Researchers at IIT Madras have demonstrated that through the use of Raman thermometry on fibre optic cables, they will obtain monitoring of power transmission cables. Interestingly, they obtain this through the use of the optical fibres which are already embedded within the power cables for establishing optical communication. The work is a component of a bigger ongoing venture on distributed fibre sensors and has been revealed lately in IEEE Sensors Journal.
Serendipity
The seeds of the thought have been sown about ten years again when Balaji Srinivasan of the Department of Electrical Engineering at IIT Madras was approached by an organization that deliberate to implement overhead power lines throughout the nation. The firm had an intriguing request. They wished Prof. Srinivasan to certify that the glass fibre they have been planning to incorporate for communication functions together with their power cables was certainly an optical fibre. Such optical fibres are historically included in cables and buried underground. This may price as much as 80% of the whole expense in organising the communication system. The firm had figured that they might save this price by intertwining a hole tube with the strands carrying the power lines, and on this hole tube, they might incorporate the optical fibres – about 48-96 in quantity – in a hole tube intertwined with power lines and thereby save the fee of digging tunnels to accommodate them.
It was throughout this certification course of that Prof. Srinivasan bought the concept one or two of the unused fibres may very well be used – owing to their proximity to the power cables – to maintain tabs on the health of the power cables. This relies on the precept that any present flowing by a conductor would trigger a temperature rise because of the Joule heating impact.
Raman impact
India’s first and up to now solely Nobel laureate in physics, C.V. Raman, received the prize for his discovery of Raman impact. This consisted of experimental observations on scattering of mild. In the Raman impact, when mild is scattered off an object, say a molecule, two bands are noticed, with increased and decrease frequency than the unique mild, known as the Stokes and anti-Stokes bands, respectively. By finding out the relative depth of the 2 bands, it’s attainable to estimate the temperature of the article that scattered the sunshine.
“The anti-Stokes component of Raman scattering is strongly dependent on the temperature that the material is subjected to. Thus, by measuring the intensity of the anti-Stokes scattered light we can estimate the temperature. This is Raman thermometry,” says Prof. Srinivasan.
He explains that the temperature measurement is carried out in not only one location, however in a distributed method utilizing an optical fibre. To obtain this, a pulse of mild is launched into the optical fibre and the backscattered radiation is noticed. “The time of flight of the backscattered radiation provides an estimate of the distance from which the light is backscattered,This constitutes a distributed measurement as the pulse propagates all along the length of fibre,” he says. This can go as much as tens of kilometre. This approach is married to Raman thermometry to get the outcomes for precise measurements over tens of kilometres.
Cost-effective answer
Alternative strategies of measuring the temperature of power cables embrace utilizing a thermal digital camera to manually monitor their size, which is cumbersome. The current technique devised by the staff is each economical and offers real-time info.
Optical fibre-embedded power cables are already out there throughout the nation, however none of them are presently used for power monitoring. “We are presently working with a leading Indian power transmission and distribution company for implementing this technology,” says Prof. Srinivasan.
The staff is exploring machine studying strategies to determine hotspots alongside the size of the cable with excessive accuracy. “Preliminary results show that our novel deep learning approach is able to provide enhanced temperature measurement accuracy as well as better spatial resolution compared to conventional filtering-based post-processing techniques,” he says.
