Tree Trimming is Essential for Reliable Power
NEC’s lines, poles, and substation structures are engineered to withstand many forces of Mother Nature. However, they may not withstand the force of a fallen tree or large branch, which could lead to interruption of service. Trees touching power lines can cause line protection devices to take a circuit out of service. Voltage dips, also caused when trees contact a power line, can damage appliances and sensitive electronic devices in homes and businesses.
If you have a tree that is too close to power lines, our tree-trimming crews must trim the tree to maintain required clearances. National standards require that a minimum distance of 10 feet from energized or potentially energized electrical equipment must be maintained. Trimmers follow guidelines established by certified arborists and the Federal Rural Utilities Service.
The crews also identify expected growth patterns of trees between pruning cycles; some faster-growing trees may require more clearance and, hence, more trimming than others. At all times, trees and shrubs must be at least 10 feet away from power lines and other utility equipment such as transformers.
Crews also identify vegetation conditions that may present an imminent threat to a power line. These threats are called a ‘danger tree’. Characteristics used in identifying a danger tree include the following:
• Encroachment within the safe distance to the conductor as a result of the tree bending, growing, swinging or falling toward the conductor;
• Deterioration or physical damage to the root system, trunk, stem or limbs, and/or the direction and lean of the tree;
• Vertical or horizontal conductor movement and increased sag as a result of thermal, wind and/or ice loading that exceeds the facility design specifications;
• Fire risk; and
• Other threats to the electric power system facilities or worker/public safety.
Vegetation management – including tree trimming – is an important aspect of NEC’s goal of delivering power to you that is safe, reliable, environmentally responsible and affordable.
If you need more information, please call NEC at 928-368-5118 ext. 330.