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Which statement correctly characterizes an impulse voltage used in high-voltage testing?

Difficulty: Easy

Correct Answer: It is a unidirectional voltage

Explanation:


Introduction / Context:
Impulse voltages simulate lightning or switching surges to test insulation. They are defined by fast rise and relatively slower fall, and crucially, they do not reverse polarity during the impulse.


Given Data / Assumptions:

  • Standard impulse notation: e.g., 1.2/50 μs (rise/fall times).
  • Used for flashover and dielectric strength tests.


Concept / Approach:
An impulse is a single-polarity, short-duration voltage. Rise time is much shorter than fall time. Chopped impulses can and do occur (e.g., due to flashover across a gap). RMS vs average is not a defining property and varies with waveform shape.


Step-by-Step Solution:

Identify unidirectional nature → correct key property.Reject statements implying symmetry of times or sinusoidal behavior.Acknowledge chopped impulse events are real in practice.


Verification / Alternative check:

Standards (e.g., IEC 60060) describe unidirectional standard lightning impulses.


Why Other Options Are Wrong:

(b) is false (chopped impulses occur); (c) false (rise ≪ fall); (d) not a general truth; (e) false (not sinusoidal).


Common Pitfalls:

Confusing AC test voltages with transient impulse tests.


Final Answer:

It is a unidirectional voltage
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