WG B2.45 Vegetation fire characteristics and the potential impacts on overhead line performance.

The current spate of bushfires raging across the east coast of Australia provides a timely reminder of the destructive capacity of these fires and the critical need to manage their impact on power line infrastructure and minimise the risk of fires being caused by faults on the network.  The economic cost, environmental damage and social impact of the fires can be very significant and there is therefore clear justification for investment to reduce risks. 

WG B2.45 was established to examine the many related areas associated with vegetation fire characteristics, the potential impacts on overhead line performance, the costs of fires to society and the costs to utilities stemming from fires.  It has recently published Technical Brochure 767, which is comprehensive and will serve a wide group of readers, from the design engineer in a utility, to the Operations and Maintenance staff.  It may also serve as a reference for persons who wish to do further study on this subject. 

The Australian members of the working group were Francis Lirios, Henry Hawes and Michael Lee and the Australian reviewer was Peter DulHunty. Significant contributions were provided by Australian utilities including Ergon Energy, Transgrid, Western Power and Aurora Energy.

The Technical Brochure begins with a general discussion on the subject of fires and this is followed by a high level discussion of the costs of the fires to society and to the electric utility.  In recent times there have been a number of very significant fires across the world including in Australia, Canada, the USA, South America, China, Russia and parts of Europe.  The costs of these fires are very difficult to estimate but are in the order of many hundreds of millions of dollars.  

The risks brought about by the fires, as they burn closer to live conductors, tower and wood pole structures and other electrical equipment, are examined together with ways that the risks can be reduced.  This is particularly important for system operators.  There is also a discussion of the safe distances that personnel should maintain from the infrastructure during a fire. 

A review of the extensive research that has been carried out on the insulation breakdown of gasses during fires is supplemented by an examination of the associated biochemical processes and the theory of insulation breakdown and conductivity of fires is presented in an appendix. 

Further work has included a novel method to predict the relative probability of flashover as a function of height, an overview of terminology and a description of the anatomy of fire. 

A review of fire behaviour provides important information for the planning of vegetation management strategies and the design and placement of towers for new lines in fire prone areas. 

Finally the impact of climate and weather on the occurrence and behaviour of fires is reviewed together with how this information can be used to predict the onset of fires by the use of weather forecasts.  An enhancement to traditional methods of predicting dangerous fire conditions is described.  This is used to predict conditions that would lead to fire induced flashovers instead of just dangerous fire conditions. 

The subject matter covered in this Technical Brochure is extensive and it is believed to be the only one of its kind covering all aspects of fire and its impact on electricity infrastructure. 

The Technical Brochure is available free to members and €300  to non members through e-cigre.