Pacific Earthquake Engineering Pacific Earthquake Engineering Research Center Research Center Development of an Electrical Substation Equipment Performance Database for Evaluation of Equipment Fragilities Thalia Anagnos San Jose State University PEER 2001/06 2002/03 PEER 2001/06 APRIL 1999 aUGUST 2002 APRIL 1999 Development of an Electrical Substation Equipment Performance Database for Evaluation of Equipment Fragilities Thalia Anagnos Department of Civil and Environmental Engineering San Jose State University San Jose, CA 95192-0083 Final Report April 1, 1999 Prepared for the Pacific Gas and Electric Company and for the Pacific Earthquake Engineering Research Center PEER Report 2001/06 Pacific Earthquake Engineering Research Center College of Engineering University of California, Berkeley April 1999 EXECUTIVE SUMMARY A database has been developed that documents the performance of substation equipment in 12 California earthquakes. The equipment in the database is owned by the Pacific Gas and Electric Company, the Los Angeles Department of Water and Power, Southern California Edison and the California Department of Water Resources. The majority of data relates to equipment operating at 220/230 kV and 500 kV. The database is organized into an Excel 5.0 spreadsheet with 68 data fields describing earthquake location, ground motion, site location and conditions, equipment characteristics, performance of equipment, failure mode, and restoration time. Each record represents a single piece of damaged equipment or several pieces of similar undamaged equipment. Ground motions in the database are based on recordings if the site was instrumented. In other cases, ground motions are based on event-specific attenuation relationships developed by Somerville and Smith (1999). The purpose of the database is to provide a basis for developing or improving equipment vulnerability functions. The probabilities of failure are calculated by dividing the number of damaged items by the total number of items of that type at each site. Using peak ground acceleration as the ground motion parameter, failure probabilities are compared with opinionbased fragility curves for a few selected equipment classes. Comparisons are somewhat crude in that the calculated failure probabilities do not include information about the mode of failure. The comparisons indicate that some of the existing fragility curves provide reasonable matches to the data and others should be modified to better reflect the data. iii ACKNOWLEDGMENTS I would like to thank Anshel Schiff for all of his help in transferring and explaining the initial equipment damage database and in providing additional support documentation for several published articles on substation equipment damage. Dennis Ostrom's insight into damage and inventory of Southern California substations was invaluable. Ed Matsuda, Eric Fujisaki, Robert White, Norman Abrahamson, and Woody Savage of Pacific Gas and Electric Company (PG&E) provided valuable guidance and data on equipment inventories, use, priorities, function, and damage. Paul Somerville and Nancy Smith of Woodward Clyde were very helpful in creating spectra for inclusion in the database. Ron Tognazzini and Rulon Fronk of the Los Angeles Department of Water and Power (LADWP) provided valuable information on LADWP substations. Nitin Christopher, a graduate student at San Jose State University, performed some of the preliminary plots of fragility curves and damage data. This work was supported in part by the Pacific Earthquake Engineering Research Center through the Earthquake Engineering Research Centers Program of the National Science Foundation under Award number EEC-9701568. iv CONTENTS EXECUTIVE SUMMARY......................................................................................................... iii ACKNOWLEDGMENTS............................................................................................................iv TABLE OF CONTENTS ..............................................................................................................v LIST OF FIGURES ....................................................................................................................vii LIST OF TABLES ................................................................................................................... xiii 1. 2. INTRODUCTION ................................................................................................................1 SUMMARY OF DATABASE CONTENTS........................................................................5 2.1 Format of Substation Equipment Database ...................................................................5 2.2 Sources of Substation Equipment Damage Data ...........................................................5 2.3 Summary of Data ...........................................................................................................6 2.4 Limitations of Damage Data........................................................................................22 3. 4. 5. ESSENTIAL PARAMETERS FOR DEFINING EQUIPMENT FRAGILITIES...............25 UTILITIES WORKING GROUP EQUIPMENT CLASSES .............................................33 COMPARISON OF DATABASE STATISTICS WITH UTILITIES WORKING GROUP FRAGILITIES .......................................................................................................37 5.1 Failure Modes ..............................................................................................................37 5.2 Data Comparisons........................................................................................................40 6. FUTURE DATABASE DEVELOPMENT ........................................................................53 REFERENCES (Note: All appendices and the database are available on the project website, which can be accessed from the project website http://www.engr.sjsu.edu/tanagnos/Substation/index.htm) APPENDIX A Description of Substation Damage Database Structure A.1 A.2 A.3 A.4 A.5 General Description of Database ................................................................................. A-1 Format of Database...................................................................................................... A-1 Earthquake Data Fields (columns A through 0) .......................................................... A-2 Substation Data Fields (columns P through AJ).......................................................... A-4 Equipment Data Fields (columns AK through BN)..................................................... A-8 A.5.1 Notes ................................................................................................................. A-8 APPENDIX B Ground Motion Spectra for Selected Substations and Earthquakes B.1 Development of Ground Motion Spectra .................................................................... B-1 B.2 Plots of Ground Motion Spectra.................................................................................. B-5 APPENDIX C Fragility Curves Developed by Utilities Working Group C.1 General Description of Fragility Curves...................................................................... C-1 C.2 Parameters and Plots of Fragility Curves .................................................................... C-1 v LIST OF FIGURES Figure 3.1 Key parameters for defining seismic damage to a disconnect switch .....................26 Figure 3.2 Key parameters for defining seismic damage to a transformer ...............................27 Figure 3.3 Key parameters for defining seismic damage to a circuit breaker ..........................28 Figure 3.4 Key parameters for defining seismic damage to a circuit switcher .........................28 Figure 3.5 Key parameters for defining seismic damage to a coupling current voltage transformer ..............................................................................................................29 Figure 3.6 Key parameters for defining seismic damage to a lightning arrester ......................30 Figure 3.7 Key parameters for defining seismic damage to a current transformer ...................31 Figure 3.8 Key parameters for defining seismic damage to a wave trap ..................................32 Figure 5.1 Comparison of UWG fragility curves with damage data for 230 kV live tank General Electric ATB4-ATB6 circuit breakers (CB9). Data plotted for each site....................................................................................................................42 Figure 5.2 Comparison of UWG fragility curves with damage data for 230 kV live tank General Electric ATB4-ATB6 circuit breakers (CB9). Data for sites with same PGA are combined..........................................................................................43 Figure 5.3 Damage data for 230 kV live tank General Electric ATB4 - ATB6 circuit breakers (CB9) for individual sites plotted against 0.2-second spectral acceleration .................................................................................................44 Figure 5.4 Comparison of UWG fragility curves with damage data for 500 kV Westinghouse live tank SF6 circuit breakers (CB72) .............................................47 Figure 5.5 Comparison of UWG fragility curves with damage data for 230 kV and 500 kV lightning arresters with low seismic design (LA1 and LA5) ......................48 Figure 5.6 Comparison of UWG fragility curves with damage data for 230 kV horizontal disconnect switches (DS3) .......................................................................................49 Figure 5.7 Comparison of UWG fragility curves with damage data for 500 kV disconnect switches (DS1) .........................................................................................................51 Figure 5.8 Comparison of UWG fragility curves with damage data for single-phase 230 kV transformers (TR1) ..................................................................................................52 (Note: All appendices and the database are available on the project website, http://www.engr.sjsu.edu/tanagnos/Substation/index.htm) APPENDIX B SS#12 SS#5 SS#24 SS#24 Coalinga 1983 -- 5% Damped Spectra Landers 1992 -- 5% Damped Spectra Loma Prieta 1989 -- 5% Damped Spectra Loma Prieta 1989 -- 5% Damped Spectra vi SS#26 SS#28 SS#39 SS#21 SS#24 SS#7 SS#3 SS#31 SS#34A SS#34 SS#36 SS#38 SS#41 SS#47 SS#44 SS#45 SS#40 SS#1 SS#8 SS#18 SS#19 SS#23 SS#41 SS#45 SS#13 SS#14 SS#1 SS#4 SS#6 SS#8 SS#10 SS#15 SS#16 SS#17 SS#19 SS#22 SS#23 SS#27 SS#29 SS#30 SS#32 SS#42 SS#43 SS#46 SS#1 SS#2 SS#4 Loma Prieta 1989 -- 5% Damped Spectra Loma Prieta 1989 -- 5% Damped Spectra Loma Prieta 1989 -- 5% Damped Spectra Morgan Hill 1984 -- 5% Damped Spectra Morgan Hill 1984 -- 5% Damped Spectra North Palm Springs 1986 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Northridge 1994 -- 5% Damped Spectra Point Mugu 1973 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra San Fernando 1971 -- 5% Damped Spectra Santa Barbara 1978 -- 5% Damped Spectra Sierra Madre 1991 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 --5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra vii SS#6 SS#8 SS#11 SS#15 SS#23 SS#33 Figure C.1 Figure C.2 Figure C.3 Figure C.4 Figure C.5 Figure C.6 Figure C.7 Figure C.8 Figure C.9 Figure C.10 Figure C.11 Figure C.12 Figure C.13 Figure C.14 Figure C.15 Figure C.16 Figure C.17 Figure C.18 Figure C.19 Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Whittier Narrows Aftershock 1987 -- 5% Damped Spectra Utilities Working Group Fragilities for Single-Phase 230 kV Transformers (TR1) ...................................................................................................................... C-2 Utilities Working Group Fragilities for Three-Phase 230 kV Transformers (TR2) ...................................................................................................................... C-3 Utilities Working Group Fragilities for Single-Phase 500 kV Transformers (TR3) ...................................................................................................................... C-4 Utilities Working Group Fragilities for Three-Phase 500 kV Transformers (TR4) ...................................................................................................................... C-5 Utilities Working Group Fragilities for 500 kV Old Cogenel Circuit Breakers (CB5)....................................................................................................... C-7 Utilities Working Group Fragilities for 230 kV Live Tank General Electric ATB4, ATB5, ATB6 Circuit Breakers (CB9) .......................................... C-8 Utilities Working Group Fragilities for 230 kV Live Tank General Electric ATB7 Circuit Breakers (CB14) ................................................................ C-9 Utilities Working Group Fragilities for 500 kV Live Tank General Electric ATB (CB15) and Other 500 kV live Tank (CB15a) Circuit Breakers ................. C-10 Utilities Working Group Fragilities for 230 kV Dead Tank SF6 Circuit Breakers (CB20)................................................................................................... C-11 Utilities Working Group Fragilities for 230 kV Dead Tank Oil C-12 Circuit Breakers (CB20a)................................................................................................. C-12 Utilities Working Group Fragilities for 230 kV Modern Live Tank Circuit Breakers (CB57)................................................................................................... C-13 Utilities Working Group Fragilities for 500 kV Live Tank Westinghouse SF6 Circuit Breakers (CB72) ............................................................................... C-14 Utilities Working Group Fragilities for 500 kV Live Tank Puffer Circuit Breakers (CB73)................................................................................................... C-15 Utilities Working Group Fragilities for 500 kV Dead Tank SF6 Circuit Breakers (CB77)................................................................................................... C-16 Utilities Working Group Fragilities for 500 kV Vertical Disconnect Switches (DS1) C-00 ........................................................................................................... C-18 Utilities Working Group Fragilities for 230 kV Vertical Disconnect Switches (DS2)..................................................................................................... C-19 Utilities Working Group Fragilities for 230 kV Horizontal Disconnect Switches (DS3)..................................................................................................... C-20 Utilities Working Group Fragilities for 230 kV Lightning Arresters (LA1, LA2, LA3, LA4) ........................................................................................ C-22 Utilities Working Group Fragilities for 500 kV Lightning Arresters (LA5, LA6, LA7, LA8)................................................................................................... C-23 viii APPENDIX C Figure C.20 Utilities Working Group Fragilities for 230 kV Current Transformers (CT1, CT2, CT3, CT4) ................................................................................................... C-25 Figure C.21 Utilities Working Group Fragilities for 500 kV Current Transformers C-26 (CT5, CT6, CT7, CT8)......................................................................................... C-26 Figure C.22 Utilities Working Group Fragilities for 230 kV Coupling Capacitor Voltage Transformers (CC1, CC2, CC3, CC4) ................................................................. C-28 Figure C.23 Utilities Working Group Fragilities for 500 kV Coupling Capacitor Voltage Transformers (CC5, CC6, CC7, CC8) ................................................................. C-29 Figure C.24 Utilities Working Group Fragilities for 230 kV Potential Transformers (PT1, PT2, PT3, PT4) .................................................................................................... C-31 Figure C.25 Utilities Working Group Fragilities for 500 kV Potential Transformers (PT5, PT6, PT7, PT8) .................................................................................................... C-32 ix LIST OF TABLES Table 2.1 Table 2.2 Table 2.3 Table 4.1 Table 5.1 Earthquakes and Substations Represented in Substation Equipment Database.........9 Summary of Substation Sites and Ground Motions.................................................10 Summary of 230 kV and 500 kV Substation Equipment in Database .....................15 Utilities Working Group Substation Equipment Classes.........................................34 Failure Modes for Substation Equipment Classes ...................................................39 (Note: All appendices and the database are available on the project website, which can be accessed from the project website http://www.engr.sjsu.edu/tanagnos/Substation/index.htm) Table B.1 Table C.1 Table C.2 Table C.3 Table C.4 Table C.5 Table C.6 Table C.7 List of Ground Motion Spectra in Appendix B Fragility Parameters for Transformers ..................................................................... C-1 Fragility Parameters for Circuit Breakers ................................................................ C-6 Fragility Parameters for Disconnect Switches ....................................................... C-17 Fragility Parameters for Lightning Arresters ......................................................... C-21 Fragility Parameters for Current Transformers ...................................................... C-24 Fragility Parameters for Coupling Capacitor Voltage Transformers ..................... C-27 Fragility Parameters for Potential Transformers .................................................... C-30 xi 1 Introduction The high voltage components of electrical power substations are critical elements in the reliable operation of the power grid. For the power grid to be capable of reliable delivery to a region immediately after an earthquake, these components must continue to function. The 1994 Northridge, California, earthquake demonstrated that damage to electrical substation components can have far reaching consequences. Communities in British Columbia, Montana, Wyoming, Idaho, Oregon, and Washington experienced outages as a result of damage to electrical substation components in the Los Angeles area (Schiff, 1995). Customers in the Los Angeles area experienced outages lasting anywhere from a few seconds to several days. Power was restored to all major substations and to about 95% of the customers within 24 hours (Schiff 1995). However, during the next few months extensive repair and replacement of equipment were required to restore the system to its pre-earthquake redundancy and capacity. As repaired, the systems are assumed to be more reliable than prior to the earthquake. The power transmission and distribution systems in California have been built over many decades and utilize equipment that was designed and installed under varying seismic criteria. Substation equipment is very expensive and unfortunately many of the equipment components such as porcelain insulators and bushings are vulnerable to seismic damage. Some of the older equipment that was designed to much lower seismic standards is particularly vulnerable to seismic loading. The repair of substation damage caused by earthquakes can be a significant expenditure for utilities. Furthermore, loss of power immediately after an earthquake can disrupt emergency response and recovery operations for the affected region. Thus utilities are interested in ways to minimize or eliminate earthquake damage and disruption to their systems. 1 PG&E and other utilities have aggressive plans to replace vulnerable older equipment with more rugged components. Other mitigation strategies include retrofitting existing equipment, modifying design and installation practices, and developing improved standards for qualifying new equipment. A key element of the mitigation plans is the establishment of priorities based on, at minimum, equipment function, importance, and vulnerability. The analysis of substation equipment damage in past earthquakes is an important step in establishing levels of acceleration that cause failure in equipment, modes of failure and component weaknesses that lead to failure. The data can be used to develop or update fragility curves for use in system reliability models that can help in the establishment of mitigation priorities. The substation network evaluation performed by PG&E (Matsuda et al., 1991) represents one type of study that has been used to establish priorities for mitigation. In that study, scenario earthquakes were developed and damage was estimated at key substations. Substations were ranked and then selected for analysis based on their exposure and on their importance to the continued operation of the system. The damage to key pieces of equipment was determined by considering damage to similar equipment in past earthquakes. The impact on customer service was assessed by considering the damage at each substation and the redundancy of transmission lines. The purpose of this project was to compile equipment performance data from past earthquakes and organize the data into a database that would be useful in the analysis of equipment vulnerabilities. Anshel Schiff had collected extensive damage data for selected earthquakes and organized the information into a Filemaker Pro database. This database was used as the starting point for this study. Supplementary data relating to ground motions and undamaged equipment were collected for substations in the database. The database was then augmented with performance data that was developed from additional substations and earthquakes. Finally, for selected equipment classes the data were compared with existing fragility curves developed using expert opinion. Specific project tasks were to
· · evaluate the existing database for content and quality; add ground motion data either from site recordings or from simulated ground motion based on earthquake-specific attenuation relations; 2 · · · · add data from additional substations and earthquakes; review existing equipment classification system developed by the Utilities Working Group; document the database; and compare the data with existing fragility curves for selected classes of equipment. 3 2 Summary of Database and Contents 2.1 Format of Substation Equipment Database The Substation Equipment Database described in this report is a modified and augmented version of the initial database developed by Anshel Schiff. The original database was in Filemaker Pro and contained graphic representations of some pieces of equipment in addition to the written descriptions of equipment and damage. The database described here is maintained in an Excel 97 spreadsheet containing 68 columns of information. The content of each column is described in detail in Appendix A. Early in the project, a decision was made to convert the substation equipment database from Filemaker Pro to Excel to better conform to software at PG&E. While converting the database made it more accessible to researchers at PEER and PG&E, it introduced several limitations. First, all of the graphical representations of equipment were lost in the conversion. Secondly, EXCEL limits on the number of characters that can be typed in a cell, and in a few cases, data were truncated during conversion. Every attempt has been made to retrieve and include the truncated data. Third, EXCEL is not a dedicated database manager, and thus is not designed for performing queries. However, with a little caution to prevent truncating data, the EXCEL file can be saved in a dBASE format and then the Microsoft Add-in Query or any other database manager can be used to perform queries. 2.2 Sources of Substation Equipment Damage Data Data contained in the Substation Equipment Database were compiled from the following sources:
· · · original database developed by Anshel Schiff Earthquake Spectra articles Electric Power Research Institute (EPRI) reports 5 · · · · · · · American Society of Civil Engineers (ASCE) Technical Council on Lifeline Earthquake Engineering (TCLEE) Monograph No. 8 internal PG&E reports internal Los Angeles Department of Water and Power (LADWP) report internal Southern California Edison reports PG&E RCMS database of transformers and circuit breakers single line drawings of specific substations; and discussions with individuals who performed post-earthquake reconnaissance at specific sites The quality and completeness of the data vary considerably for different earthquakes and substations. The data collected for more recent California earthquakes, particularly Whittier Narrows, Loma Prieta, and Northridge, are much more detailed and complete than those for earlier events. 2.3 Summary of Data The database contains information about damaged and undamaged substation equipment from 12 earthquakes as detailed in Table 2.1. Pacific Gas & Electric, Los Angeles Department of Water and Power, Southern California Edison, and the California Department of Water Resources own the equipment documented in the database. The majority of data relates to equipment operating at 220/230 kV and 500 kV. In a very small number of cases, the damage to 60 kV equipment is documented. The quality of the data varies considerably. For substations in the Loma Prieta and Northridge earthquakes, detailed reports were available that identified the locations and types of damage for key types of equipment. These reports also provided good statistics on the undamaged equipment. For most other earthquakes, undamaged equipment statistics were developed through discussions with key personnel, examination of single line drawings, and review of the PG&E RCMS database. As a result, some types of equipment such as wave traps, potential transformers, coupling current voltage transformers, lightning arresters, and disconnect switches are not well represented at many sites. For each earthquake and substation, ground motion data were added. The database contains actual values for instrumented substations with site recordings. At other sites, ground motions are based on event-specific attenuation relations modified with residuals from recordings at 6 nearby sites (Somerville and Smith, 1999). The ground motion values listed in Table 2.2 vary depending on their source. For the ground motions generated from event-specific attenuation relations, two horizontal components, fault normal and fault parallel, were available and the largest value was chosen. Only one horizontal ground motion spectrum was available for ground motions generated from the attenuation relationship developed by Abrahamson and Silva (1997). In the case of site recordings, the two components are determined by the orientation of the instrument. The soil types listed in Table 2.2 are rough descriptions of the soil at the site and do not take into account local variations at the site. Since substations cover many acres, soil conditions can vary dramatically over the site. As summarized in Table 2.2, the peak ground acceleration, 0.1-second spectral acceleration, 0.2second spectral acceleration and 0.3 second acceleration ground motions are included in the database. These values were chosen because they are in the range of the fundamental period of most pieces of equipment. It should be noted that the response of equipment may be substantially altered by the support system. For example, a disconnect switch that is mounted on a very flexible frame will have a different response than a similar disconnect switch mounted on a frame. The support system may have periods much longer than 0.3 seconds. For information about longer periods, the complete 5% damped response spectra provided by Somerville and Smith (1999) are found in Appendix B. Table 2.3 contains a summary of the equipment data contained in the database. The data is sorted by earthquake and substation. For each substation, the peak ground acceleration is listed along with the number of damaged and undamaged pieces of equipment contained in the database. In the table, each piece of equipment is listed according to the classification system discussed in Section 4; however, in the database more complete descriptions may be available. For example, information about the support frame or the anchorage may be included in a comment field. In this study, if a phase has a separate piece of equipment associated with it, such as one phase of a circuit breaker, it is considered as a separate item of equipment. Thus, for earthquake damage 7 purposes, a circuit breaker would consist of three equipment items rather than one. A transformer bank consisting of three single-phase transformers would be considered as three pieces of equipment while a three-phase transformer would be considered as a single piece of equipment. It should be emphasized that this is not how the industry defines a piece of equipment. For the purposes of damage estimation this definition does have its advantages. For example, the number of phases damaged can impact the cost of repair and the time to restore equipment to service. Sometimes different phases are connected differently to other equipment. By representing damage by phase, failures due to interaction may be more readily identified. Using damage data for each phase of equipment allows for the development of fragilities for each phase. Simple models then can be developed to combine the probabilities of failure of each phase to estimate the probability that one, two or three phases will be out of service. 8 Table 2.1: Earthquakes and Substations Represented in Substation Equipment Database Earthquake San Fernando (2/9/71, Mw = 6.6) SS#1 SS#8 SS#18 SS#19 SS#40 SS#13 SS#12 SS#20 SS#21 SS#7 SS#1 SS#4 SS#6 SS#8 SS#10 SS#15 SS#16 SS#17 SS#19 SS#1 SS#2 SS#4 SS#6 SS#9 SS#14 SS#24 SS#25 SS#26 SS#28 SS#39 SS#5 SS#3 SS#31 SS#34 SS#35 SS#36 SS#37 Substations SS#23 SS#41 SS#45 SS#44 Point Mugu (2/21/73, Mw = 5.3) Santa Barbara (8/13/78, Mw = 6.0) Coalinga (5/2/83, Mw = 6.4) Morgan Hill (4/24/84, Mw = 6.2) North Palm Springs (7/8/86, Mw = 6.0) Whittier Narrows (10/1/87, Mw = 6.0) SS#24 Whittier Narrows Aftershock (10/4/87, Mw = 5.3) SS#22 SS#23 SS#27 SS#29 SS#30 SS#32 SS#42 SS#43 SS#46 SS#8 SS#11 SS#15 SS#33 Tejon Ranch (6/10/88, ML = 5.2) Sierra Madre (6/28/91, Mw = 5.8) Loma Prieta (10/17/89, Mw = 7.0) Landers (6/28/92, Mw = 7.3) Northridge (1/17/94, Mw = 6.7) SS#38 SS#41 SS#44 SS#45 9 Table 2.2: Summary of Substation Sites and Ground Motions
Soil Type Strong Motion Record at Site Peak Acc. 0.1 Second 0.2 Second 0.3 Second Spectral Spectral Spectral Acc. Acc. Acc. Source of Spectrum Substation Owner Coalinga 0.30g 0.57g 0.66g 0.53g No Abrahamson and Silva, 1997 attenuation SS#12 PG&E (UBC S1), < 200 ft alluvium overlying sedimentary rock. Landers 0.35g Loma Prieta 0.22g 0.33g 0.43g 0.54g No 0.49g 0.81g 1.29g Yes SS#5 SCE Quaternary formation -- soil recording SS#24 PG&E event-specific attenuation 0.58g No event-specific attenuation SS#25 PG&E 0.24g 0.35g 0.47g SS#26 PG&E 0.22g 0.32g 0.43g 0.54g No event-specific attenuation SS#28 PG&E 0.13g 0.21g 0.29g 0.36g No event-specific attenuation SS#39 PG&E (UBC S1), < 30 ft alluvium overlying sedimentary rock, (NEHRP D -- stiff soil 180m/s