The VNI West project will utilise 500 kV towers, expected to be between 60m to 80m high and will look similar to those towers you would see driving into Melbourne. The towers will sit on bases of between 15m2 and 20m2 depending on the tower type and design. Towers for the VNI West project are expected to be spaced roughly 400m apart dependent on terrain.
In general, when identifying a potential route TCV will seek to maximise setbacks to residential dwellings, areas of cultural heritage value, community and tourism infrastructure, and any other areas of social, cultural or environmental sensitivity.
A typical design guideline is a setback distance of 300 metres between the transmission line and a residence, although this is not always possible.
The transmission towers are expected to be between 60 metres and 80 metres high in areas, similar to the towers you see driving into Melbourne. The lowest sag point is likely to be about 15m from the ground.
The tower will cover an area in the range of 15 x 15 metres or 20 x 20 metres, depending on the tower type and design.
The easement for VNI West will be between 70 metres and 120 metres wide to allow access for maintenance and for safe operations. The easement will not be fenced, and many farming activities can continue to take place underneath the transmission lines, as long as safety requirements are met. See the Farming and Transmission Fact Sheet.
VNI West’s transmission infrastructure will be built to the latest overhead line design standards. The transmission line, including structures and foundations, are designed for a minimum “service life” of 70 years.
Decommissioning occurs when a transmission line has reached the end of its useful life and is de-energised, and typically removed. Most overhead transmission lines have a long lifespan, so decommissioning of existing transmission lines is not common but may occur if the transmission line is being replaced with a higher voltage line. Remediation and associated costs would be the responsibility of the TNSP (Transmission Network Service Provider - the owners of the transmission infrastructure).
The distance between each tower will be roughly 400 meters, however this may vary with the terrain.
There may be new access tracks needed to support construction on some properties. Once the design is further developed, TCV will work with each landholder to create a Property Management Plan (PMP) specific to the easement on their property. The PMP will be an attachment to the easement agreement (Option Deed) entered into with each landholder. The agreed PMP will specify any required temporary fencing of the construction workspace, including access crossings (if required), as well as any other construction impacts and mitigation methods that the project can implement to ensure the broader property can continue to be utilised as usual by landholders. Where there is any productivity or access loss, this impact needs to be considered and factored into the assessment of compensation. The impact will be specific to the property.
While visual impacts and bushfire risk are reduced, undergrounding raises its own issues. A concrete trench must be installed to house the transmission, which causes significant disturbance to flora and fauna. There are many restrictions associated with farming activities above an underground line, and maintenance and repairs are more difficult and disruptive.
In addition, the cost of undergrounding is generally much greater compared to overhead lines and would add to the time construction would take – recognising that transmission projects are ultimately paid for by electricity consumers.
A recent study commissioned for the NSW HumeLink project noted that undergrounding would triple the project cost and add a further five years to the construction timeline. The NSW Government has elected to proceed with the original plan for above ground lines.
TCV is proposing to conduct an Undergrounding study as part of the EES impact assessment.
Double circuit 500kV transmission lattice towers at 90° line angles are not feasible because it would significantly increase the tower design complexity. Towers would need to have additional crossarms and insulators to accommodate the connection from back span to foarward span without violating structural clearances. As the conductors are strung at full tension in both directions, there is a possibility of greater tension imbalance and increased loading at the towers. Footings would also increase significantly in size.
