Sérgio Campello Oliveira

Optical Detection of Partial Discharges on Insulator Strings of High-Voltage Transmission Lines

Leakage current detection is a promising method for measuring pollution levels on insulators of overhead transmission lines. This paper describes the development of a leakage current sensor based on a fiber-coupled light-emitting diode, as well as the development of a processing module that detects, stores, and classifies leakage current peaks that are directly related to partial discharges on the surface of the high-voltage insulators. The relative humidity is also detected and stored for further analysis. The processing module uses a PIC 16F877A microcontroller and can register the rate of partial discharges for two months on three different levels.

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.

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.

Satellite telemetry system for pollution detection on insulator strings of high-voltage transmission lines

Leakage current monitoring is a promising method of indirect estimation of pollution levels on insulators strings of high voltage transmission lines. This paper describes the development of a complete real time leakage current monitoring sensor system. This system is composed of an optical sensor with a fiber link, a processing microcontrolled module, a satellite link and a solar panel with battery. The most important characteristics obtained from the leakage current signal are internally stored in the PIC16F877A microcontroller and transmitted through the satellite communication link. The information is downloaded from the website of the satellite link provider and inserted in a database with a web-based graphical user interface.

Real-Time Monitoring of the Leakage Current of 230-kV Glass-Type Insulators During Washing

This paper reports the real-time behavior of the leakage current flowing on glass-type insulator strings of a 230-kV substation tower during washing. Monitoring of two insulator strings in the tower is achieved by use of a pair of optical-fiber sensors that detect samples of the leakage current waveforms and transmit those samples to a processing module via an optical link. It is observed that leakage current during washing may reach high peak levels, and the effectiveness of the washing can be inferred by the degree of leakage current after drying of the insulator strings. Direct monitoring of the leakage current can thus be used as an important guideline for proper washing procedures during this type of intervention as well as for determining the effectiveness of the procedure.

Remote monitoring of the degree of pollution of high voltage insulator strings via satellite with a sensor system network

A sensor system network was developed and installed in the northeast of Brazil to monitor the degree of pollution of insulator strings of high voltage transmission lines. Monitoring systems, comprising leakage, humidity and temperature sensors, a processing electronic module and a satellite communication link were installed on 230 and 500 kV towers. Measured parameters, sent via satellite to the communication service provider are downloaded to a local server managed by a web-based GUI application. The degree of pollution in the insulator string can be inferred from the time rate of discharge pulses appearing in the leakage current signal and its correlation with local humidity and/or temperature. Preliminary real time field results measured in the network are analyzed.

Hydrogen detection using surface plasmon resonance in palladium films

We investigate the performance of Pd films for the development of H2 sensors based on the surface plasmon resonance (SPR) effect. Experimental measurements were carried out on glass substrates sputtered with Pd thin films, using a homemade automatic reflectometer based on Kretschmanns prism coupling configuration. The sensitivity for H2 detection measured experimentally was approximately 60% lower than that expected from calculations based on the optical constants tabulated in the literature, but exhibited the approximate trend in thickness dependency predicted theoretically. In spite of this difference, these results yield important findings for the design of SPR-based H2 sensors with maximum sensitivity.

Fuzzy inference system for risk classification on polluted insulator 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. This paper presents the initial analysis of one year long experiments. A fuzzy inference system was applied on the results to extract a risk level. The risk level was incremented and decremented according to the partial discharge activity and relative humidity levels. The risk level obtained in this can be used to better plan the schedules for preventive maintenance.

Experimental observation of surface plasmon resonance in a gold-coated multimode fiber

We observed for the first time evidence of the surface plasmon resonance(SPR) effect within the light distribution irradiated from a gold-coated multimode fiber immersed in a wet environment. Experimental measurements conducted with NaCl sample solutions allowed demonstrating the application of the technique in optical sensing whereby modifications in the shape of the irradiated intensity pattern are linearly correlated with changes in solute concentration. Measurement results indicate that this detection technique provides at least a 10-fold sensitivity enhancement relative to that achieved by a previously reported SPR-based fiber sensor.