Power Stays on Thanks to Tree Trimming

Nashville, Tenn. – Nashville Electric Service (NES) customers have experienced as much as a 50% increase in the reliability of their electric service in the last five years. The marked improvement began when NES started its enhanced tree trimming campaign in July 2002. The statistics continue to improve as NES routinely conducts tree trimming maintenance on a yearly basis.

NES uses industry-standard reliability targets to measure reliability. System Average Interruption Duration Index (SAIDI) dropped from 197.71 minutes in 2002 to 108.92 minutes in 2007, a 45% improvement. And Customer Average Interruption Duration Index (CAIDI) dropped from 63 minutes to 50.2 minutes, a 20% improvement. In addition, the Momentary Average Interruption Frequency Index (MAIFI) – the brief momentary outages that are often a result of trees hitting power lines – dropped from 3.06 interruptions to 2.10 interruptions per year.

NES Chief Operating Officer Allen Bradley, who presented the 2007 fourth quarter operations results at the May Electric Power Board meeting says, “Prior to implementing a more aggressive vegetation management program, NES had a very high number of tree-caused outages – at least 10 times that of best practice utilities. While we realize that trimming is sometimes unpopular, it does help us provide reliable electric power that we all depend on.”

NES crews follow the Metro Tree Ordinance and guidelines recommended by the International Society of Arboriculture (ISA) when trimming. And, NES has planted more than 20,000 replacement trees and shrubs since 2002.