DSO TSO Technopedia

DLR system was initially installed on five lines, on spans with known clearance issues when PV input is high. After seeing immediate impact, the project was quickly expanded counting a total of 37 lines being monitored per June 2025, with more to be installed after the summer.

The supplier performed an assessment to determine optimal number of sensors and their locations, considering the specific thermal limits of every span on the prospect lines. Hence, the installations are a mix of specific span monitoring and general thermal behaviour monitoring.

Dynamic line rating was proved to be an effective way of throating PV when clearance is low, optimizing the utilization of the lines. Synopsis to be accepted for CIGRE conference 2026

TRL 9

“Heimdall Power and Bayernwerk launch record DLR project,” Heimdallpower.com, 2025.

A pilot DLR system was installed on a transmission line near Budapest, equipped with two conductor sensors and two weather stations.

The objective of the DLR system is to increase the transmission capacity of power lines by leveraging real-time data to adjust line ratings dynamically. This is achieved through the installation of sensors on conductors, weather stations, and the use of AI-driven predictive analytics to forecast environmental conditions and optimize line capacity.

The central DLR application receives information about the transmission line from the line sensors, the weather stations, the SCADA system and the HungaroMET weather data and forecasting service. If accurate forecast data is received, we can predict the expected maximum load capacity of the line hours in advance.

We measure with the conductor sensors for one year. After this period, the weather stations remain in place, and the conductor sensors can be installed on a new transmission line. At the old location, the conductor temperature will be determined by an ANN (Artificial Neural Network)-based “sensor”, which is integrated in our DLR app and currently has an accuracy of ±3°C. By pairing weather stations with physical conductor sensors, measurements can be taken at new locations, and after another year, the sensors can be relocated to another transmission line. This approach allows for the cost-effective deployment of the DLR system over a few years with a smaller number of sensors.

By using ANN sensors, not only can the procurement costs of the sensors be saved, but also the periodic maintenance costs, the costs associated with installation and removal, and the need for transmission line shutdowns.

Dynamic line rating was proved to be an effective way of throating PV when clearance is low, optimizing the utilization of the lines. Synopsis to be accepted for CIGRE conference 2026

TRL 8 (after the evaluation following the test period, the system can achieve TRL 9).

This use case showcases the successful application of Dynamic Line Rating (DLR) technology by the Distribution System Operator (DSO) Viesgo a company of EDP Group to improve the integration of renewable energy—particularly wind—into its 132 kV distribution network. The main objective was to reduce curtailment of renewable generation by avoiding energy waste due to insufficient reception capacity. The DLR system allowed overhead lines to operate above their static thermal limits by calculating the dynamic ampacity of conductors using real-time weather data.

The project was executed in two major phases: a pilot phase (2011-2015) with limited deployment and monitoring, and an industrialisation phase (since 2016) expanding the DLR system across the entire 132 kV network.

The system uses two weather stations per line (one in the least-cooled segment and one in substations), power quality analyzers, and conductor temperature sensors. These stations collect data every second (every 10s for wind) and transmit it to a central data server every minute. Both steady-state and unsteady-state algorithms are used to estimate ampacity and conductor temperature, based on adapted CIGRE TB601 and IEEE 738 standards. These adaptations included handling direct solar radiation, implementing safety coefficients, and incorporating sag and hotspot considerations.

The DLR system is fully integrated with the IDbox software platform, allowing the control center to monitor and manage the network in real time. This integration supports operational decision-making and emergency management by visualizing ampacity, current flow, and conductor temperatures.

One of the main challenges was obtaining regulatory approval to operate overhead lines above their traditional thermal design limits. This required technical presentations to regional authorities and validation of safety through pilot data.

The implementation of DLR significantly improved operational flexibility. Between 2015 and 2018, it avoided around 4,100 hours of wind curtailment and enabled the injection of an additional 70.9 GWh of renewable energy, resulting in a reduction of 7,800 tons of CO₂ emissions—and up to 20,300 tons under conservative assumptions.

For 99% of the time, dynamic ampacity exceeded the static rating. On average, line current capacity increased by 56%, with peaks reaching 114%. The average ampacity boost was 380 A, and the maximum was 672 A. The additional energy transported was valued at up to €3.5 million based on market prices.

The conductor's estimated temperature averaged 16.3 °C and peaked at 80.9 °C. Temperatures exceeded 70 °C for less than 0.2% of the time, indicating that the operation did not accelerate conductor aging. In fact, the temperature monitoring provided DSO operators with enhanced insight into conductor health for asset management purposes.

The system also improved maintenance scheduling and supported safer network operations. During high-wind weeks, the DLR enabled over 4% of the total annual additional energy to be integrated in just seven days, avoiding more than 100 hours of curtailment.

Notably, dynamic management showed that conductor temperature is not solely correlated with current but also heavily influenced by environmental conditions, such as wind speed—an effect validated through operational data.

Taking into account the learnings and results achieved in Spain, DLR is also being tested in other companies from the EDP Group, such as E-REDES, which is testing different use cases for the use of DLR, including the one already deployed in Spain.

TRL 9

Mínguez R., et al. (2019). Dynamic management in overhead lines: A successful case of reducing restrictions in renewable energy sources integration. Electric Power Systems Research, 173, 135-142. https://doi.org/10.1016/j.epsr.2019.03.023 CIGRE TB601 - Guide for thermal rating calculations of overhead lines IEEE Std 738-2012 - Standard for calculating current-temperature relationships of bare overhead conductors EN 50341 - Overhead electrical lines exceeding AC 1 kV - National normative aspects for Spain IDbox Platform: https://idboxrt.com

Connecting and activating volatile renewable energy (VRE) while overhead line replacement project was still ongoing.

Instalment of weather stations, that deliver wind speed and temperature information. Applied Webs' through Taylor series into control system and started operation.

Reached 180% capacity under best conditions.

Rolled out the system to ~80% of our 110 kV overhead lines.

TRL 9

“Neues Konzept zur Windstromintegration: E.ON Netz stellt Freileitungs-Monitoring vor - TenneT TSO GmbH,” Archive.org, 2016.

DLR systems are installed on 27 lines including all High Voltage Alternating Current (HVAC) interconnection lines, and both real-time and forecast DLR data are used in intraday and day-ahead operation planning and market capacity allocation processes. The recent development of the system and its validation through surveyor measurements of sag demonstrated that up to 200% of rated capacity was available in certain circumstances.

Commercially available sensors were used to measure real-time sag directly on 70 kV, 150 kV, 245 kV and 400 kV lines. An up to 60 h-ahead forecast module has been developed.

Intraday rated capacity is raised up to 130%, whereas for CORESO processes it is raised up to 110% based on statistical risk assessment.

TRL 8

The research for BEST PATHS is focused on repowering existing power lines and enhancing the technological knowledge and application of conductor technologies through different innovations. DEMO 4 has addressed the following objective through the development of a prototype DLR system based on low-cost sensors, allowing for higher temperature operations of current line technologies. Part of the BEST PATHS project is the implementation of the DLR sensors on a transmission line in Spain [1].

Using 7 DLR sensors on existing 220 kV live line variations in a catenary angle of 0.005 º or 10 cm in sag will be measured and communicated for optimal line loading.

Using data from DLR sensors, existing corridors were optimised to carry more power. A transmission capacity increase of 15 - 30% was measured over the duration of the experiment, which lasted 3 months.

TRL 7

Kladar Dalibor. “Dynamic Line Rating in the world - Overview.” researchgate.net [online]

The DLR system covers 29 lines (6 x 400 kV, 4 x x220 kV and 17 x 110 kV). The system is fully functional and integrated into the daily operation. The main applications that support real-time operation and operation planning are the mitigation of N and N-1 overloading operational situations and calculations of transmission capacities for up to two days ahead. The system also features an inverse DLR algorithm for icing prevention and alarms for extreme weather conditions along the lines.

An indirect (non-contact) DLR system based on macro and micro-scale meteorological models supported by weather measurements. Calculations are performed for each line span. The system enables the definition of maximal operating temperature per tension field. A comprehensive modular IT system with data quality monitoring and uncertainties modules is integrated with the SCADA / EMS.

On average, 92 - 96% of the time the DLR system offers a higher transmission capacity with a median increase of 15 - 20 % of the nominal capacity. Over 20 events in N and over 500 in N-1 topologies are mitigated annually by the DLR system.

TRL 8

DLR is used on many heavily loaded OHLs. The system is integrated into most of the German TSOs' dispatching centres that exchange the ratings online.

There are different approaches for weather forecasts based on local and regional measurements as well as seasonal settings. The maximal derived ampacity differs depending on the region.

Rated capacity was raised up to 200%.

TRL 8

Terna followed a mixed approach to guarantee the high accuracy of the system and contain costs.

DLR systems have been installed on several OHLs (380 kV, 220 kV, 150/132 kV) and are currently employed in the Control Rooms. A plan to increase the number of lines monitored with the DLR system is already in place.

Terna developed a thermo-mechanical model based on the CIGRE dynamic model which estimates the main conductor parameters (sag, temperature, stress) for each span of the line using detailed meteorological short-term forecasts. In particular, the mechanical model considers the mechanical balance of the conductors on the pylon and can also be employed for High Temperature Low Sag Conductors (HTLS).

Real-time monitoring systems have been installed as feedback to the model results in the most critical spans to respect the clearance from obstacles according to Italian law.

Terna DLR solution is fully operational, supporting real-time network management. Early deployments have demonstrated the ability to increase line capacity safely, improve contingency management, and enhance network reliability under varying weather conditions.

TRL 8

EirGrid is developing a cost-effective Virtual Dynamic Line Rating (DLR) system that leverages AI and advanced weather forecasting to predict line ratings without installing physical sensors. A proof-of-concept was successfully developed and validated on the Lisheen-Thurles transmission line, demonstrating reliable performance under extreme weather conditions. The approach is being extended to other critical lines identified in the Network Delivery Portfolio (NDP), with further validation planned.

The system uses AI models trained on meteorological data to dynamically estimate line ratings. Unlike traditional DLR systems, this approach does not rely on physical sensors but instead uses virtual sensing based on forecast data and historical performance. Calibration techniques have been applied to improve model accuracy. The design aims to support grid efficiency and renewable integration while minimiszing infrastructure costs.

Proof-of-concept completed and validated. Predictions for additional lines are underway. Reliability assessment of virtual sensors vs. physical sensors is planned.

TRL 7

In 2021, a sensor-based DLR-system was implemented on two 220kV lines feeding the system with hydropower. The system has been fully operationalised since then and is now used in operations for mitigating congestions in N-1 situations, both in real-time and forecasted.

In 2025, the system was expanded to reap the benefits on selected congested lines throughout the entire country. The system is now implemented and in operations for additional lines between 220kV and 380 kV.

In addition to the physical sensors, some power lines are monitored with software-based sensors, deployed within the cloud-based application using asset data and local topography (90x90m) for precise, reliable insights about ampacity.

The supplier performed an assessment to determine optimal number of sensors and their locations to cover the expected variance in weather along the prospect overhead-lines in the Swiss Alps. The system utilizes sensors installed directly on the conductor, whereas 100% of the sensors installed in 2025 was installed by an autonomous drone system. The lines with virtual sensors were deployed along the lines with high density based on distances, change in azimuth and altitude. The entire project was scoped out, deployed and operationalised completely in just 3 months.

Per time, the average capacity increase across all lines in the project range between +27% and +54%. Further results are expected in the future.

TRL 8

Spanish transmission network has installed approximately 516 DLR sensors and 176 meteorological stations for real time monitoring of 435 km overhead transmission lines (381 km of 220 kV and 54 km of 400 kV).

In conventional operation method of electric system, wind, solar radiation, and ambient temperature values are set for each season, resulting in four annual capacity values. When DLR is used, these meteorological variables are measured continuously, allowing line capacity to be calculated according to the real environmental conditions at any given time, allowing to take advantage of a capacity adapted to the specific conditions in each case and replacing necessarily more conservative average calculation assumptions.

Spanish System Operator tries to implement DLR operation on transmission lines close to wind farms, where wind speed is usually higher and allows to increase the power at many times.

Sensors for DLR Spanish system are based on measuring the deviation angle on conductors depending on weather conditions (wind, temperature and radiation). Up to now, DLR sensors are totally supplied by one supplier. However, Red Electrica is testing new suppliers for this technology in order to widen the eligible suppliers.

Red Electrica is running a project for testing 7 different suppliers of DLR technology and a DAS system for optical fibre in order to compare the performance of each sensor to implement future projects of DLR monitoring on existing lines. All sensors are installed in the same span of Ibiza-Bossa 66 kV transmission line for getting a more precise comparison of measurements. Additionally, the measurements got by sensors are checked with conventional topographic survey.

DLR monitoring is a technology that allows to increase the ampacity above the values of seasonal ampacity.

Most of the time, ambient conditions are appropriate to increase the nominal capacity beyond the static value. Further analysis are needed to determine the benefits of this technology and the reduction of cost for the electrical system.

TRL 8