An introduction to Dynamic Line Rating
As the term ‘dynamic’ suggests, Dynamic Line Rating (DLR) is an ever-changing capacity rating for a power line that is adjusted based primarily on prevailing weather conditions in order to maximise overall grid capacity. To perhaps get a clearer idea of what DLR means, it is also known as real-time thermal rating. As more power is transferred through a power line, it becomes heated and as the cable expands it can sag and in certain instances that sagging can bring the line into contact with nearby vegetation, causing an interruption to the supply as well as risking starting a wildfire, which are well documented as being caused by power companies.
As an example, the “Dixie Fire” was the second-largest wildfire in California’s history and was ignited when power lines owned by Pacific Gas and Electric came into contact with a tree, fire officials said. The Dixie Fire started July 13, 2022, and went on to burn approaching a million acres across five counties in Northern California before being contained. According to CNN, the wildfire destroyed 1,329 structures and several firefighters were injured while working to contain the massive swath of flames. DLR-related sensors are not there solely for power grid optimisation, they are also there as a safety measure.
As a further measure, to ensure that people and buildings are also safe from sagging power lines national electric codes determine clearances from buildings, roadways and other objects.
A dynamic rating takes into account the surrounding air temperature which is constantly affected by weather and seasonal conditions on a moment-by moment basis, and through real-time grid monitoring capacity can be instantly adjusted, unlike a static line rating (SLR). If you were to compare DLR with SLR, it would be similar to comparing an HD video with a black-and-white photo as SLRs are inflexible and are set to take into account ‘worst case’ scenarios. Basically, with an SLR there is no flexibility in the amount of power that can be transferred, not because of the potential line capacity itself, but purely because of the rating allocated to it.
Understanding the difference a Dynamic Line Rating can make to a transmission line rating and the capacity of that line
Unless you have an actual comparison, it is difficult to understand why a DLR has such an advantage over an SLR. In a recent press release from (which operates the Spanish electricity grid) about its offshoot Red Eléctrica installing 750 DLR-related devices throughout the Spanish grid, it states that “Red Eléctrica aims to increase the capacity of some overhead lines by up to 30% at certain times under optimal conditions, which would allow for the transmission of more electricity, enabling greater integration of renewable energy in areas with high renewable potential.” If you didn’t know it before, you are now aware of why such emphasis is being placed on DLRs as they are a very cost-effective means of increasing grid efficiency – minimal outlay and minimal infrastructure improvements providing one of the very best grid efficiency solutions.
Effective electric grid management leads to enhanced grid reliability
In the simplest of terms, grid management for an SLR system primarily involves maintenance and repairs to ensure optimum reliability, while also managing supply and demand within narrow and immovable parameters. Because this is a ‘static’ system, there is next to nothing that can be done to improve grid efficiency. However, there are severe limitations in relation to the tools available for monitoring the power lines in a static system, with a great deal of reliance placed on visual inspections.
Once has been connected to the power lines in the grid, the whole system changes and becomes “dynamic”. By this we mean that all the sensors will send back real-time data on a multitude of factors including the temperature of the power lines, and based on those temperature readings, the appropriate power rating can be set. However, because the system is now dynamic, that rating will be changed by the operator as and when the meteorological conditions change. Such an instantly reactive approach will help to improve grid stability, reduce the likelihood of power outages and enhance the overall reliability of the grid, helping to achieve the ultimate goal of a continuous power supply.
DLR reduces the need for immediate major investment in new infrastructure by increasing grid capacity
Prior to the development of DLR, the only option available to a power company to increase supply was to invest in costly infrastructure, whether for the provision of additional above-ground or underground power lines, the former being the more common. With the introduction of DLR, this has provided the opportunity to ‘upgrade’ power girds and increase power capacity by up to 30% under optimum weather conditions at a far lower cost than adding further power lines. Better than this, installing the necessary sensors for a DLR system takes little time and uses minimal resources. It is certainly cost effective, and the ROI is far greater than investing in physically increasing the existing capacity of power lines through adding further power lines.
Dynamic Line Rating operational flexibility that never previously existed will maximise grid efficiency
The key to the success of the DLR operating system is that it offers operational flexibility and the ability to adapt to changing meteorological conditions. This flexibility, that never existed with the current SLR system, means that the maximum power rating for a power line can increase by up to 30% during optimum weather conditions (and potentially more), usually in the winter. However, it would be easy to lose sight of the fact that Spain’s climate is such that demand for electricity does not peak solely in the winter (when power lines can handle the greatest load). In the summer there is also a surge in demand for power through the use of air conditioning to combat extremely high temperatures, particularly in the evening when residents are home from work. According to Idealista, 41% of Spain’s housing stock is equipped with air conditioning.
The flexibility of a DLR system is such that at every opportunity (for example at night the air temperature drops and therefore power line capacity increases) the transmission line rating is adjusted to allow the network to operate at maximum capacity under those conditions. Consequently, during the night up until early morning, when demand for electricity is at its lowest, a maximised power rating facilitates the transmission and storage of excess power which can then be used to counteract increased demand the next evening and at weekends.
DLR and smart grid technology – a game-changing grid efficiency solution?
Over the past five years smart technology has transformed the landscape for ‘remotely operated’ technology. By remotely operated we mean, for example, sensors, cameras, alarms, etc., that can function without hands-on human intervention and instead be operated ‘remotely’. The beauty of smart grid technology is that with a sensor on a power cable, it can provide instant feedback (data) on current weather conditions – wind speed, temperature, humidity, precipitation, etc., which can be uploaded to the cloud and that data then used for real-time decisions on rating settings for that particular power line. Over time, today’s systems will likely become fully autonomous, with data analysed using algorithms and IoT computer-operated systems adjusting the power line ratings across the grid. It will not only be cost effective through the affordability of DLR sensors compared to the cost of now power lines, but the system will require nominal manpower to be operated successfully.
And the proof that Dynamic Line Rating works where power grid optimisation and grid efficiency are concerned
Unsurprisingly, with the potential to increase grid capacity without having to invest heavily in new infrastructure, the DLR system was immediately appealing. Better still, the International Renewable Energy Agency (IRENA) has estimated that the majority of grid operators can overcome challenges relating to existing power demand if line rating were increased by between five and 20 percent. The results achieved for three major electricity providers indicates that our suggestion that DLRs can increase capacity by 30 percent may even be on the pessimistic side!
According to IOT For All:
- Belgian TSO Elia has boosted line current by 30 percent with DLR.
- The New York Power Authority found that DLR would reliably increase line capacity by up to 25 percent.
- Canadian electricity provider AltaLink found that DLR would provide a line-rating increase of 72 percent over static ratings up to 95 percent of the time.
How Energiot can help with optimised grid efficiency solutions using smart grid technology
Energiot is a pioneering Spanish company specialising in autonomous IoT solutions for electrical grid monitoring. Our key product, a self-powered IoT device, utilises patented piezoelectric energy harvesting technology, allowing it to operate battery-free. We offer grid operators the benefits of real-time asset monitoring, predictive maintenance, and improved grid reliability. The devices are versatile, sustainable, and designed for global deployment, providing a practical and maintenance-free solution to enhance grid operations.
IoT systems can track all ambient conditions, which is particularly beneficial as thermal limits for transmission lines change based on the following variables:
- Current
- Wind conditions (speed, direction, etc.)
- Ambient and line temperature
- Precipitation and cloud cover
- Solar radiation levels
- Acceleration/tilt
As IoT sensors can be installed directly onto power line infrastructure, this means you can now generate dynamic line ratings based on all the above factors. With an optimised DLR system—one that is also capable of factoring in weather predictions—it becomes possible to plan ahead for optimal transmission times.
Further details can be found on our Dynamic Line Rating page.
