SAW Sensors to Monitor Power Lines

VILLACH, Austria /PRNewswire/ -- The permissible load on power lines depends on the temperature of conductor strands. So the Austrian CTR AG, specialist in the development of Surface Acoustic Wave (SAW) systems, is currently working on sensor technology to monitor temperatures in conductor strands. "So far, the temperature was estimated based on wind speed and environmental temperature, however, more detailed information requires precise measurements. Cable-based measurements do not work due to high voltage. Infrared measurements are impractical because of the intense vibrations of the strands. The SAW technology is the solution to all these problems," says Alfred Binder, CTR's SAW program director.

SAW-based systems that are based on radio technology measure the physical dimensions of power lines such as temperature, pressure or voltage. These systems transfer high frequency signals via wireless technology, operate completely passive - without energy supply - and are able to withstand extreme temperatures (ranging from -55 degrees to +400 degrees Celsius). These properties qualify the systems for monitoring conductor strands.

CTR's system works when a reader on the power pole contacts the sensor mounted on the line via radio technology; the sensor transmits the temperature information that will be used to control the network load. Basically, the SAW-system is an automated system for load monitoring in high voltage power lines. The use of the additional information provided by the SAW technology allows transmission of different amounts of energy, based on existing environmental conditions, over the monitored lines. The first installations are currently under way.

The SAW sensor is composed of a piezoelectric crystal with metallic structures. The reader sends an electromagnetic signal that a special transducer (mounted on the SAW sensor) converts into mechanical oscillations. The waves thus created spread out on the crystal's surface and are partially reflected by the reflectors and re-transformed into electromagnetic waves. Based on the reflectors' distribution, a fixed code is detected which uniquely identifies the sensor. The crystal's temperature-based contraction or expansion causes a runtime modification of the signal received. In addition to RFID, a temperature measurement with a resolution of up to 0.01 degrees C is also feasible. This additional property is especially useful in the case of challenging industrial uses.