The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper discusses a method for detection and localisation of the insulation faults in electrical equipment distributed along the body of electric and hybrid electric vehicles. At the beginning of the fault detection procedure it is required that the vehicle powertrain be shut-down. The method is based on measurement and comparison of leakage currents in every device in the electrical powertrain...
Thin thermochromic VO2 films grown by RF magnetron sputtering on various substrates (SnO2/glass, glass, Si) and with different deposition parameters, were studied in order to find the optimum conditions to produce thin film coatings with good thermochromic and thermoelectric characteristics as required for power line protection / switching applications. Regarding the electrical/electronic applications...
In order to identify the type and the location of fault, partial discharge diagnosis is a valuable method. Until now, a majority of the evaluation criteria used for partial discharge diagnosis is based on investigations performed at AC voltage. The increasing importance of DC transmission systems requires additional research concerning the behaviour of partial discharges at DC voltage. Especially...
The economics of power transmission requires operators to maximise the power through the network. Increasing knowledge of the impact of environmental factors on the current carrying capabilities of bare wire overhead lines is, therefore, important. Cost savings resulting from enhancing thermal transfer capabilities of transmission lines has motivated many utilities and power systems research centres...
Climate change and electricity cost increased the investments into renewable energy technologies. Worldwide policies are recognized to help with the wide spread of renewable energy technologies. The most commonly installed renewable energy system for residential properties is the PV solar system. Investors and governments are also investing into large scale renewable energy power stations. The PV...
This paper focuses on the design of an electronic circuit which can be used at the ac input of loads — equipment in order to maintain the voltage supply (Vpeak — peak) constant, across them, despite the mains overvoltages. It describes a proposed electronic method for ac voltage supply stabilisation. The electronic circuit keeps the single phase voltage supply constant, according to nominal level...
This study aims to evaluate the implications of the use of maritime pine non-debarked wood chips as an alternative solid fuel in industrial boilers in Portugal, highlighting the energy properties and chemical composition of the ash produced. Several samples have been collected from different sources, on which an approximate analysis is carried out to determine the volatile matter content, fixed carbon...
The key to succeed in engineering is to master information and the correct use of materials. The learning of the basic concepts of circuit theory, the type of concepts and the form of experimentation, traditionally acquired in educational laboratories, are fundamental and demand new and better tools. The teaching of electric circuit analysis requires students to compare theory and practice of “learning...
The present study is aimed to estimate service time on the emergency service orders of an electric company. For this, a sequence of steps has been developed and described for the structuring of a demand forecasting system, which must be able to design patterns and tendencies of the analyzed data from past demands. Intending to meet these assumptions, the study sought to support the prediction method...
This paper discusses a simple and cheap PV emulator based on a linear power supply that does not require a source of light to conduct laboratory experiments. The emulator has been designed to underpin students' understanding the properties of PV cell V-I characteristics and the ways to maximise the output power learned from lectures, tutorial and self-studies. The emulator has been built using “on...
A case study for the analysis of load flows in weakly meshed radio systems is presented. The problems associated with the running of medium voltage flows are quite critical especially when the network topology is rather arbitrary geospatially. Many of the software currently available on the market consume excessive memory on the calculation of the resolution of the equations of nodes to get the brownouts...
Transient overvoltages are inevitable phenomena in power systems. They occur in high voltage direct current systems for much the same as the reasons they happen in high voltage alternating current systems and could be of either internal or external origin. Moreover, the switching operation of the power electronic valves in HVDC converters add to these transient sources. The effects of such transient...
Conductivity measurements are important within the area of insulating material characterization especially for HVDC transmission application. Within first investigations a derived novel test setup showed promising results regarding overall reproducibility with regard to the test specimen production and test configurations. Based on these first results, the setup is subjected to further enhancements...
Augmented Reality (AR) promises to revolution the maintenance field in general with relevant contributions to High-Voltage Systems. The value-added can came from several aspects, namely the increasing security and reducing time and costs of intervention. However there are some aspects related to AR state-of-the-art that do not permit yet to reach all of their potential, namely the necessity of use...
This paper aims to study the sector of biomass for energy in Portugal and to analyze the logistics costs associated to the exportation of its product to international markets. The growing concern on environmental impacts associated to fossil fuels contributed to enhance the importance of exploring more sustainable sources of alternative energies. This study enhances the potential of Portugal as a...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.