A brownout is an intentional or unintentional drop in voltage in an electrical power supply system. Utility companies may use brownouts as a measure to manage high demand, thereby preventing a complete system failure (a blackout). This condition perfectly matches the scenario described: there is enough power on the grid to avoid a total loss, but not enough to satisfy the current level of demand, necessitating a voltage reduction.

A. Power Surge: This is a prolonged increase in voltage above the normal level, which is the opposite of the condition described.

B. Power Spike: This is a very short, dramatic increase in voltage, not a reduction due to insufficient power supply.

C. Blackout: This is a total loss of electrical power, which the question explicitly states is being prevented by the event in question.

1. IEEE Std 1159-2019

"IEEE Recommended Practice for Monitoring Electric Power Quality." Section 4.4

"Short Duration Voltage Variations

" and its subsections describe sags (often used interchangeably with brownouts in common parlance) as a decrease in the normal voltage level

distinguishing them from interruptions (blackouts) and swells (surges).

2. National Institute of Standards and Technology (NIST)

"Introduction to Computer Security: The NIST Handbook

" Special Publication 800-12. Chapter 12

"Physical and Environmental Security

" Section 12.5

"Supporting Utilities

" discusses various power problems. It defines a brownout (or voltage sag) as a prolonged drop in voltage

contrasting it with a blackout (power loss) and surges/spikes (power increases).

3. Patterson

D. A.

& Hennessy

J. L. (2017). "Computer Organization and Design RISC-V Edition: The Hardware Software Interface." In discussions on dependability (often in appendices or specific chapters on storage and I/O)

the text addresses power failures. It distinguishes between a complete failure (blackout) and a temporary voltage reduction (brownout/sag)

which can cause system reboots or data corruption without a total power loss. (See discussions on power supplies and system reliability).