Frequently asked questions

Why is a new transmission line required?

In 2005 Southdown Joint Venture (70 per cent Grange Resources Ltd, 30 per cent Sojitz Resources & Technology Pty Ltd) approached Western Power with a request for the supply of electricity for a proposed magnetite mine near Wellstead, located 90 km north east of Albany.

Western Power assessed a number of supply options and determined that the most suitable option would be the construction of a new ~300 km transmission line from the Muja Terminal Substation near Collie to connect to a new substation at the proposed Southdown magnetite mine near Wellstead.

A number of factors caused significant delays in progressing the project and it was put on hold in 2009. In May 2010 Southdown Joint Venture requested Western Power begin progressing with the proposed transmission line approvals again.

Why was the project put on hold in 2009?

After the proposed line route was identified and announced in October 2007, Southdown Joint Venture expected the mine to be approved by June 2009. Unfortunately there were significant delays to the project including:

  • the global financial crisis
  • unexpected delays in receiving environmental approvals
  • a significant reduction in the magnetite pellet price

What other line route options did Western Power and Southdown Joint Venture consider before choosing the currently proposed alignments?

In response to Southdown Joint Venture’s request to be connected to the grid, Western Power undertook extensive community consultation and investigated a number of line route options, including a line route via Kojonup to the Mt Barker/Albany area and then east to the mine site, before deciding on the final alignment. For more information please visit the Western Power website.

How much power does the proposed mine require?

The Southdown Joint Venture project will now require 180 megawatts (180 MW). Based upon this electrical load requirement and the distance over which the transmission line will traverse, Western Power determined that the most suitable supply option would be a new 330,000 volt (330 kV) transmission line.

What does the project involve?

The project will see the construction of:

  • a new 330 kV bay at the existing Muja Terminal Substation
  • a new 330 kV transition compound located 800 metres from the existing Muja Terminal Substation (a transition compound allows for the connection of an underground 330 kV cable to an overhead 330 kV conductor)
  • an 800 metre section of 330 kV underground cable between the new bay and the new transition compound
  • a new 87.5 km double circuit 330 kV transmission line between the transition compound and Kojonup
  • a new 190.5 km single circuit 330 kV transmission line between Kojonup and Wellstead
  • a new 330 kV terminal substation at Wellstead

Why is a section of 330 kV underground cable required?

The area surrounding the existing Muja Terminal Substation is aerially constrained by a large number of existing overhead transmission lines that emanate from the site, therefore a short section of underground cable is required to allow the new line to exit the site before transitioning to an overhead line.

Why can’t the whole line be underground cable?

The cost of underground cabling for lines of this voltage is considerably higher than the cost of an overhead option. Subject to a number of considerations such as soil type, topography and electrical capacity required, underground cables at this voltage can cost in excess of 10 times the cost of an overhead option.

What benefits will the transmission line bring to the community?

The proposed transmission line will increase the network capacity within the Great Southern Region allowing for natural load growth and the connection of future loads and generators.

The double circuit section of the line between Muja and Kojonup will provide the most significant increase in network capacity. Once the new 330 kV transmission line is constructed, an existing wooden pole 132 kV line will be removed. The timing of the removal is not yet confirmed, but is likely to be within two to three years of the completion of the new line.

Will farm GPS equipment be affected by the power line?

Western Power commissioned a study in to the potential impacts of transmission lines on GPS equipment. The study found no conclusive evidence that transmission lines cause interference to GPS equipment.

What happens if a farmer hits one of the structures with some farming equipment and ‘takes out the line’?

Western Power will immediately repair any damage to restore power supply as quickly as possible. Western Power would then seek to recover the costs of the repair from that person.

What will the new transmission line look like?

  • Construction type
    The proposed transmission line will be constructed using steel lattice towers. Between Muja and Kojonup the line will be constructed as a double circuit 330 kV transmission line. Between Kojonup and Wellstead the line will be constructed as a single circuit transmission line. A section of poles will be used to the south of Gnowangerup to minimise visual impacts on views to the Stirling Ranges.
  • Tower height
    The proposed transmission line will be constructed using steel lattice towers typically ranging from 42 metres to 58 metres, subject to tower location, topography and design constraints such as sensitive environmental areas. The section of poles will range from 33 metres to 42 metres.
  • Line height / clearance
    The proposed transmission line will be supported by steel lattice towers and the lowest conductor will be no less than 11.5 metres from the ground. The line has been designed to allow for the use of ‘over height’ equipment that is often used in cropping/wheatbelt areas, this allowance has resulted in an increase in height of the lowest conductor (wire) from nine metres to 11.5 metres from the ground.
  • Voltage
    The proposed transmission line will be operated at 330 kV.

Will the new transmission line emit high levels of electric and magnetic fields (EMFs)?

EMFs occur both naturally and from man made sources. Natural EMFs are associated with lightning, solar activity or the earth’s magnetic field. Man made EMFs occur whenever electricity is used in electrical equipment or wiring. Most people will be exposed to a variety of EMF sources during their daily lives, through use of electrical equipment and household and business wiring.

EMFs are measured in a unit called a ‘milliGauss’ (mG). When a person is standing directly under a transmission line, the EMF level is typically 10 to 200 mG, however this drops to two to 50 mG by the edge of the easement (up to 25 metres from the line). These typical levels are expected to be emitted by the new transmission line. As a comparison, an electric blanket would typically emit five to 30 mG.

Western Power and the rest of the electricity industry have followed interim guidelines for exposure to EMFs developed by Australia’s National Health and Medical Research Council (NHMRC). Under these NHMRC guidelines the recommended magnetic field exposure limit for members of the public (24 hour exposure) is 1,000 mG. Western Power has operated its electricity network, including powerlines and substations, to comply with these exposure limits.

The NHMRC guidelines have now been officially withdrawn ahead of the release of an Australian standard. In December 2006 the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) released a draft new standard for EMF exposure taking into account the latest scientific research. This draft standard includes similar public exposure limits to the NHMRC guidelines.

Whilst the balance of evidence does not indicate that exposure to EMFs results in adverse health effects, Western Power recognises there are still concerns in the community about EMF exposure and takes its responsibility seriously to help address these concerns.

Western Power will continue to:

  • provide balanced, accurate information to our employees and customers, including EMF measurements and advice
  • take prudent avoidance measures to limit field exposures from new facilities by locating and operating our electrical installations prudently within Australian health guidelines
  • closely monitor engineering and scientific research, overseas policy development and major reviews of scientific, medical and engineering research regarding EMF and health
  • cooperate fully with any bodies established by governments in Australia to investigate and report about power frequency EMF

Will this project go ahead?

Both owners of the Southdown Joint Venture project, Grange Resources and Sojitz Resources & Technology Pty Ltd have approved funding and execution of the Project Definitive Feasibility Study (DFS). The DFS will assess the profitability of the Southdown Project and is targeted for completion in early 2012.

What is Western Power doing to manage biosecurity?

Western Power in consultation with affected landowners, the Department of Agriculture and Food and the Department of Environment and Conservation will develop appropriate clean down strategies along the length of the line to ensure the risk of spreading noxious weeds and other diseases is minimised and mitigated. 

Cleaning down of all machinery and plant equipment prior to crossing landowner boundaries shall be undertaken similar to those processes used for managing dieback.  In dry conditions a brush down may be adequate whilst in wet weather conditions washing vehicles will be necessary.