Power Failures
Power supplies are affected by the quality of the local power source. Common power delivery problems such as spikes, surges, sags, brownouts, and blackouts affect the stability and operation of the main power supply and are passed on to the computer. While most users don't notice sudden changes in the quality of electrical power, computers and other sensitive electronics do and while we can't fully control these problems, there are a few things we can do to protect our equipment and data and ensure a reasonably clean electrical supply.
| Problem | Description |
|---|---|
| Surges | These are brief (and sometimes catastrophic) increases in the voltage source (very high voltage for a very short time). They can originate with the power source (the local power company), but most often are due to lightning strikes. |
| Spikes | Spikes are very short overvoltage conditions. Spikes are measured in nanoseconds, while a surge is measured in milliseconds. |
| Sags | These are brief decreases of voltage at the power source. |
| Brownouts | If a sag lasts longer than one second, it is called a brownout. The overloading of a primary power source can cause brownouts. Some brownouts are "scheduled" by power companies to prevent overloading of circuits and potential catastrophic failure of the system. |
| Blackout | This is a complete power failure, which can be caused by equipment failure (local or regional) or accidental cutting of power cables. When the power returns after a blackout, there is a power spike and danger of a power surge. |