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Project Scope

Partum Engineering was engaged to provide the detailed engineering design for a 16.5 km 220 kV single circuit overhead transmission line (OHTL), forming the SOL–QUE line connection. The new line links the existing Solomon (SOL) Substation to the new Queens (QUE) Substation.

Challenges Overcome

  • A suitable 220kV cable transition structure from overhead to underground (UGOH).
  • Cable sealing ends and surge arrester placement locations. Sealing End Compounds transitioning from underground cables to overhead lines requires sealing end compounds, which are large, complex structures that must safely terminate the cable and connect to overhead conductors. These require careful siting and design to manage electrical stress and ensure safety.
  • Earthing design for 220kV OH-UG (Overhead to Underground) transmission structures presents several unique challenges due to the complexity of fault current behaviour, soil conditions, and safety requirements. Multiple Current Paths: Fault currents can flow through tower earthing, cable sheaths, shield wires, and transformer neutrals. Accurately modelling these paths is essential to predict Earth Potential Rise (EPR) and ensure safety.
  • Overland conveyor structures crossing under 220kV transmission line presenting potential induced voltage hazard for operations personnel.

Solution

  • Custom designed UGOH structure to accommodate site needs.
  • Intensive evaluation and collaborative process for the large, complex structures that must safely terminate the cable and connect to overhead conductors. Engineering assessments for structural stresses at mounting points allowed a suitable solution to be achieved.
  • Accurate modelling of earthing system to identify multiple current paths and ensure suitable earthing integration with the substation.
  • Detailed CDEGS modelling of the overland conveyor structure to accurately assess the potential hazards induced from the new 220kV transmission line.

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