A sag is a decrease to between 0 1 and 0 9 Pu in rms voltage or current at the power frequency from 0 5 cycles to 1 minute The power quality community has used the term sag for many years to describe a short-duration voltage decrease The IEC has defined this phenomenon as a dip The two terms-dip and sag-are considered interchangeable, with the term sag being the preferred synonym in the U S Voltage sags are usually associated with system faults but they can also be associated with the energization of heavy loads or starting of large motors which can draw 6 to 10 times its full load current during starting Sag durations are subdivided into three categories, instantaneous, momentary, and temporary-all which coincide with utility device operation times
When the line voltages drop to 80 to 85 percent below normal for short periods of time Possible causes are heavy equipment being turned on, large electrical motors being started, and the switching of power mains (internal or utility) A power sag can have effects similar to those of a power surge, such as memory loss, data errors, flickering lights and equipment shutoff
Runs or sags in paint film that flows too much during application Sags are usually caused by applying too heavy a coat of paint or thinning the paint too much
These are temoprary drops in the supply voltage and are most commonly noticed when local lighting `dims' suddenly more Top
Short-term, low voltage, brownouts The opposite of surges, tese are triggered by the startup of large loads, main switching, mains equipment failure, lightning, mains supply that is too small for the building demand In addition to causing system crashes, sags can damage hardware