A brownout is a situation where a utility delivers power to a customer at a voltage that is lower than what is considered acceptable under normal operating conditions. Under normal conditions, a utility typically delivers power at a voltage within a range of plus or minus 5% of the stated voltage. In situations when the utility’s available supply is near or below system demand, power requirements can be reduced by delivering lower voltages than normal. This may allow the utility to continue operations until the supply/demand balance is restored. Although some equipment may no longer operate correctly in a brownout, this is often considered a better alternative to a blackout

Voltage along a distribution line during normal operation and during a brownout

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