• Energy Research

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.

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.

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.

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.

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.

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 light emitting diode (LED) as well as the development of a processing module that detects and stores the most important components of the leakage current signal. The relative humidity is also detected and stored for further analysis. The sensor is constructed with a single LED coupled to an optical fiber. The processing module uses a PIC 16F877A microcontroller and can register leakage current peak rates during two months in three different levels.

Experimental and theoretical studies of the electric and magnetic fields produced by compact transmission lines are described. The lateral and longitudinal field profiles at ground level within a right of way have been analyzed. The studies include measurements of the profiles of field strength of compact transmission lines as well as an analysis relative to the type of tower, size and type of conductor, and voltage level. Finally a comparison between measured and calculated values are presented.

The loss of insulation capacity caused by pollution deposition on insulator strings can be inferred from the analysis of the electric arcs due to partial discharges on the insulators. The partial discharges also cause pulses superposed to the leakage current signal. An optical sensor system network was developed and installed in the northeast region of Brazil to monitor the degree of pollution deposited over insulator strings of high voltage transmission lines. The monitoring system comprises leakage, humidity and temperature sensors, a processing electronic module and a satellite communication link. They were installed on 230 and 500 kV towers. This paper presents a correlation study comparing the information obtained from the monitoring systems and the electric arc levels obtained by traditional visual inspections. Also the rain events influence the leakage current behavior and a rain pattern recognition system is used in order to better evaluate the leakage current behavior.

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.

This paper reports the real time behavior of the leakage current flowing on 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.