3rd 6th months Flashcards
Deceleration valves are usually used in meter-out configuration.
True
Accumulators may be installed in a system to absorb
shock
What is the purpose of the blast valve
the blast valve allows air to pass through the orifice plate and orifice ring. this air blows the arc from the stationary fingers to the arcing probe. it also cools and lengthens the arc so it will be extinguished at the next current zero.
What are the links in the power system chain
generator power transformers switchgear transmission lines distribution circuits utilization apparatus
Compared to a pressure regulator, a pressure-relief valve normally
protects the system from damage
Volumetric efficiency is equal to actual output divided by the _____ output.
theoretical
A line designed to return a fluid back to a piece of equipment in order to maintain a desired fluid level, temperature, pressure, or flow
recirculating line
A single-stage sliding vane compressor normally can produce a pressure of up to
50psi
The conservator system is used on transformers to
preserve the dielectric strength of the transformer oil
The most common way to remove water vapor from the air leaving a compressor is to
cool the air
Pressure reducing valve with internal check valve permits _____ free flow
reverse
Most fixed displacement vane pumps utilize the ______ cartridge design
balanced
How is the air for breaker operation dried
By conducting the air up through an automatic drying system. As the air reaches the top of the dryer it reaches its final dryness.
Of the following statements concerning mercury control switches, the one which is most nearly not correct is:
they are generally used only where circuit voltage is 120 volts or less
An axial-piston motor transmits force from the piston to the output shaft by means of
a cam plate and gears
plastic lined pipe would most likely not be used for the transfer of
oils
Greater pressure losses occur in a pneumatic system if the air is at ____ pressure, because of greater____.
low
friction
Steel pipe is used more extensively than any other type of pipe for penstock construction because:
of the degree of flexibility it offers in satisfying design criteria in all of the above areas
The main purpose of an exhaust-flow control metering valve on a pneumatic cylinder is to
limit the return-stroke speed
Pressure reducing valves are always drained
externally
Vacuum gauges are calibrated in inches of
mercury
How is the interrupter classified
the interrupter is classified as a multi-break double pressure unit.
Protective relay zones of protection are overlapped to
avoid leaving unprotected areas
A four-way valve may have how may ports
four or five ports
A transformer developed 120v in its secondary when a 2400v source was connected across its primary. assuming a primary current of .25 amperes the secondary current is
5 amps
2500v.25a=120vI
Transformer oil will lose its dielectric strength rapidly when
exposed to air or moisture
Federal law requires that pressure regulators for air hoses used for blowing chips have a maximum setting of
29psi
the closing time of an OCB becomes more important when it is considered from the standpoint of
synchronizing generators
A four-way valve has four
connecting ports
The point at which a relief valve first opens is called its ____ pressure
cracking
A 34.5kv circuit breaker has a rated interrupting capacity of 25000 amperes. what will be its approximate interrupting capacity when used on a 20kv circuit
25000 amps
amps@operating volt= amps @ rated volt * rated volts / operating volts
In a transformer, excluding the small amount of losses, the induced voltage per turn in the secondary winding is
equal to the voltage across each turn of the primary winding
the device used to boost pressure is called an
intensifier
Most water-coolers are designed for
great structural strength
Strainers that are used to automatically strain raw water to remove silt and debris are
self-cleaning
in many pipe systems, large pipe loops are used to
permit pipe expansion
The highest power output of a pneumatic motor occurs when its speed is
medium
A device by which contacts in one circuit are operated by a change in conditions in the same or another circuit is called a
relay
Of the particles listed below, the smallest are ___ particles.
aerosol
When the unloading valve is ____ operated, the spring force and pressure in the primary port are independent of each other
remotely
A device used to store fluid under pressure is called an
accumulator
Pressure switches on sf6 breakers are temperature compensated. why?
all pressure switches are temperature compensated in order to maintain a constant gas density.
In a pt the voltage drop from the polarity to the non-polarity marked terminals on the primary side is substantially in phase with the voltage drop from the polarity to the non-polarity marked terminal on the secondary side.
true
According to the principles of pneumatic leverage, every force increase has a corresponding
travel decrease
IN a transformer a _______ must always exist between the primary and the secondary fields to maintain the required primary current to supply the transformer losses and secondary load.
balanced condition
The type of knife switch usually used to interrupt field current to generators and synchronous machines is a
field switch
Particles larger than 10u are classified as
dust particles
In most hydroelectric developments the head and water flow will
fluctuate
Air pressure of 100 psi can create hydraulic pressure of 1000 psi if an air piston drives a _____ hydraulic piston
smaller-diameter
A back pressure valve can also be used as a ______ valve
unloading
Eddy currents are circulating currents that cause
a loss of energy
Protective relays may be classified in all of the below ways except for:
a. construction
b. movement
c. contacts
d. manner
D. according to the manner in which they are connected in the circuit
What are the four basic types of electromagnetic relay operating elements?
plunger
hinged armature
induction disk
induction cup
When used as a compressor discharge line, a pipe run should slope 1 in. for every ____ ft of pipe.
10
The energy needed to rapidly open the contacts of most circuit breaker designs is usually provided by;
springs and gravity
The most distinguishing feature of pipe threads is their
taper
In a pneumatic system, what provides the force that performs work
compressed air
Transformers permit the transfer of electricity between two circuits which are:
completely insulated from each other
In a typical reciprocating compressor, the intake valves are forced open by the
atmospheric pressure
When used to support a load, the valve functions as a ____-
counterbalance
A fuse may serve the same purpose in isolating a fault as a
circuit breaker
How is clean oil made available for interruption in the general electric type fk ocb
by a spring-driven pump
Explain what is meant by operating characteristic curves.
Graph, depicting the relationship of quantities that will cause the relay to operate.
What force enables a pneumatic motor to begin rotation under full load?
starting torque
Of the following statements concerning OCB’s the one which is not correct is
the AC arc is always extinguished during the first current zero.
A line in a pipe system designed for routing the full system flow around a particular piece of equipment is called
by-pass line
Impeller compressors deliver air at ____ volume and ___ pressure
high
low
Negative water-hammer pressure is created by:
a sudden increase in the demand for water
An increase in pressure on the secondary side of a pressure-regulating valve _______ the valve.
slightly closes
IN applications where the load might tend to run away, the flow control application should be ______
meter-out
Increasing the rate of cooling on a transformer will increase its capacity.
true
Circuit breakers are generally classified by
a. continuous current rating
b. interrupting rating
c. the amount of current that they will carry for a period of four to five seconds
all the above
Open circuits on power systems occur more frequently than short circuit faults.
false
When you disconnect an air hose with quick-disconnect couplings
make sure to wear eye protection
Differential current relays are designed and installed to protect against
internal faults
when a transformer’s windings are connected wye
the line current will be the same as the phase current
Mechanical separators are used in a pneumatic system for the purpose of
moisture separation
A surge tank is normally designed to accommodate how much of the water load rejected by the turbines
all of the load rejected
The advantage of the unloading a compressor is to allow it to
run without delivering air
When a pressure reducing valve is vented its outlet pressure is at its
minimum pressure
Whenever a circuit which is carrying current is opened
the current tends to continue to flow across the contacts as they separate
Why must the air in the breaker low air pressure system be very dry
because it is used as the interrupting and insulating medium between the contacts
The induction-disc time overcurrent relay has which of the following characteristics
definite-time and inverse-time
The flow of air through a normally closed, direct-acting solenoid valve is shut off by
a spring-actuated plunger
To differentiate between pipes carrying different substances, pipe systems are often
color coded
The main purpose of an exhaust-flow control metering valve is to
restrict the flow of exhaust air
The best hydraulic rectangular cross-section occurs when
y=b/2
Speed is a desirable quality during the tripping operation of a circuit breaker to
make it less difficult to extinguish the arc, reduce the damage which could be caused by a fault, and protect equipment not directly involved in the fault area.
An advantage of wetted filters over dry filters is that wetted filters
can be cleaned many times
Flow through a pressure compensated flow control valve is subject to change with variations in oil ______
temperature
Small ice needles which form at the bottom of fairly quiet, shallow bodies of open water are called
anchor ice
Compared to the secondary of a loaded step-down transformer, the primary has
higher voltage and lower current
in a core-type transformer
a section of the primary and secondary windings are wound around each leg of the core
Cracking pressure of a simple poppet-type relief valve is determined by the
spring adjustment
All protective relaying may be classified according to the
function they perform
A device used to check oscillation or level out the movement of the fluid in a pipe system is called a ____
snubber
Compared to other kinds of compressors, centrifugal compressors
require more power
The high dielectric strength of gases, such as sf6, under static conditions is maintained by
pressurizing
If an air hose is not completely depressurized when you disconnect it, the greatest danger to you is a sudden
blowing of dust or chips
When the flow control valve controls the amount of oil going in to the actuator, the application is_____
meter-in
When is the breaker trip-free
when it is closed to a fault or when the control switch is held in the trip position after a closing operation is completed.
The device designation 52y indicates the device is a ____
circuit breaker anti-pump auxiliary
A centrifugal compressor that can deliver 150000 cfm at 150+ psi typically has all the following advantages EXCEPT:
A. delivery of oil-free air
B. nearly constant discharge pressure
c. low floor area requirement per cfm delivered
D. low horsepower requirement per cfm delivered.
d.
Wood-stave pipe would probably not be used for
heads above 500 feet
Protective relays may be classified in all of the below ways except for:
A. according to their construction
B. according to their type of movement
C. according to their contacts
D. according to the manner in which they are connected in the circuit
d
Water often collects in a pneumatic system, because when air is compressed its _____ decreases
moisture capacity
A pipe fitting used to join lengths of pipe to permit easy opening of a line is called a
union
A fine-mist lubricator should be used in a pneumatic system if the air flow is _____ and/or the distance to the equipment is ____
intermittent
long
If a sequence valve is installed in a cylinder line it should contain a
check valve
Bushings are used on transformer to
serve as entrances into the transformer for the main leads
The conditions that must be met when transformer are operated in parallel are
a. ratio of transformation approximately the same
b. voltage rating approximately the same
c. polarity must be the same
Of the following statements concerning mercury control switches, the one which is most nearly not correct is:
A. they are silent operating
B. they may be provided with single or double throw action
C. they are generally used only where the circuit voltage is 120 volts or less
D. they are maintenance free
c
Which type of positive-displacement compressor does not need timing gears to drive the compressor lobes
wet screw
Polyphase rotating equipment may be protected against single phase operation by using a
phase-balance relay
An internal spring is sometimes used to return the piston in a _____-acting, ______-rod pneumatic cylinder
single
single
The head obtained by subtracting the head loss from conveyance of the water to the turbine by conduit, through the turbine and back to the river, subtracted from the gross head is called
effective head
A valve has five connecting ports, two of which are exhaust ports. this valve is a ___ valve
four-way
A brake valve is used to prevent
overspeeding and excessive pressure
Current transformers are used with: A. ammeter B. watt meters C. protective relays D. all of the above
d
plasma is defined as
the state of matter in which electrons are removed from atoms or molecules, creating an electrically conducting gas.
The current flowing out at the polarity marked terminal on the secondary side of a current transformer is substantially in phase with the current flowing in at the polarity marked side or terminal on the primary
true
pneumatic cylinders differ from hydraulic cylinders mainly by
needing no return lines
hysteresis can be explained as
friction of the molecules due to alternating current
Where frequent cleaning is necessary, it is best to use
duplex strainer
Applying heat to a specific volume of gas in a closed container will
increase gas pressure
The primary reason for not replacing a blown fuse with a piece of copper wire is because
the desired circuit protection against overload may be lost
Rotary-screw compressors run at speeds ranging from ____ to ____ rpm
3000
12000
A back pressure type valve is normally
open
Most pipe is generally coated on the outside with paint, galvanize, or insulation to prevent
corrosion, condensation, and heat loss
A blowout coil would most likely be found in
an air magnetic circuit breaker
A well designed protective relay system should provide three basic operational characteristics. what are they
reliability
selectivity
speed
A diaphragm-type relief valve responds very quickly to a pressure change because of its
large pressure-sensitive area
Penstock velocities may range from
6 to 20 ft/sec
The relay-time setting is adjusted by means of
time-index lever
Limiting compressor output with a pressure-control valve may be accomplished by
holding open the valve ports
The minimum velocity of water in a power canal to prevent the deposit of silt is
2 to 3 feet per second
A diaphragm-type relief valve responds very quickly to a pressure change because of its
large pressure-sensitive area
The light spring in a restrictor type flow control holds the pressure compensator normally___
open
Of the following statements, the one which most nearly describes what is meant by trip-free operation is:
A. disagreement function at the control switch
B. protective relay action
C. ability to trip under load
D. the precedence which takes place over any closing operation
d
sf6 is one of the most stable compounds. in a pure state it is inert, nonflammable, nonpoisonous, odorless, and produces no harmful effects on personnel. what is the drawback of using sf6 gas in a circuit breaker
after the sf6 is exposed to an electric arc there will be some break down of the gas, and filters must be used to remove gaseous by-products and powders.
What is the definition of a protective relay
it is a device when energized by suitable currents, voltages, or both, respond to the magnitudes and relationships of those currents and voltages to indicate or isolate an abnormal condition
Small compressors generally control air pressure in a pneumatic system by
starting and stopping the motor
A series street lighting system requires what type of transformer
a constant current transformer
A transformer with more turns on the secondary than on the primary is called a
step-up transformer
A protective relay which responds to a difference in values of current at two different points in a circuit is known as a
differential relay
A fast realistic circuit breaker opening operation (arc-out time) would be
three to four cycles
How much work is done by a piston that exerts a force of 15lb through a distance of 10in
150 in-lb
What type of turbine has variable vane design and can be used for both pumping and generating
deriaz
Lines that reduce wear and make large valves easier to open are ____ lines
pressure equalizing
A relay which would normally respond to changes i8n circuit admittance, impedance, and reactance is called a
distance relay
A high current are ( in excess of 100 amperes) in air has a nearly constant drop or around ______ volts per foot
400
Proper pipe connection and installation requires that you use
straps and hangers to support long runs
The least efficient type of high-line conduit is that type which
has the greatest effect on the available head
A 90 degree pipe fitting with both inside and outside threads is called
street elbow
Two cylinders having different diameters are connected by an air line. A force applied to the smaller piston makes it move. in response, the larger piston exerts a force on a load and makes it move. the force on the load is ___ the force applied to the smaller piston, and the distance the load moves is ____ the distance the smaller piston move.
greater than
less than
The horsepower of a pneumatic motor varies with the ___ and the ___ of the motor shaft
speed
torque
If the input to a 5 to 1 step-down transformer is 100 amps at 200 volts, the output will be approximately
500 amps at 40 volts
What is the induced secondary voltage of a transformer having a primary winding of 3000 turns and a secondary winding of 300 turns, when connected to a 2400 vac source
240 volts
How does the “x”-“y” control scheme used with this breaker differ from a typical one?
what is the purpose for the difference?
the “x”-“y” control scheme differs by the introduction of a low pressure cut out switch in the high pressure system, in series with the closing circuit.
the low pressure cut out switch has two contacts, one prevents the breaker from closing when insufficient gas pressure is available to open it, the other is in the trip circuit and will trip the breaker as a low gas pressure is reached
open conduits constructed in natural ground are called
canals
Which of the following is true of inertial separators
they are used mainly to remove large particles
When CT’s are used with protective relays the direction of current flow in the transformer windings
must be carefully observed for relay types which depend on the interaction of tw3o currents for their action
The main difference between a circuit breaker and other kinds of electrical switches is that circuit breakers
open automatically when the current exceeds a predetermined limit
The ___ valve is a good throttling device and is suitable for high-pressure service. it causes ______ pressure loss in the line
needle
high
Which if the below statements does not correctly describe a means or method for quenching an arc?
A. increasing the length of the arc path
B. reducing the reluctance across the contacts
C. restricting the cross-sectional area of the arc path
D. deionizing or cooling the gas
B
Water-cooled aftercoolers are typically used with____-capacity compressors that run______ hours a day
large
ten or more
The conduit between the turbines and the surge tank is called the
penstock
an auto transformer has
one winding which is composed of both the primary and secondary winding
With a higher velocity, the cross-section of a conduit or conductor can be ___for a given quantity of flow
smaller
in circuit breakers the arc is normally quenched
by increasing the resistance across the contacts
in relation to the size of a pneumatic cylinder port, the valve port size
must be equal
A partially clogged trash rack will
cause a decrease in the effective head
An induction-disc time overcurrent relay
is adjusted separately for the degree of overcurrent at which it operates and also for the amount of time delay
Rotary actuators differ from pneumatic motors in what way
incomplete rotary motion
Transformer are classed as static AC machines
True
Laminar airflow in a piping system is made turbulent by
constrictions in the pipe
If the vent connection of a relief valve is opened to tank the pump is said to be ___
unloaded
A female end pipe fitting used for joining two lengths of pipe is called a
coupling
Disconnect switches are commonly used on 440 or higher voltages circuits to
isolate or to ground equipment or circuits not in service
A cylinder that must be free to pivot requires what type of mounting
trunnion or clevis
What is meant by the term wetted perimeter
surface area that is in contact with the water
A____ in a pipe system is normally a pipe enlargement or volume chamber having an inlet and outlet located at the top and a drain line from the bottom
separator
The term zones of protection applies most nearly to the isolation of faulted equipment
throughout the entire power system
Disconnect switches are commonly used to isolate electrical equipment or circuits during
periods of maintenance
The best way to guard against excessive pressure on the secondary side of a pressure regulator is to
use a regulator with a built-in relief valve
A riveted pipe produces a lower hydraulic loss than a fabricated welded pipe
false
a 4.8kv circuit breaker has an interrupting rating of 30000 amperes. what is its interrupting capacity when used at5.1kv
28235amps
hysteresis and eddy currents are known as
iron losses
Sudden pressure relays are for the protection of
transformers
The primary or inlet filters of many compressors should only be cleaned with
a recommended solvent
Transformers having only one winding are called
autotransformers
an alternative to lining a canal for protection against erosion is to
increase the cross-section of the canal
A trip-free operation takes place if
a circuit breaker is closed while the protective relay is energized
the most efficient method of reducing the output of a centrifugal compressor is ____, but it may not work well if the reduction is too ____
speed variation
large
A relief valve is normally
closed
Which of the following kinds of pipe would be affected least by corrosion? A. steel B. cast iron C. Brass D. stainless steel
D
How long does the reactivation process take
the process lasts the same amount of time as the compressor has run to recharge the receiver.
The circuit diagram usually gives the following three items of information about currents and voltages. eliminate one. A. location B. direction C. polarity D. magnitude
D
The differences among three-way valves mostly come from the
ways connections are made
Which of the below conditions would probably not cause the water level in the riser of a differential surge tank to fall
A. a sudden load increase
B. conduit velocity insufficient to supply the demand for water
C. negative surge waves
D. a load rejection
D
Fault power always
flows toward the fault
The cracking pressure of a simple poppet-type relief valve is determined by the
spring adjustment
all circuit breakers are provided with a means to
minimize arcing at the contacts as the contacts come together
A reciprocating compressor is one kind of _____ compressor.
positive-displacement
if operations take place in a certain order they are done in _____.
sequence
The core of a transformer is designed
to carry the magnetic field for the induction of voltages between the primary and secondary windings.
The secondary of a potential transformer should never be
short-circuited to remove the device it operates from service
A high speed relay is defined as a relay that has an operating time which does not exceed _____.
3-5 cycles
Which of the following contributes to laminar airflow? A. frequent directional changes B. a large number of fittings C. a large pipe diameter D. an increase in airflow velocity
C
The difference between a circuit breaker and other kinds of electrical switches is that circuit breakers are capable of:
A. closing into short circuit current without being damaged
B. carrying short circuit current without being damaged
C. interrupting short circuit currents without being damaged.
D. all of the above
D
A line designed to supply necessary water to form a seal at a clearance and to lubricate and cool the clearance
gland seal
Heating a gas in a sealed, rigid container, will _____ the _____ of the gas.
increase
pressure
Speed is a desirable quality during the tripping operation of a circuit breaker to:
A. make it less difficult to extinguish the arc
B. reduce the damage which could be caused by a fault
C. protect equipment not directly involved in the fault area.
D. all three
D
The only purpose of a pressure-relief valve is to
protect the system from damage
The use of a proportional valve requires the equipment contain _____ controls
electronic
What type of gas is preferred for gas charged accumulators
nitrogen
Polyphase rotating equipment may be protected against single phase operation by using a:
phase-balance relay
What is the most vulnerable portion of the chain
transmission lines
At a given temperature, the actual moisture content of air compared to what it could hold is stated as the
relative humidity
Pipe having a diameter of less than 12 inches is usually designed by its
inside diameter
One of the major advantages of using a pressure tunnel in a power conduit system is that
it permits full use if the available head
Which type of manually operated, two-way valve can be can be converted into a three- or four-way selector valve?
plug valve
The secondary of a current transformer should never be
opened to remove the device it operates from service
A desiccant removes water from air by _____ it.
absorbing
When the flow control is teed off the supply line from the pump and determines the actuator speed by metering a portion of the pump delivery to tank, the application is called___
bleed-off
A transformer developed 5 volts in its secondary when a 100 volt source was connected across its primary.
assuming a primary current of 2 amperes the secondary current is
40 amps
_____ are use to prevent excessive rise of the water at any point in a hydraulic development
spillways
The accepted industry standard for showing relay contacts on circuit diagrams is to show the contacts in the position they assume when the relay is _____
de-energized
A filter’s ability to remove 100% of the particles of a given size is referred to as its
absolute rating
Circuit breakers are generally classified by:
A. their continuous current rating
B. their interrupting rating
C. the amount of current that they will carry for a period of four to five seconds
D. all three
D
Protective relays, in general, must be able to:
A. remove or isolate the local area of a fault from the rest of the system
B. locate faults and trips only those circuit breakers directly connected to the faulty equipment
C. differentiate between permissible operating conditions and abnormal or fault conditions
D. all of these
D
Which type of media is most likely to be used in a depth filter
closely packed fine metallic wire
A blowout coil would most likely be found in
an air magnetic circuit breaker
Single-stage sliding-vane compressors can produce pressures up to____psi
50
When the chamber above the balanced piston of a relief valve is opened to tank, it is said to be______
vented
The best canal cross-section from a hydraulic point of view is defined as
the one that has a minimum wetted perimeter
The protective device for a motor branch circuit should
not be of the instantaneous type
How do relays reduce the number of alternate links
they avoid equipment damage or limit damage to a single unit
Which factor will affect your pressure calculations by increasing the air’s dynamic viscosity
raised temperature
A power transformer transfers electric power from one circuit at a certain frequency and voltage, and to a second circuit at
a different voltage and same frequency
y-type strainer should be installed
either vertically or horizontally
Greater pressure losses occur with air at ____, because of___
low pressures
friction
A line used to control the concentration of impurities in a pressure vessel is a ______ line
blow down
When should you use pipe joint compound in connecting NPT-threaded pipe
always
In a/an _____ piston pump the cylinder block turns with the drive shaft, but at an offset angle
bent axial
Most pumps have a ______ displacement which cannot be changed except by replacing certain components
fixed
Of the following statements, the one which most nearly describes what is meant by trip-free operation is
the precedence which takes place over any closing operation
Intra-vane pumps have holes drilled through the rotor segments to _____ pressure above and below each vane at all times
equalize
The force that does the work in a pneumatic system is the
compressed air
The efficiency of a well designed transformer is
an average of 98%
To make flanged joints pressure tight, ____ are usually inserted between the flanges.
gaskets
Transformer polarity markings show
the ends of the windings at which the induced voltages have the same instantaneous polarity
When the number of turns or voltage on the secondary of a transformer is grater than that of the primary, it is known as a
step-up transformer
The purpose of an intercooler between the stages of a two-stage compressor is to reduce the
power needed to run the compressor
Speed of an actuator may be regulated with a _____ valve
flow control
The device used to convert a pressure signal to an electrical signal is called a____ switch
pressure
Regardless of the percentage of fluid in a weight loaded accumulator the pressure remains
constant
The device used to protect a pressure gauge from surges is called a
snubber
Generally speaking, which method of controlling centrifugal compressor output is the least efficient
recirculation
All pipe systems should be installed in accordance with
ascpp
Two principle types of pressure gauges are the shrader and
bourdon
The main purpose of the receiver in a pneumatic system is to
maintain pressure during peak demand
A three-phase 138kv circuit breaker can interrupt 12000 amps. what is its interrupting capacity in mva
1656mva
The spool in a valve controls the flow of air by _____ from one position to another. in a high-pressure system, the spool is ____ to move
sliding
easy
The light spring in a by-pass type flow control holds the pressure compensator normally
closed
The term zones of protection applies most nearly to the isolation of faulted equipment
throughout the entire power system
Positive water-hammer pressure caused by a sudden decrease in the demand for water can be eliminated by: A. a relief valve B. a pressure-regulator C. a surge tank D. any one of the above
D
A base-load plant is a plant without pondage and where the full plant discharge is the same as the flow of the river
false
The cooling efficiency of air-cooled compressors is improved through the use of
cooling fins
A single phase transformer may have a
air core
A three-phase 138kv circuit breaker can interrupt 12000amps. what is its interrupting capacity in mva
1656mva
What is the usual method for compensating for a low-speed drive in a rotary-screw compressor
a speed increaser
The rating of a transformer is usually given in : A.VA(volt-amperes) B.KVA(kilovolt-amperes) C.MVA(megavolt-amperes) D. all the above
D
A cylinder that must be free to pivot requires a_____ mounting
trunnion or clevis
A break valve is used in the ____ line of a hydraulic motor
exhaust
An induction-disc time overcurrent relay
is adjusted separately for the degree of overcurrent at which it operates and also for the amount of time delay
Of the following statements concerning OCB’s the one which is not correct is:
A. the dielectric strength of the arc gap is improved by forcing oil into the arc path
B. the oil serves to both insulate the tank from the live parts and to extinguish the arc
C. the AC arc is always extinguished during the first current zero
D. all OCB’s are equipped with a vent which is usually located at the top of the tank
C
The purpose of a blowout coil in a circuit breaker is to
quench the arc
Which type of compressor raises air pressure by accelerating it
dynamic compressors
A 4.8 kv circuit breaker has an interrupting rating of 30000 amperes. what is its interrupting capacity when used at 5.1kv
28235
to simplify drawings of pipe systems, we use____ to represent various components
symbols
the two types of surge tanks are
simple
differential
A relay which would normally respond to changes in circuit admittance, impedance, and reactance is called a
distance relay
An advantage of four-way valve over two and three way valve is that they
simplify the controls
Protective relays, in general, must be able to:
A. remove or isolate the local area of a fault from the rest of the system
B. locate faults and trip only those circuit breakers directly connected to the faulty equipment
C. differentiate between permissible conditions and abnormal conditions
D. all of these
D
What type of gasket material would generally be used between the flanges of a piping system supplying low pressure cold services
rubber
Pumped storage type of hydroelectric developments implies a capability for:
A. improving load factors on inter-connected power system steam plants
B. providing a wider range of power system reserve capacity
C. improve peak load operation
D. all of the above
D
Pneumatic motors often fall under which classification
positive, fixed-displacement
Taps on a transformer allow the
output voltage to be varied
In an energized transformer iron losses are present even if there is no load on the secondary
true
To prevent negative pressure in a penstock where pipe is being used what is installed in the pipeline
air vents
The thrust that can be applied when the rod of a single-rod, double-acting pneumatic cylinder is moving out of the cylinder is _____the thrust that can be applied when the rod is moving into the cylinder
greater than
If flow from secondary to primary is required, the unloading valve control pressure should be______ above the spring setting
150psi
The initials TPDT would normally be used to identify a type of
knife switch
What is the purpose for the sf6 gas in a air-blast circuit breaker
sf6 gas is used to insulate the support column current transformer inside the support columns
Explain the difference between primary and backup relaying
primary is the first line of defense and isolates a minimum portion of the circuit
back-up relaying is the secondary defense and isolates a greater portion of the chain
Lubricating equipment in an air line should always be placed at what point in the system
after the regulator
When a transformer’s windings are connected delta
the line current will be greater than the phase current
A device which contacts in one circuit are operated by change in conditions in the same or another circuit is called a
relay
The purpose of lubricating oil in a compressor are to reduce friction between the moving parts and to
improve the cooling of the compressor
A fast realistic circuit breaker opening operation (arc-out time) would be
3-4 cycles
an axial-piston pneumatic motor transmits force from the piston to the output shaft by means of a
cam plate and gears
Pressure in the outlet port of an internally drained sequence valve adds to the __________ setting
spring
Differential current relays are designed and installed to protect against
internal faults
explain the multi-flow principle of arc interruption as used on the Westinghouse type gm osb’s
a number of inlet orifices and exhaust vents proportioned to the voltage rating are used. as the moving contact uncovers successive inlet orifices, the flow of fresh oil from the pressure generating chamber deionizes the entire length of the arc and interrupts it at a minimum length and in the shortest time
What is the advantage of the induction cup
instantaneous operation with the ability to monitor several electrical quantities
A major advantage of using a four-way valve in a automatic system is that it
simplifies the control circuit
Current transformers are instrument transformers used to
step current down
An unexplained drop of pressure or flow through a strainer is an indication of ______
plugging
You can determine whether a control valve can deliver air rapidly enough for a cylinder by calculating the _____ required by the valve
capacity coefficient
The energy needed to rapidly open the contacts of most circuit breaker design is usually provided by
springs and gravity
When used as a compressor discharge line, a pipe run should slope _____ in the direction of the airflow by 1 in for every ________ft of pipe
downward
10
When a load is being accelerated, pressure is maximum at the motor ____
inlet
High pressures at a gear pump outlet imposes an _____load on the gears and bearings supporting them
unbalanced
Where frequent cleaning is necessary, it is best to use
duplex strainer
The ground and the neutral point on a three phase system are by definition the same point
false
Which of the following is a common modification to single-acting cylinder construction? A. Cam valves B. limit switches C. a piston rod extending from each end D a spring piston return
D
An open conduit system implies
the presence of a free surface
In a transformer, both the primary to secondary voltage and turn ratio will vary inversely as the primay
to secondary current ratio
To determine the horsepower of a pneumatic motor, you need to know the
rpm and the torque
A trip-free operation takes place if
a circuit breaker closed while the protective relay is energized
When air flowing in a pipe reaches a section where the diameter is reduced, the speed of the air ____ and its pressure____
increases
decreases
In a transformer the winding which receives the energy inductively is called the
secondary winding
Pump ____________ is expressed in cubic inches per revolution
displacement
The plasma performs what essential function when breaking a circuit
The plasma arc provides a path for current to flow between two open contacts. if the current flow were stopped instantaneously, extremely high voltage induced by the current flow itself, would cause damage to the machinery the breaker was installed to protect.
In a typical reciprocating compressor, what causes the discharge valves to open
compressed air
Intake design has a large effect on: A. velocity B. volume C. head D. all three
D
Which of the below statements does not correctly describe a means or methods for quenching an arc?
A. increasing the length of the arc path
B. reducing the reluctance across the contacts
C. restricting the cross-sectional area of the arc path
D. deionizing or cooling the gas
B
The amount of horsepower required to drive a compressor may be reduced through the use of
two compression stages
From the below list of fuse characteristics select the one that is not true.
A. fuses are single-phase devices
B. the tripping time of a fuse is non-adjustable
C. some fuses are classified as current-limiting
D. all fuses are completely non-repetitive in design
d
The operation of an inertial separator depends on a
rapid change in the direction of air flow
The difference in pressure between the points where a relief valve first opens and passes full pump delivery is sometimes called ____
override
The gas precharge pressure in an accumulator should never be less than ___ the working pressure
1/4
The pistons in an ___ piston pump are parallel to each other and to the axis of the cylinder block
axial
Pumps are generally rated by their maximum operating pressure capability and their output in __ at a given drive speed
gpm
how much work is done when a 15lb force moves a piston a distance of 10in
150in-lb
In an ___ piston pump, the cylinder block and drive shaft are on the same centerline and the pistons retract parallel to the drive shaft
inline
What is the purpose of the auxiliary contacts
to protect the main contacts from burning by closing first and opening last
The highest torque a pneumatic motor can exert on a load is its ___ torque
stalling
Potential transformers are instrument transformers used to
step voltage down
A filter can stop 100% of the particles down to a specified minimum size. this size is called the filter’s ____ rating
absolute
A relief valve limits the ____ pressure in a hydraulic system
maximum
Piping supports or hangers are used to: A. provide rigidity B. prevent metal fatigue C. provide drainage D. all three
D
Generally OCB’s are smaller than air-blast breakers of comparable voltage and current ratings. why
Because of the higher dielectric strength of oil internal parts can be brought closer together
The term symmetrical components refers to a mathematical method of reducing any unbalanced three phase set of vectors into three ____ systems.
balanced
At a constant air temperature, the amount of moisture held in the air will
decrease as pressure increases
