You are in the middle of your favourite movie or about to have dinner and suddenly there is a power cut! Isn’t it frustrating? We all have faced this problem at least once in our lifetime and have prayed for electricity to be back soon. Slowly and gradually our dependence on electricity has increased and electricity or power is what is driving the current world economies. For better management of electricity, countries are now moving towards smart power grid systems. This smart management requires various smart sensors which can monitor power lines. Now, Prof. Balaji Srinivasan at IIT Madras along with his research collaborators has come up with a method of temperature sensing which can be used in smart grid systems to estimate the loss of electricity in transmission lines.
Currently, the electricity is produced in few central power plants and then it is distributed in other centres through transmission lines, and further to sub-centres, and thereafter to individual homes, factories and industries. Although India has made strides in electricity generation, a lot of wastage in electricity happens as there are no infrastructures to hold electricity and there is always an ambiguity with respect to demand of a particular region. Smart power grids will allow two-way communication between producers and consumers as it will give back the information regarding the estimated usage of a particular establishment which helps in better management of electricity. This is made possible through the use of smart sensors which enable data on various portions of the power grid. Temperature sensing of power which will enable estimation of the heat dissipation and corona discharges at power lines and also helps monitor power loads at various locations at various time points can be useful for monitoring.
“Distributed temperature measurement is becoming very important for safety-related applications and also for reducing energy consumption. This technology, along with the data analytics tools, can be used to predict failures and also safety hazards. Wired point temperature sensors are too cumbersome to use even for 100 measurement points, and other methods based on wireless sensors or drones are under consideration” explains Dr. Anish Bekal who works for Forbes Marshall.
Prof. Srinivasan’s team has come up with a method that utilizes the Distributed Anti-Stokes Raman Thermometry (DART) tool that can be used for temperature sensing in power grids. The research has been published in the prestigious international journal IEEE Sensors.
“Distributed temperature sensing over an extended region is a critical requirement in several applications such as downhole monitoring, real-time power monitoring, fire detection in tunnels, and leak detection. Raman scattering-based optical time domain reflectometry (R-OTDR) for distributed temperature sensing, which is also known as Distributed Anti-Stokes Raman Thermometry (DART) is a powerful tool that caters to the stringent requirements in these applications” says Prof. Srinivasan, while explaining other applications of the research.
Currently used approaches for sensing temperature in the power cable include the use of thermocouples, platinum resistance probes, non-contact infrared radiation measurements or through use of point temperature sensors. However, the major drawback of using these methods is that they allow limited number of sensing locations and are susceptible to electromagnetic interference.
Working on this problem, Prof. Srinivasan’s research team has found a novel way of using optical fibres to measure the temperature profile of the transmission line using a bi-directional anti-stokes component measurement.
“One of the key points that favours optical fibre sensors is the fact that modern power lines incorporate optical fibres in them so that they can be used for optical communication between locations wherever power is distributed. We seek to leverage this by realizing a distributed temperature sensor based on the same fibre, “ adds Prof. Srinivasan.
The team demonstrated the use of this system in real-time power monitoring of power cable. This system is an advancement over earlier ratio-based DART systems which require precise calibration to account for spectral dependence of the optical components. In this newly developed system, however, algorithm only on the anti-stokes component to measure the temperature map. To cut on the noise from attenuation along the sensing fibre, the anti-stokes component is measured from both forward and backward direction in loop configuration. The team has validated this algorithm using a controlled experiment where less than 10C temperature error with 8 m spatial resolution was achieved for 11.5 km sensing range.
“Apart from the application demonstrated, the technology is of great value in several other applications such as tunnel fire monitoring, steam tracers or pipeline temperature monitoring. Optical fibre-based temperature sensing is being considered in several countries in Europe, which has extensive tunnel networks. This technology adds to an array of fire detection platforms already existing in the tunnels. Several commercial entities are trying to offer such solutions for detecting fire in tunnels of the European countries. Second application of steam tracer is also essential where the transportation of certain chemicals produced in a refinery requires a constant temperature of the pipeline extending to several km. Optical fibre based sensing is one of the very few technologies which can efficiently perform this measurement. One of the essential requirements for the approach used in this paper is having access to both ends of the fibre used for investigation of temperature. Access to both ends may be a problem in some cases but is not in most applications. This topology provides us with a redundancy mechanism under fibre break, to switch back to conventional method until the fibre is restored. Overall this is a progressive work in the field and could help India become independent in such advanced technologies” adds Dr. Bekal.
Future plans of team entail collaboration with industry to establish the adoption of this technology for the above applications, and also with instrument manufacturers to realize a cost-effective, robust instrument that conforms to the Internet of Things (IoT) framework. Such an approach is currently being explored by the team led by Prof. Srinivasan under the newly established IoT hub at IIT Madras, Pravartak Technologies. The team is also exploring real-time decision making through machine learning approaches, thereby realizing a complete cyber-physical system based on distributed sensing.
The research team includes Amitabha Datta (National Aerospace Laboratories, Bengaluru and IIT Madras), Haritha Mamidala (Transmission Corporation of Telangana) and Prof. Deepa Venkitesh (IIT Madras) apart from Prof. Balaji Srinivasan.
Article by Aditi Jain
Here is the link to the research article: