Third Benchmarking Report on Quality of Electricity Supply

countries compared with 6 in the First <strong>Report</strong>. Comparisons of performance are made forunplanned and planned outages, outages of short duration and an attempt has been made toinvestigate unplanned performance excluding exceptional events. As in the previous two reportsdata limitations have meant that detailed comparisons could not be carried out for all countries.1.3 Main Conclusions on Continuity of Supply Regulation – Drawn from the CEER’s<strong>Third</strong> <strong>Benchmarking</strong> <strong>Report</strong>A number of encouraging trends have been observed in carrying out work on the <strong>Third</strong> <strong>Report</strong>:· The duration of unplanned interruptions shows (for most countries) a significant downwardtrend;· The number of unplanned interruptions shows (for most countries) a downward trend;· Excluding exceptional events from unplanned performance figures highlights the significantimprovements being made by many European countries in terms of both the duration andnumber of interruptions;· Countries with previously low levels for duration and number of interruptions have been ableto make further improvements; and· Short interruptions have generally not been rising despite an increased move to automationand remote control techniques.1.4 Continuity of Supply Questionnaire1.4.1 Continuity Indicators UsedThe continuity indicators which form the basis of the continuity analysis in this report 5 are:· “System Average Interruption Duration Index” (SAIDI), in some countries referred to as“Customer Minutes Lost per customer per year” (CMLs)· “System Average Interruption Frequency Index” (SAIFI), in some countries also referredas “Customer Interruptions per 100 customers per year” (CIs)· “Momentary Average Interruption Frequency Index” (MAIFI).· “Energy Not Supplied” (ENS)6· “Average Interruption Time” (AIT)7 .SAIDI measures the average duration of outages for a power system. SAIFI and MAIFI measurethe average frequency of outages for the power system, respectively for long and for short interruptions.ENS is generally based on long interruptions, as the energy not supplied during short5For a comprehensive review of continuity indicators, please see the document : IEEE Standard 1366-2003. IEEE Guide forElectric Power Distribution Reliability Indices. IEEE, New York, NY, May 20046Norway uses ENS for all voltage levels greater than 1 kV.7For some countries such as Italy (until 2004), the information relating to AIT and ENS includes outages occurring at distributionhigh voltage and may therefore result in higher values than those countries reporting solely outages on the transmission network.5<strong>Third</strong> <strong>Benchmarking</strong> <strong>Report</strong> on Quality of Electricity Supply – 2005 · Chapter 1