BPI has developed the Protean overhead line design system utilising folded steel poles for the replacement of wood poles or new lines. The Protean system features a specialist foundation design using a proprietary screw–anchor system which can be installed with minimal height plant and therefore without the requirement for a circuit outage.
Development of Protean
BPI has undertaken a detailed review of the current design methodology for wood pole overhead lines within the UK and found that there are considerable advantages in using alternative materials and design processes at voltages from 11 to 132kV. The UK power generation map has changed considerably in recent years with the introduction of numerous large renewable energy generators. Such renewable generation schemes have placed considerable load on the 11, 33 and 132kV distribution systems driving the requirement for the use of larger conductor systems to support the increased generation at many locations on the DNO’s networks.
In many instances the traditional wood pole design is proving inadequate, and alternative stronger materials with fully designed foundation systems are required to cope with the increased mechanical loading of the larger conductor systems and the application of the latest European design standards.
The Protean system
BPI has worked with a number of UK overhead line suppliers to develop and refine the Protean system. The Protean design philosophy is based on an efficient line design which is safe and constructible with limited outage requirements. This is achieved using the latest overhead line design software and specialist structural analysis to develop a bespoke line design for each application.
One advantage of the Protean system is the ability to customise the design at the concept stage. At the outset of the project the number of circuits, required line rating and requirement for earthwire and communications is agreed with the client. Following this, a design process is undertaken in which the conductor system, basic span, structure height and strength are reviewed taking into consideration the terrain and other factors such as planning and wayleave constraints, to provide an economical fit for purpose design.
A hinged pole base section means the structures can be fully assembled on the ground before a hydraulic ram is used to lift them to the vertical position. Each pole takes around six minutes to lift, meaning outage times are much less than with conventional wood pole overhead line designs.
If required, the foundation and mast can be designed to remove the requirement for supporting stays at angle and terminal structure locations, providing a more compact structure footprint to aid with planning and consents.
The Protean design pack
To ensure the Protean installation is carried out safely and meets the design specifications, a complete design pack is produced for each bespoke design. The design pack 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