What causes power outages?
Alan Mantooth, professor of electrical engineering, replies:
Short-duration power interruptions or transients, commonly referred to as power sags, surges, brown-outs or blips, can be caused by numerous things — an accident such as a squirrel getting fried on a power transformer or a car hitting a utility pole, or an abnormally high power demand on a subsystem.
On a hot and humid summer day after a thunderstorm has rolled through and downed a power line or two, other power lines experience a higher than normal load, which can lead to higher voltage drops on lines and voltage sags in local areas such as buildings and neighborhoods.
When subsystems, distribution legs or substations on the larger grid, operate at close to capacity, they are much more susceptible to loading effects, such as large industrial users switching equipment on and off. These events can also cause voltage and current “spikes” in the power grid that might lead to short outages. These outages are typically short-lived and appear as short-term power interruptions.
The electric power grid has protection devices, much like your home has circuit breakers, to open, or interrupt, the circuit when the current exceeds a certain point. The power grid is a highly capable engineering system, but it has limits. As regional growth occurs, power companies continually redesign systems to manage the needs of residents and businesses.