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Project Scope

Horizon Power’s Karratha Terminal (KRT) and Dampier Substation (DMP) is connected via a 19km single 132kV circuit KRT-DMP 81. It was Horizon Power’s intention to replace the majority of the line infrastructure due to the assets reaching its end of useful life. Approximately 5.6km of KRT-DMP 81 was replaced in 2012 as part of the Gap Ridge development and was to remain as is.

Partum was engaged to undertake the design for:

  • 13.4km of 132kV powerline.
  • New overhead fibre (OPGW) for the entire line length.
  • Earthworks design for construction pads along a 3km tidal salt flat section.
  • 650m of underground and two cable termination structures due to vicinity to airport.
  • Landing span and gantry at the existing Dampier substation.

Challenges Overcome

  • Design of foundation covering extreme variations in soil conditions along the line route – problematic alluvial sand silt mud tidal salt flats (including acid sulphates) up to fragmented and solid hard rock.
  • Ensuring clearance with the Karratha Airport Civil Aviation Safety Authority (CASA) Zone flight landing and take-off profile.
  • 650m of underground cable design including road crossings.
  • Designing the new gantry within the existing Dampier substation that had space constraints.
  • Numerous underground services and fences along line route.

Solution

  • Extensive PLS CADD modelling to confirm phase and ground clearances including the new OPGW in the existing section.
  • 3D modelling of the cable termination structures to confirm no infringement on CASA zone.
  • Refining the foundation types and designs against preliminary geotechnical data and on-site ID drilling.
  • Optimisation of the earthworks construction pads in challenging tidal terrain.
  • Detailed insulation coordination assessment for the surge arrestor selection.
  • Assessing the current ratings, costs, and practicalities for several cable installation arrangements.
  • CDEGS modelling for the powerline earthing and lightning and confirm voltages on 3rd party assets.

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