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TREE TRIMMING AND POWERLINES : Protecting You and Your Environment Trimming also allows for regrowth (based on tree species and environmental conditions), in addition to the minimum safety clearances so vegetation should not grow back within these clearances before the trees are trimmed again. For most species of tree, once the minimum safety clearance plus an allowance for regrowth is determined for each branch, it is trimmed at the nearest growth point or collar outside the limit of clearance required. This is a requirement under Australian Standard AS4373 as trimming at a growth point protects trees from infection or disease and minimises the development of weakly attached growth (see illustration). Unfortunately it is not always possible to achieve an aesthetically pleasing result, because of the:
Councils are offered the option of installing Aerial Bundled Cable (ABC) which wraps the four Iow voltage overhead wires, strung between poles along suburban streets, into one single insulated cable. The safety clearances required for ABC are less than for uninsulated wire. Trees that have already been trimmed for uninsulated wire clearances will take some time to regrow to the ABC safety clearances. ABC also reduces the likelihood of a power interruption, which can occur when uninsulated lines touch and then short-circuit. In some instances, this can cause live wires to fall to the ground. Underground electricity is also installed in new urban residential developments. Many new high voltage wires are also placed underground, and in some commercial areas, overhead wires are placed underground in conjunction with building developments. Where trees grow too close to powerlines, responsible trimming takes branches back to the nearest growth point outside the limit of clearance required (centre). If trees are not trimmed to the growth point they become susceptible to infection or disease and the development of weakly attached growth (right). Comparative costs for Low voltage overhead in an urban area
EnergyAustralia has an ongoing maintenance program to keep trees and their branches clear of powerlines and power poles. This helps prevent injury to people and damage to property. With about 75% of blackouts caused by environmental factors including tree branches, tree management can also have a significant impact on the reliability of your electricity supply. The law requires street trees to be trimmed to ensure there is a minimum safety clearance between trees and powerlines. EnergyAustralia is doing this work to protect you and your environment. Where a tree on private property is entering the safety clearances of wires in the street, EnergyAustralia will trim the tree for residents, free of charge, to meet our safety obligations.
Do workers know how to trim trees? Trimming is carried out by contractors who follow the Australian Standard AS4373 'Pruning of Amenity Trees: EnergyAustralia employs a horticulturist and an arborist to audit the work of our contractors. Each contractor also employs a horticulturist and an arborist to monitor standards and ensure they are maintained. Trimming or removal of trees near powerlines can be extremely dangerous. If trees are within three metres of our powerlines, only vegetation management workers authorised by EnergyAustralia are permitted to carry out the work. Contact EnergyAustralia, your local council or nursery for advice. Where possible, avoid planting near a powerline. You must also obtain permission from your local council if you are planting on the nature strip. |
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