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Wireless sensor ensures reliable electrical transmission

28 Jan 2014

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A 1mm-thick chip developed by researchers at the Hong Kong Polytechnic University Department of Electrical Engineering can detect electric currents without the need for additional power sources or signal conditioners. The so-called "magnetoelectric smart material" could be used in the future in roads or passage ways as an alternative to signal cables and hardwired power cords.

Electricity transmission needs to be regularly monitored to ensure a reliable operation of power grids and a proper delivery of electricity, particularly in modern cities. With this objective in mind, Professor Derek Siu-wing Or and colleagues designed a chip that can be placed on any sensing point of interest such as electrical cables, conductors, junctions and bus bars, to detect electrical currents. Unlike traditional current sensors. the chip does not require additional power supplies and signal conditioners. Therefore, they can be conveniently, safely and reliably used for early fault detection in unthinkable territories.

Made from rare earth multi-ferroics with giant magnetoelectric properties, the chip enables a direct detection of magnetic fields generated by electricity and a linear conversion of these magnetic fields into electrical voltage signals. The amplitude of the converted signals is linearly proportional to the magnetic fields, while their frequency exactly follows the magnetic fields. The "magnetoelectric smart material", as called by the team, is then specially engineered into "self-sustainable magnetoelectric smart sensors" that recognise telltale changes of electrical currents within electrical equipment.

"Our smart sensors are essentially simple, totally passive and capable of producing large and clear output voltage signals which are 2,000 times higher than the traditional current sensors. This passive and self-sustainable nature allows real-time, nonstop monitoring of the 'health' of electrical equipment, including those carrying high voltages, heavy currents and/or strong electromagnetic fields," Or said. "Besides, these smart sensors can be tailored to harvest electromagnetic radiations emitted by the electrical equipment being monitored and to turn them into useful electrical energy. The stored electrical energy can be used to power up microcontrollers, displays, wireless transmitters, etc., further advancing the smart sensor technology towards 'energy-harvesting smart wireless sensors'."

The smart wireless sensors are being tested in electrical traction systems on trains in both Hong Kong and Singapore to provide in-situ monitoring of traction conditions and to detect electrical faults that may bring train services to a halt. The research team is also working with a power company in a large scale project to supply, test and commission a significant amount of smart sensors for use in substations.

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