01.07.2010
Sensors for monitoring power lines
An innovative sensor technology is able to monitor high voltage power lines and provide information on load-oriented power flows.
SAW (Surface Acoustic Wave)-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.
The Austrian CTR AG is specialised in the development of SAW systems. CTR is currently working on the development of sensor technology to monitor temperatures in conductor strands. The Dresdner Lemke Diagnostics GmbH, a technology leader in the manufacture of diagnostic and monitoring devices for the power supply industry is especially interested in CTR’s technology. The permissible load on power lines depends on the temperature of the 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,” Alfred Binder, SAW Program Director for CTR, states.
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.
Source picture: Doble Lemke GmbH
