A novel self-powered condition monitoring sensor for harsh environments - feasibility study

Decreasing power requirements for wireless sensors coupled with the abundant supply of electromagnetic energy available within an electrical substation opens up the possibility of self-powered condition monitoring sensors that operate without the use of a battery by harnessing energy from the surrounding electric field. This paper investigates the feasibility of powering a wireless sensor by scavenging energy from an ambient electric field. Theoretical calculations are presented regarding the short circuit current and open circuit voltage available from the device. Practical measurements have also been carried out using a high voltage test rig. A prototype device has been built and the short circuit current extracted from the electric field measured directly using a small panel-mount ammeter located within the device. Two parallel plates of radius 10 cm separated be a distance of 10 cm and placed within a 200 kVm-1 electric field have the potential to supply about 300 mW to a sensor circuit. Although there is useful power available, the high output impedance of the device renders it inherently inefficient. More efficient means of converting the available power into a useful form are discusse