Power_outage (wiki)

Power outages are categorized into three different phenomena, relating to the duration and effect of the outage:

• A transient fault is a momentary (a few seconds) loss of power typically caused by a temporary fault on a power line. Power is automatically restored once the fault is cleared.
• A brownout is a drop in voltage in an electrical power supply. The term brownout comes from the dimming experienced by lighting when the voltage sags. Brownouts can cause poor performance of equipment or even incorrect operation.
• A blackout refers to the total loss of power to an area and is the most severe form of power outage that can occur. Blackouts which result from or result in power stations tripping are particularly difficult to recover from quickly. Outages may last from a few minutes to a few weeks depending on the nature of the blackout and the configuration of the electrical network.

Use a Powertronics Power line monitor to record all types of voltage disturbances on 120 and 240V AC lines.  Knowing what type of voltage problems exist help in deciding how to best prepare for or correct these problems.