CRITICAL ISSUES WORST PERFORMING FEEDER PORTFOLIO

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1 EB-0-0 Exhibit D Tab 0 Schedule Page of CRITICAL ISSUES WORST PERFORMING FEEDER PORTFOLIO 0 0 THESL S WORST PERFORMING FEEDER PROGRAM THESL uses Customers Interrupted ( CI ) and Customer Hours Interrupted ( CHI ), to monitor system reliability performance. The Worst Performing Feeder ( WPF ) program combines these two statistics to assess reliability performance at the feeder level. The WPF program focuses on forced outages. The result is a better understanding of the customer experience as it relates to reliability. This type of granular analysis allows THESL to plan more efficient feeder-based investments that ultimately helps to focus system reliability improvements on particular areas rather than system-wide. This allows THESL to target sustaining capital work to the worst performing portions of the system. The WPF program is a feeder-driven analysis and is intended to identify feeders that are experiencing sustained interruptions. Scheduled outages and interruptions due to Loss of Supply ( LoS ), and Major Event Days ( MEDs ) are not included. Accordingly, station, bus and network outages are also excluded from the analysis. For 00, forced feeder interruptions or unplanned interruptions on a feeder, constituted 0 percent of all outages (excluding MEDs), as shown in Figure. Although planned work accounted for % of the outages, this is only. percent of the annual SAIFI impact and is not significant in terms of overall system reliability. The pattern of feeder interruptions in 00 shows a shift from 00 when forced feeder interruptions accounted for percent of all interruptions, and planned or scheduled interruptions accounted for percent of interruptions. This shift is consistent with Exhibit D, Tab, Schedule, where planned interruptions are shown to have increased significantly due to increased capital spending pursuant to the Capital Plan.

2 EB-0-0 Exhibit D Tab 0 Schedule Page of 00 Outage Breakdown (Excluding MEDs) LoS % Network Station Bus % Scheduled % Feeder 0% 0 Figure : Breakdown of Outages by Type (00) The WPF methodology was chosen because it identifies feeders that contribute significantly to the System Average Interruption Frequency Index ( SAIFI ), System Average Interruption Duration Index ( SAIDI ) and total system interruptions. The feeders represent a smaller and more manageable sample of the system that allows THESL to perform in depth analysis on each feeder. The Feeders Experiencing Sustained Interruptions ( FESI ) program is a part of the WPF program and is currently focusing on FESI- feeders. The FESI- are feeders that have experienced sustained interruptions or interruptions greater than one minute, seven or more times during a -month rolling schedule that is updated monthly. The FESI- represent roughly one third of the system interruptions while only representing about

3 EB-0-0 Exhibit D Tab 0 Schedule Page of 0 three percent of the systems feeders. Also included are feeders that may not necessarily be FESI-, but are rapidly trending upwards, and are in need of proactive intervention before they hit the FESI- threshold. THESL continually monitors WPF feeders and performs analysis to determine the causes of sustained outages, reasons for long system restoration times, emerging feeder trends from both a station and system level, and the relative impacts on customers. Characteristics of outages on WPF program feeders are analyzed as follows: Outage restoration time and load transfer capabilities from a system control and field perspective Nature and root causes of the outages Asset conditions and the operational impact of system failures 0 Information is utilized from past outage causes and locations along with recent feedback, as well as from field specialists that complete patrols on identified feeders requiring analysis. Corrective actions are aimed at preventing outages, minimizing restoration time and the number of customers affected. These actions can be divided into two categories: Short-term Mitigation Actions Long-term Capital Work Short-term mitigation actions that are recommended generally include work that can be done quickly and does not require extensive civil work. The work would generally be high impact, low cost and traditionally includes activities such as tree trimming, installation of animal guards, lightning arrestor replacements, transformer replacements and replacements of glass and porcelain insulators. Short-term work that has started this past year includes Fault Current Indicator ( FCI ) and fuse installations along laterals. Small scale feeder rebuilds, concentrated in areas with high WPF or FESI impacts may also be included.

4 EB-0-0 Exhibit D Tab 0 Schedule Page of 0 Much of this short-term work has occurred around Bathurst TS, Finch TS, Sheppard TS, Fairchild TS, Fairbanks TS and Runnymede TS, as there are often multiple feeders with poor performance supplied from one station. Moving into the test years, the WPF team will continue to monitor these and other stations and feeders. A similar approach of producing short-term actions that can quickly turn around the performance of the feeders through work such as transformer replacements, animal guard installations, tree trimming, and fuse installations will be implemented. For long-term capital work, THESL plans to continue its focus on FESI feeders in 0-0 due to both the high number of interruptions and the length of time the feeders have been in the FESI condition. THESL views these feeders as having unacceptable performance requiring ongoing attention. The scope of work usually includes rebuilds that cannot be quickly executed (e.g. civil work) or work that must be completed in the next few years, but not on an urgent basis, such as replacing assets near end-of-life. This work is typically more extensive than the short-term mitigation actions and scoped for future years through the capital work program under the Overhead and Underground portfolios. 0 Work may also be accelerated based on feeder trending and unexpected rapid deterioration. From 0 to 0, many long-term projects have been generated due to FESI. This includes longer term projects on feeders that are starting to show signs of failures, but have yet to become an issue from the FESI point of view. These projects could also include work such as direct-buried cable or transformer replacement. Table shows the actual, bridge and test year spending for the Worst Performing Feeder portfolio.

5 EB-0-0 Exhibit D Tab 0 Schedule Page of Table : FESI and WPF Program Capital Summary ($ millions) Actual Actual Actual Bridge Test Test Test FESI & WPF The WPF portfolio was introduced at the beginning of 00 and improvements were made to the worst performing feeders, in terms of their SAIDI and SAIFI impact. The launch of the FESI program introduced a large amount of short-term work. In 00, 0 new feeders were added to the list as new trends developed. More work is required in 0 to continue the reliability performance improvement of these feeders and continue the downward trend in the number of FESI- feeders. For the 0 to 0 period, it is expected that the results of earlier work will reduce the number of feeders that need to be addressed and the consequent budget requirements as shown in Table. 0 DRIVERS OF THE WORST PERFROMING FEEDER PROGRAM Reliability In 00, feeders reached the FESI- threshold. Limiting the analysis to this select group of feeders allowed THESL to produce focused reviews tailored to each situation and operating environment. Table shows the number of FESI feeders during 00. Table : Number of FESI Feeders for Period of January-December 00 FESI- FESI- FESI- FESI- FESI- FESI-0 FESI- FESI- Number of Feeders 0 0 CI.%.%.%.% 0.%.%.%.% CHI.%.%.%.0%.%.0%.%.%

6 EB-0-0 Exhibit D Tab 0 Schedule Page of Although the FESI- represented only a small portion of the feeders (approximately. percent), they accounted for a large portion of CI and CHI as shown in Table. Figure shows a graphical breakdown of the FESI- impact on reliability when compared to the system as a whole. 00% CI and CHI distrubtion of FESI Feeders 0% 0% 0% 0% 0% 0% Remaining System FESI Feeders () 0% 0% 0% 0% CI CHI 0 Figure : FESI- Impact on System CI and CHI (00) To evaluate the progress of the WPF and FESI program, THESL has provided a breakdown of the CI and CHI for the ten feeders on which the majority of short-term work occurred. This includes work such as the installation of animal guards, fuses, as well as proactive tree trimming and replacements of overloaded and end-of-life transformers. Figures and show the CI and CHI contributions of these ten feeders from 00 to 00, and the steady improvements achieved through the FESI program. These feeders show a significant improvement in 00 CI due to the short-term actions

7 EB-0-0 Exhibit D Tab 0 Schedule Page of described above. In addition, long-term capital work has also been proposed and is currently ongoing for these feeders to further reduce the CI and CHI contributions. 00% % CI Contribution of 0 Feeders.%.%.% 0% % 0%.%.%.% % Remaining System CI Contribution 0 Feeders with Short Term Actions Figure : CI Contributions from Ten Feeders with Short-Term Actions (00)

8 EB-0-0 Exhibit D Tab 0 Schedule Page of 00% CHI Contribution of 0 Feeders %.%.%.% 0% % 0%.%.%.% % Remaining System CHI Contribution 0 Feeders with Short Term Actions Figure : CHI Contribution from Ten Feeders with Short-Term Actions (00) 0 CONSEQUENCES OF DEFERRING THE WPF PROGRAM In 00, the ten feeders shown in Figures and above represented more than eight percent of the CI, and almost seven percent of the system CHI, respectively. The FESI- feeders represented percent of the system CI and CHI. The FESI program added 0 new feeders in 00 that were not on the FESI list in 00. At this rate, without the FESI program, the number of feeders that are considered to be worst performing potentially could have doubled by the end of 0, with resulting negative impacts on overall system CI and CHI. The FESI program is considered a high priority given the potential for the rapid decline in feeder performance, and the urgency to improve service for customers connected to these feeders.