There are several different types of electrical disturbances. Below are the definitions of some of them. Blackout - A blackout is a complete loss of power. In some cases this includes any drop in voltage below 80V, since most equipment will not operate below 80V. Sag or Brownout - A sag or brownout is a decrease in voltage levels which is usually of short duration but can last from fractions of a second to hours. Blackout - Blackouts can be caused by excessive demand on the power grid, lightning storms, ice on power lines, equipment failure or any accident which brings down a power line.
Brownouts generally occur during the summer heat waves.
Spike - Spikes are generally caused by a nearby lightning strike, or if utility power lines are downed in a storm or as a result of an accident. They can also be caused by short circuits or undersized electrical circuits. Noise - EMI and RFI noise can be caused by lightning, load switching, generators, transmitters, transformers and industrial equipment. Sag or Brownout - A loss of optimal voltage could cause frozen keyboards, dim or bright lights, shrinking display screens and unexpected system crashes resulting in the loss or corruption of data. Sags or brownouts also reduce the efficiency and life span of electrical equipment, particularly motors.