Question 1. Do high voltage transmission lines emit radiation?
No, not the radiation that people normally think of (‘Ionising’ radiation), like that produced by Uranium or Nuclear Reactors. The emissions from electricity lines (also called radiation – or ‘non-Ionising’ radiation) consist of low frequency electric and magnetic fields which are either static in nature (DC systems) or alternate in the form of a sine wave 50 times per second (in AC systems in Australia).
Question 2. What is the difference then, between ‘Ionising’ radiation and ‘Non-ionising’ radiation?
Ionising radiation is emitted by atoms undergoing nuclear decay, such as in Uranium, Plutonium and other radioactive materials. The high energy particles that are emitted by these materials (alpha, beta and gamma, along with neutrons and other sub-atomic particles) are known to cause damage to cells because they collide with them and physically destroy their structures, including their DNA.
Non-ionising radiation is different because it is made up of electric and magnetic fields, which can influence things (like a magnet attracts metal) and can affect the way some biological matter ‘behaves’, but the changes are generally not permanent and the effects stop when the fields are removed. The exception is when the fields are really strong, where they can cause heating in items that contain water, such as inside a microwave oven. The energy from overhead high voltage towers is not strong enough to cause heating in objects at ground level.
Question 3. Do high voltage transmission lines cause cancers?
The jury is still out on this one. Some studies have shown links to some forms of cancer, however the research material is still not conclusive enough to have been accepted unequivocally by the medical fraternity. It’s possible that some people are more susceptible to developing cancer when exposed to high levels of electromagnetic radiation, however there are also many examples of people having been exposed to varying levels of electromagnetic radiation for much of their lives, without any obvious ill-effects.
Question 4. Are there any recent Australian reports which show that high voltage electricity lines are supposedly ‘safe’?
The failed attempt to stop overhead high voltage lines being commissioned at Waverley Park in Melbourne’s eastern suburbs in 2014, was influenced by the document at the following link: https://www.monash.vic.gov.au/files/assets/public/about-us/council/have-your-say/stephen-boyle-of-aecom.pdf
Mirvac’s planning permit as part of the redevelopment of the Waverley Park site required it to reconstruct the lines, replacing them with underground cables. Mirvac sought to and succeeded in varying its planning permit to provide an overhead transmission line mounted on poles instead of the underground cable as originally advised.
Question 5. Is it true that nothing grows below high voltage power lines?
No, it’s not. You only have to look at photos of where high voltage lines have been commissioned to notice that there is no perceived difference, other than the fact that it is necessary to keep vegetation controlled below high voltage power lines to reduce fire risk.
Question 6. Is it true that high voltage underground cables have to be buried 10, 20 or 60m underground?
No, they can be buried as little as a few metres underground, depending on the voltage carried and the type of cabling used.
Question 7. Do we have any major transmission lines running underground in Australia.
Yes we do. Google ‘aerial photos of Sydney’, select images, then try to spot any high voltage transmission towers on any of the pictures returned by the search. Good luck trying to find any. Sydney’s residents value the amenity of their landscapes.
We also supply power from Victoria to Tasmania via an undersea high voltage transmission cable which runs across Bass Straight. Whilst not strictly ‘underground’, it operates on the same principle and technology.
By the way, the AEMO and government market renewable energy as ‘green’, which is great, however they then negate the benefit of going ‘green’ by allowing the commissioning of overhead transmission lines, contrary to the whole principle of preserving nature and controlling greenhouse gases.
It’s interesting to note that if you perform a Google search for photos of wind farms, you’ll also notice the lack of high voltage transmission lines in any of the returned photos. Whilst most wind farms do have underground cabling and their implementations look good aesthetically, (eg. https://epuron.com.au/) the same cannot be said for the AEMO and power company’s preference to use manifestly unacceptable overhead high voltage transmission lines for the bulk transport of that generated power.
Question 8. How close to the ground can the high voltage lines drop to ?
The standards mandate that there has to be a minimum of 6.4m between the 500kV high voltage wires and other objects in the vertical direction. AusNet specifies that their 500kV lines drop to a minimum of 9.2m, so if a tractor or other machine greater than 2.4m in height were to go under the lowest point of the transmission line, there is a danger that they could be electrocuted.
Question 9. How wide does an underground trench need to be ?
That depends on the number of conductors that need to transport the power along the trench. For a single run, two HVDC cables are required as a minimum. The following photos depict what the trench would potentially look like, however it can be much less impacting, depending on location.
During a community consultation meeting, AusNet showed the image below-left, as being representative of why ‘we can’t go underground’, citing environmental impact concerns, however the image below-right shows a 220kV line laid underground by Acciona after the Mortlake community were successful in opposing the erection of an overhead 220kV transmission line.
Question 10. How do power companies prevent high voltage lines from starting fires ?
Power lines need to be separated from anything that can potentially conduct electricity to earth. If the minimum distance is reduced by an item which conducts electricity, then the high voltage electricity can ‘jump’ from the wires to the conductor and then travel through that conductor, to earth.
Electricity companies will ensure that easements are kept clear of trees and other items which can potentially reduce the space between the wires and earth in order to maintain a minimum safety buffer. Unfortunately, heavy smoke can allow electricity to conduct temporarily which can cause a bolt of electricity to jump from the wires to ground, potentially starting a fire.
Whilst power companies will argue that there is no record of that occurring during bushfires, no one can tell whether spot fires in the vicinity of high voltage wires are caused by electricity arcing or flying embers, so just because there is no record, doesn’t mean it doesn’t happen. The phenomenon has been proven scientifically, so it’s not a question of whether it’s possible, but a question of how likely and what the potential impact would be.
Power companies will also argue that their ‘systems’ can detect a fault in milliseconds and cut power to a fault. Whilst this is true in theory, in practice it’s a totally different scenario. There are numerous ongoing worldwide studies conducted by the power transmission industry into high voltage circuit breaker failures in an attempt to improve their reliability and better predict failures. Relying on a breaker to accurately detect and respond to a fault assumes ideal conditions, not real world conditions.
Question 11. How do high voltage wires impact aerial firefighting effors ?
Every pilot will tell you that high voltage power lines are a deadly hazard to air traffic and that they are to be avoided at all costs. As they are very difficult to see, particularly in inclement weather and have caused numerous fatalities, firefighting helicopters in particular cannot fly in close proximity to the high voltage lines without specific approval and will not fly near them at night. In Victoria, firefighting helicopters have flown continually to 1 a.m. in the morning, whilst fighting Lerdederg State Park and Wombat State Forest fires using night vision equipment. This would not be possible if high voltage lines were located near local water sources such as local dams and the Pykes Creek Reservoir. Smoke and poor visibility would make flying in the vicinity of high voltage lines during the daylight hours also impossible.
Question 12. Is the gas used to insulate some underground cables a danger to the Ozone Layer ?
No, the gas that is used comprises almost entirely of Nitrogen (N), with a small percentage of Sulphur Hexaflouride (SF6) mixed in. The SF6 is already used in electrical equipment worldwide and although it is a greenhouse gas like Carbon Dioxide, it does not damage the Ozone layer. Nitrogen makes up 78% of the earth’s atmosphere and is inert.