NCC Practice Test 5
Conductors connected to the high leg of a four-wire delta system be color-coded with what color of insulation or tape?
Orange
A pocket knife can be used to deburr
PVC
Which of the following eliminates wrinkling or flattening when bending PVC?
Plug set
Which of the following protect the motor and control devices against overheating?
Solid-state overload relays
Which of the following is an NEC requirements for grounding and bonding cable tray installations?
Steel or aluminum trays may be used as equipment grounding conductors
A transformer can be checked for shorted turns using a
TTR tester
Which of the following describes circumference?
The distance around a circle
Which of the following occurs when the load applied causes the fibers on the tension side of the rung to stretch and permanently deform?
Transverse failure
What kind of mounting is often used in tunnels and other underground installations where equipment is separated by long distances?
Wall mounting
A triplen harmonics neutral current can be reduced by
adding harmonic filters at the load
Before starting a cable pull, make sure that
all communications equipment is in working order
A transformer that has the secondary winding connected in series with the primary at a junction terminal is an
autotransformer
Two 90 degree bends in the same piece of conduit are required for a
back to back bend
The most desirable method of exiting cable from a cable tray is
between rungs or from the end of the tray using a dropout plate
If the resonant frequency is near the harmonic voltage, the resultant harmonic current can
blow the capacitor fuses
The radius of a circle is defined as
the distance from the center point to the edge of the circle
In short vertical runs, the cables are usually supported by
the vertical riser elbow
Which of the following is a current transformer?
Oil-filled
A cable hanger elbow is used to
suspend cables in long vertical runs
The line voltages in a Y connection are
1.732 times higher than the phase voltages
Except for Type MC, all multiconductor cables operating at or above 600V must be separated by a solid divider from cables operating under
1000V
The resistance of switchgear should be checked using a
1000V megger
A buck-and-boost transformer has a primary current of 10A and the transformation ratio of 10:1. What is the secondary current?
100A
What is the standard output voltage of potential tranformers?
120V
An SSOLR initiates a trip if the phase currents exceed what percentage of the trip current dial setting?
125%
A typical hand-crank wire puller, using 30 pounds of force, can pull up to
1500 pounds
In a step-down transformer with a 4.16kV primary delta connection and 480/277V wye secondary, the transformer turns ratio is
15:1 (4160/277)
When performing thermographic surveys, a major deficiency is indicated by a gradient of
16* C
Given a cable tray that is available in the standard widths of 6, 12, 18, 24, and 36 inches, what is the minimum width of a 3 inch deep cable tray used for the following cables that are all 4/0 or larger: two with 1.5 inch diameter; three with 1.75 inch diameter; and two with 2.5 inch diameter?
18 inches
The contactor sequence for the circuit shown in the figure above is such that during the transition from reduced-voltage operation to full-voltage operation, the energized contactors are 2S and
1S
two junction boxes are each located on different walls, 12 inches from the same corner. Given a 90* bend with a take-up of 6 inches and a gain 2-1/4 inches, what is the developed length of the conduit between them?
21 3/4"
What is the voltage of the secondary in a transformer with 200 turns in the primary, 20 turns in the secondary, and an input voltage of 2,400V?
240V
Wires from a sensor to a ground fault relay should be no longer than
25'
What is the maximum length of cable weighing 5lbs/ft that can be pulled through a 45 degree bend with a coefficient of friction of 1.48 using equipment with a maximum pulling force of 2,000 pounds?
270
Which of the following types of transformers must be installed in a vault?
35kV oil-insulated transformers
When creating an offset using 10* bends, with a multiplier of 6, to cross a 6 inch obstruction, the distance between bends is
36 inches
The expected weight of an installed cable tray system is 300 pounds. Each support must be capable of carrying
375 pounds (125%)
Refer to the figure above. A multi-tap transformer has 1620 turns in the primary. There are 40 turns between each tap. Taps 3 and 6 are connected. Which taps must be connected to reduce output voltage by 5%?
5 and 4
The voltage imbalance trip point for a programmable solid-state overload relay is typically set for
5%
In general, the sidewall load on any raceway run should not exceed
500 pounds per foot of bend
Refer to the figure above. Which taps should be connected to increase the secondary voltage by 5%?
7 and 2
Which of the following can be used to bend IMC?
A hickey
Which of the following characteristics is an advantage for using an electromechanical relay versus a solid-state relay?
Ability to withstand surge currents
When does an off-delay relay provide the time delay?
After the relay is de-energized
Which of the following refers to the total load seen by the CT secondary?
Burden
Which symbol in the figure above represents a normally open, timed open contact of a timing relay?
C
Which of the following abbreviations is used on electrical drawings to represent an oscilloscope?
CRO
What components are installed to increase the power factor and decreases the cost of electricity caused by large inductive loads?
Capacitors
The formula pi x D is used to calculate
Circumference
Most NEMA-rated general purpose motors have an overcurrent trip class rating of
Class 20
Which of the following transformers is the most appropriate type of transformer to use for series street lighting?
Constant-current transformer
What type of transformer provides 120V between center-tapped terminal and each ungrounded terminal on either side and 240V across the full winding of each phase?
Delta-Delta
Which of the following types of transformers can be ventilated, air-cooled, or sealed?
Dry-type transformers
Which of the following should be used to cut EMT?
Hacksaw
Which of the following tests is conducted in order to detect loose connections?
Heat scanning test
Which of the following readings may indicate a problem when detecting neutral overloading in a receptacle branch circuit by measuring the neutral-to-ground voltage?
Higher than 2V
Which of the following forces are always present in an AC circuit?
Inductance and true power
When voltage is stepped down in a transformer, what happens to the current in the same circuit?
It is stepped up
Which of the following refers to the condition in which two circuits share the energy of one of the circuits?
Mutual induction
Capacitors are covered in
NEC Article 460
The installation of resistors and reactors is covered in
NEC Article 470
The three sections of switchgear enclosures are the front section, the bus section, and the
cable or termination section
To select a buck-and-boost transformer, use
charts provided by the manufacturer
A die used to
cut the threads in conduit
Field marking of service equipment shall include the
date fault current calculations performed
Welding cable may only be installed in a
dedicated cable tray
The insulating oil in a liquid filled transformer should be regularly tested for
dielectric strength
The method of supporting cable trays using threaded rods and hanger clamps is known as
direct rod suspension
Gain is best described as the
distance saved by the arc of 90* bend
Which of the following provides a curved surface for the cable to follow as it passes from the tray?
dropout plate
Most control transformers are
dry-type step-down
According to the NEC, neutral conductors size No. 6 and smaller must have a continuous marking of white or
gray
When installing single conductor cables in tray systems with conductors size 4/0 and larger, they must be
installed in a single layer
The voltages and currents used in the primary circuits of substations are reduced to usable levels by
instrument transformers
To ensure maximum safety in a control transformer, the secondary control circuit is
isolated from the primary line circuit
Nonstandard abbreviations on electrical prints will typically be defined on the
legend
Symbols used to show cable tray systems on working drawings are explained in the
legend
In a potential transformer, the voltage across the secondary terminals is always
lower than the primary voltage
An ampacity adjustment of conductors in cable tray is more likely to be required when installing
multiconductor cable
In a three-phase, four wire system, the conductor that is most likely to be affected by nonlinear loads is the
neutral
Circuit breaker ratings are given
on the breaker nameplate
A right triangle is any triangle with
one 90* angle
The preferred method for checking for damaged conduit before pulling cable is
performing a test pull
A downed power line is most likely to result in a
phase failure
Which of the following is most commonly used to cut RMC and IMC?
pipe cutter
A device that is used to step up generated voltage to make it suitable for commercial transmission is called a
power transformer
The basic purpose of switchgear is to
provide power system protection by automatically isolating faulty components
The continuous current that a circuit breaker can carry without exceeding a standard temperature rise is known as the
rated current
One of the advantages of an SSR over an EMR is its
response time
The most important consideration for selecting a current transformer for relaying is the
saturation characteristics
Which winding of a transformer is connected to the load?
secondary
Magnetic leakage in a transformer causes a decrease in ______ when the transformer is loaded.
secondary voltage
Connection diagrams should be used to
show the internal wiring connections between the parts that make up an apparatus
A residence with 120V and 240V loads is likely to be served by a
single phase transformer with two secondaries
The developed length of a bend is equal to the
sum of the horizontal and vertical distances minus the gain
When three solid-state relays are connected in series, the supply voltage must be
triple the minimum operating voltage for a single relay
Specialty step-down transformers are often
used for small work, such as doorbells and other signaling systems
The maximum 60Hz voltage that can be applied to a switch for one minute without causing insulation failure is known as the
withstand rating
A three phase, four wire system that has the advantage of providing three-phase power and allowing lighting to be connected between any of the secondary phases and the neutral would have a
wye secondary
The three basic methods of sensing ground faults are ground-return, residual, and
zero sequence
