Asset Management and System Reliability Group Review

Transcription

1 Final Report: Asset Management and System Reliability Group Review Prepared for: Prepared by: Contact: Southern California Edison InfraSource Technology Richard Brown, PhD, PE 4020 Westchase Blvd., Suite 375 Raleigh, NC (V) (M) May 17 th 2007

2 Executive Summary The Asset Management and System Reliability Group (AMSR) of Southern California Edison (SCE) has requested an independent review of its objectives, methodologies, and resources. InfraSource has accomplished this through a review of data provided by SCE and a series of on-site interviews. The InfraSource assessment focuses on reliability assessment, aging infrastructure assessment, infrastructure replacement planning, and credibility of results with respect to internal budgeting and general rate case funding requests. AMSR has oversight responsibilities in three categories of spending: the replacement of subsurface switches, worst circuit rehabilitation, and proactive cable replacement. In each of these areas, AMSR is making appropriate spending recommendations as benchmarked against the requirements of asset management, the overall objectives of Southern California Edison, and the approaches of other large investor-owned utilities in the United States. This finding is based on an assessment of organization, data, reliability management, and aging cable models. Organization. The AMSR group is situation organizationally within SCE in a manner suitable for its stated mission and goals. AMSR is slightly understaffed, and will increasingly require higher levels of staffing as the amount of proactive equipment replacement activity increases. Data. The data available to AMSR for making proactive equipment replacement decisions is better than at most large utilities. This is especially true for equipment population age data. The present outage management system has only been active since the beginning of 2006, and data from this system must currently be supplemented from an old system (the data is not as complete in the old system). This limitation is being well-managed, and data from the old system will eventually not be needed by AMSR. Reliability Management. AMSR is appropriately considering all capital aspects of potential reliability improvement projects for both overhead and underground. In addition, AMSR is properly coordinating with other groups within SCE to ensure that the most appropriate projects are identified. AMSR does not presently recommend inspection or maintenance projects. However, it is the plan of AMSR to include inspection and maintenance work in its work scope for 2009 and beyond, which will increase its ability to address the reliability in a cost effective manner. Aging Cable Models. AMSR has advanced cable failure rate models and aging system reliability models when compared to the industry as a whole. The resulting predictions have the opportunity to become more specific over time with better data and better analytical models, but the current predictions for escalating cable failures and the corresponding impact to system reliability are able to identify appropriate levels of cable replacement and appropriate replacement projects. SCE will have to significantly increase the amount of proactive cable replacement in the near future to avoid significant worsening of system reliability. For higher levels of cable replacement that will be seen in five years and beyond, it will become increasingly desirable to use more detail data and more detailed models. The data and methodologies used by AMSR are appropriate and have resulted in credible reliability predictions with regards to increasing cable failures, the impact of increasing cable failures on system reliability, and the impact of proactive cable replacement on future reliability. The approach of AMSR for proactive equipment replacement is more sophisticated and produces results with higher confidence when compared to most other large utilities. Spending requests by AMSR are reasonable, higher spending request levels could be justified at this time, and higher levels of spending on proactive equipment replacement will be required in the future. SCE AMSR Group Review FINAL REPORT Page 2 of 28

3 Table of Contents EXECUTIVE SUMMARY INTRODUCTION ORGANIZATION RELIABILITY DATA AND REPORTING RELIABILITY MANAGEMENT PROACTIVE CABLE REPLACEMENT CONCLUSIONS AND RECOMMENDATIONS...20 APPENDIX A: QUALIFICATIONS OF RICHARD E. BROWN...21 SCE AMSR Group Review FINAL REPORT Page 3 of 28

4 1 Introduction The Asset Management and System Reliability Group (AMSR) of Southern California Edison (SCE) has requested an independent review of its objectives, resources, methodologies, and resources. InfraSource has accomplished this through a review of data provided by SCE and a series of on-site interviews conducted by Richard Brown at the Santa Ana SCE site. This report is presents the results of Dr. Brown s findings. The AMSR Group of Southern California Edison (SCE) has the following mission: AMSR Mission Asset Management & System Reliability will enhance distribution reliability by ensuring timely, sufficient, and cost-effective replacements of aging infrastructure, by impelling cost-effective improvements in system design, maintenance, and operation, by providing data and analysis to organizations whose activities impact system reliability. Specific objectives of the Asset Management and System Reliability Group are the following: AMSR Objectives With a quantitative measure of uncertainty and employing auditable analyses, predict reliability over the next 25 years at the system and circuit level, with and without various levels of preemptive infrastructure replacement and/or automation. Utilize the above analyses to (1) enable informed decision-making at the senior and executive management levels regarding resource expenditures, and (2) support, with empirical evidence, SCE s request for capital funding of infrastructure replacement in the 2009 General Rate Case. Considering the above mission and objectives, the InfraSource assessment focuses on reliability assessment, aging infrastructure assessment, aging infrastructure planning, and credibility of results with respect to internal budgeting and general rate case funding requests. As such, this report first describes the AMSR group in terms of the greater SCE organization. It then discusses data, modeling, and reliability management. Last, it discusses the AMSR approach to proactive reliability management in general and proactive cable replacement in detail. SCE AMSR Group Review FINAL REPORT Page 4 of 28

5 2 Organization Southern California Edison (SCE) is one of the largest investor-owned electric utilities in the United States. It serves more than 13 million people in a 50,000 square-mile area of central, coastal and Southern California, excluding the City of Los Angeles and certain other cities. SCE has consolidated assets of approximately $25.3 billion, and employs about 15,000 people. When examining a relatively small group like AMSR, it is critical to examine its place within the greater corporate organization. In this case, AMSR falls within the SCE Transmission and Distribution business unit within the Engineering and Technical Services division. The SCE organizational chart showing AMSR is shown in Figure 2-1. Figure 2-1. SCE Organizational Chart SCE AMSR Group Review FINAL REPORT Page 5 of 28

6 As shown in Figure 2-1, AMSR is located under both planning and engineering, but excludes both field engineering and transmission planning. Therefore, the AMSR group is organizationally suitable for addressing issues related to distribution planning, reliability, and proactive infrastructure replacement. This organizational structure supports the AMSR mission and goals as stated in Section 1. Not visible on the organizational chart is the fact that AMSR is only responsible for examining issues impacting capital budgets (as opposed to inspection, maintenance, and/or operational budgets). This is typical industry practice. There are potential benefits for an asset management group being responsible for both capital and expense budgets, but this is not common industry practice at the present time. AMSR is presently in the process of proposing the addition of some expense dollars to the worst circuit rehabilitation program. Because AMSR is only responsible for examining issues impacting capital budgets, the remainder of this report will focus primarily on projects and issues that impact capital budgets. Within AMSR, there is a manager and eight additional people. Of these eight people, two are focused on asset model development, three are focused on reliability data collection and reporting, and three are focused on project identification and scoping. Together, this group is responsible for identifying and justifying about $30 million in project work for 2006, ramping up to roughly $90 million in project work for AMSR is slightly understaffed for the present activity level of $90M in infrastructure replacement. As the activity level increases, the need for a higher level of staffing will increase. There is no obvious way to automate present job tasks. In fact, the current AMSR plan to utilize predictive reliability modeling in its processes will further increase staffing needs (see Section 4). SCE AMSR Group Review FINAL REPORT Page 6 of 28

7 3 Reliability Data and Reporting System Reliability Data Prior to 2006, SCE collected reliability data through a system called DTOM, (Distribution Transmission Outage Management). This system was robust in data collection, but collected data primarily associated with total distribution circuit interruptions (referred to at circuit outages ). This means that most interruptions occurring downstream of fused lateral taps were not recorded in DTOM. At SCE, interruptions occurring downstream of fused lateral taps are called area outages. At the beginning of 2006, SCE began using its new outage management system called ODRM, (Outage Database Reliability Metrics) to collect interruption data. This system is able to collect information on all distribution interruptions, including area outages. Based on data collected from ODRM, SCE regularly computes the following reliability indices: SAIFI, SAIDI, and MAIFI. These indices are appropriate for tracking high-level reliability trends for the SCE system. SCE is also able to (1) compute the percentage of indices due to circuit outages versus area outages, and (2) compute the percentage of indices due to weather, overhead equipment, underground equipment, vegetation, and so forth. This type of data reporting capability is typical for the industry. At the time of this report, a little over 1 year of data from ODRM is available. ODRM is exclusively used for (1) computing the contributions of failures to SAIDI and SAIFI, and (2) computing mainline versus area outage ratios. A combination of DTOM and ODRM is used for cable outage data. It is appropriate at the present time for SCE to supplement ODRM data with DTOM data for asset management decisions in the absence of sufficient ODRM data. However, AMSR should gradually move towards the exclusive use of ODRM data, which is its plan. Reliability data for 2006 by month is shown in Figure 3-1. This figure shows that consistently high contributions to overall SAIDI come primarily from overhead equipment, underground equipment, and third party issues. It also shows that weather contribution is highly variable from month to month. SCE is further able to break down these high-level causes into sub-categories. For example, a failure attributed to underground equipment can be further classified as to whether it is cable, and whether this cable failure was due to bad cable or to some other cause. SCE AMSR Group Review FINAL REPORT Page 7 of 28

8 30 25 Weather UG Equip. SAIDI (Sustained Minutes) OH Equip. 3rd Party Animal Vegetation 5 Operation Other - Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure SCE Reliability Data In addition to tracking overall performance, SCE also tracks its worst performing circuits and identifies work to improve their reliability as part of its worst circuit rehabilitation (WCR) program. Unlike many utilities that use a single measure to track worst performing circuits, SCE creates several lists based on separate measures. For example, there is one list for each of the following metrics: - Feeders contributing most to system SAIFI - Feeders contributing most to system SAIDI - Feeders with the most circuit outages - Feeders contributing most to outage frequency x peak feeder load / customers on feeder Creating multiple lists identifies a group of feeders that (1) have a high impact to overall reliability, and/or (2) are likely to result in customer complaints. AMSR coordinates with field engineers (who have local knowledge of concerning circuits) to select the specific circuits to target for reliability improvement. This is a robust process and helps to ensure that WCR work is done on circuits that are truly problematic from a system, customer, and/or field operations perspectives. Equipment Reliability Data SCE has two computerized equipment management systems which work somewhat in parallel. The primary function of the DPI system (Distribution Project Information) is to track physical assets. The primary function of the Passport system is to schedule and document maintenance and inspections of those physical assets. When equipment is installed, removed, or replaced, DPI is updated via Work Orders. DPI contains information such as installation and/or removal dates, removal reasons, voltage, load rating, manufacturer, type, location, etc. This information is copied over to Passport on a daily basis. In additional to the data from DPI, Passport also includes inspection requirements, schedules, and results, as well as schedules for replacement. SCE AMSR Group Review FINAL REPORT Page 8 of 28

9 Figure 3-2. Sample DPI Work Order Figure 3-3. Sample DPI Account Transaction Summary SCE AMSR Group Review FINAL REPORT Page 9 of 28

10 A screen shot from a DPI work order is shown in Figure 3-2. This work order contains a material code, a location, an associated ledger account, and other useful information. Presently, there is not an easy way to access summary information from the DPI work orders, but AMSR should consider investigating this possibility. DPI work orders are reconciled to property record ledger accounts in the CARS system (Corporate Accounting Records System) via CPR (Continuing Property Records). There are underground cable accounts for each year, and each cable removal project results in the amount of removal being subtracted from the associated account. Neither cable locations nor removal reasons are recorded in CARS. CARS is also not able to segregate cable by voltage class (e.g., 4 kv, 12 kv, 16 kv) nor is it able to distinguish primary from secondary cable. However, this information is potentially accessible from DPI work order records. CARS contains data sufficient to calculate how much cable was installed in any given year, and how much of the cable installed in that year was removed in every subsequent year. Based on samples performed, SCE s primary cable system is estimated to comprise 50% of the total distribution cable inventory (except PILC) with the remainder being the secondary cable system. Therefore, present calculations assume that half of each CARS account reflects primary cable and the other half reflects secondary cable. Because SCE (for the most part) has only purchased a single type of cable insulation in any given year, it can infer cable insulation type for each year. These cable types are PILC (paper insulated lead covered), HMW (high molecular weight), XLPE (cross-linked polyethylene), and TR-XLPE (tree retardant crosslinked polyethylene). From the data in CARS, SCE is able to produce a histogram of its current inventory of installed cable by year of installation (and therefore type). It is also able to estimate average cable failure rates as a function of age. A chart showing cable age distribution based on accounting records is shown in Figure 3-4. The level of accuracy achieved by AMSR for population data is better than that achieved by many utilities. Most utilities are able to identify the amount of cable purchased each year from accounting records, but most do not reduce these accounts based on specific cable removal work orders. Instead, removal quantities are typically allocated across accounts using techniques such as Iowa curves. The cable population data presently available to AMSR is sufficient for most asset management functions. In addition, there is the potential to extract additional useful data from DPI. SCE AMSR Group Review FINAL REPORT Page 10 of 28

11 Conductor-miles In conductor-miles PILC = 4,495 HMW = 1,451 XLPE = 29,589 TR-XLPE = 10,769 Total = 46,304 PILC HMW XLPE TR-XLPE Year of Installation Figure 3-4. Primary Cable Age Histogram Based on Accounting Records SCE has a set of Field Inventory Maps (FIMs) which are essentially scanned images showing a geographic representation of distribution infrastructure. These maps contain useful information for certain types of equipment that are not available elsewhere. For example, the age, insulation type, conductor size, and voltage rating for each cable section is shown. FIMs are used when dates of failed equipment are not available, and to identify cables to proactively replace. This is done by displaying the appropriate map on a computer screen and visually examining the image, which can be time consuming. SCE has attempted to automatically capture information from these images with limited success thus far. In summary, the data sources used by AMSR are more complete than those used by many other large investor-owned utilities in the United States. This data is appropriate and useful for both reliability reporting and for making asset management decisions. SCE AMSR Group Review FINAL REPORT Page 11 of 28

12 4 Reliability Management Although electric utilities presently address asset management in many different ways, the best approaches to asset management all contain several elements. These include the following: (1) decisions are data-driven; (2) decisions consider cost, performance, and risk; and (3) processes are in place to ensure that decisions are efficient. The present mandate of AMSR is to recommend capital projects that efficiently address reliability and risk concerns on the distribution system. Therefore, an appropriate working definition of asset management for AMSR is the following: Working Definition of Asset Management for the SCE AMSR Group Asset management is a data-driven business approach that strives to identify appropriate levels of infrastructure replacement that maximize reliability and risk benefits subject to financial and human resource constraints. AMSR makes certain spending recommendation based on risk. For example, AMSR recommends subsurface switch replacements due to operational safety concerns. A specific category of oil-filled switches have been identified as vulnerable to catastrophic failure when operated. AMSR has prioritized these switches for replacement. AMSR is concerned with two aspects of reliability. First, it is interested in system reliability as measured by the reliability indices SAIFI, SAIDI, and MAIFI. Second, it is interested in worst circuit reliability. AMSR expects reliability indices to become worse over time due to aging infrastructure, and is developing scenarios to address this problem (see Section 5). Worst circuits are a potential source of customer dissatisfaction, and are addressed through the previously-mentioned WCR program. Although AMSR is only concerned with capital budgets, it is useful from a benchmarking perspective to look at reliability holistically. The activities of AMSR can then be examined from this broader perspective. This approach is now taken by (1) considering the reliability of overhead distribution, and (2) separately considering the reliability of underground distribution. The reliability of overhead distribution for SCE is driven by weather, overhead equipment failures, thirdparty-related failures, and trees. The major maintenance activities performed by SCE that can affect these areas are vegetation management and pole inspections (these help to reduce failures associated with weather, overhead equipment, and trees, but not third-party issues such as vehicular accidents). SCE is required by the California Public Utilities Commission (CPUC) to perform vegetation management in a specific manner. In addition, SCE is required by the CPUC to perform wood pole inspections in a specific manner. Given these factors, SCE has a limited influence on the reliability overhead circuits through changes in maintenance practices. As the overhead distribution equipment at SCE ages, reliability will generally not go down. Certain types of overhead equipment wear out over time (e.g., steel-core wire), but these types of failures generally only contribute a small amount to reliability indices. Similarly, aging pole-mounted transformers may begin to fail more often, but these failures only impact a small number of customers. Also, SCE has a transformer load management program that identifies heavily loaded distribution transformers that are likely to fail due to overloading. Aging wood poles in principal could begin to fail more often, but SCE is required (as previously mentioned) by the CPUC to periodically test and treat its wood poles. Aging infrastructure is SCE AMSR Group Review FINAL REPORT Page 12 of 28

13 simply not a major issue for overhead SCE distribution circuits with regards to its impact on SAIFI, SAIDI, and MAIFI. Overhead reliability can be improved through capital projects such as lateral fusing, the addition of new manual switches, the addition of new automated switches, and the addition of new circuits. Typically the most cost effective capital approaches are lateral fusing, the addition of new manual switches, and automation. With regards to these options, the following observations are made: Potential Capital Project to Improve Overhead Reliability - More fuses. It is estimated that about half of all radial taps are fused. Fusing radial taps is presently being done through the WCR program. Fusing radial taps on feeders not addressed by the WCR program is an opportunity for SCE. - More switches. An interview with a system operator with 6 years of experience indicates that the number of manual switches on overhead circuits is sufficient for fault isolation and system restoration. - More automation. SCE has a separate group in charge of the deployment of automated distribution switches (for both overhead and underground). Presently SCE has about 2500 automated distribution switches and an additional 1000 automated reclosers. Of the 4300 SCE distribution circuits, this represents about 1300 circuits with automated switching devices. At this point, most of the overhead circuits that would benefit significantly from automation are already automated, and the program is primarily focused on underground circuits. For AMSR, there is a limited ability to address the reliability of overhead circuits. When a primarily overhead circuit is addressed in the WCR process, typical recommendations for reliability improvement include lateral fusing, FCIs, automation, and automatic reclosers. It is the plan of AMSR to include inspection and maintenance work in its work scope for 2009 and beyond, which will increase its ability to address the reliability of overhead circuits. The reliability of underground circuits for SCE is primarily a function of equipment failures, especially cable failures. In addition, cable failure will increase as cables age, causing reliability to gradually become worse over time. SCE does not have specific CPUC requirements with regards to cable inspection and replacement, and therefore has a large amount of control with respect to cost and reliability for its underground distribution circuits. It is more difficult to improve the reliability of underground systems due to logistical factors such as the difficulty of obtaining new locations for new equipment. Therefore, capital reliability improvement options are generally limited to cable replacement and the automation of existing switches. With regards to these options, the following observations are made: Potential Capital Project to Improve Underground Reliability - More automation. As mentioned previously, SCE has a separate group in charge of the deployment of automated distribution switches. This group coordinates switch placement with the AMSR group. In addition, WCR recommendations may include automation, which are coordinated with the SCE automation function. - Proactive cable replacement. SCE has a large amount of old distribution cable in service, and this cable will start to fail with increasing frequency. This will lead to worsening reliability indices and increased operational costs. Proactive cable replacement can help with this situation, but should only be done if the right cable is replaced and the right amount of cable is replaced. This issued is discussed in detail in Section 5. SCE AMSR Group Review FINAL REPORT Page 13 of 28

14 AMSR has three primary spending categories: proactive cable replacement, sub-surface switch replacement, and WCR. Each of these three categories is now discussed briefly: Switch Replacement The present sub-surface switch replacement program is justifiable based on risk and safety considerations. Worst Circuit Rehabilitation (WCR) WCR spending is justified as long as (1) the identified circuits are appropriate, and (2) the projects recommended are cost effective. The first criterion is satisfied by AMSR and has previously been discussed in Section 3. The second criterion is treated qualitatively by AMSR by having designers work with field operations to identify a scope of work for a WCR circuit that is cost effective based on local knowledge and experience. This process has an opportunity for improvement through the use of predictive reliability modeling. A predictive reliability model is able to compute the reliability characteristics of a circuit based on system topology, device locations, and operational characteristics. This allows the reliability benefits of potential projects to be computed before they are actually performed. By using predictive reliability models, SCE could identify the appropriate amount of investment for each WCR circuit based on either achieving acceptable reliability or reaching a point where the benefit-to-cost ratio of additional projects are not acceptable. In addition, predictive reliability models can help to identify the combination of reliability projects that is able to achieve reliability benefits for the least possible cost. SCE is presently undertaking a pilot study in partnership with a consultant to create predictive reliability models for 15 circuits. This is an opportunity to begin the integration of predictive reliability modeling into their processes in an appropriate manner. When pursuing predictive reliability modeling, the benefits of improved incremental decision making must always be balanced against the cost associated with the modeling and analysis process. Proactive Cable Replacement AMSR is presently identifying cable sections for proactive replacement, which is required in order to effectively manage the aging cable population. Proactive cable replacement is a problematic issue for many utilities around the county since there is commonly an aversion to replacing functioning in-service equipment. However, not pursuing proactive cable replacement will almost certainly lead to unacceptable future system reliability and unacceptable numbers of cable failures that are difficult to address with existing resources. The AMSR proactive cable replacement activities are described in the next section. SCE AMSR Group Review FINAL REPORT Page 14 of 28

15 5 Proactive Cable Replacement The primary issue facing AMSR is proactive cable replacement. This is because (1) aging cables are starting to result in lower levels of system reliability, (2) there is often an aversion by interveners and regulators to replace equipment that is in service and functioning, and (3) proactive cable replacement requires significantly higher levels of spending than historical levels. To be successful in recommending proactive cable replacement, any regulated utility must have compelling answers to the following questions: Important Questions to Answer with Regards to Proactive Cable Replacement - Why should we proactively replace cable? - Why should we start now? Should we have started sooner? Can we defer this for a few years? - Which cables should be replaced first? Do we know the location of these cables? - How much proactive replacement is appropriate? AMSR is able to sufficiently answer all of these important questions. This is with regards to proactive cable replacement considering the current amount of proposed replacement each year. The remainder of this section elaborates on this finding. The first step in proactive cable replacement is to examine the reliability of cable as it ages. These failure rate models can then be used to project system reliability into the future for a variety of proactive replacement scenarios. AMSR has documented both its cable failure rate models and system reliability models in report AMSR dated April 11, This report goes far beyond the efforts of most utilities, and can be considered best-in-class. A summary of these models is now provided. AMSR is able to identify the amount of installed cable per year from ledger accounts in the CARS database. AMSR is also able to compute the difference in ledger accounts from year to year. With this information, AMSR is able to compute failure rates for cable installed in a specific year. To do this, account changes from 2002 through 2006 are used (five years). For example, consider cable installed in Assume there are 1000 conductor miles of 1980 cable in the ground at the beginning of At the end of 2006, there are only 800 conductor miles of 1980 cable left in the ground. This corresponds to 200 miles of replacement over five years, or 40 miles per year on average. This calculates to an average of 40 / 1000 = 4% replacement per year (these numbers are illustrative). As previously discussed, each ledger account combines both primary and secondary cable; AMSR assumes that half of the cable in each account is primary and that the other half is secondary. AMSR has computed the replacement rate for all cable ages dating back to 1957 using cable replacement data from 2002 through Since each year corresponds to a specific cable type (for the most part), failure rates for different cable ages are available and can be used to create unreliability functions (unreliability is the percentage of cable that has failed at a certain age). These functions are shown in Figure 5-1. SCE AMSR Group Review FINAL REPORT Page 15 of 28