DSO TSO Technopedia

380kV lines on Dutch HV ring commissioned between 2019 and 2025 under the “BBB380” programme (BBB = Beter Benutten Bestaand).

Implemented Advanced Conductors following CBA comparison against All Aluminium Alloy conductors (AAAC) and Gap conductors, yielding 27% lower cost over 40 years savings.

Projects and justifications described in Cigre Paper B2/10574, presented to the Paris Conference in 2024 [1].

Upgrading 380kV transmission backbone (Triple-bundle, double-circuit).

Country-specific Factors

• Uprate circuit capacity from 2,500 to 4,000A
• Adhere to strict magnetic field zone rules in the Netherlands
• Maintaining/improve on existing catenary profile
• Minimise impact on existing towers and associated civil works

Difficulties/Challenges with Implementation

Challenge	Solution
Final sag and conductor creep respecting desired final sag profile	Pre-tension conductors to 1.5X installation tension for 1 hour/conductor
“Live-line” working, adjacent circuit remaining energised	Additional earthing provisions to prevent inductive
Contractors unfamiliar with “new” Advanced Conductor technology	Conductor suppliers present during stringing works to provide supervision.

Gains and Advantages

• Increased transmission capacity from 2,500-4,000A on existing infrastructure
• Short project duration (start planning till energizing upgraded line within 3 year)
• Lower cost over 40 years compared with AAAC (70km line):

TRL 8

Advanced Conductors being serially applied on TenneT Netherlands 380kV network and occasionally on 110kV.

https://www.e-cigre.org/publications/detail/b2-10574-2024-design-challenges-and-recommendations-in-uprating-the-existing-380-kv-overhead-lines-the-netherlands.html

The first prototype was installed in northern Germany in 2010. The next prototypes were installed in southern Germany in 2017 and 2018. Large-scale installations are expected to begin in 2026.

This technology was introduced to our network to increase the capacity of the existing lines from 2,720 A to 4,000 A per phase. The objective was to use the existing towers without modification. The main challenge is to ensure compliance with all clearance requirements in all weather and loading conditions (temperature, ice and wind).

Using a composite core in combination with the correct type and shape of aluminium wires enables different conductor types to be designed for clearance requirements, noise reduction requirements, or to reduce mechanical loads on towers.

For our purposes, the biggest advantage is the increase in ampacity from 680 A per conductor at 80 °C to 1,000 A per conductor at 150 °C without exceeding the available clearance.

Using tubes in combination with a carbon core increases the diameter and improves the noise level by 2 to 3 dB(A) [1].

Using shaped wires with a carbon core reduces the conductor's Drake coefficient from 0.9 to below 0.6 for critical wind ageing on overhead lines. A new characterisation of this parameter enables new probabilistic calculations for existing lines [2].

TRL 8

Unterfinger, J. et al., CIGRE PARIS SESSION 2024 - 11132, Noise-reducing conductors for reconductoring projects: system development and pilot installation,

Steevens, S. et al., CIGRE 2025 CSE 036, Drag coefficient modelling for OHL conductors.

To increase the transmission capacity of 3 existing overhead transmission lines, it was reconducted former ACSR conductor by ACSS conductors (ACSS Condor AW) in the following projects:

L/220kV Cartelle-Castrelo (Northwest of Spain)

• Simple circuit single bundle,42.6km length, commissioning date: 30/07/2024

L/220kV Almaraz CN-Trujillo (Western of Spain)

• Simple circuit single bundle, 47.6 km length, commissioning date: 24/03/2025

L/220kV Escatrón-Espartal (Northeast of Spain)

• Simple circuit single bundle, 49.2 km length, commissioning date: 30/04/2025

The technology was introduced to increase the capacity of the existing lines about 50-80% (increasing maximum temperature from 85°C to 200°C). The objective was to use the existing towers adding some panels on the bottom section to increase the height of the conductors above the ground.

The main challenge was the stringing on the conductors due to annealing aluminum of ACSS conductors, that requires more careful handling than conventional ACSR conductors.

ACSS was not used in the past in Spanish transmission network. The necessity to increase the ampacity of existing lines and the problems for building new lines, has made to consider the use of high temperature conductors to get extra capacity of existing lines.

For this purpose, it has been used ACSS conductors for reconductoring existing lines, with the following challenges:

• Elaborate technical specification for ACSS conductors and testing the conductors for different suppliers (national and international)
• Elaborate technical specification for ACSS hardware and testing the components.
• Improve the handling of conductors during the transportation and stringing activities.

Additionally, for reconductoring the lines without increasing the strength of existing towers, the design of the project has maintained the maximum tension of the conductors in each section of the line and the weight supported for the structures, in order not to modify the original designing of the line.

The main advantage of the project is the increase the ampacity of the line from 1173 A per conductor at 85°C to 1748 A per conductor at 200°C without reinforcement of existing towers. It was needed the increasing of the total height of some towers to allow the higher sag on conductors.

TRL 9

UNE-EN61284 Standard OVERHEAD LINES. REQUIREMENTS AND TESTS FOR FITTINGS

IEC 62641 Conductors for overhead lines - Aluminium and aluminium alloy wires for concentric lay stranded conductors

IEC 63248 Conductors for overhead lines - Coated or cladded metallic wire for concentric lay stranded conductors

UNE-EN 50540 Conductors for overhead lines - Aluminium Conductors Steel Supported (ACSS)