Power cables in ducts and tunnels may overheat and ignite for a variety of reasons. The impact of the resulting fire can cause serious problems for utility companies and their customers.

In July 2001, underground cables in Yaesu, Japan, caught fire and subsequently caused an explosion, temporarily cutting off the power supply to 1300 buildings.

Fiber-optic linear-temperature sensors continuously monitor the temperature of cables in ducts and tunnels as well as buried power cables to detect power cable hot spots. This monitoring provides critical temperature information before it is too late.

Sensa (Southampton, Hampshire, U.K.) designed Tunnel Plus software to enable users to make cable temperature and fire detection measurements. Sensa uses fiber-optic technology to monitor temperature over the entire length of a power cable.

Sensa provides distributed-temperature sensor (DTS) solutions capable of monitoring cables in dirty, dusty and electromagnetically active areas, ranging from 100 m to 8 km (328 ft to 5 miles) from a single optoelectronics unit.

The Sensa system, using technology developed by York, is in use on critical circuits and process vessels across the world. The latest combined cable monitoring and fire detection system was installed in the 5-km (3-mile) Woodhead Tunnel, under the Pennines, U.K., as part of a tunnel safety upgrade.

In the near future, Sensa will install a system in the City Road to Backhill cable tunnel in London.
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