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
The polarization index (PI) is calculated by dividing the insulation resistance measured at 10 minutes by the reading at:
Answer: 1 minute
PI = IR at 10 minutes divided by IR at 1 minute; a value of 2.0 or above generally indicates acceptable insulation condition.
Which safety precaution is mandatory before connecting a megohmmeter to a large capacitive load such as a cable run?
Answer: Verify the load is de-energized and fully discharged
Capacitive equipment stores dangerous charge; the equipment must be de-energized and discharged (verified with a voltmeter) before connecting the megohmmeter.
In a transformer turns ratio (TTR) test, a ratio error exceeding what percentage typically triggers further investigation per NETA MTS?
Answer: 0.5%
NETA MTS flags a turns ratio deviation greater than 0.5% from the nameplate ratio as requiring further evaluation for possible winding faults.
When performing an AC high-potential (hipot) test on cable insulation, the test voltage is typically applied for:
Answer: 1 minute
The standard AC hipot withstand duration for cable insulation per NETA MTS is 1 minute at the specified test voltage.
A very low frequency (VLF) test on medium-voltage cable uses a test frequency of:
Answer: 0.1 Hz
VLF testing uses 0.1 Hz (or 0.01–0.1 Hz range) to stress cable insulation at a fraction of the normal power frequency, reducing the required kVA from the test set.
During a sweep frequency response analysis (SFRA) test on a power transformer, the primary purpose is to detect:
Answer: Winding deformation or displacement due to mechanical stress
SFRA compares frequency response signatures to detect physical winding movement, deformation, or damage caused by through-faults or transportation.
What test is performed to verify that a protective relay correctly operates at the designed current pickup level?
Answer: Secondary current injection test
Secondary injection testing applies a calibrated current directly to the relay's current input terminals to verify pickup, timing, and trip function without energizing primary equipment.