BPI has undertaken a detailed review of the current design methodology for overhead lines using wood poles within the UK, and has found that there are considerable advantages in using alternative materials and design processes to provide efficiencies at voltages from 11–33 and 132kV. The UK power generation map has changed considerably with the introduction of large renewable energy generators. The renewable generation schemes have placed considerable load on the 11–33 and 132kV distribution systems. This has driven the requirement for the use of larger conductor systems to support the generation at numerous locations on the UK DNO networks.
The traditional wood pole design requires alternative stronger materials with fully designed foundation systems due to the increased imposed loading of the larger conductor systems and the application of the latest codes of practice. As a result BPI has introduced the Protean OHL design system.
The Protean system
BPI has worked with a number of UK overhead line suppliers to develop and provide the Protean system. The Protean design philosophy is based on using the latest overhead line design software and specialist structural analysis of the mast. The resultant foundation loads require specialist foundation design using a proprietary screw–anchor without the requirement for supporting stays at angle and terminal poles.
A feature of the Protean system is the ability for the client to customise the design at the concept stage. At the outset of the overhead line design the following are user definable: the number of circuits, conductor size and operating temperature, the requirement for a conductor shield and communications conductor together with the basic span and maximum structure height. Once these variables are agreed, a design process is followed to complete the Protean design for the selected route.
The Protean design pack
The Protean system can be designed to meet the specific requirements of the selected overhead line route. To ensure the Protean installation is carried out safely and meets the design specifications, a complete design pack is produced for each design. The design contains as a minimum the following drawings and documents:
- Overhead line route maps
- Overhead line profiles
- Protean structure setting out coordinates
- Engineering compliance document
- Erection sag and tension document
- Protean general arrangement and erection drawings
- Protean foundation design with drawings and calculations
- Design risk management schedule
- Protean fixtures and fittings document
- Geotechnical survey data
- Installation method statements
- Access maps with working areas
The design pack is discussed at the start of each project.