During a routine inspection of an industrial motor control centre (MCC), an electrician notices a burnt smell and discoloration on the busbar insulation behind a section. The MCC is fed by a 400 A main breaker and supplies several 600 V motors. What is the most appropriate and safe immediate action?

Question: During a routine inspection of an industrial motor control centre (MCC), an electrician notices a burnt smell and discoloration on the busbar insulation behind a section. The MCC is fed by a 400 A main breaker and supplies several 600 V motors. What is the most appropriate and safe immediate action?

Answer options:

• Open all circuit breakers in that section of the MCC to isolate the problem.
• Continue with the inspection, noting the observation for later repair. ✅ Immediately isolate and de-energize the entire MCC, then investigate the fault.
• Use a thermal imaging camera to pinpoint the exact hot spot while energized.

Correct answer: Immediately isolate and de-energize the entire MCC, then investigate the fault.

Explanation: A burnt smell and discoloration indicate an active fault that could escalate into an arc flash or fire. The most appropriate and safe immediate action is to de-energize the entire MCC to eliminate the hazard before further investigation. Opening individual breakers or using thermal imaging on an active, escalating fault is unsafe.