Electrical Testing Procedures & Equipment Operation Flashcards
7 cards from real NETA 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 Testing Procedures & Equipment Operation flashcards as text
When thermographically scanning energized electrical equipment, which condition indicates a critical (priority 1) deficiency?
Answer: A 15°C rise above a similar component under identical load
NETA and NFPA 70B classify a temperature differential of 15°C or more above a reference component (same load) as a priority 1 condition requiring immediate corrective action.
Which type of oil sample test is the best single indicator of active arcing inside a transformer?
Answer: Dissolved gas analysis (DGA) for acetylene
Acetylene (C2H2) in DGA is the key fault gas produced by high-energy electrical arcing inside a transformer, making it the most specific indicator of arcing.
The purpose of the guard terminal (G) on a megohmmeter is to:
Answer: Eliminate surface leakage current from the measurement path
The guard terminal intercepts surface leakage current and routes it back to the generator without passing through the measuring circuit, ensuring only true volume insulation resistance is measured.
During a DC high-potential test on switchgear, the leakage current is monitored. A sudden sharp rise in leakage current before reaching the test voltage indicates:
Answer: Impending insulation breakdown
A sudden uncontrolled rise in leakage current during a DC hipot test is a classic pre-breakdown signature indicating imminent insulation failure; the test must be stopped immediately.
Per NETA MTS, what is the primary purpose of performing a contact timing test on a circuit breaker?
Answer: To verify opening and closing times and simultaneous pole operation are within manufacturer's tolerances
Contact timing tests confirm that each pole opens and closes within the manufacturer's specified time and that all poles operate simultaneously to prevent current unbalance during switching.
A transformer's excitation (no-load) current test is compared between phases. A significant deviation in one phase most likely indicates:
Answer: Shorted turns in that phase winding
Elevated or abnormal excitation current in one phase is a strong indicator of shorted turns in that winding, which increases the magnetic flux path loss in that phase.
When testing ground electrode resistance using the fall-of-potential (three-point) method, the current electrode should be placed at a minimum distance of approximately how many times the ground electrode's longest dimension?
Answer: 10 times
IEEE 81 recommends the current electrode be placed at a distance of at least 10 times the longest dimension of the ground electrode system to ensure resistance areas do not overlap.