ELECTRIC INFRASTRUCTURE RELIABILITY PERFORMANCE INDICATORS

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1 Page of 7 ELECTRIC INFRASTRUCTURE RELIABILITY PERFORMANCE INDICATORS FIVE-YEAR HISTORICAL RELIABILITY PERFORMANCE General THESL tracks reliability performance indicators System Average Interruption Frequency Index ( SAIFI ), System Average Interruption Duration Index ( SAIDI ), and Customer Average Interruption Duration Index ( CAIDI ) in three ways: ) Including all events; ) Without Major Event Days ( MEDs ); and ) Without MEDs and Loss of Supply. An MED is defined by standard P/D of the Institute of Electrical and Electronics Engineers ( IEEE ) as events that are beyond the design and/or operational limits of a utility. The removal of MEDs allows a utility to normalize its reliability data to make trending and goal setting possible. An example of a normalizing application was the OEB-allowed modification of 00 reliability data in light of the August, 00 provincial blackout. MEDs experienced by THESL since 00 are shown in Table below:

2 Page of 7 Table : Major Event Days Date Description SAIDI August, 00 Blackout days September 9, 00 Hurricane Isabel 8.0 minutes July, 00 Loss of Supply to Esplanade TS.9 minutes August 9, 00 Major storm (thunderstorm) 9. minutes August 0, 00 Major storm (thunderstorm). minutes July 7, 00 Major storm (thunderstorm). minutes August, 00 Loss of Supply to Scarborough TS 7.0 minutes March, 007 Major ice storm. minutes June 8, 007 Major storm (thunderstorm). minutes January, 009 Dufferin TS flooding.98 minutes April, 009 Major storm (thunderstorm).9 minutes August 0, 009 Major storm (thunderstorm).9 minutes August, 009 Major storm (thunderstorm) 0. minutes Five-Year Historical Reliability Performance Tables, and along with Charts, and illustrate THESL s five-year historical reliability performance. With reference to Table, the SAIFI and SAIDI targets for 00 excluding MEDs are. interruptions per customer and. hours of interruption per customer, respectively. The targets are based on the five-year (00-009) system average and incorporate the expected reliability improvement from the capital programs. Table, Reliability Performance without MEDs and Loss of Supply, is the most accurate reflection of the performance of the distribution system as it excludes major events that are not part of normal operation and loss of supply events over which THESL has no direct control.

3 Page of 7 Table : Reliability Performance (including all events) Service Reliability Indicators Actual Performance Measures (all events) SAIFI (number of interruptions per customer) SAIDI (number of hours of interruption per customer) CAIDI (number of hours per interruption)

4 Page of 7 Table : Reliability Performance without MEDs Service Reliability Indicators Performance Measures (without MEDs) SAIFI (number of interruptions per customer) SAIDI (number of hours of interruption per customer) CAIDI (number of hours per interruption) Actual

5 Page of 7 Table : Reliability Performance without MEDs and Loss of Supply Service Reliability Indicators Performance Measures (without MEDs and Loss of Supply) SAIFI (number of interruptions per customer) SAIDI (number of hours of interruption per customer) CAIDI (number of hours per interruption) Actual

6 Page of Table and Chart show the reliability performance excluding MED and Loss of Supply. The performance reliability indicator SAIFI increased from 00 to 00 but has shown modest improvement from 00 to 009. The performance reliability indicator SAIDI increased from 00 to 007 but has stayed relatively constant from 007 to 009. The performance reliability indicator CAIDI increased from 00 to 009. CAIDI is directly proportional to SAIDI. Overall, average system interruption duration increased from 00 to 009 and consequently the average customer interruption duration increased as well. Increase in average system interruption duration may be attributed to an increase in the frequency of outages caused as a result of defective equipment between 00 and 008. Outages caused by defective equipment generally have a longer restoration time. The performance reliability indicators are monitored closely to align with various capital and maintenance programs. Generally, system reliability performance has shown improvement between 008 and 009, some of which may be attributed to THESL s investment programs Cause Code Analysis THESL tracks causes of service interruptions using the ten primary cause codes as specified in Table. of the Electricity Distribution Rate Handbook. Charts and show the reliability performance for customers interrupted ( CI ) and customer hours interrupted ( CHI ) from 00 to 009 for the ten primary cause codes. In 009, Defective Equipment continued to be the main cause of service interruption (contributing percent in CI and 0 percent in CHI). Contributing factors of defective equipment are equipment aging, operating conditions and operation past the expected end of life.

7 Page 7 of 7 The other top causes that contributed to CI in 009 were Foreign Interference ( percent), Unknown (ten percent), Loss of Supply (nine percent), Tree Contacts (eight percent), Lightning (seven percent), and Adverse Weather (four percent).

8 Page 8 of 7 Defective Equipment Analysis THESL tracks detailed causes of service interruptions by additional sub-classification of causes in order to stratify the reliability data and ascertain root cause trends. For example: the primary cause code Defective Equipment is further categorized by the system types: Overhead Equipment, Underground Equipment and Station Equipment.

9 Page 9 of Charts and 7 show the CI and CHI performance from 00 to 009, excluding MEDs, by system type for the two most prevalent causes: overhead and underground systems. The distribution equipment reliability contribution in 009 for CI is as follows: percent for underground equipment and percent for overhead equipment. The distribution equipment reliability contribution in 009 for CHI is percent for underground equipment and 0 percent for overhead equipment. Comparison of the overhead and underground system components (presented in Charts and 7) shows that the underground system continues to fail more frequently and is more difficult to restore.

10 Page 0 of 7 Overhead and underground equipment reliability analysis Charts 8 and 9 show the CI and CHI performance of the top four Overhead Equipment outage causes for (excluding MEDs). Contribution from overhead lightning arresters and insulators was high in 009 and remains the largest contributor to overhead system failures. THESL will continue to monitor both types of equipment and analyze failure modes to improve performance.

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12 Page of 7 7 Charts 0 and show the CI and CHI performance of the top four underground equipment outage causes for (excluding MEDs). Underground direct buried cable was the major contributor to both CI and CHI in 009. There was a small improvement in underground direct buried cable performance in 009, which was attributed to THESL s direct-buried cable replacement program. Underground cable remains a significant issue in system performance and requires immediate attention. Underground cable failures contribute two to three times higher CI and CHI compared to

13 Page of 7 any other component failure. As a result, a cable replacement program has been established to improve performance of this distribution component. 7 In summary, the top contributors to Underground Equipment CI and CHI performance in 009 were Underground Cables, Elbows, Terminators and Potheads, Underground Switches and Underground Transformers. These are key capital investment areas identified for reliability improvement. 8

14 Page of 7 Unknown Cause Reliability Analysis Interruptions due to an unknown cause are defined as interruptions with no apparent cause or reason for the outage. Experience indicates that the majority of unknown cause interruptions are occasioned by tree or animal contacts.

15 Page of 7 Charts and, shown previously, show that the unknown cause reliability contribution in 009 was 0 percent for CI and percent for CHI. Unknown cause interruptions are generally of short duration although they produce a substantial number of customer interruptions Tree Contact Cause Reliability Analysis Charts and, shown previously, illustrate that tree contact caused interruptions increased from 00 to 00 and decreased between 008 and 009. In 009, the tree contact cause contributed to 8 percent of the total CI and 8 percent of the total CHI In 008, Toronto Hydro adopted and implemented a reliability-based tree trimming program. It is a departure from the traditional fixed area and cycle approach. The new methodology takes into consideration reliability performance of each feeder from treerelated outages as well as the cost of trimming around each feeder. The analysis yields a trimming cycle for each feeder that will deliver the optimum reliability performance for the amount of resource spent. Going forward, THESL will monitor all tree-related outages and investigate their causes along with historical trimming information to update and further improve the program. Expanded use of tree proof construction for historically problematic areas will also help to reduce tree-related outages. 7 8 Foreign Interference Cause Reliability Analysis THESL tracks detailed causes of foreign interference by internal sub-secondary cause codes. Charts and show the CI and CHI performance of the detailed causes of foreign interference for (excluding MEDs). The top causes for foreign interference are animals, vehicles, and other. Animal contact continues to have a large

16 Page of 7 impact on system reliability performance. Toronto s large tree canopy provides animals with access to the overhead system. In addition to the tree trimming program, the installation of animal guards on overhead transformer high voltage bushings will help prevent animal contact. To manage outages due to vehicle interference, THESL utilizes options such as pole relocation and pole protection along with other design practices.

17 Page 7 of Summary The reliability performance indicators provide THESL with an overall measure of the performance of the electrical distribution system. Further analyses provide information on areas of the distribution system requiring attention. Capital and maintenance programs are set up to target the various systems and sub-systems for performance improvement. The reliability performance indicators have increased from 00 to 008 and have shown improvement in 009. The underground system, and in particular underground direct buried cable, continues to have a significant impact on system performance. Sustained capital and maintenance programs for high impact components affecting system reliability are required to maintain and improve system performance.