NICET EPT flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Arc flash boundary
- The distance from exposed live parts at which a person without arc-rated protection would receive second-degree burns, defined as an incident energy of 1.2 cal/cm².
- Restricted approach boundary
- An NFPA 70E boundary inside which only qualified persons using shock protection and insulated tools may reach, and crossing which requires an energized electrical work permit.
- CAT III rating
- A measurement category for test instruments used on distribution circuits such as panelboards and feeders; the instrument rating must meet or exceed the location category and voltage.
- Live-dead-live test
- A three-step verification of de-energization: test the instrument on a known live source, test the isolated conductors, then retest the known source to prove the meter still works.
- Incident energy
- The thermal energy impressed on a surface at a stated working distance during an electric arc, expressed in calories per square centimeter or joules per square centimeter.
- Per-unit impedance
- Actual impedance divided by base impedance, where base impedance equals base voltage squared divided by base apparent power; per-unit values are unchanged across a transformer.
- Symmetrical components
- A method that resolves an unbalanced three-phase set of phasors into balanced positive-, negative-, and zero-sequence sets so faults can be solved with single-phase networks.
- Power factor correction
- Adding shunt capacitors to supply reactive power locally; required capacitive kVAR equals real power times the difference between tangents of the original and target power-factor angles.
- Wye connection relations
- In a balanced wye, line current equals phase current and line-to-line voltage equals the square root of three times line-to-neutral voltage, with line voltage leading by 30 degrees.
- X/R ratio
- The ratio of reactance to resistance at the fault point, which determines DC offset and therefore the peak asymmetrical first-cycle current the equipment must withstand.
- Subtractive polarity
- The ANSI standard transformer polarity in which the H1 and X1 bushings are diagonally opposite; when H1 is instantaneously positive, X1 is also positive.
- Percent impedance
- The voltage, as a percentage of rated, that must be applied to the primary to circulate rated current with the secondary shorted; it fixes available fault current and regulation.
- Turns ratio test
- A field test that applies a known voltage to one transformer winding and measures the induced voltage on the other to verify nameplate ratio and polarity.
- Buchholz relay
- A gas-actuated device installed in the pipe between an oil-filled transformer tank and its conservator; it alarms on accumulated gas and trips on a sudden oil surge.
- Close-and-latch rating
- The maximum asymmetrical current a switchgear assembly can withstand while closing and holding closed, covering the first-cycle mechanical duty of a fault.
- Synchronous speed
- The speed of the rotating magnetic field, equal to 120 times frequency divided by the number of poles; at 60 Hz with four poles it is 1800 rpm.
- Polarization index
- The ratio of insulation resistance at ten minutes to that at one minute; a value below 2.0 suggests moisture, contamination, or degradation in the winding insulation.
- NEMA Design B motor
- The general-purpose AC induction motor design with normal starting torque and locked-rotor current typically five to seven times full-load current; the most common industrial motor.
- Inverter duty motor
- A motor whose insulation and bearings are designed to withstand the fast voltage pulses and high rate of voltage rise produced by pulse-width-modulated variable-frequency drives.
- Motor overload relay
- A device that models winding heating with an inverse-time current-squared characteristic and trips at a level set from the motor nameplate full-load amperes.
- Device 87
- The ANSI device number for differential protection, which compares currents entering and leaving a protected zone and trips when the difference exceeds a restraint-based threshold.
- Harmonic restraint
- A differential relay feature that blocks tripping when second-harmonic content in the measured current indicates magnetizing inrush rather than an internal fault.
- Secondary injection test
- A relay test in which precise currents and voltages are injected at the relay terminals to verify pickup, timing, and logic without energizing primary equipment.
- Live zero 4-20 mA
- An analog signal convention in which 4 mA represents the minimum value and 20 mA the maximum, so a broken wire reads 0 mA and is distinguishable from a valid low reading.
- Very low frequency test
- A cable withstand test applying 0.1 Hz AC, preferred over DC hi-potential testing for shielded XLPE cable because it limits trapped space charge and insulation damage.
- Fall-of-potential test
- A three-point ground resistance measurement with the potential probe at 62 percent of the distance to the current probe; flat readings at 52 and 72 percent confirm validity.
- Wenner four-pin method
- A soil resistivity test using four equally spaced pins in a straight line, where resistivity in ohm-meters equals two pi times the pin spacing times the measured resistance.
- Time domain reflectometry
- A cable fault-location method that launches a pulse and measures the round-trip echo time, giving distance as half the product of propagation velocity and elapsed time.
- As-found test data
- Measurements recorded before any adjustment or repair of the equipment; they establish baseline condition and are compared against acceptance criteria in the test report.
- Factory acceptance test
- A structured test program performed at the manufacturer's facility before shipment to demonstrate that equipment meets specification and contract requirements.
- Point-to-point check
- A continuity verification that each field conductor is landed on the terminal shown on the drawings, performed before energization to prevent misoperation or equipment damage.
- Baseline thermographic survey
- An infrared scan of energized equipment under load that records normal temperature patterns for later comparison, typically requiring at least 40 percent of rated load.