for sustainability

Innovative Repowering of AC Corridors


Demo 4 objectives are addressed in three parallel sub-projects:

The first aims to research, analyze and model existing high-temperature low-sag (HTLS) conductors with a focus on ageing behaviour (temperature, electrical and mechanical effects) and determine the benefits of insulated cross-arms.

The second intends to validate all potentials for innovative design and field working processes, including retrofit process and live line working.

The third consists in the development of a prototype dynamic line rating (DLR) system based on low cost sensors allowing higher temperature operations of current line technologies.

Nature of work that will be performed

  • The main goals of the HTLS and cross-arms research and demonstration are to identify and evaluate existing HTLS technologies, analyze physical line parameters (mechanical, electrical, thermal) relevant for long-term fatigue and creep modelling, identify predominant ageing mechanisms as a function of working parameters (temperature, load profiles, etc.) and implement improvement options of existing overhead line models (capacity and sag modelling). Research will focus on tests for long-term behaviour, including ageing, and operation under real conditions. The main purpose of the simulation is to determine the conductor sag of HTLS conductors and the loads on towers. Insulated cross-arms research will include water-induced corona tests, pollution tests as well as tracking and erosion tests on the insulated cross-arms with a duration of 5,000 h.


  • The objectives of the innovative design and field working research and demonstration are to increase the safety during construction and operation of the AC lines, reduce the overall costs and decrease the building time. These will be done through one of the pilot projects: either replacing of simplex with duplex conductors in the same corridor; 'upgrading' some simplex to duplex with as few outages as possible or; focusing on new tower design using composite towers for 420 kV lines. The aims of the life line working (LLW) research and demonstration are to take into account the constraints of electric and magnetic fields and conductor car motion through the insulators and insulator string replacement of glass and composite insulators.


  • The main goals of the DLR are the development of a new type of DLR implementation, the increase of efficiency of existing conductors, and implementation of the conductor monitoring with a new sensor and software development.

Expected results and benefits

The results will be packaged into a self-standing line upgrading package which will help TSOs to deliver overhead lines that are more:

  • compact and therefore more acceptable on visual standpoints and less demanding in right-of-way,
  • robust to face fluctuating power profiles,
  • flexible in exploitation (reducing the need for new AC overhead line corridors) and
  • affordable to run (acceptable CAPEX and OPEX figures including maintenance).

The combination of the solutions enhances the existing system approach to AC overhead line repowering. It will also help TSOs and utilities to keep overhead lines reliable and resilient under the light of the developments in the European energy system, and allow replication by other ENTSO-E members.

Partners involved

50Hertz Transmission (Leader), Elia, Statnett, Mavir, STRI, EFLA, BME Viking, BAM, TU Dresden