NETA Switchgear and Busway Inspection 2 — Questions and Answers
Question 1: According to NETA standards, what is the maximum allowable temperature rise for bolted bus connections measured via infrared thermography under load?
- 5°C above ambient
- 10°C above ambient
- 15°C above ambient
- 30°C above ambient (Correct answer)
Correct answer: 30°C above ambient
NETA allows up to 30°C temperature rise above ambient for bolted bus connections before action is required.
Question 2: During a switchgear inspection, you notice the arc chutes on a draw-out circuit breaker are cracked. What is the correct course of action?
- Clean and return to service
- Replace the arc chutes before returning to service (Correct answer)
- Reduce the breaker's trip setting
- Apply insulating varnish to the cracks
Correct answer: Replace the arc chutes before returning to service
Cracked arc chutes cannot safely interrupt fault currents and must be replaced before the breaker is returned to service.
Question 3: What does the NETA MTS specify regarding the frequency of medium-voltage switchgear maintenance intervals for normal service conditions?
- Every 6 months
- Every 1 year
- Every 3 years (Correct answer)
- Every 6 years
Correct answer: Every 3 years
NETA MTS recommends medium-voltage switchgear maintenance every 3 years under normal service conditions.
Question 4: When performing a dielectric withstand test on switchgear, the test voltage is applied for how long according to NETA standards?
- 10 seconds
- 60 seconds (Correct answer)
- 5 minutes
- 15 minutes
Correct answer: 60 seconds
NETA specifies a 60-second duration for dielectric withstand (hi-pot) tests on switchgear insulation.
Question 5: Which busway condition most directly indicates that joint resistance has increased due to connection degradation?
- Discoloration of the busway housing
- Elevated hot spot temperature at a joint compared to adjacent sections (Correct answer)
- Moisture condensation on the exterior enclosure
- Vibration noise during operation
Correct answer: Elevated hot spot temperature at a joint compared to adjacent sections
A hot spot at a joint that is elevated compared to adjacent bus sections is the classic indicator of increased contact resistance from connection degradation.
Question 6: What is the purpose of the phase barrier insulation installed between phases inside metal-clad switchgear?
- To reduce eddy current losses
- To prevent phase-to-phase faults during maintenance and operation (Correct answer)
- To improve heat dissipation from the bus bars
- To reduce audible noise from magnetic forces
Correct answer: To prevent phase-to-phase faults during maintenance and operation
Phase barriers provide isolation between energized phases, preventing accidental phase-to-phase contact faults during operation and maintenance.
Question 7: When inspecting a low-voltage switchgear bus, a technician finds the silver plating on a bus bar joint has worn through to bare copper. What is the recommended action?
- Apply NO-OX-ID compound and re-torque to specification (Correct answer)
- Replace the bus bar section with properly plated material
- Polish the bare copper and re-torque
- Apply electrical tape over the exposed area
Correct answer: Apply NO-OX-ID compound and re-torque to specification
Applying an appropriate anti-oxidant compound and re-torquing to specification is the recommended remedy for worn silver plating on copper bus joints.
