The main components of overhead line are towers, tower foundation, conductors and insulators. The task of the tower is to carry the conductors, that are spanned between 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 experience little acceptance in public. Hence, the new tower concepts aim to minimize visual impact and optimise the emissions and support public acceptance.
In HV and EHV following types can be differentiated:
Components & enablers
Advantages & field of application
The target of new tower concepts is to create compact, environment friendly and affordable tower design, that potentially increase the acceptance in public.
Moreover, the compact design can allow to increase the capacity in right of way, if the latter one cannot be extended (e.g. 2x380 kV circuits in previous 2x220 kV right of way), or allow to reduce 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.
Challenging is to design a new compact tower while keeping present invest and maintenance costs, degrees of freedom for maintenance and repair works and also reducing the electromagnetic and noise emissions.
Best practice performance
Typical EHV lattice tower
Number of circuits: 2x380 kV
Power rating: 2x2600 MW
Voltage rating: 420 kV
Nominal current: 4000 A
Conductor: Quad-bundled Al/ACS 550/70
Tower height: approx. 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.
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 Zwarts and Jansma Architects. High Voltage Pylons. [Link]
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