Electrical Equipment Maintenance & Inspection Flashcards
7 cards from real ESC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Equipment Maintenance & Inspection flashcards as text
During a visual inspection of a motor control center (MCC), you notice discoloration and charring around one circuit breaker. What is the most appropriate immediate action?
Answer: De-energize and lock out the affected circuit before further investigation
Charring and discoloration indicate a potential arc flash or overheating condition requiring immediate de-energization and LOTO before any further work.
What is the recommended minimum frequency for infrared thermography (IR) scanning of critical electrical equipment under NFPA 70B guidelines?
Answer: Annually
NFPA 70B recommends infrared thermography at least annually for critical electrical equipment to detect hot spots before failures occur.
A technician performing maintenance on a distribution transformer measures insulation resistance. Which test method applies a stepped voltage to evaluate insulation condition over time?
Answer: Step voltage test
The step voltage test applies progressively increasing voltages to identify insulation weaknesses that would not be detected at a single test voltage.
When inspecting flexible cords used with portable electrical equipment, which defect requires immediate removal from service?
Answer: Exposed or damaged inner conductor insulation
Exposed or damaged inner conductor insulation creates a direct shock and fire hazard, requiring the cord to be immediately removed from service.
What does a Polarization Index (PI) value below 1.0 indicate about electrical insulation?
Answer: The insulation has absorbed moisture or is contaminated and likely defective
A PI value below 1.0 indicates severely deteriorated, wet, or contaminated insulation that poses an imminent failure risk.
Which OSHA standard requires employers to establish and implement written procedures for the control of hazardous energy during electrical equipment servicing and maintenance?
Answer: 29 CFR 1910.147
29 CFR 1910.147 (the Control of Hazardous Energy standard) requires written LOTO procedures for equipment servicing and maintenance.
During switchgear inspection, what condition in a draw-out circuit breaker's racking mechanism indicates it should be taken out of service?
Answer: Damaged or missing secondary disconnect fingers
Damaged or missing secondary disconnect fingers prevent control power and protective relay signals from reaching the breaker, rendering protection systems inoperable.