RTTR, or Real-Time Thermal Rating, is a method of assessing real-time operational thermal rating of the equipment, or the amount of electrical current that a power line or an electrical facility can endure before suffering critical damage. Thermal rating devices can be used to measure the temperature of overhead power lines, transformers, underground and subsea cables.
Real-time thermal rating systems rely on real-time data from environmental conditions rather than theoretical assumptions and predictions. These systems are able to not only measure the thermal ratings in real-time but also to measure the stress levels of certain areas and determine their capacity. The calculation of the thermal ratings happen on the basis of: 1) weather conditions; 2) electrical current; 3) temperature of the equipment. However, other factors may need to be considered; this depends on the environment where real-time thermal rating needs to be performed. For example, soil condition, burial depth, and configuration must be considered for temperature measurement of underground cables, the mass of the transformer and type of the cooling mechanisms for temperature measurement of transformers, etc.
The key to the real-time thermal rating system, the temperature of the asset, should be continuously measured to avoid heating of the asset to dangerous levels. Distributed temperature sensing (DTS) systems should be used for this purpose, otherwise, only predictions about the temperature can be made.
The main advantage of real-time thermal rating systems is their ability to accurately measure the thermal behavior of assets, taking into consideration factors that static ratings do not. Static rating calculations are often overly conservative, therefore some power lines are often not used up to their full potential, while others are overloaded, which causes premature aging.
Thermal rating systems may be implemented into different types of power assets. Underground cable monitoring benefits greatly from introducing real-time thermal rating systems as they measure soil ambient temperature and soil thermal resistivity; these measurements help to determine actual thermal headroom to indicate unused network capacity.
The thermal rating of the overhead power lines, depending on the actual system used, takes either the sag of the lines, the tension of the line conductor, the temperature of the line conductor, or environmental conditions into account during calculation.
Transformer load, ambient and transformer temperatures, oil temperature, and winding hot spot temperature are utilized by RTTR systems for transformers.
DTS optic sensing fibers are important for real-time thermal rating; they are installed along the length of the power cable and provide a continuous temperature profile.
If you would like to purchase DTS (Distributed Temperature System), please contact us: info@optromix.com or +1 617 558 98 58.