Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms anelectromagnetic carrier wave that is modulated to carry information. First developed in the 1970s, fiber-optic communication systems have revolutionized the telecommunicationsindustry and have played a major role in the advent of the Information Age. Because of itsadvantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world.
The process of communicating using fiber-optics involves the following basic steps: Creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal, and converting it into an electrical signal.
Power line and connector splice sensor
The first application targeted for this technology is power line connector splices. These components connect sections of power line and are critical to reliability because they are in the series path of power transmission. With current levels commonly more than 1 kA (kiloAmpere), excess resistance in a splice connection will cause it to overheat and make it susceptible to catastrophic failure (such as a downed power line). Presently, line inspectors use infrared imaging to look for hot spots, but this has been ineffective because the emissivity of conductors and splices varies, making it difficult to interpret results. The approach to the splice sensor is twofold: to directly measure the temperature of the conductor/splice using a thermocouple, and to measure the current flowing through the line using a coil with a high-permeability core to sense the magnetic field strength. Both pieces of information are important because the temperature rise depends on the amount of current flowing through the line.
When the current through the line is at least 80 Amps (which is normal), the signal from the coil is sufficient to self-power the sensor and a separate battery is not required. The sensor reading for this design contains four values: the present temperature, the present line current, the peak temperature and the line current measured at the time of the peak temperature. Proto-type backscatter splice sensors were successfully tested at EPRI’s high-voltage test facilities in Lenox, Mass., with currents up to 2 kA, voltages up to 140 kV and line temperatures to nearly 150 degrees Celsius. Mechanical testing was successfully performed at SwRI facilities for vibration and slip using existing standards for power line vibration dampers. Range testing beyond 200 feet was also successfully demonstrated.
The insulator sensor is designed to fit around the Y-bolt that attaches the bell to the grounded structure. Thumb screws are used to secure the two halves of the current transformer. Leakage currents are continually monitored and peak levels are stored in a histogram.