The Commission requires and supports actions by distribution utilities to preserve electric service to the greatest number of customers, which can mean limiting service to some customers, using voluntary or mandatory actions.
During the power crisis (2000-01) the Commission revisited those programs by opening Rulemaking R.00-10-002. The goal was to examine and coordinate the many interruptible, curtailable and demand response programs, to highlight ways for customers to reduce usage during peak demand periods, and to revise the priorities for curtailing customers when necessary during Electrical Emergencies (energy or transmission shortages). The resulting revisions to the Commission's curtailment planning, and the overarching role of the California Independent System Operator (CAISO) are described following.
The CAISO Alerts Distribution Utilities and Manages Bulk Energy Shortages
Operators in the CAISO control room continuously monitor electricity supply and demand in California. If reserve levels begin to drop below seven percent, the CAISO communicates with local utilities and electrical generators, asking them to produce more power if possible. Referred to as an Emergency Stage One, the CAISO also issues news releases and public calls for conservation. Often, consumers respond by using less electricity, and raising the percent reserves.
In an Emergency Stage Two, when reserve levels are below five percent, the CAISO can also call on voluntary commercial and industrial customers paying lower interruptible rates for nonfirm service to reduce their loads. Such loads remain off if a Stage 3 follows; however, operation of the nonfirm tariff schedules is independent of the Stage 3 firm service rotating outage process which affects residential and small commercial customers.
If generation operating reserves continue to fall, below 1-1/2%, then involuntary load reduction, or Emergency Stage Three rotating outages, may become necessary. CAISO operators determine how many megawatts of load reduction are needed, and that figure is divided among the state's utility distribution companies on a pro-rata basis. It is up to the utilities to actually determine how and where they can reduce their load by the assigned number of megawatts.
See the CAISO's Stages of Electrical Emergencies.
The CPUC Regulates Distribution Utility Response to Shortages
The CAISO called several dozen Stage 3 events during the 2001 power crisis, but never before and only twice since. Typically Stage Three rotating outage blocks consisted of equally sized (e.g. 100MW) dispersed groups of distribution circuits which could be sequentially interrupted. The utilities would interrupt (blackout) a block of approximately 1 to 1-1/2 hrs then move on to the next block until the CAISO lifts the emergency. The last block interrupted would be the last interrupted in future emergencies.
Essential customers, as determined by the Commission, and other users on the same circuits, are exempt from rotating outages. Essential customers include government and other agencies providing essential fire, police and prison services, hospitals, communication and broadcasting facilities.
The utilities perform periodic internal reviews or customer surveys to confirm that essential customers continue to qualify. Customers may request inclusion on the list and if refused, may file a formal complaint with the Commission.
Electrical Emergencies can occur at any time due to accidents, natural causes or events beyond utility control. As much notice as possible of emergency Stage events is given, but a utility is not liable for customer damages when it must implement rotating outages.
CAISO orders for curtailments may be required in 10 minutes or less. As circumstances (and time) permit, the utilities will notify by telephone or otherwise, critical care customers and those on life support equipment, and large customers having a demand of 300 kW or more, that rotating outages are imminent.
For all other customers, warning imminent blackouts and other relevant information is given by mass media. Also utilities indicate the Rotating Black assignments on their customer bills, or will broadcast on mass media, the number of the next block of circuits to be blacked out, giving extra warning time, although for operational or maintenance reasons customers may be switched temporarily to other circuits.