Reliable electric service is a critical public need. Our nation’s economic success and security depends upon our ability to preserve this fundamental resource. We expect electricity to be there all the time to power the machines, electronics and systems that drive just about everything we do. As we modernize the grid, we are improving reliability for customers.
We track our transmission and distribution reliability performance with several metrics that are used industry-wide. These indicators show us how reliable our system is and how our customers are impacted when it is not. They do not include major storms. The investments we are making in our transmission and distribution system improve reliability and operating efficiency and prepare the system for new technologies.
The System Average Interruption Duration Index (SAIDI) represents how many minutes the average customer experiences an interruption in electric service in a given year. During 2015, the AEP System SAIDI was 229.5 minutes, excluding major events, a 4.4 percent increase from 2014. The growth of vegetation contributed to about 32 percent of SAIDI results and failure of distribution line equipment accounted for about 21 percent of SAIDI.
The System Average Interruption Frequency Index (SAIFI) represents the number of interruptions experienced by customers in a year. During 2015, the system’s SAIFI was 1.468, a 6.8 percent increase from 2014. Vegetation and distribution line equipment failures were also the major contributors to SAIFI performance.
The Customer Average Interruption Duration Index (CAIDI) represents the average length of time it takes to restore service when an outage occurs. AEP’s 2015 CAIDI was 156.3 minutes, a 2.3 percent decrease from 2014.