About The Workshop

Installation of residential units that cool and dehumidify indoor air–i.e., air–conditioning units, or AC–is at an all time high in the United States today and continues to grow. Utilities have expressed concern that high penetrations of residential AC units pose new challenges for reliability. The purpose of this workshop is to bring the electric utility industry and AC manufacturing industry together to discuss the current understanding regarding the role that "stalled" residential AC units may be playing in increasing the risk of power system blackouts.

Workshop attendees will obtain a better understanding of what is and is not currently known about this national issue and learn about research that is currently being conducted to improve our understanding. The workshop will include an engaging discussion of the following topics:

  • Recent Utility Experiences with and Responses to Fault-Induced Delayed Voltage Recovery due to Residential AC Stalling
  • The Current State of Electric System Studies on the Technical Basis of Fault-Induced Delayed Voltage Recovery
  • Improving Our Understanding of the Dynamic Performance of Residential Air Conditioning Units

Panelists will include experts from utilities, induction motor manufacturers, the Western Electricity Coordinating Council (WECC), EPRI, DOE, and others.

Background: What is AC Stalling?

The induction motors used in residential AC units can "stall" following a system fault when line voltage drops by over 30% (e.g., when a transmission line comes into contact with a tree). Stalling means that the AC units greatly increase their consumption of reactive power (by a factor of 4 or more) virtually instantaneously (i.e., within milliseconds). If the system cannot respond with increased reactive power production, voltages will drop. If local reactive power resources are not adequate, voltages will decline to a point from which they cannot recover and a blackout will ensue. The likelihood and potential spread of such a blackout depends on many factors, including the area that is affected by the fault, the amount of AC that is in use, and the design and operation of the transmission and distribution system.

View FAQ for more details on AC Stalling