Cesar Carvalho

Detection and Monitoring of Leakage Currents in Power Transmission Insulators

An optoelectronic sensor for real-time leakage current monitoring on high-voltage (500 kV) and medium-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultrabright light-emitting diode producing an amplitude modulated light signal. The optically intensity-encoded signal is coupled to a plastic optical fiber cable and transmitted from the high potential measurement point to the remote unit in ground potential. After the demodulation, the leakage current root mean square values are concentrated in a data logger and sent to a remote station 150-km away by general packet radio service technology. Field tests at real operational conditions on coastal regions have been performed; all data collected are stored in a structured database, which can be consulted from the Internet, while a serially produced head was developed and the sensor is ready for commercialization. Since leakage current on high-voltage insulators depends on local air pollution and microclimate changes, several sensors have to be used to cover the region monitored. For this reason, research has been conducted to determine the sensor representativeness, i.e., the actual area, which can be covered by only one sensor.

Detection and monitoring of leakage currents in distribution line insulators

An optoelectronic sensor for real time leakage current monitoring on high-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultra-bright green LED producing an AM light signal. The optically intensity-encoded signal is coupled to a 1-mm plastic optical fiber and transmitted from the high potential measurement point to the Remote Unit in ground potential. After the demodulation, the leakage current values are concentrated in a data logger and sent to a remote station 150 km away by GPRS technology.

Plastic optical fiber sensors applied to electric energy industry

The Photonics and Instrumentation Laboratory (LIF) at the Universidade Federal do Rio de Janeiro is a R&D laboratory mainly involved in optical sensors applied to Energy, Oil & Gas and Biotechnology areas. This paper demonstrates some techniques used by LIF to measure, detect and monitor several physical parameters applying plastic optical fiber (POF) either as sensor or as a communication channel for telemetry. The applications to be presented include measurement of electrical current in high voltage, temperature and leakage currents over insulators. We take advantage of the POF for its high insulation property, applying them to measure electrical parameters in high voltage environment. For each example presented, it will be shown the measurement principle, laboratory tests and field application.

Automatic calculation of vascular indexes with a microcomputer-based directional Doppler system

It is described a Doppler system which is accessed by a microcomputer. The flow waveforms can be shown at the computer video monitor and printed by a simple matrix printer. The system also averages the now signal in order to obtain a representative cycle and then calculates four vascular index used for diagnosing vascular diseases. Thirteen normal individuals and twenty pathologic patients were examined and their resulting indexes were compared.