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Overhead lines

Mott MacDonald provides all design, engineering and management services for the development of transmission lines. Using the latest analysis and simulation software, we deliver profile optimisation and tower design which complies with all international codes. We also possess extensive foundation design capabilities.

Our experience in transmission lines covers a huge variety of terrains and climate conditions.

Our experience in transmission lines covers a huge variety of terrains and climate conditions. We've worked on 11kV lines (distribution network) to 750 kV lines as part of many backbone transmission systems.


Our overhead transmission line team specialise in services for lines from 11kV up to 750kV, including:

  • Engineering - management of transmission line projects including route selection, design, specification, environmental assessment, tendering, auditing detailed designs, inspection and testing of materials and line components, foundation testing, site supervision and commissioning.
  • Structure design - the latest tower modelling software to help us design transmission line towers, substation structures and radio masts. These can be new designs or re-assessment of existing structures to carry different loads – such as larger conductors for transmission lines or a different array of antennae or aerials for radio masts/towers. We undertake designs for all types of structures, including: steel lattice, wood poles, concrete poles, tubular steel and folded plate poles.
  • Tower testing - We have experience with tower testing stations globally and regularly witness full-scale tests to prove tower design capabilities.


Our overhead transmission line team specialise in the following services:

  • Condition assessment
  • Conductor ratings
  • Emergency restoration systems
  • Engineering
  • Foundation design
  • Insulation
  • Line profiling and routing
  • Line working procedures
  • Optical fibre
  • Structure design
  • Tower testing
  • Training courses

Some of these services are detailed below:

  • Insulation - Our experience in insulation design standards is considerable and covers the widely diverse performance requirements of climates across the world. Services include establishing insulation levels, appropriate insulator materials and shed shapes, insulator washing systems and insulation co-ordination throughout the line.
  • Foundation design - Mott MacDonald has many years of experience in foundation design to suit a wide variety of structure types and various soil conditions. These include pile, pad and chimney, raft and rock anchors.
  • Line profiling and routing - We utilise PLS-CADD for the optimisation of tower positions on line profiles. We also undertake conductor and earth wire sag/tension calculations, creep calculations and erection sags/tensions using this software or our own in-house software.
  • Routing - Undertaken on the ground and by aerial survey to investigate viable alternatives leading to the most cost effective route. In tandem with the survey process, we're also able to undertake environmental impact studies.
  • Conductor ratings - These include the calculation of continuous and short circuit ratings for conductors on transmission lines and in substations.
  • High temperature conductors - We've undertaken several projects around the world which have involved the installation of specialized high temperature conductors, including GAP-Type and ACCC (composite core) conductors.
  • Optical fibre optical systems - Used on many of our transmission line projects, self-supporting, and wrap-around systems and their fittings.
  • Line working procedures - we can develop procedures for the erection and maintenance of conductors and insulators, including the selection and application of appropriate equipment. We can also provide advice for the installation of foundations and the erection of towers
  • Condition assessment - Condition assessment and monitoring of existing assets has become significant in recent years. To aid us in this area, we've developed a risk-based strategic analysis process that provides a cost effective approach to this work. The information gained can be used to develop asset management, refurbishment and maintenance plans.
  • Emergency restoration systems - We design emergency restoration schemes for overcoming temporary loss of an overhead line, including the development of procedures and the selection and application of appropriate equipment.
  • Energised or live line work - We've assisted and guided specialist contractors that carry out transmission line construction and refurbishment under energized conditions. The work can include replacement or rehabilitation of existing hardware, conductors and entire structures. We've assisted contractors or projects where conventional conductors are replaced with high temperature conductors under energized conditions.
  • Training courses - Mott MacDonald has provided training courses on overhead line design to various utilities throughout the world.

Customer benefits

A detailed knowledge of all overhead transmission line options to suit local conditions.

Savings/value added demonstrated

An optimised solution with respect to

  • Route selection
  • Tower design
  • Conductor design

Selected project examples

We have worked on major projects of up to 750kV in locations worldwide, including:

  • UK
  • Hong Kong
  • Indonesia
  • Jordan
  • Malaysia
  • South Africa
  • Botswana
  • Zambia
  • Mozambique
  • Malawi
  • Ghana, Namibia
  • Nigeria
  • Oman
  • Syria
  • Ukraine
  • Slovak Republic
  • USA
  • United Arab Emirates.
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