Resisting heavy ice loads in the Carpathian mountains with Nexans LoSag conductors

Optimize capital expenditure without compromising performance

Transelectrica, the Romanian TSO, needed to upgrade its Stejaru – Fantanele – Gheorgheni 220kV line, representing a total of 448 km of conductors. The objective was to double ampacity while keeping existing clearances. 

The line route crosses several topologies of specific climatic constraints. Especially, one section passes over mountain peaks and is exposed to heavy ice load conditions. 

ACSS in valleys, HTLS LoSag in mountains

Nexans proposed and supplied a reconductoring solution including 2 conductor designs. This allowed to optimize project CAPEX by adapting the mechanical performance of the conductor to the topological and climatic constraints of the each section :

• ACSS 423-AL0/58-5MS8A conductor for sections located in lowland areas (354 km)
• ACPR LoSag 408-AT1/57 conductor for sections at higher altitude (94 km) and subjected to heavy ice load conditions.

Nexans solution

LoSag conductors were first commercialized by Nexans in 2011. They feature a composite core exclusively  made of long carbon fibers. This lightweight strengthening element provides high modulus and breaking load compared to standard solutions. When combined with thermal aluminum wires, LoSag conductors allow to double line ampacity while respecting existing clearances even in case of ice accretion on the conductor.

For this project, Nexans ACPR LoSag 408-AT1/57 was selected by Nexans OHL technical experts as a result of a thorough sag tension study.

The conductor was installed in 2024 as a single bundle.

Main features:

• Conductor diameter: 25.4 mm
• Linear weight: 1.26 kg/m
• Breaking Load: >14.7 mtons
• Elasticity modulus above knee point: 160 GPa
• Design Ampacity: 1320A at 150°C
• Maximum continous operating temperature: 150°C by design
• Line Voltage: 220kV