Friday, 29 September 2006

Fire Risk posed by Electric Fencing

It was recently suggested to me that the use of electronic fencing in areas such as Grenfell creates an unacceptable fire risk, especially during the summer months. With this as a backdrop I set about conducting some research on the subject. Below are the organisations and people I contacted or gathered information and views from, together with what I found out.

Wesfarmers Federation Insurance (WFI)
I contacted one of the WFI Regional Managers who in turn spoke with a couple of his peers. In short WFI does not consider electric fencing to constitute a material fire risk and thus does not charge a premium over conventional fencing where these types of fences are used.

Gallagher Australia Pty Limited (GAP)
Gallagher is one of the leading global designers and manufacturers of “Power Fence Systems”. I contacted GAP and received an email response which in part reads:
“Re starting fires - the voltage is sent through at a very low ampere which makes it very difficult for a fire to start. On extremely hot days you can turn your fence off for greater piece of mind as the animals won't be moving around anyway on the really hot days.”

Australian Government Department of Environment & Heritage
A web search brought to light the following on the Federal Government Department of Environment & Heritage website (see link to full article if required):

“7.3.3 Fire risk posed by electrical fences
Electric fences have been suspected of causing several fires (McCutchan 1980, Sexton 1984), however McCutchan (1980) concluded that the combination of conditions necessary to ignite surrounding vegetation make electric fences a possible but improbable cause of bushfires. He found that an arc can pass through the air between an electric wire and another electrical conductor if these components are separated by several millimetres or less. Alternatively, an electrical 'flashover' can occur across a suitable green leaf that contacts an electric wire and a conductor separated by 20 mm or less. These events will only be capable of starting a fire if very dry, finely divided tinder, such as thistle down, is present between the conductors, and there is also sufficient dry vegetation within the immediate vicinity to be ignited. High temperatures, low humidity and the presence of wind are conditions that will cause the tinder to become suitably dry (McCutchan 1980).
To reduce any potential fire risk in areas where bushfires are a hazard it has been recommended that fences be well maintained, porcelain insulators be used (Sexton 1984), vegetation be cleared in the immediate vicinity of the fence line (Australia Standards and Standards New Zealand 2003) and, in high fire risk seasons, the output voltage be reduced or current-limiting resistors installed (Australia Standards and Standards New Zealand 2003, Sexton 1984). However, Coman and McCutchan (1994) point out that reducing the voltage is unlikely to greatly reduce the fire risk and, because higher voltages are likely to be necessary in the drier months to counteract the poor conductivity of animal fur, this may reduce the effectiveness of the fence."

NSW Rural Fire Service - Forbes
I spoke to the Forbes office of the NSW Fire Service. In the 20 years the person I spoke to has been employed by the NSW Rural Fire Service he is aware of 1 or 2 instances where fires started on farms that had electric fencing, but it was not clear what the cause of the fire was i.e. electric fencing was suspected but not proven. Electric fencing is not considered to be a material fire risk. The major ‘man-made’ causes of fires on farms include angle grinders, welders, headers, slashers and power poles (cross-arm breaks).

NSW Rural Fire Service – Volunteer – Orange
A family member who lives on a farm at Orange and is a volunteer member of the local bushfire brigade advised that he went to a fire a few years ago that burnt down the local gun club. The fire was allegedly started by an electric fence but is at present subject to a Coronial inquiry (as the damage caused was over $50,000) and cause cannot be confirmed.
“Farm fire causes are many and range from machinery sparks, stubble burns (& burn off in general) that have got away, hot mufflers and cigarette butts in stubble/grass, lightning strikes etc. and of course arson. The inquiry into a fire at Alectown a few years ago found that the fire started by a tree touching power lines.”

NSW Rural Fire Service - Sydney
The Customer Support office advised that the RFS does not have statistics regarding research into the fire risk associated with electric fencing. They referred me to Section 7.3.3 of the 'Cost effective feral animal exclusion fencing for areas of high conservation value in Australia' document produced by the Australian Department of the Environment and Heritage - which I'd already located (and have included above).
For information in relation to Asset Protection Zones or other Bush Fire Protection Methods for building in a bush fire prone I was referred to the link below; http://www.rfs.nsw.gov.au/dsp_content.cfm?CAT_ID=518

3 comments:

Chris R said...

At the end of Summer there are often very fine materials like seed down and wind-blown matter that collect in between metal parts of some electric fence systems due to wind and arcing could easily ignite them in humidity conditions under 15% RH. Any bushie in an emergency can start a fire with a 12 volt battery and some really dry grass with a bit of blowing so it makes sense to avoid leaving electric fences OFF in windy, dry conditions. Most fencing systems are only single insulated between the charger and the wires, and across steel posts and this is insufficient insulation to prevent sparking. Adding a sleeve of old garden hose can stop all of that. The charged wires themselves should not spark to dry vegetation though. Real research and not just post-hoc RFS investigations should be the basis of policy on this.
Chris Rush, M.App.Sci. UWS Hawkesbury. Rush Ecology Services.

Phillip Diprose said...

Thanks Chris. Great input.

Chris R said...

There's a mistype in my comment: avoid leaving fences ON (not off). Sorry.