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Common Power Disturbances
Common power quality disturbances include surges, spikes and sags in power source voltage and harmonics (or “noise”) on the power line. Each of these occurrences is discussed briefly below.
Surge – A rapid short-term increase in voltage. Surges often are caused when high power demand devices such as air conditioners turn off and the extra voltage is dissipated through the power line. Since sensitive electronic devices require a constant voltage, surges stress delicate components and cause premature failure.
Spike – An extremely high and nearly instantaneous increase in voltage with a very short duration measured in microseconds. Spikes are often caused by lightning or by events such as power coming back on after an outage. A spike can damage or destroy sensitive electronic equipment. Turn the equipment off during a power outage. Wait a few minutes after power is restored before turning it on, then turn on one device at a time.
Sag – A rapid short-term decrease in voltage. A sag typically is caused by simultaneous high power demand of many electrical devices such as motors, compressors and so on. The effect of a sag is to “starve” electronic equipment of power causing unexpected crashes and lost or corrupted data. Sags also reduce the efficiency and life span of equipment such as electric motors.
Noise – A disturbance in the smooth flow of electricity. Often technically referred to as electro-magnetic interference (EMI) or radio frequency interference (RFI). “Harmonics” are a special category of power line noise that causes distortions in electrical voltage. Noise can be caused by motors and electronic devices in the immediate vicinity or far away. Noise can affect performance of some equipment and introduce glitches and errors into software programs and data files.
Outage – Total loss of power for some period of time. Outages are caused by excessive demands on the power system, lightning strikes and accidental damage to power lines. In addition to shutting down all types of electrical equipment, outages cause unexpected data loss.