Eduardo Fontana

Novel sensor system for leakage current detection on insulator strings of overhead transmission lines

We report the development of a measurement system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. A capacitive sensor connected to the processing module allows recording the relative humidity of the outer environment. At the present stage, six measurement units have been deployed on CHESFs electrical transmission system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings

Thickness optimization of metal films for the development of surface-plasmon-based sensors for nonabsorbing media

The surface-plasmon resonance (SPR) effect in metals is highly sensitive to fluctuations in the optical properties of the interface and has been frequently employed in the Kretschmann configuration for optical sensing. The operating conditions required for using the SPR effect for probing nonabsorbing media under maximum sensitivity are derived analytically under the Lorentzian approximation. It is found that the film thickness that maximizes sensitivity occurs when the radiation damping of the oscillation is half the intrinsic damping. Numerical results are presented for the spectral dependence of the optimum thickness as well as of the SPR parameters of gold, copper, silver, and aluminum films, useful for the design of optical sensors for both gaseous and aqueous environments.

Novel routing algorithm for transparent optical networks based on noise figure and amplifier saturation

We propose and demonstrate a novel dynamic routing algorithm for transparent optical networks based on physical layer impairments such as amplifier noise accumulation, amplifier gain saturation, wavelength dependent gain and losses along lightpaths. The metrics of our algorithm is based on the calculation of the noise figure using the well known formulation for cascade of elements in lightpaths. We assume no wavelength conversion capabilities in our network and we assign wavelengths using a first fit algorithm. For a given call, our algorithm assigns the first available wavelength and calculates the best route (minimum noise figure). Upon the calculation of the noise figure of the lightpath, we obtain the bit error rate (BER). Our algorithm blocks a call if there is no wavelength available or if the BER for the available wavelength is above a given level, which guarantees a pre-defined quality-of-service for the network operation. We present simulation results of dynamic traffic in a hypothetical meshed network in terms of blocking probabilities as a function of network load and amplifier characteristics. We show that our algorithm outperforms the traditional shortest path routing algorithm.

Theoretical and experimental study of the surface plasmon resonance effect on a recordable compact disk

The surface plasmon resonance (SPR) effect on noble-metal surfaces has been explored by several investigators for the development of chemical and biological sensors as well as for the design of optical devices for other applications. The effect can be observed by use of prism couplers, diffraction gratings, and specially configured optical fibers. In an attempt to seek a new configuration that minimizes costs of fabricating media that support SPR in conjunction with designing a new format suitable for large-scale chemical and biological sensing, I have investigated the feasibility of using a commercially available, gold-type, recordable compact disk for observation of the SPR phenomenon. Experimental and theoretical results of this investigation are reported.

Sensor Network for Monitoring the State of Pollution of High-Voltage Insulators Via Satellite

This paper describes the design and development of a sensor system network for remote monitoring of the state of pollution on high-voltage insulators, its deployment among four states in Northeast Brazil and preliminary analysis of the data gathered by the system. Six monitoring units, each composed by leakage current, humidity, and temperature sensors, an electronic processing module, and a satellite-communication link, were built and installed on 230- and 500-kV transmission towers. Measured data are sent by the different systems via satellite to a database controlled by a web-based graphical user interface, incorporated into the supervision-management system of the electric utility company. Sample field results on one of the sensor systems, both for short- and long-term measurements, show a direct correlation of the activity recorded by the system with the pollution level expected to occur near the corresponding monitoring point.

Leakage Current Activity on Glass-Type Insulators of Overhead Transmission Lines in the Northeast Region of Brazil

This paper describes a study of the leakage current activity on glass-type insulators of high-voltage transmission lines over a three-month period. Three pairs of sensor systems were installed, one on a 500-kV field tower and the other two on 230-kV and 500-kV substation towers, all in the northeast region of Brazil. The locations were chosen due to their particular environment characteristics and the previous knowledge of pollution severity in these locations. The correlation of the leakage current attributes with in situ humidity records, insulator positions on the tower, and seasonality are discussed.

Fiber-optic sensor system for leakage current detection on insulator strings of overhead transmission lines

In this paper we report the development of an optical system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. At the present stage, six different systems have been deployed on CHESFs electrical distribution system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings.

Fiber-optic-based Corrosion Sensor using OTDR

We propose and demonstrate for the first time an optical sensor for the corrosion process in metal (Aluminum) using the optical time domain reflectometry (OTDR) technique. Our proposed sensor system consists of several sensor heads connected to a commercial OTDR by a single-mode optical fiber and fiber couplers. Each sensor head consists of an optical fiber having the cleaved end coated with an aluminum film. For laboratory measurements the corrosion action was simulated by controlled etching of the Al film on the sensor head. The OTDR detects the light reflected by each sensor head. As the aluminum is etched the reflection decreases. Our proposed sensor system is multipoint and can detect the corrosion rate for each head several kilometers away from the OTDR. This system may have applications in harsh environments such as in deepwater oil wells, for the evaluation of the corrosion process in the inner wall of the casing pipes.

Surface plasmon resonance on a recordable compact disk

The surface plasmon resonance (SPR) effect on noble metal surfaces has been explored by several investigators for the development of chemical and biological sensors as well as for the design of optical devices for other applications. The effect can be observed using prism couplers, diffraction gratings and specially configured optical fibers. In an attempt to seek for a new configuration that minimizes fabrication costs of the SPR supporting media in conjunction with the design of a new format suitable for large scale chemical and biological sensing, we have investigated the feasibility of a commercially available, gold-type, recordable compact disk (CD-R) for observation of the SPR phenomenon. In this paper we report experimental and theoretical results of this investigation.

Flashover risk prediction on polluted insulators strings of high voltage transmission lines

Partial discharges on high voltage insulator surfaces are directly related with the deposition of pollution over the insulators. A complete partial discharge sensor network was previously developed and has been in operation for approximately one year. A fuzzy inference system was applied on the results to extract a risk level. In this paper the risk level signal was applied as a neural network input to predict the flashover risk ten days ahead. Two sensors installed on transmission towers submitted to match environments provide the data sets used as training and test. The risk predicted follows the behavior of the observed risk and could be used to better plan the schedules for preventive maintenance.