During a routine inspection of an electrical panel feeding a critical process, an electrician notices that the phase sequence indication light for L1-L2-L3 is dim, while L2-L3-L1 is bright. All voltages measure correctly between phases. What does this observation most likely indicate?

Question: During a routine inspection of an electrical panel feeding a critical process, an electrician notices that the phase sequence indication light for L1-L2-L3 is dim, while L2-L3-L1 is bright. All voltages measure correctly between phases. What does this observation most likely indicate?

Answer options:

• The panel is experiencing an internal ground fault condition.
• One of the phase conductors has an unusually high impedance. ✅ The incoming phase rotation is reversed from the expected L1-L2-L3 sequence.
• The neutral conductor connection is compromised, leading to voltage imbalance.

Correct answer: The incoming phase rotation is reversed from the expected L1-L2-L3 sequence.

Explanation: Phase sequence indicators are designed to illuminate brightly for the correct rotation and dimly or not at all for incorrect rotations. If the L2-L3-L1 indicator is bright, it means the incoming phase rotation is L2-L3-L1, which is the reverse of the standard L1-L2-L3 sequence. This is critical for motors and some sensitive electronic equipment.