Data Mining - Concepts and Techniques.

An Introduction to MultiAgent Systems.

The objective of this paper is to discuss the design and implementation of a multi-agent system that provides intelligence to a distributed smart grid — a smart grid located at a distribution level. A multi-agent application development will be discussed that involves agent specification, application analysis, application design and application realization. The message exchange in the proposed multi-agent system is designed to be compatible with an IP-based network (IP = Internet Protocol) which is based on the IEEE standard on Foundation for Intelligent Physical Agent (FIPA). The paper demonstrates the use of multi-agent systems to control a distributed smart grid in a simulated environment. The simulation results indicate that the proposed multi-agent system can facilitate the seamless transition from grid connected to an island mode when upstream outages are detected. This denotes the capability of a multi-agent system as a technology for managing the microgrid operation.

Multi-agent systems in a distributed smart grid: Design and implementation

Multiagent Systems is the title of a collection of papers dedicated to surveying specific themes of Multiagent Systems (MAS) and Distributed Artificial Intelligence (DAI). All of them authored by leading researchers of this dynamic multidisciplinary field.

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Multiagent systems: a modern approach to distributed artificial intelligence

This review describes induction coil sensors, which are also known as search coils, pickup coils or magnetic loop sensors. The design methods for coils with air and ferromagnetic cores are compared and summarized. The frequency properties of coil sensors are analysed and various methods for output signal processing are presented. Special kinds of induction sensors, such as Rogowski coil, gradiometer sensors, vibrating coil sensors, tangential field sensors and needle probes are described. The applications of coil sensors as magnetic antennae are also presented.

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Induction coil sensors—a review

The lack of synchronization between the sampling rate and the signal frequency represents the main source of errors in the frequency analysis of periodic signals performed by means of digital techniques. Several algorithms have been proposed in the literature to reduce these errors, at the cost of an increment in the computational burden imposed by the instrument. The complete elimination of these errors can be achieved only when the sampling rate is synchronized to the fundamental frequency of the signal to be analyzed. It is shown how this can be attained, and the results of fast Fourier transforms (FFTs) performed on multifrequency signals under synchronous sampling conditions are indicated. The accuracy of these measurements is discussed. >

High-accuracy Fourier analysis based on synchronous sampling techniques

The calibration of measurement transformers represents a classical task in the practice of electrical measurements. Most commercial instruments that are expressly designed for this purpose found their working principle on a scheme that is based on the idea of Kusters and Moore. Although they can assure very high accuracy, the need to employ a high-performance electromagnetic circuit makes them very expensive and usually not suitable for measurements at frequencies that are higher than 50 or 60 Hz. For this reason, these kinds of instruments cannot be employed for the calibration of the new generation of current and voltage transducers, such as electronic measurement transformers, whose employment is growing in all the applications where wide bandwidth is required. In this paper, a new method for the calibration of electromagnetic voltage and current measurement transformers (VTs and CTs) and electronic voltage and current measurement transformers (EVTs and ECTs) is discussed, and a deep metrological characterization is carried out. The novelty of the proposed method is represented by a completely different approach to the measurement of the ratio and phase errors of the measurement transformers. The method is based on the proper digital signal processing of the signals that are collected at the secondaries of the transformer under test and of a reference transformer when the same signal is applied to their primary. Since no auxiliary electromagnetic circuits are required, this solution can be easily implemented in a simple and cost-effective way. In spite of its simplicity, the tests that are developed on a prototype clearly point out that the proposed system is suitable for the calibration of measurement transformers with precision class up to 0.1 in the frequency range from 50 Hz to 1 kHz.

A Simple Method for the Calibration of Traditional and Electronic Measurement Current and Voltage Transformers

The need for high-current transducers featuring wide-band and high-insulation levels is becoming a more and more impelling need in the electric power network, as the current distortion increases due to the proliferation of nonlinear, time-variant loads. The closed-loop Hall-effect current transducers show a good compromise between cost and metrological performance. On the other hand, they may introduce an unacceptable nonlinearity error when the dynamic range of the input current is a reduced portion of the dynamic range of the transducer and may show a large drift of their gain with temperature. The paper proposes a simple method for reduction of the nonlinearity error when the input signal is an unbiased sinewave and the automatic calibration of the gain. Experimental results are also reported, showing the method effectiveness.

A linearization method for commercial Hall-effect current transducers

The continuous progress in magnetic sensor research provides increasing accuracy in measurement systems based on magnetic sensor arrays. Many industrial applications in the field of protection for low-voltage electrical systems require novel technologies of AC current sensors characterized by lower costs and wider measuring range in amplitude and frequency. For this purpose, a promising solution is the utilization of sensor arrays provided with signal processing techniques. In the paper, we propose a new principle for simultaneous measurement of polyphase currents flowing in parallel conductors of arbitrary cross-sections based on processing magnetic sensor signals. After describing the analytical solution of the measurement problem, theoretical uncertainty analysis is carried out. Preliminary experimental results confirm the validity of the new approach.

Processing magnetic sensor array data for AC current measurement in multiconductor systems

Steel-fiber-reinforced concrete is a composite material which is becoming more and more widely employed in building construction, due to its better resistance to cracking and to crack propagation with respect to plain concrete. Its mechanical behavior strongly depends on the choice of fiber properties and their volume fraction in the concrete mixture. As any material used in building construction, the “on-site” test of its properties represents a very important task. Often, this requires the employment of noninvasive and nondestructive measurement procedures that have to be carried out directly in situ. In this paper, a new method for the estimation of the fiber density and their average orientation is presented. The measurement technique is based on the employment of a probe that is sensitive to the magnetic properties of the steel fibers. The performance of the method has been theoretically and experimentally analyzed.

Roberto Ottoboni

Papers

High-accuracy Fourier analysis based on synchronous sampling techniques

A Simple Method for the Calibration of Traditional and Electronic Measurement Current and Voltage Transformers

A linearization method for commercial Hall-effect current transducers

Processing magnetic sensor array data for AC current measurement in multiconductor systems

Nondestructive Testing of Steel-Fiber-Reinforced Concrete Using a Magnetic Approach