LCRA Transmission Services Corporation (LCRA TSC), an affiliate of the Lower Colorado River Authority (LCRA), is responsible for maintaining all its transmission lines so they operate in a safe and reliable manner. As a transmission service provider, LCRA TSC is regulated by the Pubic Utility Commission of Texas. Like many other utilities, LSCRA TSC maintains vegetation on the transmission lines to the clearance requirements of the American National Standards Institute’s ANSI Z133.1-2000 standard. The ANSI Z-133.1-2000 clearances were developed for safe and reliable operation of high-voltage lines.
LCRA TSC maintains trees on its rights of way on a five-year maintenance cycle. Keeping the right of way clear of vegetation and other obstructions is necessary so large equipment can access transmission lines during emergencies and for regularly scheduled inspections and maintenance. LCRA TSC's primary purpose for inspecting and maintaining its rights of way is to assure that the lines are operating safely and reliably. Keeping the line clear of vegetation is also necessary to minimize the risk of potential hazards such as fires or electrocution caused when trees grow too close to energized power lines.
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| Since trees can conduct electricity, the electric current could follow the tree trunk to the ground and endanger anyone in the area. |
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To determine if vegetation could interfere with transmission lines, LCRA staff first identifies the danger zone and then evaluates the location and height of vegetation.
The danger zone is the safety clearance area that surrounds the energized wires of a transmission line. This area is based on Table 2 of the ANSI Z-133.1-2000 standard for minimum approach distances from energized conductors for persons other than qualified line-clearance arborists and line-clearance arborist trainees. These distances vary depending on the voltage of the line. Engineers calculate the potential swing of the line caused by wind and the sag from high ambient temperatures. The danger zone clearances are added to this calculation with an additional distance added to assure that no vegetation grows near or into the danger zone during the maintenance cycle.
Typically, very tall or fast-growing vegetation, such as hackberry or ash trees, is removed to ensure safety and reliability.
Trees with trunks within the wire zone, that have the potential to grow into the danger zone at their mature height, must be removed and any limbs extending into the danger zone are trimmed to the edge of the zone. Tree removal and trim work usually involves the use of large trucks and other vehicles along the right of way.
LCRA uses the American National Standards Institute's (ANSI A300) pruning standards when trimming trees. LCRA TSC is also committed to using environmentally sound practices to maintain its rights of way.
How you can help ensure safety
You can help LCRA avoid electrical accidents and outages while protecting yourself and your property by following these guidelines:
- As a general rule, do not plant trees or shrubs in the rights of way.
- Talk with your local utility if you are considering planting near a transmission line right of way. Your utility can help you select plants that will not conflict with power lines.
- When thinking about what to plant, it is important to know how tall and wide the full-grown plant will be. Generally, trees and shrubs with a mature height of 10 feet or less will not cause problems within the utility rights of way unless they prevent access to the lines, towers or poles.
- Trees and shrubs that are adapted to our climate that can withstand local storm conditions are recommended.
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