Declaring Emergencies in California: The Realities of ISO Operation
An independent system operator's view on the energy crisis and the realities of maintaining reliability.
What is happening to the deregulation of California's electric energy market? It started out as an ideal concept. Energy would be provided to the California consumers at a much lower price, while maintaining a highly efficient system to accommodate generation, transmission and the distribution of energy. How has this dream gone so awry? The answer is that a chain of events have produced a breeding ground for the current absurd and almost farcical situation we are dealing with today.1
In a variety of forums and through articles appearing in the media and the press, several stakeholders and observers have asserted that the California Independent System Operator (CAISO) prematurely declares Stage 3 Emergency Notices1 and has called for firm load curtailments (rotating blackouts) while there seemed to be a surplus of resources to meet system demand. It may seem like simple math for observers external to the CAISO to derive such conclusions; however, these assertions are based on incomplete data and erroneous assumptions related to the resource mix in California. In this article, an attempt is made to explain how the system operators at the CAISO calculate available supply and projected demand in order to conclude that energy is needed to ensure that the rest of the demand on the grid can be served in a safe and reliable manner. Let's also consider the resource mix in California and demonstrate through examples that the actual generation capacity in the CAISO system during Stage 3 emergencies and firm load curtailments was well below values necessary to maintain electric grid reliability.
Traditionally in almost all electric utility practices worldwide, the system operator's primary responsibility is to constantly balance supply and demand. When demand exceeds supply and the system operator is not able to continue balancing the system and has no option but to take drastic actions and follow regional and national reliability standards in order to maintain the overall integrity of the grid. If the system operator does not attempt to balance demand with supply, or is unable to do so due to lack of supply, short of any action, the electric system would be in real danger of total disintegration resulting in total blackout. The system operators in every control area follow very similar guidelines in their constant attempt to balance the system. Deregulation of the electric energy system in California has made the system operator's actions public and more transparent than ever. Emergencies had taken place many times prior to deregulation. However, utilities followed different communication protocols, which led to much less public awareness of crises in the electric energy industry.
The California Energy Crisis: Product of deregulation?
Many people ask the question whether the energy crisis would have existed if California had not deregulated its wholesale energy markets. It is abundantly clear with factual evidence throughout this article that California would have had the current energy crisis even if deregulation had not taken place. Regardless of sufficiency of market rules as demonstrated throughout this article, the total available dependable capacity in California is simply well below its current demand. Therefore, lack of generation supply would have led to rotating blackouts regardless of deregulation. However, it should be noted that if deregulation had not taken place and the utilities had kept the ownership and operation of their California generating plants, the current financial crisis in California's electric energy industry may have been different.
Historically, California has heavily relied on importing electricity from the Pacific Northwest and Southwest. This discouraged building generation to keep up with the growing economy and has gambled on out-of-state purchases of electricity to supply the growing population. This is a key contributing factor to the current energy crisis. The lack of supply within California, recognizing that the existing generation fleet in California is old and plagued with environmental restriction, high growth in the Northwest and Southwest and below-normal water conditions combined with the unworkable market design, have collectively led to current energy crisis.
The Supply & Demand Issue: Adequacy of Supply and Load Growth
Statistics show that the actual capacity (i.e. supply) in the West is less than 2 percent over the demand. This is extremely inadequate by any US standards, especially since the system operators are required to maintain 7 percent of supply on standby as operating reserve. In addition, supplies are not available 100 percent of the time and their availability is subject to many factors: planned maintenance, forced outages, water availability, gas supply, environmental restriction, etc. The fact is that the entire western power grid is deficient in generation capacity and the aforementioned inadequacies further deteriorate the supply picture to unacceptable levels.
(Figure 1 shows the extent to which supply has kept up with demand. It should be noted that California actually lost supply due to early retirement of some plants.)
Moreover, the average demand growth in the West, including California, has been between 2 percent and 3 percent per year for the last 10 years. This translates to about 1,000 MW per year for California alone (enough electricity for one million households). In the last 10 years, California required 10,000 MW of growth in peak demand. During the same time frame, added generation capacity is nowhere near the required 10,000 MW. In California alone, 2279 MWs of new generating capacity has become operational as of September of 2001. The neighboring Western states are in about the same condition as California and are all building new generating plants frantically.
Figures 1 and 2 show the load growth in the last three years and that the fact baseline demand has also gone up, (i.e., the number of days that demand exceeded 35,000 MW has gone up from 51 days in 1998 to 84 days in 2000). This creates not only a capacity problem but also a MWh energy problem.
Not Fit For Print: The Newspapers Get Installed Capacity Wrong
A number of newspaper articles have asserted that there has been enough installed capacity to meet the need, but somehow it is being withheld or otherwise manipulated to create an artificial shortage (this article does not intend to offer complete treatment to artificial shortage or market manipulation). Rather, lets examine the total supply availability and compare it to the demand. "Installed or nameplate capacity" is the maximum capability of every generating unit in absolute perfect conditions. "Available or dependable capacity" is a subset of the installed or nameplate capacity actually capable of generating at any given time. The actual availability of generation, also referred to as dependable capacity, on any given day is generally less than the nameplate for several reasons:
- Hydro resource availability is dependent on water levels, stream flow, irrigation and environmental requirements, water storage capacity, precipitation and snow pack in a given year.
- Over 64 percent of the fossil supply fleet in the ISO area is over 30 years old and requires frequent maintenance combined with a higher rate of break-downs or forced outages.
- Typical generator availability is between 70 to 90 percent. This means that a generating unit is only available 70 to 90 percent of the time.
- Intermittent resources (i.e. wind and solar) are only available when conditions permit. For some of these resources availability of this type of generation can be less than 20 percent of installed capacity.
- Qualifying Facility installed capacity may not all-available to supply demand across the state since significant amounts of its capacity supply "on-site" load within the premises of the qualifying facilities.
- Other realities that could limit the availability of supply include transmission limitation, gas supply, and environmental restrictions.
Emergency Notifications: How it Works
The CAISO uses emergency notifications2 to communicate system conditions that threaten electric system reliability. This includes such dangers as CAISO grid instability, voltage collapse or under-frequency caused from transmission or generation trouble-conditions which could also impact the Western Systems Coordinating Council (WSCC) grid. It is important to realize that Emergency Notices are not only declared when an emergency condition exists, but are also used to help prevent an uncontrollable system emergency before it occurs. For example, stage emergencies may be declared at any time it is clear that an operating reserve shortfall is unavoidable or is forecast to occur within the next two hours. In its process of determining whether or not to declare emergencies, the CAISO assesses different factors on a day-ahead, hour-ahead, and minute-by-minute basis. It looks for times when actual demand exceeds forecasts, when the hour-ahead market is short on scheduled energy and ancillary services, and most importantly, when operating reserves do not satisfy WSCC operating reserve criteria.
Consequences of the Shortages: Day-to-Day Realities
California is facing an electricity shortage of unprecedented proportions coupled with a market that is not workably competitive. The consequences have been serious, and the realities that regularly confront the CAISO operators are complex at best. The CAISO strives to keep supply and demand in equilibrium and endeavors to avoid the shedding of load until it becomes inevitable. The CAISO only declares emergencies when it is absolutely necessary to do so if a system emergency is to be averted. Accusations that the CAISO's perception of a shortage is erratic and unverifiable are inapposite and can only heighten the crisis.
The energy situation has never been so severe compared to previous years. Within the first five months of 2001, the CAISO has already surpassed the number of emergency declarations for the prior three years.
The complexities of the CAISO system grid, its markets, and the magnitude of data captured to analyze certain instances make it difficult to fully understand the emergency declaration process unless you spend a day in the life of a CAISO grid operator. System operators look at many different aspects that contribute to keeping supply and demand in equilibrium. Each relevant aspect involved in the emergency declaration and curtailment decision process is discussed below. Throughout the description of the core elements, we present specific examples on the process the CAISO conducted in declaring emergencies for nine selected days.
Looking into the Future: CAISO Demand Forecast, Scheduled Load, and Actual Load
Not addressing the intricacies of load forecast methodologies, the CAISO's short-term forecast is an important aspect in identifying periods during which supply deficiencies will require electricity demand to be curtailed. The CAISO forecasts demand (including the required operating reserves for that demand) for every hour eight days in advance of the operating hour. It continues to update each hour's forecast up to one hour prior to the operating hour. Overall, the average CAISO forecast accuracy has been within 2 percent of actual load levels.
In evaluating the need for emergency declarations, the CAISO forecast is compared to 1) scheduled load (both day-ahead and hour-ahead), and 2) actual load on an hourly basis. It is important to note that emergency declarations may be made in an effort to preclude an emergency before it occurs. On a typical day, the CAISO faces a 5,000 to 7,000 MW shortfall between scheduled generation and expected load with as high as 16,000 MW over last summer. As the following examples show, the CAISO deals with underscheduled load of a magnitude that is substantially above the 5 percent level that was originally anticipated. The examples present that there were times with up to a 35 percent (11,942 MW) shortfall of scheduled load during our selected case days. The CAISO generally can obtain a little more scheduled load between the day-ahead and hour-ahead, yet scheduled load still falls significantly short of actual load. This underscores the CAISO's reliance on real-time purchases to make up for resource deficiencies.
After the CAISO analyzes expected operating conditions, it takes a more detailed look at the make-up of its internal generating resources and imports it can rely on to cover its load.
Internal Generation Resources: Where's the Power?
There are several factors that contribute to the available generating capacity within the CAISO's control area.3 These include:
- Qualifying Facility Resource Limitations
- Hydroelectric Generation Limitations
- Transmission Constraints
- Generating Unit Outages: Planned and Unplanned (Forced)
The CAISO calculates net dependable capacity, which takes into account 1, 2, and 3 from above. The net dependable capacity is the capacity available during a given operating hour. Furthermore, this net dependable capacity is adjusted to reflect generating unit outages. This report will explain each factor and how the CAISO calculates the net dependable capacity and generator outages. The section begins with the installed generation within the CAISO control area and walks through how the CAISO determines what resources it can rely upon to serve load for a given operating period.
Though the capacity of existing resources in CAISO control area capacity is approximately 46,612 MW, not all that capacity is available at all times. Capacity limitations must be factored in for a true representation of available capacity; however, several types of these limitations are very difficult to forecast.
General estimates of an average expected unavailability of generating resources for 2001 considering the limitation of Qualifying facilities (QFs)-is the most difficult limitation to discretely estimate. Also, one must take into consideration qualifying facility limitations due to weather conditions including ambient temperature, wind speed and humidity. Also consider the native load4 of qualifying facility operations which is served by those units (netted load behind the metering point), outages which are not required to be submitted to the CAISO, the affects of power purchase agreements5 with the utilities, the fact that the simultaneous output of a field of geothermal and portfolio of cascading hydro units is typically not equal to the maximum output of each unit, and depleting steam field pressure that affects the power output of geothermal units. All of these factors thereby reduce the overall maximum "dependable" generating capability of qualifying facilities. In evaluating emergency situations, the CAISO relies on qualifying facility data submitted by the Utility Distribution Companies6 (UDCs) to the CAISO to determine the level of qualifying facility output.
For our example dates, data was obtained for the peak time period identified under the operating date. The level of qualifying facility output ranged from 3,311 MW to 5,855 MW out of a maximum nameplate capacity estimated at 10,313 MW. The total dependable capacity for these dates is generally lower than the average estimated dependable capacity (42,113 MW) shown in, but is within 6 percent of the estimated average.
In addition to limitations from qualifying facilities, many other factors contribute to the reduction of MW that can be considered dependable and available to the CAISO. The actual generating capacity available to meet load on any given day is dynamic and is interrelated to planned transmission limitations (congestion), unit de-rates, hydro conditions and forced outages. Furthermore, numerous generating plants within the CAISO control area are near or beyond their expected life. As plants get older, availability rates of those plants decline. The following elaborates further on the various factors that contribute to lower than maximum (actual nameplate value) capacity levels available to the ISO to meet system load at all times.
Dealing with the Dreaded Transmission Constraint on Path 15, and other issues
Due to the locational dispersion of generation resources in California, the CAISO usually transmits power from generation capacity in Southern California to Northern California to meet Northern California load under high demand situations. Path 15 is used to transmit power to the north or south on a daily basis; however congestion usually occurs when Northern California's load is high and generation and imports from the north are not sufficient to cover the demand. Under these circumstances, there may be available and dependable generation capacity in the south that cannot assist in averting firm load curtailments in the north. For example, on Jan. 17 and 18, 2001, excessive Path 15 flows were a significant factor for firm load to be shed on those days. From April 1, 1998 to Jan. 15, 2001, there were 228 instances where Path 15 was constrained in the south-to-north direction. Path 157 limitations could limit additional power to be transmitted into Northern California (where there continues to be more resource deficient).
Moreover, the generation from the hydroelectric resources in California and in the Northwest varies on a daily basis due to the following factors: snow pack conditions, water availability, run of the river issues, contractual requirements, and unit outages. In addition to capacity limitations, hydroelectric resources are energy limited. Only a finite amount of water storage (energy) is available during any given day. Furthermore, during any peak summer hour, the simultaneous peak capacity of a portfolio of hydro resources on a cascading watershed is simply not equal to the sum of the peak output of each resource of the watershed. These resources are and will continue to be limited due to low water levels and related environmental restrictions. Hydroelectric limitations are another component that is hard to accurately quantify.
For the examples, limitations were estimated by first subtracting the hydro load measured for the peak period of each date from the total maximum hydro (11,801 MW) as presented in the CAISO 2001 Summer Assessment. Then, since the known hydro load considers hydro outages, any planned and unplanned outages for hydro facilities were subtracted out so not to double count the limitations. The CAISO was faced with situations where actual hydroelectric facility resources operated as low as 43 percent of normal available capacity. This translates into reductions ranging up to 6,800 MW that would normally be available to meet system demand. Hydroelectric limitations of this magnitude increase reliance (24 hours per day) on thermal resources, which further contributes to the increased number of unplanned outages of the thermal generation fleet in the California system.
Like the other internal generation components, these hydro limitations must be subtracted from the maximum installed internal generation.
Power Plant Outages: How to explain the Increase in Frequency
Outages are one of two types: planned and unplanned (forced). Historically, the CAISO experienced approximately 2,500 MW in unplanned outages, with fewer outages in the summer due to deliberate efforts to prepare generation for the peak summer period. The number of forced outages has significantly increased since the summer of 2000 due to (a) mechanical failures caused by high usage rates on aging generation units in California, and (b) environmental constraints8 including emissions limits. In general, these aging plants that have been run harder than ever before have suffered from boiler tube leaks, casing problems, turbine seal leaks and turbine blade wear, as well as valve and pump motor failures. The higher outage levels are expected to continue until the much-needed repairs are made. In addition, in-area facilities are exhausting their allowed operating hours or are consuming their allowed nitrogen oxide (NOx) emission credits due to unprecedented duration of operation.9 Due to the need for increased operation to avert rolling blackouts, some power plants in the CAISO control area have jeopardized future operation of their facilities.
Moreover, planned outages can no longer be deferred; these units must be readied for the upcoming summer. For the example dates, total outages have ranged from 3,000 to over 15,000 MW, with forced outages during the summer well above the 2,500 MW the CAISO typically experienced.
Figure 4 provides a brief history of in-state generation capacity (MW) that was curtailed (including planned and unplanned outages) for various reasons in year 2000 and the beginning of 2001.
While there has been considerable effort to reduce the number of outages, significant capacity that has been returned to service resides in the southern part of California and is not always available, due to congestion, to alleviate conditions in Northern California. To that end, there is and will continue to be for the foreseeable future a large amount of California generation unavailable due to outages.
Changes California should Consider
- Greater coordination of generator outages across California and the West,
- Improved market design which adheres to the engineering principles and laws of physics,
- Increased coordination between state and federal regulators and their perspective roles,
- Clearly defined roles and responsibilities for the CAISO: obligation to serve and resource/transmission planning,
- Established demand response programs,
- Streamlined environmental policies,
- Firm rules to resolve market power, and
- Well-practiced conservation and use of renewable energy sources.
Special thanks to Kevin Graves and Clyde Loutan, Kristen Kelley, Eddie Dehdashti and many others at the CAISO for their valuable contributions.
Given the limitations previously addressed, the actual generation capacity available to the CAISO to meet system demand is well below the values reported to the media by the WSCC, observers and industry professionals who base their calculations on the system nameplate generation capacity. Using nameplate ratings and assumptions about planned and unplanned outages leads to erroneous conclusions that a surplus of capacity exists in California, and thereby only hinders the efforts of all involved to effectively deal with California's energy crisis.
Furthermore, there are a few other components that actually assist in meeting CAISO system load. These include net interchange volume (imports), dynamics, demand reduction programs, and UDC Interruptible load and firm load curtailments. But before we introduce the other generation resource components, it is important to understand the information regarding other resources the system operators rely on in analyzing emergency situations. System operators estimate additional resource capacity (other than internal generation resources) by the volume of pre-scheduled imports into the control area.
Disappearing Imports: Being Forced To Go It Alone
The pre-scheduled net interchange represents imports that have been scheduled through the day-ahead and hour-ahead markets. This volume is calculated by subtracting the total export from the total imports (including dynamics) for the ties connected to the CAISO control area. The majority of the time the CAISO Control Area is resource deficient, making imports significant to the CAISO's ability to serve system load.
For the example, imports still do not provide enough generation to meet load and operating reserve requirements. More often than not, the shortfall exceeds even the WSCC operating reserve requirement.
System operators usually have this sort of picture of the operating situation one day, and more often one hour, prior to the operating day and will draw upon all of its options to try to procure additional generation resources in advance of the expected period of shortage. Unfortunately, the CAISO has limitations in its authority and can only purchase sufficient energy in real time during the operating hour as allowed by its tariff. Since the CAISO cannot force suppliers outside its control area to provide power, the actual supply that is "available" to the CAISO is ultimately the supply that can be voluntarily sold and delivered to the ISO. It is at this point that the CAISO considers and negotiates during the operating hour (as appropriate) out-of-market purchases to meet reliability criteria when insufficient power is offered through the hourly energy markets. It is these out-of-market purchases that appreciably contribute to the high cost of electricity. Any resource deficiency is addressed by implementing the following: (1) Interruptible load curtailments, (2) Firm load curtailments, (3) Voluntary conservation, (4) Obtaining additional energy only available when stage emergencies are declared, and (5) Maintaining less that 7 percent of operating reserves.
The actual net interchange volume is calculated by subtracting the total export from the total import for the ties connected to the CAISO Control Area. Import levels have declined by 28 percent between 1999 and 2000 (see Figure 5), which has significantly contributed to California's current energy crisis.
While overall imports have been declining, the volume of imports scheduled into the forward market has deteriorated to crisis levels. As the examples show during declared emergencies, the CAISO seems to bring in additional imports than what was originally scheduled. However, this capacity often becomes available at out-of-market prices that extend well beyond the real-time market-clearing price. The CAISO is virtually held hostage to higher costs while it endeavors to keep the state's lights on.
CAISO's over reliance on real-time purchases demonstrates the lack of market incentives to pre-schedule in the day-ahead or even hour-ahead markets.
Meanwhile, resources on dynamic scheduling are virtually a part of imports into California. Dynamic scheduling generally refers to generation resources geographically located in one control area, which are dynamically scheduled by a second and separate control area. The CAISO has more information about these resources with some even on automatic generation control. These resources are scheduled in the forward markets through scheduled imports and are included in the pre-scheduled net interchange data presented above. There is a maximum total of 1,857 MW of dynamically scheduled resources available to the CAISO. Similar to our internal generation resources, whether or not the CAISO gets the full capacity of these resources depends on the limitations of these units and the relationship with exports. Due to exports, the maximum net dependable dynamics is closer to 1,300-1,450 MW.
For our example dates, the CAISO was able to count on 42 percent to 78 percent of dynamic schedules.
Reserve Requirements: How much to maintain Reliability
To achieve a high degree of reliability, maintain frequency and avoid loss of firm load following the loss of generation resources or transmission system components, the CAISO adheres to the Western Systems Coordinating Council's (WSCC's) Minimum Operating Reliability Criteria (MORC). The CAISO's ability to maintain MORC requirements has consistently become more difficult to meet since 2000. The CAISO's percentage of operating reserves generally falls between 6.5 percent and 7.5 percent.
For the example dates, the CAISO was in a Stage 2 or Stage 3 situation for most of these days with difficulty in meeting WSCC required operating reserves each day without additional resources and conservation efforts.
While observers may criticize the CAISO's methodology to calculate its requirements, the CAISO does not and cannot include emergency out-of-market purchases in its calculation of "available market supply." The CAISO supports its methodology on the grounds that such calculations are based on the view that emergencies should be called upon when the ISO cannot purchase sufficient energy under its tariff. Since the CAISO cannot force suppliers outside its control area to provide power, the actual supply that is "available" to the CAISO is ultimately the supply that can be voluntarily sold and delivered to the ISO. Out-of-market purchases represent purchases that must be made to meet reliability criteria (absent some other authority or market mechanism) when insufficient power is offered through the hourly energy markets upon which California's market design is based.
Focusing on Demand-Side Resources: CAISO's Demand Reduction Programs
While established demand reduction programs can offset some anticipated supply, demand reduction efforts can not be dependably forecast or measured. Thus, there is low confidence in deferring emergency declarations based on uncertain and unmeasured demand responses. As individual demand metering progresses and demand programs become more widely practiced, the CAISO will consider heavier reliance on such measures in the declaration of emergencies.
While the CAISO has difficulty in forecasting or measuring demand reduction programs, it has experienced very significant conservation efforts that have assisted in averting firm load curtailments. Under some instances, the CAISO has experienced up to 11 percent of voluntary conservation in recent months.
Furthermore, interruptible load curtailments are currently associated with SCE's air conditioner cycling and agricultural pump load programs. There was approximately 2,800 MW of interruptible service available for use from the utility distribution companies (UDCs) for mitigation of emergencies; however, only 400 MW is available currently because of the following: 1) PG&E has exhausted their 500 MW curtailment of industrial load earlier this year; and 2) penalties can not be administered to 1,940 MW of contracted load in SCE's and SDG&E's industrial load programs due to CPUC's decision 01-01-056 dated Jan. 29, 2001. Page 10 lists the interruptible and firm load curtailments for the example dates.
Learning From The Crisis
There exists many complex and ever changing conditions on the supply, demand and the transportation system (transmission) that the system operators must consider in managing the electric grid in real-time. It is easy for many to "second guess" the operators' action. The operators are well trained to perform their duties under ever-stressful conditions. They must make real-time decisions in accordance with CAISO, regional and national reliability requirements in a very short amount of time with limited information. The California crisis has brought much needed publicity and attention to many important electric energy industry issues that have been ignored for decades. Furthermore, it is clear that many measures are needed to efficiently run the system and maintain reliability. Some of these measures are the articulation of a clearly defined role for the CAISO, increased regional coordination, enhanced internal coordination between the CAISO and Municipal districts, UDC's and generator owners, to name a few.
- Stage 3 Emergency Notice is declared by the ISO any time it is clear that an Operating Reserve shortfall (less than 1-1/2 percent) is unavoidable or when in real-time operations, the Operating Reserve is forecast to be less than 1-1/2 percent after dispatching all resources available.
- The formal "ISO Alerts, Warnings, and Emergencies" procedures as well as related tariff and dispatch protocol sections are posted on its website at www.caiso.com.
- The CAISO control area geographically includes most, but not all of California. While the previous control areas of Pacific Gas and Electric, Southern California Edison, and San Diego Gas and Electric are part of the CAISO control area, municipal utilities such as the Los Angeles Department of Water and Power (LDWP), Imperial Irrigation District (IID) and others have their own control areas for which their generating resources in California are not included as CAISO internal resources.
- Even if qualifying resources (QFs) are running at full nameplate capacity, only a fraction of this capacity may be available to meet system loads. Only "surplus" output after that which is directly used to meet the owner/host's native load may be viewed as "available" to meet CAISO system loads. The CAISO is currently working with the utilities to determine the amount of native load associated with each QF to accurately assess the net generation capacity available from these resources to support the grid.
- The operations of Northern California QFs have been cycled off and on daily in accordance with the terms of their power purchase agreements. These QFs do not typically ramp to full output until noon each day or shortly thereafter. While not at full output, Path 15 mitigation is sub-optimal and overloads are more difficult to manage. If these Northern California QF resources were base loaded around the clock, QFs could assist in mitigating Path 15 overloads.
- The UDCs include Pacific Gas and Electric, Southern California Edison, and San Diego Gas and Electric.
- "Path 15 Reliability Upgrade Analysis", CAISO Operations, Page 1.
- While emission-limited facilities have contributed to unplanned outages recently, cooperative measures between the California Air Resource Board (CARB), the California Energy Commission (CEC), the Environmental Protection Agency (EPA) and local Air Pollution Control Districts (APCDs) are being implemented to help alleviate future outages related to environmental constraints.
- Annual energy production from resources located within the CAISO control area increased by 14 percent between 1999 and 2000.
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Declaring Emergencies in California: The Realities of ISO Operation
An independent system operator's view on the energy crisis and the realities of maintaining reliability.