning system depends on many factors. Some of these are the following: the use of high performance devices, the utilization of these in the optimum efficiency range, a correct control strategy, a proper maintenance, etc.

In air conditioning facilities most of the energy consumption corresponds to the thermal production, this being heat and cold. This thermal supply is commonly accomplished with boilers, chillers and heat pumps.

In this article the efficiency of the reversible water–water heat pumps is analyzed, proposing a design that optimizes these elements. This improvement hardly requires modifications at manufacturing and operation levels, and it also contributes towards optimizing the energy consumption of these machines.

The utilization of Clarke’s transformation in the estimation of power system frequency provides the classical singlephase methods with more robustness because the estimated frequency is computed using the information provided by the threephase 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.

In the present article, the authors analyze different possibilities for providing heating, air conditioning and hot tap water to a hospital center. For this, several cogeneration systems with diesel engines and gas turbines were considered. From the study of the results, it is observed that the size of the facility and the control strategy have a strong influence on the system economy, showing that the most important parameter is the electricity produced. So, the solutions with diesel engines are more efficient than the equivalent ones with gas turbines, since they have a higher electrical performance.

The total harmonic distortion (THD) ratio is a wellknown parameter that characterizes the distortion degree at a specific point of the grid. In this paper, a decomposition of the THD will be presented in order to determine the responsibility of the distribution company and the electrical energy consumer for the harmonic distortion measured at the point of common coupling (PCC). For this study, the power quantities proposed in the new Standard IEEE 1459–2000 and developed by L. Czarnecki were considered. The algorithm of the decomposition will be implemented on a measurement platform based on a digital signal processor (DSP). The general structure of the system—hardware and software—are also discussed. Finally, the apparent powers, defined by both L. Czarnecki and the IEEE Standard, are also compared for single-phase and threephase systems.

CIGRE TB601 guide for thermal rating calculations recommends the use of ultrasonic anemometers over mechanical devices. This paper aims to compare the mechanical and ultrasonic wind speed measurement technologies for the purpose of dynamic ampacity rating. The comparison consists of applying the measurements of both anemometers (placed in the same spot) to the computation of ampacity in the same overhead line, and evaluating the diferences at different speed ranges.

In the last 20 years, installed wind power capacity in North of Spain has grown from 24 to more than 1,650 MW. In this geographical region, wind energy farms are located in places that are far away from the transmission networks so they have to be integrated into distribution networks. Build new overhead lines dedicated for a distribution energy is not the best way to increase the evacuation energy of the wind farms because the cost is quite strong. So, the aim to solve these issues, is by means of an increase in the capacity of existing lines using the dynamic management of the network. This paper is devoted to show the difference of the conductor temperature between the parameter of solar radiation measured by a pyranometer and the use of the theoretical solar radiation which is explained in CIGRE TB601 [1] and IEEE Std. 738-2012 [2] algorithms.

The grid integration of renewable energy supposes an important problem to deal with for Distributor System Operators (DSO). Distributor and transmission system operators have been using static rates for a long time to manage electric systems. Currently operators deal with one, annual, static rate or four, seasonal, static rates. This paper is devoted to the analysis of a real case of ampacity management in a 132 kV overhead line for the purpose of stablishing new static rates based on different temporal intervals.

The grid integration of renewable energy, and particularly in Spain, supposes an important problem to deal with for Distributor System Operators (DSO). Most of the times Wind Energy Farms are located in places that are far away from the transmission networks so they have to be integrated into distribution networks that are frequently next to their static rate. Current regulations make almost impossible to build new overhead lines so the increase of the capacity of the existing lines is a new target for the DSO. One of the developed options to solve this issue is the dynamic management of the network. This paper is devoted to the analysis of a real case of ampacity management in a 132 kV overhead line placed in a high-wind generation area. The obtained results show that this approach can increase the lines capacity in a significant percentage.

This paper describes a preliminary experience with the installation and use of a no-gap power quality meter network along a distribution grid in the North of Spain. No-gap power quality meters record all cycles of voltage and current waveform for all the monitored channels. This approach extends the analysis further than the classical approach provided by other power quality meters that records only survey data and events triggered according predefined rules. A comparison with the classical approach is discussed and the results of a two year power quality survey are also provided.

Ampacity techniques have been used by Distributor System Operators (DSO) and Transport System Operators (TSO) in order to increase the static rate of transport and distribution infrastructures, especially those who are used for the grid integration of renewable energy. One of the main drawbacks of this technique is related with the fact that DSO and TSO need to do some planning tasks in advance. In order to perform a previous planning it is compulsory to forecast the weather conditions in the short-time. This paper analyses the application of the neural network to the estimation of the ampacity in order to increase the amount of power produced by wind farms that can
be integrated into the grid.

Ampacity techniques have been used by Distributor System Operators (DSO) and Transport System Operators (TSO) in order to increase the static rate of transport and distribution infrastructures, especially those who are used for the grid integration of renewable energy. One of the main drawbacks of this technique is related with the fact that DSO and TSO need to do some planning tasks in advance. In order to perform a previous planning it is compulsory to forecast the weather
conditions in the short-time. This paper analyses the application of the neural network to the estimation of the ampacity in order to increase the amount of power produced by wind farms that can be integrated into the grid.

This paper is devoted to the development of a methodology suitable to be used to determine the impact of the grid integration of wind farms in distribution networks that are also supplied with other classical generation facilities based on thermal and hydraulic energy. The methodology is based on an automated analysis system that varies the level of the electric generation for both the hidraulic and thermal generators by using PSS, Phyton and Matlab. The user can define multiple scenarios considering wind, thermal and hydraulic generators so the line capacity can be computed and compared in order to know where the system bottleneck is located and which situations occur. All the results computed can be analysed in a single or compared way by using tables and plots and considering the static rate of the distribution lines. The developed system can also be applied to the computation of the sensitivity of the power flow to the variation of the parameters that define the power system.

The grid integration of renewable energy, particularly in Spain, supposes an important problem to deal with for Distributor System Operators (DSO). Most of the times Wind Energy Farms are located in places that are far away from the transmission networks so they have to be integrated into distribution networks that are frequently operating close to their static rate. Current regulations make almost impossible to build new overhead lines so the increase of the capacity of the existing lines is a new target for the DSO. This paper is devoted to the analysis of a new methodology and monitoring system that have been developed to overcome the existing static rates by moving the operation point of the overhead lines close to their dynamic rate. This new rate is computed by using both the IEEE and CIGRÉ algorithms and a local weather forecast. The obtained results show that this approach can increase the capacity of the lines in a significant percentage.

This research work is devoted to the study of the Power Quality (PQ) impact of small wind energy conversion systems (SWECS) connected to the low voltage grid. A common coupling point (CCP) has been monitored using a PQ meter that fulfils the standard IEC 61000-4-30 class A. The PQ survey has been conducted with and without the SWECS and the results were compared with the limits defined by the standard EN 50160.

Power quality disturbances like voltage sags and harmonics are an important cause of many ill effects and economic losses in industrial productive processes. Among others problems, production down times, equipment malfunctions and/or destruction of devices and even quality defects in final products can be originated by voltage dips. Power quality surveys and electromechanical device testing are previous steps for achieving an effective mitigation solution. This paper discusses a power quality survey conducted in an automotive company. In addition, a portable test platform for evaluating voltage dip immunity of industrial robots and components is presented. The results obtained from this survey and the immunity test may be useful for improving the power quality of this type of installation [3,4,6].

The decomposition of voltage, current and power is presented in order to determine the responsibility of the distribution company and the electrical energy consumer for the harmonic distortion measured at the point of common coupling, PCC. This way, three types of variables should be managed, namely fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with the consumer distortion. These magnitudes can be also measured in relation to power factor compensation and harmonic elimination problems in power distribution systems. Moreover, the power factors resulting from the new decomposition are also analyzed. The algorithm of the decomposition will be implemented on a measurement platform based on a digital signal processor, DSP.

Wave energy conversion can be done by using several technologies and oscillating bodies constitute an important class of wave energy converters, especially for offshore deployment. This research work focuses on the development of a Matlab toolbox able to analyze the performance of this class of converters considering specific wave conditions

This research work is devoted to the comparison of some proposed high-frequency (HF) models of transformers and their application to power quality (PQ) studies. The models are classified according their structure, physical description and experimental methodology and set-up facilities needed to obtain the parameters.

Thermal solar energy offers a huge opportunity to reduce fuel dependency and environmental impact created by fossil fuel consumption. One of the main disadvantages of this renewable energy is its intermittence which decreases thermal solar power plants performance. In order to reduce cost electricity is necessary to create thermal solar plants which include thermal storage. There are different options of thermal storage: sensible, latent and chemical heat. It has been demonstrated that latent heat could store large amount of energy per unit mass. Moreover, latent heat storage could store fusion heat at a constant temperature which is the phase transition temperature of the phase change materials (PCM). However, these materials have a critical limitation that needs to be resolved in order to reduce operation cost of solar plants. This limitation is their low heat conductivity. This paper gathers the main solutions that are being analyzed in order to increase the possibilities to use PCMs in a high temperature thermal storage that is essential to develop optimum thermal solar power plants.

This research work is devoted to the development of a set-up facility for testing Permanet-Magnet Synchronous-Machines (PMSM) used in small wind energy generators. The developed test system can be used not only for PMSM parameters characterization but also for the study of the performance of the power electronic associated to the electrical machine.

This paper develops the comparison of two cogeneration systems that are suitable to perform heat energy recovery of the smoke produced by a casting process.

The paper analyzes the propagation of voltage sags through the distribution network of an industrial company. For this, power quality is monitoring in high voltage, 44kV, and low voltage, 400V. The theory of M. Bollen is used for the study of the sags recorded by the meters at different points of the installation. It is necessary to know the connection of transformers in order to determine the transmission of the sags.

This research work is devoted to the critical evaluation of the role of the dc-bus in the behavior of threephase adjustable-speed drives with voltage sags. In particular, the dc-link voltage variation under voltage sag and its dependence on bus capacity, dc-link resistance and inductance and source impedance. The analysis can be used to introduce additional capacitance in the dc-link in order to increase the ride-through capability of the ASD. Both an electromagnetic transient model and a set-up facility have been introduced. This test platform can be used in order to study the sensitivity of ASD to different disturbances.

This research work introduces the architecture of a low-cost advanced metering infrastructure (AMI) named DANCA with the ability to record up to six different current channels with the same voltage. This watt-hour meter can send the recorded power and energy data in real-time to a web server using both an ethernet wired and an IEEE 802.11b WiFi wireless connection. The server stores the data measured by the meters and can elaborate reports with useful data for the users. The clients can access the data in real-time using a web browser. From a instrumentation point of view the developed system can measure the power and energy consumption of clusters of loads in residential and small industrial applications. From the point of view of the connectivity the system can communicate with the server using the domestic internet access point. The amount of data to be transmitted is very low so the impact of the system in the network bandwidth can be considered negligible.

A stochastic linear model have been developed to analyze the Generation Expansion Planning in 2013-2032, through the programming language specific to the application GAMS. In this model the nuclear technology has been considered as generation option in several scenarios of costs of the fossil fuels. Also, two of clean coal technologies have been taken into account. The evolution of supply security has been assessed by means the determination of the vulnerability and degree of independence of the generator system with respect to primary energy sources. On the other hand, the determination of the reserve margin and the percentage of the capacity with regulation capability have allowed to analyze the evolution of its reliability. Lastly, the generation mix of smaller total cost and with less emissions of CO2 has also been determined. The final conclusion would be that a generator system should have the biggest possible number of types of generation.

This paper analyzes the energy potential which waste from the forestry eucalyptus globulus in Cantabria, with particular reference to their potential for direct combustion in power plants. This has made a software in which introducing the values for the various parameters that affect combustion, provides results in flame temperature and electrical performance.

The supply security of the primary energy sources (coal, natural gas, enriched uranium…) and the reliability of the system in terms of the oscillations of the frequency and voltage are two aspects to assess in the Generation Expansion Planning. In this article, for the first criterion, the evolution of vulnerability and degree of independence of the generator system with respect to primary energy sources has been assessed by the indexes of Shannon-Weiner and energy independence, espectively. For the second approach, the evolution of the reserve margin by means the coverage index and the progression of the inertia and regulation capacity by means of its percentage regarding the total installed capacity. These four indexes have been applied on the obtained results of a stochastic lineal model developed with the software GAMS. In this model the nuclear technology has been considered as generation option in several scenarios of costs of the fossil fuels, coal and natural gas. Also, two of clean coal technologies with greater possibility of putting into service have been taken into account. The final conclusion would be that each technology carries out several functions in the generator system but not all them. That is, a generator system should have the greatest possible number of types of generation to be reliable and have supply security.

Quality assessment during dc motor manufacturing should be accomplished by quality controls in order to detect the different fault conditions associated to the components included in the machine. However, some defects can be produced by the automatic manufacturing process during the assembly of the individual components. Among others, inter-turns short-circuit, turn to earth short-circuit and open-winding can result from the rotor insertion inside the stator. The main problem with these kind of faults is that the motor can operate but there is a high probability of motor breakdown in the near future. In this work, the above fault conditions are analyzed and an electromagnetic field and thermal monitoring method is proposed

In the last decade, the emergence of leaf disease caused by the fungus Mycosphaerella sp. is jeopardizing the development of some species of the genus Eucalyptus at its juvenile life stage. The development of forest species for energy purposes, namely to generate biomass in shorter periods, must take into account this circumstance at the time of measuring the energy density generated by these species.

This paper defines a method which relates the measure of the severity of the disease with the energy lost per Ha. First, it has been characterized from the energy point of view, thus, it has quantified the calorific value of the biomass of Eucalyptus globulus decomposing it in their respective fractions at certain moisture. Then, depending on the degree of severity of the disease, it has been estimated the amount of dry biomass per tree at the age of 27 months and crossing it with the calorific values it has been determined the energy loss per unit of area according to the overall damage index.

Finally, a brief economic analysis considering the consequences of this disease in a stand of Eucalyptus globulus for energy production, has been performed.

In this work a new design for reversible air-air heat pumps is proposed. This design is based on the inversion of the air flow on the ducts, instead of the refrigerant changeover, as is proposed by ASHRAE. Thanks to this modification it is possible to use any conventional air-air refrigeration machine for air conditioning as a reversible heat pump.

The new design is more efficient, especially when a great air quality it is required in the building and therefore a larger amount of outdoor air it is used. Compared with traditional designs it also increases the efficiency as the outdoor temperatures become more extreme. This improvement will make it possible to use heat pumps, with acceptable performances, in more rigorous climates than those in which they are used today.

Nowadays, energy efficiency is a hot topic in a very demanding environment. In this way, improvements in lighting applications, which is a significant point of energy consumption, could be very much welcomed. Electronic ballast may serve to this goal since they are focused on achieving energy savings, reduction in the utility line harmonic content and reactive power, as well as on implementing dimming control and some other parameter of interest in lighting applications. On the other hand, power quality problems are very common in our power system and any new electric device should be designed taking into account these events. One of the typical problems in electrical distribution systems are voltage sags. These have a great incidence on the electrical equipment connected to the network in the same area. The sags cause more damages than the rest of disturbances because these have a greater frequency of occurrence. In this work, the effects of voltage sags on several 150-W high- pressure sodium lamps combined with two different types of electronic ballast have been studied. One of the ballasts supplies the required voltage to minimize the reactive component in the resonant inverter, while the other regulates the power supplied by the utility line to be constant in long term, the resonant inverter being also in open loop at constant switching frequency providing the short term stability. The results of these electronic ballasts will be compared with those obtained with the traditional electromagnetic ballast. The influence of the lamp age will be also considered in the approach. The final goal of this study is to improve the performance of the ballast prototypes under voltage sags.

The IEC has standards covering both a flickermeter and a flicker definition. These documents have been adopted in Europe by the CENELEC as EN norms. The limits of the severity of flicker caused by voltage fluctuations is defined in Europe by the standard CENELEC EN 50160. Under normal operating conditions, flicker level measured according to IEC 61000-4-15 will not exceed the long term severity Plt=1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten coiled coil filament of 60 W and 230 V that is gas-filled produces a flicker perceivable by 50% of the population when it is supplied with a voltage that verifies Plt=1. Other light sources like fluorescent lamps and discharge lamps with ballasts exhibit a different behavior under the same supply conditions. This means that the flickermeter should be different for each type of illumination technique in order to provide accurate information about flicker phenomena. At the same time, lamp age also plays an important role in flicker generation. The above are the main objections given for not adopting the IEC flickermeter in countries as USA. In this research work, a test system and a methodology able to measure the optical fluctuation produced by different types of lamps and ballast is presented. This experimental platform allows to obtain a correlation between voltage flicker levels and optical flicker perception. It can be considered the first step in the definition of new lamp models. This work also shows that age lamp has a significant correlation with flicker generation.

The limits of the severity of flicker caused by voltage fluctuations is defined in Europe by the standard CENELEC EN 50160. Under normal operating conditions, flicker level will not exceed the long term severity Plt=1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten coiled coil filament of 60 W and 230 V that is gas-filled produces a flicker perceivable by 50% of the population when it is supplied with a voltage that verifies Plt=1. Other light sources like fluorescent lamps and discharge lamps with ballasts exhibit a different behavior under the same supply conditions. This means that the flicker meter should be different for each type of illumination technique ir order to provide accurate information about flicker phenomena. At the same time, lamp age also plays an important role in flicker generation. In this research work, a test system and a methodology able to measure the optical fluctuation produced by different types of lamps and ballast is presented. This experimental platform allows to obtain a correlation between voltage flicker levels and optical flicker perception. It can be considered the first step in the definition of new lamp models. This work also shows that age lamp has a significant correlation with flicker generation.

Quality assessment during dc motor manufacturing should be accomplished by quality controls in order to detect the different fault conditions associated to the components included in the machine. However, some defects can be produced by the automatic manufacturing process during the assembly of the individual components. Among others, inter-turns short-circuit, turn to earth short-circuit and open-winding can result from the rotor insertion inside the stator. The main problem with these kind of faults is that the motor can operate but there is a high probability of motor breakdown in the near future.

In this work, the above fault conditions are analyzed and an electromagnetic field and thermal monitoring method is proposed.

The European standard CENELEC EN 50160 establishes that the severity of flicker caused by voltage fluctuations, under normal operating conditions, will not exceed the long term severity Pu = 1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten coiled coil filament of 60 W and 230 V that is gas- filled produces a flicker perceivable by 50% of the population when it is supplied with a voltage that verifies Pu = 1. Other light sources like fluorescent lamps and discharge lamps with ballasts exhibit a different behavior under the same supply conditions. This means that the flickermeter should be different for each type of illumination technique. A test system and a methodology able to measure the optical fluctuation produced by different types of lamps is presented. This experimental platform allows to obtain a correlation between voltage flicker levels and optical flicker perception. It can be considered the first step in the definition of new lamp models and the specification for new electronic ballast design.

Quality assessment during dc motor manufacturing should be accomplished by quality controls in order to detect the different fault conditions associated to the components included in the machine. However, some defects can be produced by the automatic manufacturing process during the assembly of the individual components. Among others, inter-turns short-circuit, turn to earth short-circuit and open-winding can result from the rotor insertion inside the stator. The main problem with these kind of faults is that the motor can operate but there is a high probability of motor breakdown in the near future.

In this work, the above fault conditions are analyzed and an electromagnetic field and thermal monitoring method is proposed

At the present time the generation expansion planning (GEP) has become a problem very difficult to solve for multiple reasons: many objectives, high uncertainties, very great planning horizon, etc. Its resolution by means of the exact traditional techniques, in numerous occasions, is not viable by the excessive time that is needed. For that reason, technical modern that allow the resolution in smaller time and with smaller accuracy in the solution are applied. Most of the approximate techniques are included inside a wider concept that is denominated Artificial Intelligence. In this article the more promising techniques of IA are studied indicating their applications in the PEG as well as their advantages and disadvantages

In air conditioning facilities most of the energy consumption corresponds to the thermal production, this being heat and cold. It depends on many factors, one of the most important in the use of more efficient devices (boilers, chillers and heat pumps)for supply thermal energy. In this work the efficiency of the reversible waterwater heat pumps is analyzed, proposing a new better design that optimizes the nergy consumptiom. This improvement hardly requires modifications at manufacturing, therefore, it could be easily developed by manufacturers.

Voltage sags are nowadays the first power quality problem in the distribution power system. This work evaluates the real implementation of a voltage sag characterization based on a DSP platform. Several classification methods for voltage sags have been presented in the literature. Here the Bollen’s classification is tested. Automation of sag assessment is desirable because manual analysis may be quite difficult.Thus, the fuzzy logic technique is chosen for this aim. This logic system generalizes the classical two-valued logic for reasoning under uncertainty. The fuzzy algorithm was first tested by simulation and then it was translated into C code in order to be implemented in a DSP based measurement platform, obtaining a satisfactory result.

In this work a power characterization of adult stages of the species Eucalyptus globulus and Eucalyptus nitens has been made.

The study has been made in six different plantations in Cantabria (North coast of Spain), located at a latitude 43º28’N, and a longitude 3º48’W. The region has approximately 30,000 Ha dedicated to the growth of Eucalyptus. After the collection of samples they were weighed, analyzed and burned, resulting a mean net calorific value of 17,384 kJ/kg and 17,927 kJ/kg for the E. globulus and E. nitens, respectively.

Finally, the economic and environmental consequences that the crop of these species would suppose for the region of Cantabria were analyzed.

This research work is devoted to the development of an electrical and mathematical model able to simulate the static and transient phenomena in a small power polymer electrolyte membrane fuel cell (PEM) system. At present, there are different electrochemical models available to capture the steady state behavior by estimating the equilibrium voltage for a particular set of operating conditions. However, it is difficult to find models capable of describing transient phenomena. Dynamic models are very interesting from a practical point of view when the loads exhibit large variations. Some examples are powertrains of land-based vehicles or submarines. In that cases, the output power from the fuel cell shows large variations during acceleration and deceleration.

The electric generation produces damages (externalities or environmental costs) that are not contemplated in the costs of this activity. A way to include these damages in the cost is based on the emission rights. In these instruments the total amount of allowed contamination is fixed. It is assigned to the polluting agents by means of emission permissions, creating a market of these, in which the agents can exchange them based on their interests. In 2005, Spain undertook the National Plan of Allocation of Emission Rights 2005-2007 (PNA 2005-2007). This plan has established an emission limit to the electrical sector and it has been translated in the allocation of emission rights. If this emissions limit is surpassed they must acquire rights that cover the exceeded. Thus, the companies must reduce their emissions without increasing their costs. What mix of generation is have to be implement in order to minimize the emissions, avoiding to charge the emission rights in the total generation cost?. If it is impossible to cover the demand without this extra cost, how to diminish it? These questions can be responded using optimization methods.

When a power transformer is energized there is an important transient inrush of current that it is necessary in order to establish the magnetic field of the transformer. Some power transformers exhibit peak current demand up to eight or ten times the nominal value. In addition, during the first cicles high values of the homopolar components of current are also requested by the transformer. If the power transformer is placed in a substation that works as a common coupling point
for distributed generation facilities some specific power quality problems can be found. This paper analyzes the problem from a general point of view considering not only the theoretical approach but also the results obtained in a real case including two 180 MVA power transformer and a 120 MW distributed generation

It is well known that the power factor is the relation between active power and apparent power. Moreover, the square of the power factor represents the relationship between the minimum power loss and the present power loss. This paper deal with the decomposition of the latter ratio into three factors; the first related to the current imbalance, the second to the current distortion and third to the reactive power consumption. Once the contribution of each factor is known, it is posible to determine which disturbance produces the greatest losses. This concept is applied to a three phase-four wire system, with and without neutral resistance.

The utilization of Clark’s transformation in the estimation of the power system frequency provides more robustness to the classical single-phase methods. One of the advantages of this technique is that extract the frequency information contained in the three-phase system. This is particularly important when asymmetric sag generates a zero voltage in one of the three phases.

In this paper the authors analyze different alternatives to provide energy utilities to a hospital center with cogeneration systems with diesel engines and gas turbines. The study considers several power sizes and control strategies, so it shows the influence of these parameters, showing that in this case the options with diesel engines are more efficient than the equivalent ones with gas turbines.

In this work, the authors analyze productive, power, environmental and economic aspects of the forest biomass in the north of Spain. All these points will determine the future development of this power resource, making special reference to the case of the province of Cantabria.

Currently, there are two energy meters types installed: electromechanicals and electronics. The first ones are still the most frequent. However, new facilities tend to use electronics energy meters based on solid-state technology. Electromechanicals devices present characteristics already well known that allows us to measure only energy consumption. However, now the rules that manage the energy supply are totally new, there is a competitive electricity market. This way, detailed information on the energy consumption of each client is needed. In this point, electronic meters seem to be the best option to face the new challenges. This study will review the operating principles of solid-state energy meters. The behavior of some three phases models under nonsinusoidal conditions is studied. Experimental setup and test methodology are discussed as well.

Frequency measurement is an important issue in electrical engineering. Electric power systems have become increasing complex over the last decade. The use of distributed generation, the connection of non-linear loads and the presence of unexpected system faults are the main causes of frequency variations. In addition, power quality includes frequency as an important index. From a hardware instrumentation point of view, frequency measurement has different requirements:

i.) Large power systems have slow frequency variation due to the high inertia of the overall network. This kind of problem requires frequency measuring methods capable of detecting small and also slow frequency variations.
ii.) Small power systems can have frequency variation due to their reduced short-circuit power capacity. This type of problem requires fast methods with the capacity to detect large frequency variations.

There are different groups of methods intended for frequency measurement. The methods can be compared in terms of computation and dynamic response, especially when the main voltage is disturbed.

This research work focuses on frequency measurement under non-sinusoidal conditions. The paper studies the behaviour of a modified version of Sezi’s method and its hardware implementation using a microcontroller. This system can be used for frequency measurement or as a synchronized sampling source in harmonic measurement (e.g. EN 61000-4-7)

The fast time response of the system enables it to be used in almost all kinds of application: small and slow frequency variations; frequency triggering in power system protection and power quality index characterisation.

These days, the ability to make brilliant presentations is increasingly valued. In the academic world, it is commonplace for each professor to elaborate his own materials. In the business world, however, a great deal of audiovisual documentation is generated which certain employees are then required to present, either to groups of clients or to university groups. When a presentation is imposed on speakers in this way, they must have the skill to defend a tool designed by someone else with the same conviction as they would defend their own work. In the professional Presentation Test, the student is immersed in this situation.
The students of Advanced Electric Circuits of the current study plan of the Industrial Engineering and Telecommunications School of the University of Cantabria have been informed that this test will be offered to the two students with the highest and second-highest marks. If either or both of them renounced it, it will be offered to the student with the next highest mark, and so on.

The aims of this test are:

– To provide training for future oral presentations.
– To develop skills in use of external aids.
– To promote the vocation for teaching.
– To encourage the students to improve their academic record.

Before the test, each student must select the three topics s/he prefers. One of these, chosen by the professor, will be the subject of the presentation. There will be a period of between five and ten days between the selection of the topics and the test. The test regulations are as follows:

– The student is handed the material which s/he will use for a presentation in public lasting thirty minutes.
– Once the documentation receives the material, s/he has thirty minutes to prepare the presentation, using any bibliographical aids that s/he considers appropriate.
– Once the presentation is finished, the professor may discuss it with the student for a maximum time of 15 minutes.

The examining board will be made up of the teachers of the subject or, alternatively, teachers from the field of Electrical Engineering. Once the test is finished, after the deliberation of its members, the board will inform the student of his mark, comment on any errors and make any suggestions they deem appropriate.

En este trabajo describiremos los sistemas de arranque más empleados con los motores eléctricos monofásicos que accionan los compresores herméticos de los pequeños equipos de aire acondicionado y refrigeración, caracterizando su funcionamiento según configuración de arranque, y su ámbito de aplicación óptimo. Palabras clave: Ciclo frigorífico, arranque de motor monofásico, compresores herméticos.

Power Quality assessment in distribution networks requires distributed measurements in order to verify the PQ state of the art. This process cannot simply be considered as an extension of a measurement at a given point because several variables need to be considered: number of PQM; election of optimal measurement location; synchronisation of instrumentation and management of captured data.

This work focuses on the problems related with the simultaneous utilisation of different flickermeters in large electric networks.

From a classical instrumentation point of view, several flickermeters from different customers are tested in the laboratory in order to determine the differences in the accuracy of the results. Both Pst and Plt are statistical parameters calculated using a large number of samples of the instantaneous flicker level IFL . The number of captured samples can vary from one instrument to another, so different flickermeters provide different values.

The European standard CENELEC EN 50160 establishes that the severity of flicker caused by voltage fluctuations, under normal operating conditions, will not exceed the long term severity Plt=1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten filament of 60 W and 240 V, produces a flicker perceivable by 50% of the population when it is supplied with a voltage that verifies Plt=1. This work makes an analysis of this threshold, establishing as hypothesis the fact that incandescent lamps have little use nowadays, specially in industrial and commercial environments. In order to make a revision of the current thresholds, we have proposed an electro-optical equipment and the associated methodology. The device simulates the behavior of the eye plus human brain set, avoiding large clinical experiments. A methodology is also proposed in order to characterize the perceptibility threshold of a generic lamp. Finally, the proposed instrumentation and methodology is applied to two types of lamps: incandescent and fluorescent.

This paper deals with the use of the geometrical properties of phase-space representation in the problem of disturbance detection and classification. Time-domain periodical signals can be represented using phase-space diagrams which plot trajectories defined by (x(t),x˙(t)). The trajectories traced show different geometrical characteristics which can be used to distinguish between different types of disturbances. The paper outlines a set of procedures developed for extracting and classifying geometrical parameters. This kind of technique can be used when disturbances have to be classified according to previously registered patterns. The method is developed for voltage or current waveforms of arbitrary sampling rates and numbers of cycles. It has been tested using a power quality instrumentation designed by the authors’ research group. The ultimate goal is to obtain a general disturbance dictionary and a classification method which can be used to classify disturbances automatically.

This paper outlines the effects that voltage distortion has on current waveforms when the voltage supplies nonlinear loads. This is a serious problem when a power quality disturbance dictionary has to be built because some nonlinear loads show different current waveforms when they are supplied by distorted voltage. The paper develops a method and a database organization to represent voltage distortion sensitive loads. This method uses a programmed three-phase arbitrary waveform generator in order to obtain the distortion dependent current consumption. The roadmap obtained is organised using a relational database and the proposed entity-relationship model is presented. This is a step towards the target of automating the process of collecting disturbance data in order to build a power quality disturbance dictionary.

As a result of the increasing use of electronic devices and other non-linear loads, the wave-forms of the electricity supply voltage are being distorted and inequalities are appearing between the phases. This deterioration is associated with problems of electromagnetic incompatibility and reductions in the efficiency of loads such as motors. This paper investigates the additional losses caused to induction motors when connected to supply systems which suffer from these distortions or inequalities. A specific formula is presented for the power factor associated with motors supplied by non-sinusoidal or unbalanced voltages; this has the characteristic of reflecting both the machine’s efficiency and that of the supply voltage.