Search results for "Partial"
showing 10 items of 1477 documents
Photovoltaic plant array reconfiguration: Design of a new device
2014
An efficient strategy to improve unequally irradiated PV plants performances is based on the reconfiguration of the connections between the modules. In this paper, an algorithm, for this purpose conceived, is presented. Moreover, the design, realization and finally also the set up of a new reconfiguration system device is fully shown and discussed. The algorithm conceived simulates several possible series-parallel connections under varying irradiation conditions, and determines the optimal modules connection in order to get the maximum output power. In this way, the reconfiguration system may set up the reconfiguration strategy. The reconfiguration system prototype set up, basically consist…
A portable instrument for the location and identification of defects generating PD
2011
A portable instrument based on an antenna probe and suitable for partial discharge detection, have been characterized through both laboratory and on-site experiments carried out on coils and stator windings of ac rotating machines. The antenna probe allows the capture of electromagnetic waves in a bandwidth of 0.1–100 MHz. Pulse signals and ac supply voltage reference are obtained by means of high-pass and low-pass filters, respectively, so avoiding the need of a direct connection with the objects under test. By this way, real-time phase resolved partial discharge patterns can be derived. Results of a comparison of the diagnostic information provided by PD patterns due to conducted and irra…
Computational fluid dynamics and its application to transport processes
2007
Fluid transport behaviour is of great importance within the chemical process industry and in biotechnology. The complexity of this behaviour, reflected in the nature of the fundamental partial differential equations which describe it analytically, means that it has to be treated by numerical methods. In this paper the basic equations are given, and the approaches necessary to treat laminar and turbulent flows are carefully explained. As digital computers have increased in size, so has the comprehensiveness of the problems which can be treated, and the development of typical computer programs is described. Problems of accuracy and experimental validation are also surveyed, and it is shown th…
Technical and economical evaluation on the use of reconfiguration systems in some EU countries for PV plants
2017
This paper shows the technical and economical evaluation of the application of a reconfiguration system for photovoltaic (PV) plants, considering the incentives system in some European Union countries. The reconfiguration system is an alternative to the distributed maximum power point tracking technique which used to increase the power production in the PV plants under the mismatch phenomenon. The reconfiguration techniques employ a microprocessor-based or field-programmable gate array-based system that modifies the layout of the PV plant through the change of the connections among modules. After having presented the main features working of the PV reconfiguration system allowing the improv…
CFD simulations of dense solid–liquid suspensions in baffled stirred tanks: Prediction of solid particle distribution
2013
Abstract Industrial tanks devoted to the mixing of solid particles into liquids are often operated at an impeller speed N less than Njs (defined as the lowest speed allowing the suspension of all particles): under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work is devoted to assessing the capability of Computational Fluid Dynamics (CFD) in predicting the particle distribution throughout the tank. The CFD model proposed by Tamburini et al. [58] and successfully applied to the prediction of the sediment amount and shape was adopted here to simulate the particle distribution under partia…
Performance of the Shape of Partial Discharge Signal Wireless Probes
2013
This paper focuses on the evaluation of the performances of three different antenna sensors suitable of Partial Discharge (PD) measurements. Monopole, triangular and spherical antennas were simulated by means of the surface moment method. The transmitting system is modeled by a power electronic device with a fault current between two metal plate. The shape of the simulated transmitted and received signals have been compared to verify the sensor the provides the best fidelity among the three. The auto-correlation function and the Pearson correlation index are adopted here for the comparison. A discussion on the dynamic characteristic of the different antenna probes and their use in different…
A two-end traveling wave fault location system for MV cables based on LoRa technology
2017
In this paper a new low cost device is proposed for fault location in power distribution system. The device is part of a system that should include several units installed in couples at the two ends of MV cable lines. Their low cost justifies a widespread installation of these devices, moreover other functionalities could be considered so as to enrich the potential of the system for MV cables monitoring and asset management. The system exploits a two-end traveling wave technique, low complexity and low cost solutions both for the analog front end as well as for the communication infrastructure. A LoRa network is indeed considered as wireless modulation technique perfectly suited when commun…
A computer‐aided instrument for pattern recognition of partial discharges
1998
In this paper a new computer‐aided digital system for partial discharge (PD) measurements is presented. The system is able to collect a great number of data, up to a pulse repetition rate of 100kHz, during the acquisition phase, thus allowing an off‐line analysis of PD data. After a description of the instrument, some experimental tests performed on epoxy specimens are here presented in terms of amplitude, phase and energy resolved histograms. Finally, emphasis is given to the very interesting use of the instrument for pattern recognition techniques in the discrimination and classification of discharges in HV components.
A Robustness Approach to Reliability
2012
Reliability of products is here regarded with respect to failure avoidance rather than probability of failure. To avoid failures, we emphasize variation and suggest some powerful tools for handling failures due to variation. Thus, instead of technical calculation of probabilities from data that usually are too weak for correct results, we emphasize the statistical thinking that puts the designers focus on the critical product functions. Making the design insensitive to unavoidable variation is called robust design and is handled by (i) identification and classification of variation, (ii) design of experiments to find robust solutions, and (iii) statistically based estimations of proper safe…
Partial discharges on IGBT modules: Are sinusoidal waveforms sufficient to evaluate behavior?
2014
In recent years, the increasing use of AC-DC converters, especially in the field of renewable energy sources has led to the implementation of new modulation techniques, in particular the ones based on the pulse width modulation. The purpose of the present work is to verify the different behavior that is obtained when the components are subjected to the partial discharge test carried out with a sinusoidal waveform, and when they are subjected to PWM stress-type, similar to the actual signal generated by this type of electronic components. By considering equal rms value of the fundamental sine wave, the comparison has shown different partial discharges patterns.