Notification that electric reserves are lower than normal and steps are
being taken by utility personnel to maintain the integrity of the
on-line generation and transmission facilities.
An almost instantaneous cutting of power to customers because demand for electricity has outstripped supply.
Advisories to be announced when conditions are such that further steps to manage capacity could affect the public.
Temporary interruption of electrical service. ISO New England would
implement rolling blackouts only if and when New England's electrical
system is unable to meet heavy peak demands because of an extreme
deficiency in the power supply. By temporarily disconnecting electrical
circuits on a rotating basis, a majority of customers have power,
inconvenience is minimized and a more serious widespread problem is
averted. Each rotation is of a specific duration, usually no longer than
a few hours, but it could take longer in some locations due to the
manual nature of the operation.
Public appeals when an immediate reduction in power usage is necessary
to avert overload of the electrical system. Public appeals are made when
other efforts (e.g. emergency purchases, voluntary curtailment,
contracted curtailment and voltage reduction) have been unsuccessful in
bringing supply and demand back into balance.
If, after other steps to manage capacity have been taken and the demand
for electricity continues to exceed generating capacity, the electric
utility can reduce voltage by five percent. This reduction essentially
stretches out the available supply of electricity to all customers. It
is rarely noticed by customers but may affect sensitive electronic
Public appeal to customers to conserve electricity in anticipation of
heavy electrical demand and unhealthy air quality conditions, usually
due to humid weather.
When possible, the public would be alerted that load shedding or rolling blackouts are imminent.