Little Barford

The brief

UK Power Networks required a detailed feasibility study and concept design for the routing of new multiple 5 km long 132kV cable circuits.  In addition, an extensive redesign of Little Barford substation was required, as well as the design for a new 132kV substation at an existing National Grid site at Eaton Socon.  The new cable route required an existing 132kV overhead line to be terminated at two locations to receive the new cable circuits.  The fifth circuit required an existing overhead line to be terminated with a new terminal tower and the dismantlement of the remainder of the route.

The approach

BPI used the latest LiDAR aerial survey technology to undertake a large 5 km x 5 km survey across the existing substations and cable route.  From the LiDAR survey data, multiple potential route corridors were identified, enabling the wayleave and consents team to finalise a best option route.  Full 3D CAD models of the substations, plus stage by stage dismantlement and construction plans were also produced from the data.  Based on the LiDAR data set, a directional drilling design was produced for a number of road crossings.  Overhead line terminations were designed ensuring the correct terminal tower extensions were specified to meet statutory ground clearance.

The challenges

The Little Barford design project encompassed a very large working site with a number of landowners, road and existing infrastructure constraints.  Little Barford substation contained hazardous areas with limited access, so a traditional survey approach was not possible.  Using LiDAR at a safe working distance, high resolution images and HD video provided a data set to allow BPI engineers to investigate a number of design options not available using traditional survey methods or aerial photography alone.  

The delivery

With a tight delivery programme BPI processed the design using specialist software and working closely with the consents team and the client to produce an agreed cable route and final positioning of all terminal towers.  A suite of drawings and reports detailed the cable route, joint bays, and tower locations.  The design was complete with outline planning drawings of the new 132kV substation at Eaton Socon and detailed drawings at Little Barford supporting the dismantlement and new circuit arrangements.