According to NEC, what can voltage variation be?

In the context of the National Electrical Code (NEC), voltage variation is indicated as + or - 5%. This specification is significant for ensuring that electrical systems operate reliably and safely within acceptable limits.

A voltage variation of + or - 5% is commonly used for utility systems and is essential for maintaining proper equipment function and longevity. When voltage strays beyond this range, it can lead to inefficient operation, overheating, and potential damage to electrical devices. Adhering to this standard supports the integrity of electrical installations, ensuring they can handle small fluctuations without adverse effects.

The other choices reflect variations that exceed the standards outlined by the NEC, which would not typically be acceptable in most residential and commercial electrical systems. Understanding this standard helps linemen and electrical professionals to design, evaluate, and troubleshoot electrical systems effectively.