An Examination of Temporal Trends in Electricity Reliability Based on Reports from U.S. Electric Utilities

Abstract

Since the 1960s, the U.S. electric power system has experienced a major blackout about once every 10 years. Each has been a vivid reminder of the importance society places on the continuous availability of electricity and has led to calls for changes to enhance reliability. At the root of these calls are judgments about what reliability is worth and how much should be paid to ensure it.In principle, comprehensive information on the actual reliability of the electric power system and on how proposed changes would affect reliability ought to help inform these judgments. Yet, comprehensive, national-scale information on the reliability of the U.S. electric power system is lacking.This report helps to address this information gap by assessing trends in U.S. electricity reliability based on information reported by electric utilities on power interruptions experienced by their customers. Our research augments prior investigations, which focused only on power interruptions originating in the bulk power system, by considering interruptions originating both from the bulk power system and from within local distribution systems. Our research also accounts for differences among utility reliability reporting practices by employing statistical techniques that remove the influence of these differences on the trends that we identify.The research analyzes up to 10 years of electricity reliability information collected from 155 U.S. electric utilities, which together account for roughly 50% of total U.S. electricity sales. The questions analyzed include:1. Are there trends in reported electricity reliability over time? 2. How are trends in reported electricity reliability affected by the installation or upgrade of an automated outage management system? 3. How are trends in reported electricity reliability affected by the use of IEEE Standard

A method to estimate the costs and benefits of undergrounding electricity transmission and distribution lines

“…It is likely that these specific assumptions will increase over time, which could affect the benefit-cost ratio. It is also possible that a national model of electric utility reliability (Eto et al, 2012;Larsen et al, 2015) may not be appropriate for regional or local analyses. More research is needed to explore the factors that affect local utility reliability.…”

“…The System Average Interruption Frequency Index (SAIFI) is one of the most commonly used metrics to assess electric utility reliability (Eto et al, 2012). 1 Eq.…”

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“…Berkley National Laboratory concluded that reported reliability of the North American electric power system has been decreasing at an average of 2% per year over the past ten years (Eto et al, 2012). Increasing attacks on the electric grid coupled with decreasing operational reliability suggest that the overall security of the grid system is likely deteriorating with the passage of time.…”

Assessing Changes in the Reliability of the U.S. Electric Power System

“…Recent work has begun to address these limitations by examining trends in reliability data collected annually by electricity distribution companies (see, for example, Eto et al 2012). In principle, all power interruptions experienced by electricity customers, regardless of size, are recorded by the distribution utility.…”

“…The Eto et al (2012) study applied econometric methods to account for utility-specific differences among electricity reliability reports and found that average annual duration and frequency of power interruptions had been increasing annually per year from 2000 to 2009. In other words, reported reliability was getting worse.…”