Troubleshooting & Diagnostics Flashcards
7 cards from real AEP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Troubleshooting & Diagnostics flashcards as text
During a cable hi-pot DC test, current increases steadily rather than decreasing after initial charging. This indicates:
Answer: Insulation breakdown or leakage path
After capacitive charging, current should stabilize or decrease; a rising trend indicates a resistive leakage path or insulation failure.
A transformer oil sample shows elevated acetylene levels in dissolved gas analysis (DGA). This is specifically associated with:
Answer: High-energy arcing or sparking
Acetylene is a key indicator of high-energy electrical arcing inside a transformer, distinguishing it from thermal faults.
A protection relay shows 'loss of potential' alarm. Which protection function is most at risk of maloperation?
Answer: Distance (21) or directional elements
Distance and directional relays depend on voltage measurements; loss of potential (VT failure) can cause them to see an artificial fault impedance.
A switchgear bus shows intermittent phase-to-ground faults during humid weather. The most likely cause is:
Answer: Contaminated or tracking insulators
Contaminated insulators absorb moisture, creating a conductive tracking path that causes intermittent ground faults in high-humidity conditions.
You use time-domain reflectometry (TDR) on a buried cable and see a reflected pulse at 40% of the cable length. This indicates:
Answer: A fault or impedance discontinuity at that location
A reflected pulse before the cable end indicates an impedance discontinuity such as a fault, splice defect, or damage at that distance.
A synchronous generator loses excitation while on-line. The immediate electrical effect on the system is:
Answer: Reactive power absorption and possible voltage depression
Without excitation, the generator acts as an induction generator and absorbs reactive power from the system, which can depress system voltage.
After replacing a potential transformer fuse, a technician notices the relay still reads zero voltage on one phase. The next diagnostic step is:
Answer: Verify fuse continuity and check VT secondary wiring connections
After confirming fuse replacement, verifying secondary circuit continuity and terminal connections is the next logical step before condemning other equipment.