POWER LINE FAULT-DETECTION SYSTEM FOR POWER GENERATION AND DISTRIBUTION INDUSTRY
In power distribution lines, faults such as short circuits, ground faults, and lightning strikes on the conductors must be detected in a very short time to prevent damage to equipment and power failure, and to enable quick repair. If the transmission line is divided in sections and a current or magnetic-field sensor is mounted in each section, a faulty section can be determined by detection of a change of the level and phase of the current on the power line. A system was developed as a hybrid optical approach to a fault-locating system that detects the phase and current difference between two current transformers on a composite fiber-optic ground wire (OPGW) wherein, due to induction, current is constantly passing (Fig. 6.34).
The signal from a local electrical sensor, powered by solar cells and batteries, is transmitted over a conventional optical-fiber communication link. By three-wavelength multiplexing, three sensor signals can be transmitted over a single fiber. Seven sensors, three at each side of a substation and one at the substation itself, can monitor one substation on the power line, using one fiber in the OPGW.
Another system uses current transformers to pick up lightning current and thus detect lightning strikes. The signal is transmitted to a central detection point using the OPGW. Every sensor has its own OPGW fiber. This system is on a 273-kV power line in Japan.
The OPGW opens the possibility for using all kinds of sensors along the transmission line. These sensors may not only be for locating faults, but also for monitoring structural integrity. The use of optical time-domain reflectometry combined with passive intrinsic (distributed) sensors along the OPGW has future potential for providing a convenient and powerful monitoring method for power lines.
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About the Author
Sabrie Soloman, Ph.D, is the Founder, Chairman and CEO of American SensoRx, Inc.
Excerpted from Sensors Handbook, 2nd Edition by Sabrie Soloman (McGraw-Hill; 2010) with permission by McGraw-Hill.
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