The main components of OHLs are towers, tower foundation, conductors and insulators. The task of the tower is to carry the conductors that span two towers on insulators. In HV and EHV applications, mostly lattice towers are used because of their high efficiency, security in operation and cost effectiveness. Nevertheless, the conventional lattice tower concepts are understood as old and receive little acceptance by the public. Hence, the new tower concepts aim to minimise visual impact and optimise both the emissions and public support.
In HV and EHV, the following types can be differentiated:
Components & enablers
Advantages & field of application
The target of new tower concepts is to create a compact, environment friendly and affordable tower design that potentially increases public acceptance.
Moreover, the compact design can allow the capacity to be increased in right of way if the latter cannot be extended (e. g. 2 x 380 kV circuits in previous 2 × 220 kV right of way), or allow a reduction in the height of the towers by reducing the conductor sag (e. g. 50 Hz example).
Technology Readiness Level
TRL 9 – Lattice towers
TRL 7 – New designs in pilot stage (e.g. full wall)
TRL 4 – Ideas and studies
Research & Development
Current fields of research:
Different approaches for full wall tower designs; insulated cross arms; compactness; reduction of air clearances by application of surge arresters.
Challenges are the design of a new compact tower while maintaining the current investment and maintenance costs, degrees of freedom for maintenance and repair works, and also reducing the electro-magnetic and noise emissions.
Best practice performance
Typical EHV lattice tower
Number of circuits: 2 × 380 kV
Power rating: 2 × 2,600 MW
Voltage rating: 420 kV
Nominal current: 4000 A
Conductor: Quad-bundled Al / ACS 550 / 70
Tower height: Approximately 60 m
Best practice application
Netherlands to the border with Germany
Given the densely populated area of Randstad in Netherlands, conventional steel lattice pylons could no longer be installed to expand the grid as it would restrict building construction on a 300 m radius along the power line. The circuits are attached to two full wall steel pylons by insulated cross arms. The circuits are placed close to each other in two horizontal planes and phase twisted correspondingly in other to reduce total magnetic fields.
The building restriction was reduced to a 200 m radius and the tower design is visually less disrupting.
Germany to the border with Netherlands
In order to increase the local public acceptance and gain experience with innovative tower designs, the German part of the OHL to Netherlands has been realised with full wall steel pylons, and full wall steal cross arms. The two 380 kV circuits consisting of three phase quad-bundled aluminium-steel 550/70 conductors (1050 A per conductor) are arranged on both tower sides in delta arrangement on two cross arms.
The building of full wall steel pylon towers is more expensive comparing to conventional one, mostly due to transportation requirements/limitations and foundation works. Moreover, for many components the standards are not available.
 Hydro Quebec. Power Transmission Towers. [Link]
 Zwarts and Jansma Architects. High Voltage Pylons. [Link]
 Kumar S, Kumar A. Design of Steel Structures. [Link]
 IJSETR. Design Transmission Tower and Its Foundation. [Link]
 IJMER. Analysis and Design of Transmission Tower. [Link]
 Pearce, D. Environmental valuation in developed countries: Case studies. [Link]