Logging Safety Along High Voltage Power Lines

Steve Narolski
Program Manager for Vegetation Management and Access Maintenance
Bonneville Power Administration

Power line3Bonneville Power Administration (BPA) has a safety motto that no job is so important or service so urgent that it can’t be done safely. BPA believes that this holds true for harvesting timber along high voltage power lines.

To be successful, timber harvest operators must take many variables into account. But when power lines are involved, even more thought and consideration are necessary to ensure that felled trees do not come into contact with energized power lines.

When this happens, flashover occurs where the energy contained within the conductor runs into the ground. A condition known as step-down occurs at the base and roots of the tree, where electricity radiates outward like ripples in a pond. It is within those ripples that property damage or fatalities can occur.

Flashover can occur even if a grounded object fails to come into contact with a power line but falls close enough. We call this flashover distance minimum vegetation clearance distance, or MVCD.

BPA has incurred an increased number of logger-caused outages across its service territory lately. Contributing factors have included not halting felling during strong wind events and not using guy lines or safety cables to assist in directional felling.

Here are some safety tips to ensure the safety of your timber harvest operations when felling trees near power lines:

  • When reviewing your timber harvest plan, identify all targets that involve energized power lines to develop specific strategies for safe removal.
  • Plan contingencies when variables change, such as ceasing felling operations when wind speed passes a certain threshold.
  • Don’t leave logging fringe or a stringer of uncut trees along power lines.
  • Don’t fuel equipment within the power line corridor.
  • Avoid decking logs within the power line corridor.
  • Ask the local utility for an onsite visit by a transmission line foreman or equivalent for consultation.
  • Use safety lines of a non-conductive material to aid in directional felling.
  • Never pull a tree, limb, or top off of an energized power line. Instead, contact the appropriate utility to address the problem.

If you have any questions, please contact me at 360) 418-2984 or via email: swnarolski@bpa.gov.