NETA ETT Level 2 cheat sheet

Energized electrical work at 50 V or more requires an approved permit and documented justification unless the work is infeasible de-energized or involves diagnostic testing by qualified persons.

The arc flash boundary is the distance where incident energy equals 1.2 cal/cm² (5 J/cm²); arc-rated PPE is required inside that boundary.

Limited approach boundary: unqualified persons may not cross unless escorted. Restricted approach boundary: only qualified persons with shock protection may cross.

Absence-of-voltage verification requires a tester rated for the voltage and category, checked on a known live source before and after the test.

Arc-rated clothing must have an arc rating at least equal to the calculated incident energy; nonmelting natural-fiber layers are worn beneath.

Minimum approach distance increases with system voltage; crossing it requires voltage-rated tools, gloves, and sleeves appropriate to the voltage.

Incident energy decreases as distance from the arc increases; the arc flash boundary is calculated at the 1.2 cal/cm² threshold.

A qualified person has demonstrated skills, knowledge, and training to identify hazards and perform work safely; unqualified persons require escort and hazard awareness.

Ohm's law: V = IR. Power: P = VI = I²R = V²/R for DC and resistive AC.

Balanced three-phase real power: P = √3 × V_LL × I_L × cosθ; apparent power S = √3 × V_LL × I_L.

Power factor = kW/kVA = cosθ; reactive power Q = √3 × V_LL × I_L × sinθ.

Transformer voltage ratio equals turns ratio (Vp/Vs = Np/Ns); current ratio is inverse (Ip/Is = Ns/Np).

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

Impedance Z = R + jX; series impedances add directly, and parallel impedances combine by reciprocals.

A one-line diagram shows major equipment and power flow with single lines; a three-line diagram shows all three phase conductors and connections.

ANSI/IEEE device numbers identify functions: 50 instantaneous overcurrent, 51 AC time-overcurrent, 87 differential, 27 undervoltage, 59 overvoltage.

Polarity dots on transformer and CT symbols mark terminals that are in phase; reversed polarity causes incorrect metering or differential operation.

Insulation resistance testers apply DC test voltage; select voltage by equipment class and compare temperature-corrected results with baseline and acceptance limits.

Polarization index = 10-minute IR ÷ 1-minute IR; low PI suggests moisture, contamination, or insulation deterioration.

Four-wire Kelvin measurement separates current and voltage leads, eliminating lead and contact resistance from low-resistance readings.

Fall-of-potential ground test: drive current and potential stakes in a straight line; place the potential probe at about 62% of the current-stake distance.

Clamp-on ground testers require a bonded grounding system with parallel paths; they do not validly measure an isolated ground electrode.

True-RMS meters are required for distorted waveforms; average-responding meters may misread non-sinusoidal signals.

A meter's CAT rating and voltage rating must meet or exceed the circuit category; CAT IV applies to service-entrance and utility-side measurements.

Discharge insulation test specimens after IR testing; capacitive stored charge can cause shock and damage.

Phase sequence meters indicate A-B-C or C-B-A rotation before motor connection or paralleling.

Perform visual inspection before electrical tests; record nameplate data, cleanliness, connections, and mechanical condition.

Transformer tests include turns ratio, winding resistance, insulation resistance, and oil tests; compare phases and prior results.

Circuit breaker contact resistance is measured with a low-resistance ohmmeter; trending upward indicates contact wear or loose connections.

Primary injection tests current transformers and breaker trip elements at realistic currents; secondary injection tests relay logic and settings.

Grounding system tests include electrode resistance, equipment grounding continuity, and bonding; a low-resistance path is required for fault clearing.

Thermographic surveys are performed under load; compare phase-to-phase and phase-to-ambient temperatures to find loose or overloaded connections.

Terminations must be torqued to manufacturer values with a calibrated wrench; re-torque after thermal cycling if specified.

Battery tests include float voltage, specific gravity or conductance, and capacity discharge; weak cells show low voltage under load.

Motor insulation resistance is measured with windings disconnected; compare phases and prior readings, and calculate PI when appropriate.