Highly Multiplexed, Low Cost Fiber-Optic Sensor Array for Underground Cables Condition Monitoring

Our nation has a significant underground cable infrastructure that represents 15% to 20% of installed electric distribution capacity (many millions of feet). A portion of this infrastructure is reaching the end of its design life or reliable service life. Complete replacement of old or failing cable systems is a costly option and, at any rate, unnecessary because, depending on their environment, cable systems do not age uniformly. It has been recognized in the electrical power transmission community that the use of new and improved instrumentation for on-line condition monitoring of underground cables would be highly beneficial. The key parameters of interest include partial discharge at splice joints and in cable insulation, and cable temperature. A low-cost multifunction fiber optic sensor system will be developed. It will be capable of detecting events, such as partial discharge, that can reduce cable life. The system also will be capable of monitoring cable structure stresses and temperature. This system, with multiplexed sensors along the same light weight fiber cable, will facilitate ease of installation and long term condition monitoring. Data signals will be able to travel over many miles without corruption, enabling acquisition and analysis at a central station. The system will have two other significant features: (1) it will be smart, providing prognostics for condition based maintenance and repair; and (2) it will require zero power at the sensor deployment points. Proof-of-concept was successfully executed and deployment feasibility was demonstrated for detecting partial discharge events and temperature. In Year 1, a functional prototype system will be developed. In Year 2, a pre-production model will be developed, addressing both new and retrofit markets. Collaborative support will be leveraged from an academic institution with involvement in a national committee on electric systems, and from a prominent industry partner that is a leading center of excellence in the electricity sector. Commercial Applications and Other Benefits: Smart grids use enabling technologies to save energy, reduce cost, and increase safety and reliability. The proposed technology will extend cable life, eliminate costly interruptions, and reduce maintenance and repair costs. Cable manufacturers can integrate this technology for next generation smart cables. Service providers can deploy the system onto aging infrastructures. According to a 2009 technology market report, smart grid markets will reach $17 billion by 2014.