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Advantages of Underground Cables vs Overhead Lines

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    Advantages of Underground Cables vs Overhead Lines

     

    There are a number of advantages associated with undergrounding of the transmission line across the development which include the following:

    • Reduced visual impact by removing tower No. 11 in the centre of the development and the two aerial conductor spans on each side of the tower;
    • Underground cables do not emit electric fields as the over burden of the backfill material in the cable trench provides a barrier through which the electric field cannot pass;
    • Short length of proposed cable run (approx. 750m) can be installed in a single run without the requirement for cable joints;
    • Underground section of line is not susceptible to failure from wind events (other than landing poles in the transition enclosure), i.e. eliminates the risk of tower 11 experiencing structural failure during an extreme wind event and causing damage or harm to the public;
    • May reduce public perception of electromagnetic field (EMF) issues;

     

    Disadvantages of Underground Cables vs Overhead Lines

     

    There are a number of disadvantages associated with undergrounding a short section of overhead line including the following:

     

    • Increased footprint and visual impact from installation of two underground to overhead transition enclosures;
    • Increased visual impact from two new strain towers, which would be larger and more robust than existing suspension towers;
    • Introduces different maintenance requirement for that specific section of line. SP AusNet would require a specially trained maintenance provider to respond to operation, maintenance and fault issues;
    • Slight increase in EMF directly above the buried location of the cable;
    • Introduces new potential points of failure along the transmission line;
    • Increase in time to repair in the case of a cable or sealing end fault;
    • Introduces non-standard arrangement into SP AusNet network by operating a hybrid line of both underground and overhead sections;
    • Increased risk of public exposure to Earth Rise Potential in the vicinity of the transition enclosures;
    • Increased risk of electrocution to public from illegal access to the transition enclosures;
    • Underground cable run would potentially relocate the transmission line route closer to some residences;
    • Increased risk due to buried electrical asset for anyone performing excavation work in the vicinity of the cable route;
    • Landscaping options within immediate proximity of underground cables will be limited.

     

    Reference: AECOM Australia 

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