vegetation or tower frameworks, the line is automatically disconnected by control systems at both ends to protect the system and surroundings from damage. The effect of a disconnection was shown in Victoria, Australia on January 16 th , 2007. Fire conditions were extreme with high temperatures (for Melbourne, it was the second hottest day of the summer), freshening winds and erratic fire behaviour. A total fire ban had been declared for all areas of the state and all available fire fighting resources were responding to new threats and managing 166 active fires. The Tatong fire escaped a back-burning done the previous night and spread southwards under the influence of freshening gusty north winds. The transmission lines in the easement, which were swept by the fire, included two 330kV lines that comprised Victoria’s main electricity link to the Snowy Mountain Scheme and NSW. At the time of the incident, the gap between the line conductors and vegetation below them was as little as three metres. Clearly the vegetation in this case was too close to the power lines and thus enabled the encroachment of fire. The following steps 108 can be made by the relevant companies and authorities, who are in charge of poles and transmission lines, to reduce both the risk of infrastructure from being disabled from a bushfire and to reduce the risk of infrastructure causing a bushfire: - Maintain clearances between vegetation and network assets and undertake vegetation clearing around fuse poles, switched poles and transformer poles. 109 - When wires or poles break and fall down, dry undergrowth may ignite and start bushfires. So companies should accelerate the replacement of rusted or corroded conductors in areas of high bushfire risk. Power companies should ensure the structures supporting power lines are secure. 110 - Pole top fires can be caused by system faults which cause sparks to fall to the ground. These can ignite dry leaves and undergrowth and start bushfires. The risk of this can be reduced by applying silicone coatings on pole top insulators. When poles and/or cross-arms are replaced, steel cross-arms and polymer insulators should be used to eliminate any risk of this occurring. 111 - Conductor clashing causes sparks which have been known to cause bushfires. Strategies to mitigate clashing conductors include a Low Voltage (LV) Spreader program to ensure that the 107 The Nous Group (2007) 16 January 2007 electricity supply interruptions in Victoria: What happened and why and Opportunities and recommendations , Executive summary, The Nous Group, p20, $FILE/071023%20Exec%20Summary%20-%2016%20Jan%202007%20Incident.pdf , accessed 21 October 2008. 108 Western Power (2007) Bushfire Management Plan , Western Power, accessed 15 November 2008.
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