Explanation/Reference:
Explanation:
When power companies are experiencing high demand, they frequently reduce the voltage in an electrical grid, which is referred to as a brownout. Constant voltage transformers can be used to regulate this fluctuation of power. They can use different ranges of voltage and only release the expected 120 volts of alternating current to devices.
Interference interrupts the flow of an electrical current, and fluctuations can actually deliver a different level of voltage than what was expected. Each fluctuation can be damaging to devices and people.
The following explains the different types of voltage fluctuations possible with electric power:
Power excess:
Spike Momentary high voltage

Surge Prolonged high voltage

Power loss:
Fault Momentary power outage

Blackout Prolonged, complete loss of electric power

Power degradation:
Sag/dip Momentary low-voltage condition, from one cycle to a few seconds

Brownout Prolonged power supply that is below normal voltage

In-rush current Initial surge of current required to start a load

Incorrect Answers:
B: A blackout is a prolonged complete loss of power, not a prolonged low voltage. Therefore, this answer is incorrect.
C: A surge is a prolonged high voltage, not a prolonged low voltage. Therefore, this answer is incorrect.
D: A fault is a momentary power outage, not a prolonged low voltage. Therefore, this answer is incorrect.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 462-463