Cost of deferred maintenance

2019 | Phil Chen (CN Utility Consulting)

Tree-powerline conflicts cause safety and reliability risks. In Oregon the most common public electrical contacts in 1996-2015 were tree-related. Trees contacting power lines can also ignite wildfires, such as the recent catastrophic fires in California. Trees are also a significant source of power interruptions. Utilities have a responsibility to clear trees from powerlines, and they spend vast sums of money doing so. Utility vegetation management has a considerable effect on public safety and reliability, and it is amongst the costliest maintenance expenses of North American utilities.

The large amounts of money spent on utility line clearance make effective management critical and understanding the optimal time to work trees is central to that management. Many utilities are behind in their maintenance cycles. Utility vegetation managers have long believed that falling behind on cycles increases long-term cost, but there is little objective research to support the view. Browning and Wiant conducted the only related study in 1997, focusing on three utilities in the U.S. They identified a positive correlation between the number of years a tree grows, and the time required to prune it. Further, their results found the time and cost to provide clearance from powerlines escalate as trees grow beyond the conductors.

Utilities generally keep detailed records regarding utility vegetation management expenditures and a host of other vegetation data. This study intends to apply a data mining approach to updating Browning and Wiant’s work. It will compile ten-years of production data across a broad range of cycle-lengths from North American utilities to investigate the relationship between labor hours and cycle length. We hypothesize that the longer it has been since a circuit was last worked the greater the number of trees requiring work, the more time it will take to complete the work, and the costlier it will be to regain required powerline clearances. We also hypothesize that the longer it has been since an area was worked, the worse the vegetation-related reliability.

Year: 2019

Funding Duration: 1 Year

Grant Program: Utility Arborist Research Fund Grant

Grant Title: Cost of deferred maintenance

Researcher: Phil Chen

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For more information on this project, contact the researcher via TREE Fund at