Blackouts and Sags (Brownouts)
A blackout is a complete loss of power.
Popped fuses, downed power lines, and blown transformers cause blackouts.
A partial loss of power is sag or brownout.
This may be intentional by the power company during times of high power usage.
Sags cause frozen keyboards, unexpected system crashes, and lost or corrupt data. Sags also reduce life of equipment.
You can use backup generators to protect against blackouts and sags.