Safety
15%of exam
Electrical Testing Fundamentals and Theory
25%of exam
Component Testing
55%of exam
Systems and Commissioning
5%of exam
Quick Facts
- Exam
- NETA ETT Level 2
- Credential
- Certified Assistant Technician
- Items
- 100 multiple-choice
- Time
- 2 hours
- Pass
- 410 scaled (200-500)
- Format
- Closed-book, onsite proctored
- Delivery
- Pearson VUE
- Scheduling
- Set testing periods; schedule early
- Practice exam
- $100, one hour, 60-day review
- Eligibility
- 2 years, NAC employed
- Training
- 40 safety, 160 electrical hours
- Supervision
- Under Level 3 or 4
Ground Lead Order
Ground end first, remove it last
Apply: ground then conductorRemove: conductor then groundBoth ends: equipotential zoneVerify absence first
Level 2 vs Level 3
Level 2
- Limited testing work
- Direct supervision required
- 15/25/55/5 weights
Level 3
- Supervises Levels 1-2
- Performs power switching
- 13/23/47/17 weights
Assist vs supervise
Shock Boundary Picker
- 208 V panel, fixed parts→3 ft 6 in limited
- 480 V, qualified entry→1 ft 0 in restricted
- 13.8 kV gear, fixed parts→5 ft 0 in limited
- 13.8 kV qualified entry→2 ft 2 in restricted
- 25 kV gear, fixed parts→6 ft 0 in limited
- Overhead movable conductor→10 ft 0 in limited
- Unqualified person present→Qualified escort required
- Need arc flash boundary→Calculate it(Not a voltage table)
Approach Boundaries
- Limited approach
- Unqualified needs qualified escort
- Restricted approach
- Qualified plus shock PPE
- Arc flash boundary
- 1.2 cal/cm2 incident energy
- Prohibited boundary
- Deleted in 2015 editionNFPA 70E
- 50-150 V fixed
- 3 ft 6 in limited
- 151-750 V fixed
- 3 ft 6 in limited
- 151-750 V restricted
- 1 ft 0 in
- 751 V-15 kV fixed
- 5 ft 0 in limited
- 751 V-15 kV restricted
- 2 ft 2 in
- 15.1-36 kV restricted
- 2 ft 7 in
- Movable conductor
- 10 ft through 72.5 kV
- Boundary table
- NFPA 70E 130.4(E)(a)
PPE Cal Ladder
Four, eight, twenty-five, forty
Cat 1: 4 cal/cm2Cat 2: 8 cal/cm2Cat 3: 25 cal/cm2Cat 4: 40 cal/cm2
Limited vs Restricted Boundary
Limited
- Outer shock boundary
- Unqualified needs escort
- Fixed by voltage
Restricted
- Inner shock boundary
- Qualified plus shock PPE
- Documented work plan
Escort vs shock PPE
PPE and Glove Classes
- PPE Category 1
- 4 cal/cm2 minimum rating
- PPE Category 2
- 8 cal/cm2 minimum rating
- PPE Category 3
- 25 cal/cm2 minimum rating
- PPE Category 4
- 40 cal/cm2 minimum rating
- Category limits exceeded
- Incident energy analysis required
- Glove Class 00
- 500 V ac maximumASTM D120
- Glove Class 0
- 1,000 V ac maximum
- Glove Class 2
- 17,000 V ac maximum
- Glove Class 4
- 36,000 V ac maximum
- Glove retest
- Every 6 monthsOSHA 1910.137
- Sleeve and blanket retest
- Every 12 months
- Leather protectors
- Mechanical shield, not insulation
LOTO and ESWC
- OSHA 1910.147
- Machine servicing energy control
- OSHA 1910.333
- Electrical safety-related work practices
- OSHA 1910.269
- Utility generation, transmission, distribution
- NFPA 70E Article 120
- Electrically safe work condition
- Visual verification
- See the open gap
- Stored energy release
- Springs and capacitors
- Live-dead-live
- Prove tester before and after
- Temporary protective grounds
- Applied after voltage verified
- Equipotential zone
- Ground both work-zone ends
- Energized work permit
- Justifies infeasible de-energization
Meter Safety Ratings
- CAT II
- Receptacle-connected single-phase loadsIEC 61010
- CAT III
- Building distribution, three-phase equipment
- CAT IV
- Service entrance, outdoor conductors
- Higher category
- Higher transient withstand
- Voltage alone
- Never proves meter suitability
- Meter fuses
- High-interrupt rated only
- Non-contact tester
- Never proves absence
- Known live source
- Needed to prove tester
Ohm's Law and Power
- V = I x R
- Ohm's law
- P = V x I
- Real power, watts
- P = I^2 x R
- Heating in loose joints
- P = V^2 / R
- Resistive load power
- Series circuit
- Resistances add, current equal
- Parallel circuit
- Below smallest branch resistance
- 1 ohm
- 1,000,000 microhms
- 1 megohm
- 1,000,000 ohms
- Contact resistance units
- Microhms
- Winding resistance units
- Milliohms
- Insulation resistance units
- Megohms or gigohms
Three-Phase Relationships
- Wye line voltage
- sqrt(3) x phase voltage
- Wye line current
- Equals phase current
- Delta line voltage
- Equals phase voltage
- Delta line current
- sqrt(3) x phase current
- 480 V wye
- 277 V to neutral
- Apparent power S
- sqrt(3) x VLL x IL
- Real power P
- S x power factor
- Power factor
- Watts over volt-amperes
- Voltage unbalance
- Max deviation over average
- Delta ground reference
- Needs grounding transformer
ANSI Device Numbers
- 27
- UndervoltageIEEE C37.2
- 46
- Negative sequence, phase balance
- 49
- Thermal overload
- 50
- Instantaneous overcurrent
- 51
- Time overcurrent
- 52
- AC circuit breaker
- 59
- Overvoltage
- 67
- Directional overcurrent
- 86
- Lockout auxiliary relay
- 87
- Differential
- Suffix N or G
- Ground element
- Suffix V
- Voltage-restrained element
Drawings and Curves
- One-line
- Power path, sources, ratings
- Three-line
- Each phase and secondary
- DC schematic
- Trip and close logic
- Connection diagram
- Terminal-by-terminal wiring
- TCC curve
- Operating time versus current
- Pickup
- Minimum operating current
- Time dial
- Shifts the 51 curve
- Coordination
- Downstream device clears first
- Short-circuit study
- Available fault current source
Level 2 Domain Weights
Safety 15, Theory 25, Parts 55, Systems 5
Safety: 15%Theory: 25%Component: 55%Systems: 5%
ATS vs MTS
ANSI/NETA ATS
- Before initial energization
- New installations
- Acceptance criteria
ANSI/NETA MTS
- In-service equipment
- Maintenance intervals
- Trend against baseline
New install vs upkeep
IR Test Voltage Picker
- Manufacturer data exists→Manufacturer value(Tables are fallback)
- 600 V switchgear bus→1,000 V dc(100 Mohm)
- 5 kV class apparatus→2,500 V dc(1,500 Mohm)
- 15 kV class apparatus→2,500 V dc(5,000 Mohm)
- 480 V dry transformer→1,000 V dc(500 Mohm)
- 4,160 V liquid transformer→2,500 V dc(1,000 Mohm)
- 480 V motor stator→500 V dc(Table 100.11)
- 13.8 kV stator winding→5,000-10,000 V dc(Table 100.11)
- Reading below minimum→Investigate(Do not hipot)
IR Test Voltages
- 250 V class
- 500 V dc25 Mohm
- 600 V class
- 1,000 V dc100 Mohm
- 5,000 V class
- 2,500 V dc1,500 Mohm
- 15,000 V class
- 2,500 V dc5,000 Mohm
- Table 100.1 role
- Used absent manufacturer data
- Select voltage by
- Equipment rating, not supply
- Below the minimum
- Investigate before energizing
- Guard terminal
- Diverts surface leakage current
- Temperature rule
- Halves per 10 C rise
CT Open, PT Short
CT open kills; PT short kills
CT: short the secondaryPT: fuse the secondaryPT: never back-feedBoth mistakes are lethal
Insulation Resistance vs Hipot
Insulation resistance
- Lower dc voltage
- Nondestructive
- Megohm reading
Hipot
- High applied stress
- Pass or fail
- Can break insulation
Measure vs stress
Which Test For What
- Suspect wet stator→Polarization index(10 over 1)
- Ten minutes unavailable→DAR(60 over 30)
- Bolted joint suspect→Micro-ohmmeter(Four-wire Kelvin)
- Tap changer suspect→TTR on all taps(0.5 percent)
- Shorted transformer turns→Excitation current test
- Service-aged MV cable→VLF withstand(Not dc hipot)
- Rank cable replacement→Tan delta(Diagnostic)
- Lost vacuum suspected→Vacuum bottle integrity(Megger cannot see)
- CT accuracy in doubt→Saturation test(Knee point)
- Breaker did not trip→Primary injection(Whole loop)
- Isolated ground rod→Fall-of-potential(Disconnect electrode)
- Multi-grounded system→Clamp-on tester(Parallel path needed)
- Surface contamination suspected→Guarded IR reading
PI, DAR and IEEE 43
- PI
- 10-minute over 1-minute
- DAR
- 60-second over 30-second
- PI minimum
- 2.0 for Class BIEEE 43
- PI near 1.0
- Moisture or contamination
- PI not required
- IR above 5,000 Mohm
- Ratios need no correction
- Same temperature both readings
- Form-wound after 1970
- 100 Mohm minimum
- Older and field windings
- kV + 1 Mohm
- Random-wound stators
- 5 Mohm minimum
- IEEE 43 base
- Corrects to 40 C
- NETA conversion base
- Corrects to 20 C
- Step-voltage test
- Disproportionate drop reveals aging
PI and DAR Times
PI ten over one; DAR sixty over thirty
PI: 10 min / 1 minDAR: 60 s / 30 sMinimum PI: 2.0No temperature correction
DLRO vs Megohmmeter
DLRO
- Microhm range
- Four-wire Kelvin
- Conducting path
Megohmmeter
- Megohm range
- High dc voltage
- Insulating path
Through vs across
Transformer Testing
- TTR tolerance
- Within 0.5 percentANSI/NETA
- Test every tap
- Defects hide on unused
- Turns ratio a
- V1/V2 = I2/I1
- Impedance transforms
- By the ratio squared
- Subtractive polarity
- Reads less than applied
- Additive polarity
- Reads more than applied
- Additive permitted
- 200 kVA and below
- Excitation current pattern
- Center leg reads lower
- Liquid-filled, 0-600 V
- 1,000 V dc, 100 MohmTable 100.5
- Dry-type, 0-600 V
- 1,000 V dc, 500 Mohm
- Liquid-filled, 601-5,000 V
- 2,500 V dc, 1,000 Mohm
- Winding resistance
- Finds loose or open
PI vs DAR
PI
- 10 min / 1 min
- IEEE 43 minimum 2.0
- Full charging curve
DAR
- 60 s / 30 s
- Quick screening ratio
- No IEEE minimum
Long vs short ratio
Cable Testing
- VLF frequency
- About 0.1 Hz
- Why VLF works
- Charging current drops sharply
- DC hipot on XLPE
- Injects trapped space charge
- DC still acceptable on
- PILC laminated dielectrics
- Tan delta
- Loss over charging current
- Tip-up
- Loss rises with voltage
- Withstand test
- Go or no-go
- Diagnostic test
- Grades and trends condition
- Shield continuity
- Over 10 ohms per 1,000 ft
- Post-hipot grounding
- Drain trapped charge first
Bonding vs Grounding
Bonding
- Joins metal parts
- Carries fault current
- Operates the breaker
Grounding
- Reference to earth
- Lightning and static
- Poor fault path
Clears faults vs references
Breaker Testing
- MCCB
- Sealed, fixed instantaneous trip
- ICCB
- Drawout, short-time capability
- LVPCB
- Maintainable, short-time withstand rating
- Thermal-magnetic trip
- Fixed curve, ambient sensitive
- Electronic trip
- Adjustable LSIG functions
- LSIG
- Long, short, instantaneous, ground
- Contact resistance current
- 100 A dc minimumIEEE C37.09
- Pole deviation limit
- 50 percent above lowest
- Primary injection
- Proves the whole loop
- Secondary injection
- Proves trip unit only
- Vacuum bottle integrity
- Overpotential across open gap
- Vacuum test hazard
- X-rays at high voltage
Primary vs Secondary Injection
Primary
- Whole current loop
- Finds bad CTs
- Commissioning test
Secondary
- Trip unit only
- Proves settings
- Misses sensors
Loop vs logic
Instrument Transformers
- Open CT secondary
- Lethal voltage, core saturates
- Before lifting CT lead
- Install the shorting screw
- Short PT secondary
- Damaging fault current
- Back-feed a PT
- Full primary on terminals
- 600:5 CT
- 120:1 ratio
- Polarity marks
- H1 in, X1 out
- Reversed CT polarity
- Differential trips on load
- C400 class
- 400 V at 100 AIEEE C57.13
- C-class error limit
- 10 percent ratio error
- Saturation test
- Finds the knee point
- Burden
- Total secondary circuit load
Withstand vs Diagnostic
Withstand
- Go or no-go
- VLF or hipot
- May fault it
Diagnostic
- Condition number
- Tan delta, partial discharge
- Trendable
Can energize vs remaining life
Grounding and Batteries
- Bonding
- Low-impedance fault return path
- Grounding
- Voltage reference to earth
- Earth as fault path
- Poor, will not clear
- Grounded conductor
- Neutral, carries load current
- Equipment grounding conductor
- Carries fault current only
- Fall-of-potential
- Three-point, 62 percent rule
- Clamp-on ground test
- Needs parallel return path
- Flooded cell
- Specific gravity, temperature corrected
- VRLA cell
- No hydrometer, ohmic trending
- IEEE 450
- Vented lead-acid maintenance
- IEEE 1188
- VRLA battery maintenance
- Capacity proof
- Discharge test only
CT vs PT Secondary
CT secondary
- Never open it
- Short before lifting
- Behaves as current source
PT secondary
- Never short it
- Never back-feed it
- Fused, voltage source
Open kills vs short kills
Test Order Rule
Components first, system function last
As-found before adjustingAs-left after workFunction proves interaction
Restore and Report
- All component tests pass→System function test
- Relay element picks up→Verify breaker trips
- Before any adjustment→Record as-found
- After the work→Record as-left
- Grounds still applied→Remove conductor end first
- Ready to energize→Confirm settings match study
Commissioning and Records
- System function test
- After all component tests
- As-found data
- Recorded before any adjustment
- As-left data
- Baseline for next interval
- ATS functional test
- Simulate normal source loss
- NFPA 110 monthly
- 30 minutes under load
- Monthly load target
- 30 percent nameplate kW
- Annual supplemental test
- 50 percent then 75 percent
- Level 1 triennial
- 4 hours or class duration
- GFP performance test
- Required when first installedNEC 230.95
- Troubleshooting
- Find cause, not symptom
Common Traps
Boundary vs arc flash
Shock boundaries from table ≠ Arc flash is calculated
Category vs severity
Category is PPE rating ≠ Not a hazard score
De-energized vs safe
De-energized only means opened ≠ Safe adds test and ground
Wrong OSHA rule
1910.147 covers machines ≠ 1910.333 covers electrical work
Prefix mistakes
Contact resistance in microhms ≠ Insulation in megohms
Wrong correction base
IEEE 43 uses 40 C ≠ NETA table uses 20 C
Resistance vs withstand
Megohmmeter measures resistance ≠ Hipot applies dielectric stress
Wrong injection test
Secondary proves trip unit ≠ Primary proves whole loop
Only one tap tested
TTR needs every tap ≠ Unused taps hide defects
Vacuum vs insulation test
Megger misses lost vacuum ≠ Overpotential across open gap
Neutral vs ground
Neutral carries load current ≠ EGC carries fault current
Last Minute
- 1.Pass is 410 scaled, 200-500
- 2.100 items, 2 hours, closed-book
- 3.Component Testing is 55 percent
- 4.Safety 15, Theory 25, Systems 5
- 5.600 V class: 1,000 V dc
- 6.5 kV class: 2,500 V dc
- 7.PI = 10 min / 1 min
- 8.DAR = 60 s / 30 s
- 9.Minimum PI is 2.0
- 10.TTR within 0.5 percent, every tap
- 11.Contact resistance at 100 A
- 12.Never open a CT secondary
- 13.Never back-feed a PT
- 14.Ground end first, conductor last
- 15.Arc flash boundary: 1.2 cal/cm2
- 16.PPE cal: 4, 8, 25, 40
- 17.Restricted at 480 V: 1 foot
- 18.Record as-found before adjusting
- 19.Function test after component tests
- 20.Practice exam: $100, one hour
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