NICET EPT cheat sheet

NFPA 70E defines the arc flash boundary as the distance from exposed live parts where incident energy equals 1.2 cal/cm², the threshold for second-degree burns.

NFPA 70E limited approach boundary for exposed live parts 0–750 V is 10 ft 0 in for movable conductors and 3 ft 6 in for fixed circuit parts.

Restricted approach boundary is 1 ft 0 in for 301–750 V and 'avoid contact' below 301 V; crossing it requires shock protection and an energized work permit.

OSHA 29 CFR 1910.333(a)(1) requires de-energizing live parts before work unless doing so introduces a greater hazard or is infeasible due to equipment design or operational limitations.

OSHA 29 CFR 1910.147 governs lockout/tagout; zero-energy state must be verified by test, not by indicator lamps or relay position alone.

Test instrument CAT rating must meet or exceed the location: CAT IV at service entrance and utility, CAT III at panelboards and feeders, CAT II at receptacle branch circuits.

Live-dead-live verification: test the instrument on a known live source, test the isolated conductor, then retest the known live source; a non-contact tester alone is not proof of de-energization.

IEEE 1584 calculates incident energy empirically from bolted fault current, electrode gap, working distance, and protective device clearing time; clearing time dominates the result.

Arc-rated PPE system rating in cal/cm² must equal or exceed the calculated incident energy; non-melting underlayers are required beneath arc-rated outer layers.

Three-phase power: P = √3 × V_LL × I_L × cos θ; apparent power S = √3 × V_LL × I_L; reactive power Q = √3 × V_LL × I_L × sin θ.

Wye: V_LL = √3 × V_LN and I_line = I_phase. Delta: V_LL = V_phase and I_line = √3 × I_phase.

Per unit: Z_pu = Z_actual / Z_base, where Z_base = V_base² / S_base; using kV and MVA gives Z_base directly in ohms.

Capacitor size for power-factor correction: Q_c (kVAr) = P (tan θ₁ − tan θ₂), where θ₁ is the existing and θ₂ the target power-factor angle.

Available secondary short-circuit current with an infinite primary bus: I_sc ≈ I_FLA / (%Z / 100); a 5%Z transformer yields about 20 times rated current.

Symmetrical components resolve an unbalanced three-phase set into positive-, negative-, and zero-sequence sets so unbalanced faults can be solved with single-phase networks.

X/R ratio at the fault point sets the DC offset; a fault at voltage zero gives maximum offset, and the first-cycle peak can approach 2.7 times the RMS symmetrical value at high X/R.

Voltage THD = √(Σ V_h² for h ≥ 2) / V_1 × 100%; K-rated transformers are specified where harmonic currents from non-linear loads are significant.

Real power flows from the generating source to the load; reactive power oscillates and is controlled locally by capacitors, reactors, and generator excitation.

Ideal transformer relations: V₁/V₂ = N₁/N₂ and I₁/I₂ = N₂/N₁; the kVA rating is essentially the same on both windings.

Percent impedance fixes both voltage regulation and available fault current; a lower %Z gives better regulation but higher short-circuit duty on downstream equipment.

ANSI standard polarity is subtractive: H1 and X1 bushings are diagonally opposite, and when H1 is instantaneously positive, X1 is also positive.

Delta–wye transformers introduce a 30° phase shift; paralleling requires matching ratio, polarity, impedance, and phase displacement.

Turns-ratio test (TTR) verifies nameplate ratio and polarity; deviations beyond roughly 0.5% of nameplate warrant investigation of taps or shorted turns.

Sweep frequency response analysis (SFRA) compares a winding fingerprint to a baseline to detect winding deformation, core movement, or clamping loss.

Switchgear interrupting rating is the maximum symmetrical RMS short-circuit current it can clear at rated voltage; close-and-latch (momentary) rating covers peak first-cycle mechanical duty.

Basic impulse level (BIL) is the lightning-impulse withstand voltage of the insulation; it must be coordinated with, and exceed, the surge arrester protective level.

A Buchholz relay on an oil-filled transformer alarms on accumulated gas and trips on a sudden oil surge caused by an internal fault.

Synchronous speed N_s = 120 f / P; percent slip = (N_s − N_r) / N_s × 100.

NEMA Design B is the general-purpose induction motor design; locked-rotor current is typically 5 to 7 times full-load current.

Running overload protection is set from motor nameplate FLA using an inverse-time (I²t) characteristic; branch-circuit short-circuit protection is a separate device.

IEEE 43 rule of thumb for minimum insulation resistance: IR_min (MΩ) = rated winding kV + 1, measured at the specified DC test voltage.

Polarization index = R at 10 minutes / R at 1 minute; values below 2.0 indicate moisture, contamination, or insulation degradation.

Across-the-line starting draws the highest inrush; reduced-voltage methods (star-delta, autotransformer, soft starter, VFD) limit starting kVA and mechanical shock.

PWM drive output produces high dv/dt and reflected-wave overvoltage on long motor leads; inverter-duty motors, load reactors, and filters mitigate the stress.

Service factor 1.15 permits continuous output up to 115% of nameplate only when voltage, frequency, and ambient are at rated conditions.

Voltage unbalance produces negative-sequence current and rotor heating; NEMA MG1 requires derating when unbalance exceeds 1%.

ANSI/IEEE device numbers: 50 instantaneous overcurrent, 51 AC time overcurrent, 87 differential, 27 undervoltage, 59 overvoltage, 21 distance, 86 lockout relay.

Coordination sets pickup and time dial so the device closest to the fault clears first; time-current curves must not overlap in the fault-current range.

CT performance is defined by accuracy class and burden in VA; a saturated CT distorts secondary current and can cause slow or failed tripping.

Transformer 87T differential schemes use second-harmonic restraint to block tripping during magnetizing inrush and fifth-harmonic restraint for overexcitation.

Current-loop convention: 4 mA is live zero and 20 mA is full scale; a 250 Ω sense resistor converts the loop to 1–5 V for the input card.

Secondary injection verifies relay pickup, timing, and logic at the terminals; primary injection verifies the full CT, VT, and wiring path.

Protective zones must overlap at each boundary so no bus, breaker, or conductor is left unprotected.

Directional overcurrent (67) requires the correct polarizing quantity and correct CT/PT polarity; reversed polarity makes a forward fault appear reverse.

NEC ampacity tables give base values that must be corrected for ambient temperature and adjusted for more than three current-carrying conductors in a raceway or cable.

Insulation resistance testing uses DC at a level set by the standard: commonly 500 V DC for equipment rated up to 1 kV and higher voltages for medium-voltage apparatus.

IEEE 400.2 identifies 0.1 Hz very-low-frequency AC as the preferred field withstand test for shielded power cable; DC hi-potential testing is not recommended for XLPE.

Wenner four-pin soil resistivity: ρ = 2πaR, with pin spacing a in meters and measured resistance R in ohms, giving ohm-meters.

Fall-of-potential grounding test places the potential probe at 62% of the distance to the current probe; flat readings at 52% and 72% confirm a valid measurement.

NEC 250.53(A)(2): a single rod, pipe, or plate electrode must show 25 Ω or less to ground, otherwise a supplemental electrode is required.

IEEE 80 substation grounding design limits step and touch voltages to body-withstand values computed for the actual protective clearing time.

Time-domain reflectometry locates a cable fault from the round-trip echo: distance = (propagation velocity × time) / 2.

Partial discharge testing detects voids, delamination, and tracking at voltages below breakdown; results are judged against baseline or specified picocoulomb limits.

ANSI/NETA ATS specifies acceptance testing for electrical power equipment and systems; ANSI/NETA ETT covers qualifications of electrical testing technicians.

As-found data are recorded before any adjustment and as-left data after; the comparison against acceptance criteria drives the accept, repair, or replace decision.

Energization sequence: visual and mechanical inspection, insulation resistance, continuity and point-to-point wiring checks, protective device functional tests, then energization.

Motor rotation and phase sequence must be verified before the motor is coupled to driven equipment.

Factory acceptance testing occurs at the manufacturer's works; site acceptance testing verifies installation, wiring, and interfaces in the field.

Loop checks verify the complete measurement path from field sensor through scaling, display, and alarm setpoints in the control system.

Infrared surveys are meaningful only under load; a commonly used minimum is about 40% of rated load so loose connections produce detectable temperature rise.

Handover documentation includes as-built drawings, O&M manuals, final relay settings, test reports, and calibration certificates for test instruments.