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Publicações

2016

The IEC 61850 in the Portuguese distribution substations: Contemporary challenges and possible solutions

Autores
Leite, H; Martins, D; Ferreira, J; Pinto, A;

Publicação
IET Conference Publications

Abstract
Interoperability may be defined as the ability of intelligent electronic devices (IED's) to exchange and use information correctly. Although the IEC 61850 standards define a consistent methodology for interconnecting IEDs in substation using LAN based technologies to promote interoperability, this ability to exchange information correctly is not always achieved between different IED's from different manufactures. This paper reports the assessment of IED's, featured with IEC 61850 standards and connected to the same communication network from different manufactures. Different interoperability tests are performed and the difficulty and challenges to exchange and receive information is also reported. Possible solutions on the XML schema to generate a compliant SCL file as well as the way to scale up the standardization of the substation project is also explored and discussed in this paper.

2016

Overloading Analysis of an Industrial Client Distribution Transformer in a Portuguese Island

Autores
Godina, R; Rodrigues, EMG; Shafie khah, M; Matias, JCO; Catalao, JPS;

Publicação
2016 IEEE INTERNATIONAL ENERGY CONFERENCE (ENERGYCON)

Abstract
In this paper an analysis is made of the impact of emergency loading made by several inductive loads on the thermal ageing of a distribution transformer belonging to a private industrial client. The analyzed system is a fragment of an isolated electric grid in a Portuguese Island. A transformer thermal model is used to estimate the hot-spot temperature and top-oil temperature given the load ratio. Real data are used for the main inputs of the model, i.e., private industrial client load, transformer parameters and the characteristics of the factory. Finally, a smart transformer protection method is proposed by the authors with the aim of monitoring and protecting it from similar upcoming challenges.

2016

A state estimator for LV networks: Results from the evolvDSO project

Autores
Teixeira, H; Pereira Barbeiro, PN; Pereira, J; Bessa, R; Matos, PG; Lemos, D; Morais, AC; Caujolle, M; Sebastian Viana, M;

Publicação
IET Conference Publications

Abstract
The increasing connection of new assets in LV networks will surely require a better monitoring of these systems in a real-time manner. In order to meet this purpose, a Distribution State Estimator (DSE) module clearly appears as the most cost-effective and possibly the only reliable option available. In this sense, in the scope of the evolvDSO project, a DSE tool exploiting the concept of ELM-AE was developed and tested in two distinct real LV distribution networks. In this paper the main results achieved with the proposed DSE tool are presented and discussed.

2016

Multiple manipulators path planning using double A

Autores
Tavares, P; Lima, J; Costa, P; Moreira, AP;

Publicação
INDUSTRIAL ROBOT-AN INTERNATIONAL JOURNAL

Abstract
Purpose - Streamlining automated processes is currently undertaken by developing optimization methods and algorithms for robotic manipulators. This paper aims to present a new approach to improve streamlining of automatic processes. This new approach allows for multiple robotic manipulators commonly found in the industrial environment to handle different scenarios, thus providing a high-flexibility solution to automated processes. Design/methodology/approach - The developed system is based on a spatial discretization methodology capable of describing the surrounding environment of the robot, followed by a novel path-planning algorithm. Gazebo was the simulation engine chosen, and the robotic manipulator used was the Universal Robot 5 (UR5). The proposed system was tested using the premises of two robotic challenges: EuRoC and Amazon Picking Challenge. Findings - The developed system was able to identify and describe the influence of each joint in the Cartesian space, and it was possible to control multiple robotic manipulators safely regardless of any obstacles in a given scene. Practical implications - This new system was tested in both real and simulated environments, and data collected showed that this new system performed well in real- life scenarios, such as EuRoC and Amazon Picking Challenge. Originality/ value - The new proposed approach can be valuable in the robotics field with applications in various industrial scenarios, as it provides a flexible solution for multiple robotic manipulator path and motion planning.

2016

On the Cost of Safe Storage for Public Clouds: an Experimental Evaluation

Autores
Burihabwa, D; Pontes, R; Felber, P; Maia, F; Mercier, H; Oliveira, R; Paulo, J; Schiavoni, V;

Publicação
PROCEEDINGS OF 2016 IEEE 35TH SYMPOSIUM ON RELIABLE DISTRIBUTED SYSTEMS (SRDS)

Abstract
Cloud-based storage services such as Dropbox, Google Drive and OneDrive are increasingly popular for storing enterprise data, and they have already become the de facto choice for cloud-based backup of hundreds of millions of regular users. Drawn by the wide range of services they provide, no upfront costs and 24/7 availability across all personal devices, customers are well-aware of the benefits that these solutions can bring. However, most users tend to forget-or worse ignore-some of the main drawbacks of such cloud-based services, namely in terms of privacy. Data entrusted to these providers can be leaked by hackers, disclosed upon request from a governmental agency's subpoena, or even accessed directly by the storage providers (e.g., for commercial benefits). While there exist solutions to prevent or alleviate these problems, they typically require direct intervention from the clients, like encrypting their data before storing it, and reduce the benefits provided such as easily sharing data between users. This practical experience report studies a wide range of security mechanisms that can be used atop standard cloud-based storage services. We present the details of our evaluation testbed and discuss the design choices that have driven its implementation. We evaluate several state-of-the-art techniques with varying security guarantees responding to user-assigned security and privacy criteria. Our results reveal the various trade-offs of the different techniques by means of representative workloads on top of industry-grade storage services.

2016

Scalable hardware architecture for disparity map computation and object location in real-time

Autores
Santos, PM; Ferreira, JC; Matos, JS;

Publicação
JOURNAL OF REAL-TIME IMAGE PROCESSING

Abstract
We present the disparity map computation core of a hardware system for isolating foreground objects in stereoscopic video streams. The operation is based on the computation of dense disparity maps using block-matching algorithms and two well-known metrics: sum of absolute differences and Census transform. Two sets of disparity maps are computed by taking each of the images as reference so that a consistency check can be performed to identify occluded pixels and eliminate spurious foreground pixels. Taking advantage of parallelism, the proposed architecture is highly scalable and provides numerous degrees of adjustment to different application needs, performance levels and resource usage. A version of the system for 640 x 480 images and a maximum disparity of 135 pixels was implemented in a system based on a Xilinx Virtex II-Pro FPGA and two cameras with a frame rate of 25 fps (less than the maximum supported frame rate of 40 fps on this platform). Implementation of the same system on a Virtex-5 FPGA is estimated to achieve 80 fps, while a version with increased parallelism is estimated to run at 140 fps (which corresponds to the calculation of more than 5.9 x 10(9) disparity-pixels per second).

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