NETA Level 2 Study Guide Flashcards

Flashcards generated from NETA 2 study guide lecture notes focusing on electrical testing, safety standards, power systems, and transformer calculations.

In a balanced Delta system, what is the relationship between line voltage and phase voltage, and line current and phase current?

Line voltage equals phase voltage ($\text{V}_{\text{line}} = \text{V}_{\text{phase}}$), and line current equals phase current multiplied by $1.732$ ($\text{I}_{\text{line}} = \text{I}_{\text{phase}} \times 1.732$).

How is the time rating of an electric motor typically expressed?

In minutes.

A relay device number 51 is connected to an 800/5 CT, set to time dial 3 and tap 10. What primary current must flow to cause the relay to start timing out?

$8000\text{ A}$ (calculated by finding the CT ratio $800/5 = 160$ and multiplying by the tap setting $10$).

In a purely inductive circuit, what is the phase angle shift between the voltage waveform and current waveform?

A $90^\circ$ phase shift.

According to NETA acceptance testing standards, when should the transformer manufacturer be consulted regarding winding-resistance test values?

If winding-resistance test values vary by more than $1.00\%$ from factory test values or between adjacent phases.

A wye-delta transformer has a turns ratio of 2:1 and a secondary line voltage of $480\text{ V}$. The secondary is connected to a wye-connected three-phase resistive load of $50\text{ ohms}$ in each phase. How much is the secondary phase current?

$5.54\text{ A}$ (Phase voltage = $480\text{ V} / 1.732 = 277\text{ V}$; Phase current = $277\text{ V} / 50\text{ }\Omega = 5.54\text{ A}$).

What position is a circuit breaker in if its main stabs are disconnected and its auxiliary stabs are connected?

The test position.

How do metal oxide surge arresters limit overvoltage conditions during surges?

By conducting the surge current to ground.

According to NFPA 70B Chapter 5, what is required for compliant electrical safety-related work practices?

Qualified persons and adherence to state and federal codes.

What is the maximum rated voltage for low voltage circuit breakers?

Less than $1000\text{ V}$.

Upon the outbreak of a fire in a facility, what should your first action be?

ALERT and ALARM.

How is instantaneous trip time best described?

No intentional delay.

How can an electrolyte be checked to ensure that it has the correct chemical composition?

By measuring its relative resistance.

What construction features characterize the field coils of a series-type DC motor?

A low-resistance winding made up of a few turns of large-diameter wire.

How are weak spots in the stator core of a large rotating machine detected during a low flux test?

By scanning the stator surface using a Potentiometer or Rogowski coil.

Who is the main federal agency charged with the enforcement of safety and health legislation?

OSHA.

What light source can be used to field test arc-flash detection relays?

A camera flash.

Which gate is NOT one of the basic logic gates used in combinational logic circuits?

MEM GATE.

What is the turns ratio for a 69000-12470/7200 Transformer using the primary voltage and secondary voltage?

$9.58$ ($69{,}000 / 7{,}200 = 9.58$).

What type of abrasive material is used for abrading cable insulation?

Aluminum oxide.

An instantaneous trip test on a circuit breaker with electronic trip units specifies an expected trip current of $9600\text{ A}$. What is the acceptable trip current range per NETA standards ($\pm 30\%$)?

$6720\text{ A to } 12450\text{ A}$.

Which type of Electric Vehicle Supply Equipment (EVSE) is best suited for locations where quick charging is essential?

DC Charging stations.

Once placed into service, how often must rubber insulating gloves be cleaned, inspected, and electrically tested?

Every $6\text{ months}$.

What does “MTA” stands for when reviewing the settings on a 67 protective relay?

Maximum Torque Angle.

Why are Single Bus configurations generally not considered reliable systems?

They result in complete shutdowns during maintenance or faults.

At what operating voltage threshold to earth should stress-relief cones be applied at cable shield ends?

More than $2\text{ kV}$ to earth.

According to NFPA 70E, what is the acceptable Arc-Flash PPE Category for a $600\text{ V}$ panelboard fed by a transformer with $24{,}000\text{ A}$ fault current and a breaker clearing time of $0.025\text{ seconds}$?

Category 1, with a Arc-Flash Boundary of 19 in (486mm)

Which device is designed to distribute electrical power to servers, networking hardware, and telecom equipment in a data center?

PDU (Power Distribution Unit).

What does the abbreviation SF6 stand for?

Sulphur hexafluoride.

In a capacitor, what is the phase relationship between current and applied voltage?

The current LEADS the applied voltage by $90^\circ$.

What happens to the inductive reactance of an inductor as frequency increases?

It increases.

What is the general rule of thumb for selecting test current during contact-resistance testing?

Use the highest current possible without exceeding the current rating of the device under test.

What is the main disadvantage of a Double Bus Single Breaker configuration?

It cannot handle circuit breaker maintenance without interrupting service.

How many horsepower is approximately equivalent to an electrical device listed as $3000\text{ watts}$?

Approximately $4\text{ hp}$ ($3000\text{ W} / 746\text{ W per hp} \approx 4\text{ hp}$).

What electrical components are installed to reduce harmonics in a power system?

Filters.

What type of transformer protective device is used specifically on liquid-filled transformers for gas detection?

Buchholz relay.

What is the full load secondary current of a three-phase $75\text{ kVA}$ transformer connected to a $480\text{ V}$ primary and a $120/208\text{ V}$ secondary?

$208.2\text{ A}$ $\text{I} = \text{S} / (1.732 \times \text{V}) = 75000 / (1.732 \times 208) = 208.2\text{ A}$ .

When does an Insulation Resistance Profile (IRP) graph appear as an inverse exponential function?

When the insulation system is operating under normal conditions.

In what order should backup power systems be placed according to the NEC hierarchy?

1. Emergency power systems, 2. Legally required standby systems, 3. Optional standby systems.

Which standard low-voltage fuse type is NOT current-limiting?

Class H.

Which Level of Electric Vehicle (EV) charger is exclusively designed for public charging stations?

Level 3 (also known as DC Charging stations).

Which material system or element should NOT be used as grounding electrodes?

Aluminum.

What action should be taken if rubber insulating gloves become contaminated with oil-based compounds?

Discard and replace them.

Which device provides an insulated entrance for an energized conductor into a high-voltage apparatus tank or chamber?

Bushing.

What is the instantaneous output voltage of a single pole $120\text{ V}$ generator at a rotation angle of $22^\circ$?

$44.95\text{ V}$ ($\text{V} \times \sin(\theta) = 120 \times \sin(22^\circ) = 44.95\text{ V}$).

According to NEC Section 250.52(A)(2), what is the permissible action if multiple metal in-ground support structures exist at a structure?

Bond only one of them into the grounding electrode system.

What gas can be produced by overcharging a lead-acid battery?

Hydrogen.

In high-voltage circuit breakers, what is the sum of steady state contact stroke plus overtravel distance called?

Maximum dynamic contact gap.

How is the Polarization Index (PI) ratio defined?

10-minute insulation resistance reading divided by the 1-minute insulation resistance reading ($10\text{ min} / 1\text{ min}$).

What are the three main hazard groups defined by the Globally Harmonized System (GHS)?

Physical, Health, and Environmental.

To what “standard reference temperature” is Insulation Resistance for electrical apparatus corrected?

$20^\circ\text{C}$.

At what ATPV rating probability are arc-flash protective clothing and equipment specified to prevent a second-degree burn?

$50\%$ probability of a burn.

How much torque is produced by the $41{,}000\text{ RPM}$ turbine section of a $5\text{ kV}$, $300\text{ HP}$ gas turbine engine?

$38\text{ lb-ft}$ $\text{Torque} = (\text{HP} \times 5252) / \text{RPM} = (300 \times 5252) / 41000 = 38.43\text{ lb-ft}$

What does clockwise rotation of a synchroscope indicate?

The generator has a higher speed or frequency than the electrical system.

How is the term 'competent' defined in relation to qualified persons under NFPA 70E?

Sufficient skills, knowledge, or experience for a specific purpose.

How long does it take for a $120\text{ V}$, $60\text{ Hz}$ sine wave to reach an angle of $120^\circ$?

$0.00555\text{ seconds}$ ($t = (\text{angle} / 360) \times (1 / \text{frequency}) = (120 / 360) \times (1 / 60) = 0.00555\text{ s}$).

What is a 'pilot cell' in a battery system?

The cell used for monitoring a bank of cells.

What is the key operational difference between online and offline Partial Discharge (PD) testing?

Online testing is performed under real-world operating conditions without removing equipment from service; offline testing requires taking equipment out of service and using external voltage sources.

What is the purpose of transient earth voltage (TEV) testing in medium-voltage metal-clad switchgear?

To find partial discharge inside the switchgear.

Why are battery cells connected in parallel?

To increase current capacity.

In alternating current circuits, what term describes the total opposition to current flow?

Impedance.

When monitoring confined spaces involving vertical descent into potentially stratified atmospheres, what is the required testing distance?

Approximately $4\text{ feet}$ in the direction of travel and to each side.

In what unit is reactive power measured?

VARS (Volt-Amperes Reactive).

What are the basic layers of medium voltage (MV) cable construction, ordered from the inside conductor outward?

1. Conductor Shield, 2. Insulation, 3. Insulation Shield, 4. Neutral, 5. Jacket.

What term defines the periodic overload capacity at which an electric motor can operate without overheating under rated voltage and frequency?

Service Factor.

On a transformer with $100\text{ total turns}$ (X1 to X5), what is the calculated voltage across taps X1 to X3 ($30\text{ turns}$) when $200\text{ V}$ is applied to the full secondary winding?

$60\text{ V}$ $\text{Applied Voltage} / \text{Total Turns} \times \text{Tap Turns} = 200\text{ V} / 100 \times 30 = 60\text{ V}$ ).

What is the main construction difference between older surge arresters and metal oxide surge arresters?

Metal oxide arresters contain blocks of zinc oxide and air gaps, whereas older arresters consist of silicon carbide resistor blocks.

Why can an induction relay NOT be used in DC control circuits?

Because direct current circuits produce a constant magnetic flux.

What is the ANSI/IEEE device number for a Phase-sequence or phase-balance voltage relay?

Device number 47.

Why are metals with low emissivity difficult to detect using infrared scanning?

Because they emit energy inefficiently and reflect their thermal surroundings.

What function do laminations in the stator core of a rotating machine perform?

They reduce eddy current losses.

If a current of $30\text{ A}$ is measured using a $100\text{ A}$, $3\%$ full-scale ammeter, what is the maximum percentage error relative to the actual measured reading?

$10\%$ (Maximum error = $3\%$ of $100\text{ A} = 3\text{ A}$; Actual error = $3\text{ A} / 30\text{ A} = 10\%$).

When drawing a liquid sample from a transformer, how much waste fluid should be flushed through the sample valve prior to collection?

Two quarts.

What is the best indicator of the state of charge of a flooded lead-acid battery?

Specific gravity.

In what order do medium voltage cable insulation types rank by dielectric losses, from lowest to highest?

1. PE (Polyethylene), 2. XLPE (Cross-linked Polyethylene), 3. PILC (Paper Insulated Lead Covered), 4. EPR (Ethylene Propylene Rubber).

What minimum load condition does NETA recommend when performing infrared thermographic scans?

A minimum of $40\%$ load.

What is the primary function of a Variable Frequency Drive (VFD)?

To control the speed of AC induction motors.

At what depth below earth surface must a ground ring be installed?

Not less than $30\text{ inches}$ below the surface.

What is the conversion factor from Megawatts to Kilowatts?

$1\text{ MW} = 1000\text{ kW}$ (e.g., $15\text{ MW} = 15{,}000\text{ kW}$).

How often must CPR recertification training occur for electrical workers?

Annually.

How often must rubber insulating blankets undergo electrical retesting?

Every $12\text{ months}$.

According to safety standards, is an electrically safe work condition considered a procedure or a state?

It is a STATE.

How is an ammeter connected to measure the current of a circuit component?

In SERIES with the component.

What is the calculated MVA rating for a $15\text{ kV}$ Vacuum circuit breaker operating at $13.8\text{ kV}$ with a short circuit rating of $25\text{ kA}$?

Approximately $597.54\text{ MVA}$ ($\text{MVA} = \text{SC kA} \times \text{Max Voltage} \times 1.732 / 1000 = 25 \times 13.8 \times 1.732 \approx 597.54\text{ MVA}$).

What are the percentage phase deviation tolerances permitted by NETA for fuses, contacts, and batteries?

Fuses = $15\%$, Contacts = $50\%$, Batteries = $20\%$.

What physical evidence indicates sulfation on flooded-cell lead-acid battery plates?

White salts appearing on the surface of the plates.

In a balanced Wye system, what are the relationships between line and phase voltage, and line and phase current?

Line voltage = Phase voltage $\times 1.732$; Line current = Phase current.

What is the definition of a circuit breaker?

A switch with overcurrent protection.

What is the primary role of an automatic circuit recloser in power distribution?

To automatically reclose following a trip operation due to a transient fault, minimizing outage duration.

What is the maximum allowable interval between arc flash hazard data reviews?

5 years.

What is the nominal cell voltage of a lead-acid battery?

$2\text{ volts}$ per cell.

What physical property of a circuit breaker “contact measurement” is LEAST affected by ambient temperature?

Contact resistance.

What is the range of K-factor values assigned to K-rated transformers?

$1\text{ to } 50$.

What is the purpose of harmonic restraint on a transformer differential relay?

To prevent the relay from tripping on magnetizing inrush current.

At what body current range is ventricular fibrillation expected to occur from a 1-second, $120\text{ V}$, $60\text{ Hz}$ hand-to-foot shock?

$100\text{ to } 2000\text{ mA}$.

Facing the low-voltage side of a transformer with subtractive polarity, where is terminal X1 located?

Over the left shoulder.

What do the letters P, S, and Q represent in electrical power calculations?

P = True Power (Watts), S = Apparent Power (VA), Q = Reactive Power (VAR).

How much voltage must Electrical Hazard (EH) rated safety footwear withstand under dry conditions according to OSHA standards?

$14{,}000\text{ V}$.

According to NETA ATS, what minimum certification level must an on-site crew leader hold in electrical testing?

Level 3 or higher.

How many members of a confined space rescue team or service must hold current certification in CPR?

At least 1 person.