10 Physical Vulnerability of Electric Systems to Natural Disasters and Sabotage Box A―The Armenian and San Francisco Earthquakes' Effects on Electric Power Systems On December 7, 1988, Armenia was struck by a 6.9 magnitude earthquake the most destructive to hit the region in centuries. Hundreds of buildings, including hospitals, schools, apartments, and industrial facilities, were destroyed. At least 30,000 people were killed and some 500,000 were either left homeless or jobless. Several large cities in the epicentral region sustained massive damage and high casualties. Leninakan, population 290,000, was 80 percent destroyed and Kirovakan, population of 150,000 was also heavily damaged. The city closest to the epicenter, Spitak, was completely destroyed.1 The high death toll was caused by the collapse of buildings, many of which were constructed of masonry and precast concrete. Building materials-such as structural steel and wood, which are more flexible than concrete-are in short supply in Armenia. Steel-frame buildings and other steel structures, such as construction cranes, sustained far less damage than concrete structures. Also, the lack of emergency preparedness planning contributed to the catastrophe.2 In contrast, the October 17, 1989 San Francisco Bay Area earthquake did not result in the catastrophic loss of life and property that was experienced in Armenia. The 7.1 magnitude earthquake was the strongest to hit the area since 1907. The death toll is at least 66 people and approximately 3,000 injured. The quake caused an estimated $7 billion in damage in northern California.3 However, the growing California population, particularly in the earthquake-prone areas, could lead to a much greater loss of life and property in the future. Like Armenia, California lies within a large seismically active area. Unlike Armenia, though, California has one of the most comprehensive and up-to-date emergency preparedness plans in the United States and perhaps the world. For example, in June 1989, Pacific Gas & Electric (PG&E), the largest electricity supplier in the area, performed a company-wide earthquake emergency exercise. This exercise proved invaluable in responding to the real thing 4 months later, according to PG&E.4 In addition, a great deal of attention is given to seismic considerations in structural design, engineering, and construction. These and other factors can mitigate the impacts of a major earthquake disaster. Armenia3—In Armenia, electricity was interrupted for 4 to 7 days in the epicentral area. Two substations were severely damaged or almost totally destroyed. A 220-kV facility in Leninakan sustained damage to capacitor racks, ceramics, and circuit breakers. The 110-kV facility near Nalband was almost totally destroyed. The under-reinforced masonry and precast concrete control house collapsed and struck nearby equipment as it fell. Transformers, circuit breakers, and capacitor banks were severely damaged. Soviet authorities had to bring in a rail-mounted substation to restore power to the region. The two-unit Armenian Nuclear Powerplant, located 75 kilometers south of the epicenter, continued to operate during and after the earthquake. But, the plant was eventually closed because the units required substantial additional seismic reinforcement to remain safe, and the price was considered prohibitive. No damage to steel transmission towers throughout the region was reported. Wooden poles also survived intact, except for a few cases where partially rotted poles snapped at their bases. San Francisco-About 48 hours after the San Francisco earthquake, electricity had been restored to all but 12,000 of the 1 million customers affected. About half were those in the Marina District of San Francisco, which sustained heavy damage. The Moss Landing powerplant and high-voltage switchyards, located near the earthquake's epicenter, were heavily damaged. PG&E indicated that a 340-ton air preheater was knocked off its pedestal and the bottom dropped out of an 800,000-gallon raw water tank, creating a bog. Only one section of a 230-kV circuit near Moss Landing was knocked down. However, substantial damage was reported to distribution lines, especially in the Santa Cruz area. Damage to distribution lines in San Francisco was limited because most are located underground. 1"Real-World Lessons in Seismic Safety," EPRI Journal, June 1989, p. 23. 3"California Governor Signs Earthquake Relief Measures," Washington Post, Nov. 7, 1989, p. A-14. 4" PG&E Credits Mock Earthquake Drill in Responding Quickly to Real Thing," Electric Utility Week, Oct. 30, 1989, p. 3. 6"PG&E Credits Mock Earthquake Drill in Responding Quickly to Real Thing." op. cit., footnote 4. 7"Coping With Loma Prieta: How PG&E's Gas and Power System Fared," The Energy Daily, vol. 17, No. 234, Dec. 12, 1989, p. 3. 8"*Earthquake Cuts Off a Million PG&E Customers; Two-Thirds Back in Day," Electric Utility Week, Oct. 23, 1989, p. 2. Chapter 2-Causes of Extended Outages • 11 potential for earthquake damage.3 An earthquake similar to the New Madrid series would seriously affect 12 million people in seven States.4 Impact on Electric Power Systems More than any other natural hazard, major earthquakes are capable of producing almost complete social disruption in modern urban areas. Infrastructure, both above and below ground, may be shattered, and quick repair of below-ground items is almost impossible. Earthquakes can destroy all types of power system equipment, but the damage drops off rapidly with distance from the epicenter. Most structural research has gone into multi-story buildings, dams, nuclear powerplants, and storage tanks.5 Except for structures located at points of earth slippage, foundations in reasonably firm soil will tend to move with the ground without damage or relative displacement. Above grade, however, natural modes of vibration of the structure may be excited, amplifying the ground motion. Depending on its age or size, a powerplant itself may survive a moderate-to-severe quake, but its stacks might not. The only large generating plant damaged by the 1989 San Francisco earthquake was the Moss Landing facility, located about 20 miles south of Santa Cruz, the earthquake's epicenter. In addition, two 104-MW generating units at the Hunter's Point powerplant in San Francisco were briefly shut down manually after the earthquake shed the load, but were returned to service within 24 hours. The quake also knocked out of service five small generating plants, totaling 467 MW, near San Luis Obispo, some 230 miles south of San Francisco, but did not affect the Diablo Canyon nuclear plant.? The increase in transmission voltage over the years has resulted in larger substation equipment whose size makes it more seismically vulnerable. The increased susceptibility to damage is caused by two principal factors: 1) a drop of the frequencies of vibration into a lower and more severe region of the characteristic seismic frequency range, which produces an amplification of the seismic forces in the equipment; and 2) the inherent structural deficiencies the brittle nature and low-energy dissipation properties of electrical insulating material such as porcelain.8 In the 1971 San Fernando earthquake, failures occurred in many new extra-high-voltage (EHV) substations which had not previously been subjected to a strong seismic event. Subsequent studies by manufacturers and utilities resulted in modification of some of the existing equipment and extensive revision of the specifications for future substation equipment. The design criterion for seismic acceleration increased from 0.2 to 0.5 Gs in the most seismically active areas. The 1972 standard in Japan, where earthquakes are frequent, was 0.3 Gs.9 The Institute of Electrical and Electronic Engineers has seismic qualification standards for power transformers, lightning arresters, circuit breakers, relays, etc. 10 During the 1989 San Francisco earthquake, PG&E experienced significant internal damage to a 500-kV substation located near the Moss Landing powerplant. Damage to circuit breakers and transformers at the substation isolated two 112-MW units that were operating at the Moss Landing facility at the time of the earthquake.11 Performance of transmission lines, towers, and poles under earthquake conditions generally has been excellent. Steel towers move with the ground and the acceleration stresses are well within the 3Coordinating Committee on Energy of the Public Affairs Council, American Association of Engineering Societies, Vulnerability of Energy Distribution Systems to an Earthquake in the Eastern United States An Overview, December 1986. 4U.S. Geological Survey, National Center for Earthquake Engineering Research. "Gilbert F. White and J. Eugene Haas, Assessment of Research on Natural Hazards (Cambridge, MA: The MIT Press, 1975). "L.W. Long, "Analysis of Seismic Effects on Transmission Structures," paper presented at the IEEE PES Summer Meeting and EHV/UHV Conference, Vancouver, BC, Canada, July 1973. 7" PG&E Credits Mock Earthquake Drill in Responding Quickly to Real Thing," Electric Utility Week, Oct. 30, 1989, p. 3; "Earthquake Cuts Off a Million PG&E Customers; Two-Thirds Back in Day," Electric Utility Week, Oct. 23, 1989, p. 2. 8K.M. Skreiner and L.D. Test, “A Review of Seismic Qualification Standards for Electrical Equipment,” The Journal of Environmental Sciences, May/June 1975. Ibid. 10IEEE 323-1974, standards for safety-related equipment. II"PG&E Credits Mock Earthquake Drill in Responding Quickly to Real Thing," op. cit., footnote 7. 12 Physical Vulnerability of Electric Systems to Natural Disasters and Sabotage margins required for wind resistance. Wood poles are inherently more flexible than steel towers, and the flexibility reduces the seismic stress substantially.12 However, earthquakes can cause transmission outages when tower foundations are subject to earth slippage. Detailed soil analysis, adequate footing design, and periodic inspection of existing foundations are essential. In the 1971 San Fernando earthquake, tower foundations failed that over the years had their strength reduced by erosion or adjacent excavation for roads or buildings.13 The only major transmission line damage reported during the 1989 San Francisco earthquake was a section of 230-kV circuit between the Moss Landing powerplant and Watsonville. However, substantial distribution line damage was reported in areas close to the earthquake's epicenter.14 Hurricanes The losses caused by a landfall hurricane are a function of the storm's strength and path and the area's population and economic development. Hurricanes are accompanied by torrential rains, typically 3 to 6 inches but more if the forward progress is slow. Winds can exceed the design of a total structure or its components and cladding, or cause hazards from windborne debris. The winds also produce disastrous sea surges and waves. A large proportion of the damage to coastal areas is caused by the storm surge, an influx of high water accompanying the hurricane. Other hazards include flooding of streams induced by the heavy rainfall and accelerated coastal erosion. Occasionally tornadoes accompany a hurricane. 15 In the United States, most hurricane damage occurs in a narrow zone along the coastlines of the Atlantic Ocean and Gulf of Mexico. The trend is toward fewer deaths due to improved storm warning and management. However, property loss is increasing because of greater coastal development.1 12Long, op. cit., footnote 6. 16 Effects on Electric Power Systems Hurricanes primarily affect T&D lines. High winds can damage or uproot T&D poles. Poles can also fall when soils become water saturated by accompanying torrential rains, as was the case in 1982 when Hurricane Iwa struck the Hawaiian Islands and in 1989 when Hurricane Hugo hit the Carolinas. Hurricane Hugo knocked out power to more than 1 million customers in the Carolinas. Many people were left without power for several weeks. High winds and flying debris downed transmission towers and several hundred miles of transmission lines, and falling trees knocked out thousands of distribution lines. Four utilities hardest hit by the September 22, 1989 storm have indicated that the cost of restoring service and cleanup may exceed $170 million. Insurers are expected to pay for about 10 percent of the cost.17 See box B for a discussion of Hurricane Hugo's effect on the largest supplier of electricity in South Carolina. Tornadoes and Thunderstorms In the United States, tornadoes are most prevalent in a region known as "Tornado Alley" that extends from the western Texas Panhandle across Oklahoma, Kansas, southern Nebraska, and Iowa, but have been known to occur in all States.18 Tornadoes kill hundreds of people and destroy property valued at billions of dollars every year. The combination of high winds and the sudden drop in air pressure causes heavy destruction of everything in a tornado's path. 19 Heavy rain and large hailstones often fall north of the tornado's path. Tornado families occur when up to six tornadoes are spawned from the same thunderstorm.2 20 Severe thunderstorms can produce damaging lightning and high winds with the potential to cause extended blackouts. For example, the 1977 New York blackout began with a series of severe lightning strokes. Also, in 1989, a severe thunderstorm 13 Albert W. Atwood, Jr., and Kenneth L. Griffing, comments on Long, op. cit., footnote 6. 14" PG&E Credits Mock Earthquake Drill in Responding Quickly to Real Thing," op. cit., footnote 7, p. 3. 15 White and Haas, op. cit., footnote 5. 16Ibid. 17"Damage Estimates From Hurricane Hugo Pegged at up to $170 Million," Electric Utility Week, Nov. 13, 1989, p. 5. 18" Tornado," McGraw-Hill Encyclopedia of Science and Technology, vol. 18, 1987. 19"Tornado," Encyclopedia Americana, vol. 26, 1986. 20 Tornado," McGraw-Hill Encyclopedia of Science and Technology, vol. 18, 1987. Chapter 2-Causes of Extended Outages • 13 Box B-Hurricane Hugo's Effect on South Carolina Electric & Gas Co.1 Hurricane Hugo was one of the most powerful hurricanes to strike North America in this century and the most powerful to strike the Carolinas. Property damages in North and South Carolina alone are estimated to be about $6.5 billion:2 The hurricane caused extensive darnage to electric utilities in its path. Hardest hit was South Carolina Electric & Gas Co. (SCE&G), the largest supplier of electricity in South Carolina. Of SCE&G's 430,000 customers, 70 percent were blacked out during the storm. After 5 days, about 140,000, or 33 percent, were still without power. Full service was restored in less than 3 weeks.3 In Charleston and Summerville, transmission and distribution circuits were especially hard hit by high winds, flying debris, and falling trees. The distribution system in these two areas was almost completely leveled. While there was damage to the transmission system, the delay in repair was primarily due to the extent of the damage to the distribution system. No significant damage was reported to generating units or transmission substation equipment. However, a cooling tower at one 600-MW unit was destroyed. Temporary repairs were made and the unit was back in service in less than a week. Only one power transformer, a 115/230-kV unit, which served a distribution station, was damaged in the storm. There was a lot of damage from trees that were broken and blown into the distribution and transmission systems. Before repairs could be made, roads, lines, and access had to be cleared. Since it had been over 30 years since a major hurricane had struck the area, there was an unusually large amount of debris from wooded areas. The debris, while often not damaging the system, still required crews to physically remove branches, etc. from the transmission towers, distribution poles, and conductors. Throughout the SCE&G system, two-thirds of the transmission circuits were out of service immediately following the storm. About 300 towers, out of a total 24,000, were either toppled or broken. Contributing factors in the damage to the transmission system were the number of wooden pole transmission towers in the 230-kV and 115-kV systems and the amount of rain that preceded the storm. Soil conditions were especially poor in wet and low-lying areas. Transmission towers in those areas fell because the footing had become too soft and weak from the rain. SCE&G and other coastal utilities are reevaluating the foundation requirements of towers near marshes, swamps, and river crossings. As many as 3,600 workers labored to restore electric service at SCE&G, with 75 percent of them working on the transmission and distribution systems. Over 90 percent of the workers were from neighboring utilities and private contractors. Line crews came from Alabama, Arkansas, Florida, Georgia, Mississippi, Louisiana, Maryland, Tennessee, Virginia, and Illinois. Many of the crews brought their own vehicles and specialized equipment. This was done as part of mutual assistance agreements among utilities. 1 Casazza, Schultz & Associates, Inc., "Vulnerability of Electric Power Systems to Sabotage and Natural Disasters," contractor report prepared for the Office of Technology Assessment, Nov. 24, 1989. 2 Edward V. Badolato et al., Clemson University, The Strom Thurmond Institute of Government and Public Affairs, "Hurricane Hugo Lessons Learned in Energy Emergency Preparedness," 1990, p. 1. 3 There were still customers without service, but the problem was with the customers, not the utility. Many homes and businesses were too severely damaged to have service restored. blacked out portions of the Washington, DC area for several days, primarily because of the number of downed trees. Effects on Electric Power Systems In general, property damage from tornadoes has declined sharply due to improved prediction and increased public awareness. Tornadoes are more likely to cause damage to transmission and distribution lines over a small geographic area than wipe out a substation or generating plant. Thunderstorms are more widespread and consequently more disruptive. High winds, torrential rains, and lightning can wreak havoc on distribution lines. Geomagnetic Storms Large fluctuations in the Earth's magnetic field caused by solar disturbances are called geomagnetic storms. The Sun continuously emits a stream of protons and electrons called the solar wind. Solar disturbances such as sunspots and solar flares create gusts in the solar wind, with a more intense stream of charged particles emitted. When the solar wind hits the Earth's magnetic field it produces electric currents in the atmosphere, altering the magnetic 14 • Physical Vulnerability of Electric Systems to Natural Disasters and Sabotage field (as well as causing the aurora borealis). Both solar activity and geomagnetic storms ebb and flow in an 11-year cycle, although large storms may occur at any time. The peak of the current geomagnetic storm cycle, which is expected to be the most violent yet recorded, is anticipated to arrive in approximately 1991.21 Effects on Electric Power Systems Fluctuations in the Earth's magnetic field create electric potentials (differences in voltages) on the Earth's surface. The resulting electric potential differences of 5 to 10 volts per mile fluctuate very slowly and are typically aligned from east to west. Geomagnetically induced currents (GICs) flow wherever a power line connects areas of different electric potential. The magnitude of GIC depends on several factors including a power line's location, length, and resistivity relative to the resistivity of the ground. Areas with long east-west transmission lines and highly resistive geology typical of igneous rock formations are most likely to experience large GICs. GIC produced in a power system may either damage equipment or merely take it out of service during the course of the geomagnetic storm. Both may lead to system outages. When struck by GICs, EHV transformers may overheat, resulting in permanent damage or reduced life. Voltages in transformers may drop significantly, leading to unacceptable loadings on generators and transmission lines resulting in their being taken out of service by protective relays. Harmonic distortions created in the transformers may cause misoperation of relays, too. Relays may operate when they shouldn't, resulting in equipment being taken out of service unnecessarily; they may also fail to operate when needed, resulting in damage to the attached equipment. A very strong geomagnetic storm on March 13, 1989 damaged voltage control equipment in Quebec, resulting in the collapse of nearly the entire system for a 9-hour blackout. The same storm tripped protective relays in several areas of the United States and damaged several large transformers. One of these transformers, a step-up unit at the Salem Nuclear Plant in New Jersey, had to be removed from service, forcing the plant to shut down for 6 weeks. SABOTAGE No long-term blackouts have been caused in the United States by sabotage. However, this observation is less reassuring than it sounds. Electric power system components have been targets of numerous isolated acts of sabotage in this country. Several incidents have resulted in multimillion-dollar repair bills. In several other countries, sabotage has led to extensive blackouts and considerable economic damage in addition to the cost of repair. Some terrorist groups hostile to the United States clearly have the capability of causing massive damage the loss of so many generating or transmission facilities that major metropolitan areas or even multi-state regions suffer severe, long-term, power shortages. The absence of such attacks has as much to do with how terrorists view their opportunities as with their ability. U.S. electric power systems are only one target out of many ways of striking at America, and not necessarily the most attractive. This section briefly reviews the range of acts of sabotage against electric power systems and the capabilities of different types of saboteurs. However, an analysis of the motivations and intentions of terrorists is beyond the scope of this study. Several referenced studies have considered this subject. The reader is also referred to a forthcoming OTA study "The Use of Technology To Counter Terrorism." Experience With Sabotage United States Over the past decade there were few notable acts of sabotage, and apparently none that were intended to cause harm other than to the local utility. The most common cause has been labor disputes. In July 1989, a tower on a 765-kV line owned by the Kentucky Power Co. was bombed, temporarily disabling the line. No arrests have been made. In 1987-88, power line poles and substations were bombed or shot in the Wyoming-Montana border area. Later in 1988, similar attacks were experienced in West Virginia. Such attacks had also occurred in 1985 in West 21 This discussion is drawn from: "A Storm From the Sun," EPRI Journal, July/August 1989, pp. 14-21; V.D. Albertson, "Geomagnetic Disturbance Causes and Power System Effects," IEEE Power Engineering Review, July 1989, pp. 16-17; J.G. Kappenman, "Power System Susceptibility to Geomagnetic Disturbances: Present and Future Concerns," IEEE Power Engineering Review, July 1989, pp. 15-16; and D. Soulier, "The Hydro-Quebec System Blackout of March 31, 1989," IEEE Power Engineering Review, July 1989, pp. 17-18. |