Question

The rated voltage of a three-phase power system is given as _______.

• A. rms phase voltage
• B. peak phase voltage
• C. rms line to line voltage
• D. peak line to line voltage

Hint:

In power systems, the rated voltage is always RMS line-to-line, not peak or phase unless stated.

Answer 1

The Correct Option is C

Step 1: Understanding system ratings
In electrical systems, ratings such as voltage and current are usually specified in RMS (Root Mean Square) values because they directly relate to the power delivered.
Step 2: Three-phase system convention
For three-phase systems, unless otherwise specified, the voltage rating refers to the RMS value between any two lines (line-to-line voltage), not line-to-neutral (phase) voltage.
Step 3: Phase vs Line Voltage
\[ V_{LL} = \sqrt{3} \cdot V_{ph} \] Where \( V_{LL} \) is line-to-line voltage and \( V_{ph} \) is phase voltage.
Conclusion:
So, standard rated voltage = RMS line-to-line voltage.