2-2-1 Introduction to Test Instruments
4) AC voltage is voltage in a circuit that reverses its direction of flow at regular intervals and is stated and measured as a peak, average, or __?__ value.
RMS
35)Danger
Red One
8) The metric system adopted the __?__ as the standard unit of time measurement.
Second
9) Turns ratio is the ratio of the number of turns in the primary winding to the number of turns in the __?__ winding.
Secondary
11) Large power transformers are generally manufactured with __?__ polarity.
Subtractive
5) Indicate the polarity of the following transformer: 4,160 volt, 333kVA
Subtractive
13) A closed switch that is operating properly has continuity.
True
13) Always ensure that the jack position of the test leads corresponds to the setting of the meter function and selector switch before taking a measurement.
True
14) A 15kVA transformer is checked and is carrying 19.5kVA, it should be reported as overloaded?
True
14) If you use too small a fuse to test a transformer, it may blow due to exciting current.
True
16) During a temporary overload, the signal light will come on but the transformer will remain in service.
True
16) The polarity of a distribution transformer can be changed by exchanging the internal leads on the secondary between X1 and X3.
True
16) The primary of a transformer designates the winding that is supplied with electricity.
True
16) With the secondary coils in series, the full load current remains the same as one coil.
True
17) A CSPs primary lead should be taken off line before working on the secondary because the secondary might have enough capacitance to shock.
True
17) The nameplate on a new distribution transformer shows the polarity of the transformer as it was manufactured.
True
18) A dry type transformer is cooled by ventilators cut into the metal case.
True
29) Michael Faraday discovered the principle of electromagnetic induction.
True
5) Older transformers, pre1959, had all the taps below 100% in order to always increase the secondary voltage.
True
7) Under short circuit conditions, the red light and the secondary breaker will trip at the same time.
True
7) Voltage is induced in the secondary coil of a transformer by electromagnetic induction.
True
13) With the coils connected in series, a dualvoltage transformer will operate on __?__.
the higher of the two voltages
15) Checking the winding continuity of a transformer is not important because transformers on the loading dock can be relied on.
False
17) In a star system, the phase angle displacement through a transformer bank (primary to secondary) is either 0º or 160º.
False
8) If the secondary voltage is listed on a transformer as 120\240 or 240\120, it makes no difference as both internal secondary coils can be connected in parallel or series.
False
8) It takes three maximeters to properly record a singlephase transformer.
False
10) The absolute zero scale of centigrade is often called the __?__.
Kelvin
13) It is the __?__ responsibility to check the internal connections on a four bushing transformer prior to making the connections externally.
Linemens
36) Warning
Orange One
8) The product of the primary voltage and current is equal to the product of the __?__.
secondary current and voltage
7) A dash () between the primary and secondary voltages of a transformer is used to __?__.
separate the voltages
9) Two types of electrical transformer cores are __?__.
shell and core
2-2-11 SinglePhase Transformer Connections 1) When the secondary coils of a 120\240 singlephase transformer are connected in parallel, the transformer will only deliver 240 volts phase to ground.
False
2-2-15 Vectors 1) The term for the lines which represent the relationship between phases is vector (phasor in some sections of the industry).
False
2-2-4 Transformer Construction 1) Round wire is the only type used in transformer coils.
False
3) Long term voltage peaks can be shown by taking several clipon amp readings.
False
29) An arc __?__ is an extremely hightemperature discharge produced by an electrical fault in the air.
Flash
9) One advantage of voltage testers is that they have a lower impedance (resistance) and draw more current than voltage indicators, which allows them to be used for testing __?__.
GFCIs
16) Most distribution transformers are cooled by oil and air.
True
4) A transformer explosion can result from a(n) __?__.
permanent fault
4) A transformer will burn out if connected to DC because of the selfinduction that DC generates.
False
4) In order for a singlephase transformer to produce any secondary voltage, the X2 grounding strap must be in place.
False
4) PCBs may be present in distribution transformers manufactured after 1980.
False
4) There is only one set of secondary contacts in a CSP transformer.
False
5) The higher the number of turns on the secondary side, the lower the output voltage.
False
6) The high voltage winding is normally placed next to the core to increase EMF.
False
19) When using a test instrument with test leads, the __?__ lead should be connected first.
Ground
16) A neutral is a grounded conductor while a ground wire is a(n) __?__ conductor.
Grounding
21) A broken wire at the transformer grounding lug, on a single bushing transformer, is dangerous because it connects __?__ to __?__.
H 2 \the system neutral
15) The primary link will remove a(n) __?__ faulted transformer from the system.
Internally
16) When voltage is consistently __?__, a company will, as a temporary measure, change the tap setting on the transformers, if the transformers are so equipped.
Low
26) Voltage measurements using the __?__ on a digital multimeter are useful in identifying low voltage conditions.
MIN MAX mode
5) Two reasons other than followthrough current which may overheat a transformer are a Short circuited secondary and a(n) __?__.
Overload
12) A popsicle stick connector is a __?__ terminal connector which is squeezed onto the end of the wire and inserted into the secondary terminals of a transformer.
Pin
17) Distribution transformers have offload tap switches, which do not in any way regulate the __?__ voltage.
Secondary
10) When voltage measurements are different from what is expected, the voltage measurement is most likely to be lower than normal.
True
12) Connecting the secondary leads marked A, C and B, D on a 120\240 volt transformer for 120 volt service is the same regardless if the transformer has three bushings or four.
True
12) Current flows into a singlephase transformer in the H1 terminal and out the X1 terminal at the same instant.
True
12) Graphical illustrations using vectors show direction and magnitude.
True
12) If the turns ratio is shown as 10:1, it is a stepdown transformer. If the ratio is shown as 1:10, it is a step up transformer.
True
12) Since a singlephase distribution transformer has two secondary coils, it is possible for only one coil to be overloaded.
True
12) The most commonly used CSP transformer in the electric industry has two mounting brackets.
True
12) The primary coils of a dualvoltage transformer can be connected in series or in parallel.
True
14) It is critical to check polarity on older distribution transformers because it might be of either additive or subtractive polarity.
True
14) The main reason for the increase in the use of digital electronic technology is for greater measuring capability.
True
15) One reason to be careful if you have to change internal taps on a transformer is because PCBs may be present in the oil.
True
15) When using an ohmmeter, the resistance of all components connected in parallel with the component being tested affects, and typically lowers, the resistance reading.
True
34) The resistance of test leads must be less than __?__ Ohm(s).
1
5) The internal transformer lead marked D is always connected to X__?__ in an additive transformer.
1
10) On a CSP transformer carrying 250 amps that has tripped, using the emergency handle will give __?__ hour(s) of power.
1 1\2
17) With the secondary coils in parallel, the full load current is doubled, but the voltage is cut in half.
True
18) Analog test instruments are less accurate than digital test instruments.
True
2) A permanent test instrument is a device that is installed in a process or at a bench to continually measure and display quantities.
True
2) A two bushing singlephase transformer can be connected to a wye or delta system.
True
2) On a transformer nameplate, a slash (\) between the secondary numbers means both voltages shown are available.
True
2-2-12 Transformer Protection 1) Heat and voltage surge are two reasons for insulation breakdown in a transformer.
True
2-2-14 Specific Hazards Working With Transformers 1) OSHA does not require a written job briefing if you are working alone.
True
2-2-2 General Use Test Instruments 1) A portable test instrument is used to take real time (momentary) measurements.
True
2-2-3 Introduction to Transformers 1) The largest advantage AC has over DC is that it can be transformed from one voltage to another.
True
2-2-8 Tap Changers and Tap Changer Operation 1) Ratio adjustment of a distribution transformer is accomplished by the use of a tap changing switch.
True
21) A clamp on ammeter is typically used to measure current in a circuit with over one amp of current.
True
21) The primary purpose of rubber insulating gloves is to insulate the hands and lower arms from possible contact with live conductors.
True
28) Knowing the vector displacement of a bank becomes critical when paralleling three phase banks.
True
28) With the use of CTs and PTs, conventional meters can be used to measure high current and high voltage circuits.
True
5) Paralleling transformers is often done to avoid outages.
True
5) The point where high voltage leads are brought out of a coil are considered critical points for insulation.
True
6) The red indicator needle on a maximeter indicates the load at the time of the reading.
True
7) A transformer tank may become energized on a single bushing transformer if the tank is not grounded and a backfeed situation happens.
True
7) Double bushing tapped transformers normally have one tap above 100% in order to lower the secondary voltage.
True
8) During an outage, a customers generator can cause backfeed at the transformer.
True
9) A conventional transformer can be used as a primary booster but must be marked as a hazard.
True
37) Caution
Yellow one
20) Another requirement of the 1996 Migratory Bird Treaty Act regarding new transformer installations to protect birds from electrocution is to install __?__.
insulated transformer leads
19) A polarity test should be performed on a transformer with a missing or damaged nameplate and the polarity __?__ on the transformer case.
marked
2) The Romans refined distance traveled to a unit of length called the __?__.
mile
4) The bakedon insulating compound used in transformer coils prevents __?__ from getting into the windings.
moisture, dust and dirt
20) Inline ammeters require the circuit to be __?__ so the ammeter can be inserted into the circuit to acquire a reading.
opened
4) A transformers secondary must be __?__ when used as part of a 120\208 threephase bank.
paralleled
9) A current limiting fuse in series with the cutout will __?__.
reduce the risk of violent transformer failure
22) If a transformer was ordered 24,940 Grd Y\14,400, the transformer would have __?__ insulation at the H 2 end.
reduced
16) While doing a preinstallation check on a transformer, the check that should not be done unless permission is granted from your employer is to __?__.
remove the lid
3) The basic subunit of the ancient Egyptians royal cubit stone is the span.
False
13) On a fully loaded 25kVA transformer, the drop leads would normally be __?__ stranded copper.
#2
14) In order to plot a threephase system or systems, you need special tools or equipment.
False
9) Total phase current times line to neutral voltage equals kVA.
False
23) The arrowhead on a vector line indicates the __?__ polarity.
Positive
11) The winding which receives the energy is the __?__ winding.
Primary
13) To vector a threephase system, it is essential to establish a __?__ of the phases.
fixed reference
17) Transformer oil must have a __?__ strength.
high dielectric
13) Adding more turns to a coil __?__ the magnetic effect.
increases
21) A power plant transformer __?__ the voltage and __?__ the current on a transmission line.
increases\reduces
3) The process which limits current flow on the primary winding is self__?__.
induction
6) The red light on a CSP comes on as the transformer __?__.
is reaching overload
4) A followthrough current initiated by __?__ may overheat a transformer.
lightning
16) One reason paralleling two small transformers for increased demand is not economical is because the __?__, when added together, is\are greater than in one large transformer.
losses of each transformer
2-2-7 Transformer Polarity\Connections 1) The industry standard for the location of an H1 terminal when facing the __?__ is the left hand side.
low voltage side
8) As the primary voltage drops, you __?__ the percentage on the tap changer to raise the secondary voltage.
lower
8) Transformer output voltages have __?__, __?__ phase angle, and phase sequence.
magnitude\direction
2) In a Wye connection, the tail of the lines is connected, which represents the __?__ of the lines.
negative
15) Paralleling two small transformers for increased demand is not economical because __?__.
of the cost of the transformers
3) A distribution transformer with taps has its primary in __?__.
two coils
22) Safety __?__ are an eye protection device with special impact resistant glass or plastic lenses, reinforced frames, and side shields.
Glasses
27) __?__ is the process of removing the source of electrical power and installing a lock that prevents the power from being turned on.
Lockout
19) A clamp on ammeter is a test instrument that measures current in a circuit by measuring the strength of the __?__ field around a single conductor.
Magnetic
31) The __?__ is a federal act that requires all employers to provide a safe environment for employees.
OSH Act
10) In order for current to flow, the conductor must be a closed circuit.
True
12) Laminating an iron core directs the maximum amount of magnetic flux lengthways in the iron core.
True
16) A megohmmeter is a high resistance ohmmeter used to measure insulation deterioration on various wires by measuring high resistance values during high voltage test conditions.
True
19) The kVA that is being drawn off of a transformer can be found by multiplying secondary voltage times secondary amperage and dividing the result by one thousand.
True
22) Measuring current is useful because only current can be used to determine how much a circuit is loaded (working).
True
24) Electricity is the number one cause of fires.
True
5) Mass is used as a standard instead of weight.
True
6) The magnetic field surrounding a coil rises and falls in unison with the current.
True
8) The main purpose of a transformer core is to direct the magnetic flux.
True
9) Both Fahrenheit and Celsius thermometers have scales based on the freezing and boiling points of __?__.
Water
23) An arc __?__ is an explosion that occurs when the air surrounding electrical equipment becomes ionized and conductive.
blast
32) The life expectancy of a test instrument depends on the __?__.
care of the meter
14) An ohmmeter is used to measure the __?__.
continuity
7) The thin, insulated sheets of steel in a transformer core reduce __?__ and __?__.
core loss, heating
20) Using Ohms law, when reducing voltage through a transformer the __?__ to supply the load.
current will increase
9) The magnetic field must be __?__ in order to induce a voltage and cause a current to flow in the circuit.
in motion
11) The __?__ concentrates and directs the magnetic field and makes transformers possible.
iron core
8) To obtain maximum induction, the coils must be __?__ and __?__ so the field is able to cut across the conductors of the other.
parallel, sufficiently close
5) The __?__ value of a sine wave is the maximum instantaneous value of either the positive or negative values in the sine wave.
peak
28) Lockout\Tagout is normally removed by the __?__, other than in an emergency.
person who installed it
11) The signal word used to indicate a potentially hazardous situation which could result in death or serious injury is the __?__.
warning
20) To close a CSP secondary breaker that has tripped, you move the indicator to R and then back to __?__.
C
21) If more than one popsicle stick connector is to be installed in a basket type transformer terminal, __?__ leads should be brought out to connect the services.
Copper
18) __?__ is measured in amperes.
Current
4) When drawing a WyeDelta threepot bank, the directions of the vectors (phasors) from the primary to the secondary are shown in the same direction.
True
4)In all tap settings on a transformer terminal board, 3 and 4 are always connected together.
True
11) On a singlebushing transformer, the tank ground is __?__.
also the neutral connection of the high voltage winding
9) Per this lesson, if the primary goes up to 2,508 volts, in order to lower the voltage to 120\240 volts on a distribution transformer, the tap selector would be set to __?__%.
104
21) When doing a polarity test, if the source voltage is 117, and the transformer is subtractive with a ratio of 10:1, the voltmeter reading will be __?__.
105.3
19) When paralleling two transformers, the impedance of the two transformers must be within __?__% and __?__% of each other.
107.5\92.5
10) In threephase systems, voltage vectors of individual phases are separated by __?__ degrees.
120
5) AC at 60 hertz per second increases and decreases in value __?__ times per second.
120
22) What voltage would be present at the primary bushings if 120 volts were applied to the secondary X 1 and X 3 bushings of a 2,400\4,160Y120\240 transformer?
1200 volts
22) An electric provider is allowed to have extreme voltages on a 120 volt service of 106 low and __?__ high.
127
20) When doing a polarity test, if the source voltage is 117 volts and the transformer is additive with a ratio of 10:1, the voltmeter reading will be __?__.
128.7
13) A transformer with 14,400 primary turns and 500 secondary turns produces a secondary voltage of 480. Assuming 100% transformer efficiency, the primary voltage is __?__.
13,824
14) The most common dualvoltage distribution transformer is rated at __?__.
14,400x7,200 120\240
10) A 15 kVA singlephase distribution transformer shows 75 amps on X 1 and 60 amps on X 3 . Voltage is 120 volts from each secondary bushing to the neutral. The transformer has exactly __?__ kVA of load.
16.2
13) Your engineer wants an accurate spot load check on a singlephase service. The A conductor has 115 volts and 95 amps and the B conductor has 113 volts at 78 amps. There is __?__ kVA being pulled off the transformer.
19.7
21) The transformer ratio is 10:1. The secondary voltage is 210 volts, the primary voltage is __?__ volts.
2,100
27) Current transformers are installed on single phase circuits when the current exceeds 400 amperes and on three phase circuits when the amperage exceeds __?__ amperes.
200
15) Using your reference books, a rule of thumb for current ratings per kVA, at 120 volts singlephase, __?__ amps are available from a 25 kVA transformer.
207.5
25) If the secondary of a threephase bank is connected 120 Wye, the voltage phase to phase is __?__volts. (Rounded off)
208
19) Prior to changing taps, recording voltmeters should be set and left to record for at least __?__ hours.
24
27) If your system uses 14,400 volt transformers connected phase to ground, the system voltage phase to phase is __?__ volts.
24,912
6) An oilfilled transformer can withstand an overload of __?__ times the rated current for 2 seconds.
25
9) On a 25kVA carrying 180 amps, the signal light will be energized after __?__ hours.
3
6) How much voltage will be available at H 1 on a 7,200 to 120\240 transformer if the lead from X 1 contacts a wire phase energized at 120 volts?
3,600 volts
15) The vector wheel graphically divides a circle into __?__ degree increments.
30
20) Recording voltmeters should be set at the customers service entrance because there may be a __?__% drop in voltage between the transformer and the customers service entrance.
4
7) The scale on the side of the maximeter should be set to __?__ if placed on a 25kVA singlephase transformer.
40\1
2) Overload peaks of __?__ minutes do not affect a transformer.
5
24) Current transformers reduce the current being metered to a value that should not exceed __?__ amps.
5
21) If a ¾" vector line represents 750 volts, a line 5 ¼" long represents __?__ volts.
5,250
3) According to U.S. standards, all transformers 200kVA in all voltage classes and in voltage ratings above __?__ volts are subtractive.
8,600
18) Given: a primary voltage of 2,292. To maintain a secondary voltage of 240 volts, the tap Changer should be set to 4.5%, which means that __?__% of the primary windings are in use.
95.5
2) According to this lesson, the U.S. standard for the polarity of singlephase transformers is __?__ for transformers 200kVA and 8,600 volts or below.
Additive
16) The __?__ feature on a digital multimeter allows a meter to automatically adjust to a higher range setting if the set range is not high enough for the application.
Autoranging
5) A CSP transformer contains a(n) __?__ and a(n) __?__ breaker.
Correct internal HV fuse, secondary
6) If the transformer nameplate shows 14,400\24,940 Y, it is suitable for a __?__ connection because it has full insulation at the H 2 .
Delta
10) It is a good practice to leave an extra length of copper or to curl primary risers from the transformer to the live line in case the lead breaks.
False
10) The current available out of the primary bushings is exactly twice the secondary.
False
11) Once you use the emergency handle to restore service, you do not have to replace the transformer as it has reset the transformer to a higher current value.
False
11) Secondary drop leads are not needed for a single triplex service as the conductors can be put directly into the transformer terminals.
False
12) A surge arrestor is installed after the transformer primary terminal in order to stop over current.
False
13) A CSP will not carry the same amperage as a conventional transformer because of the additional internal equipment.
False
13) A broken grounding conductor is of no concern if the secondary ground is still in place.
False
13) An isolation link of an underground transformer can be easily replaced in the field.
False
13) Removing the grounding strap of a singlephase transformer results in one phase of 480 volts.
False
14) Transformer capacity is rated in kW.
False
14) When paralleling transformers, the connection cannot be made if your voltmeter reads 8 volts between the conductors to be joined.
False
15) A tap changing mechanism works by adding in windings to the secondary side of a transformer.
False
15) The direction the primary and secondary are wound on the core has nothing to do with polarity.
False
15) The neutral and ground connections are interconnected on a transformer and are therefore interchangeable.
False
15) When it blows open, the internal primary fuse of a CSP will deenergize everything above it to the main line.
False
17) There is only one fusing schedule that must be used for refusing transformers.
False
17) To energize a transformer, a loadbreak elbow on an underground transformer should be inserted by hand.
False
19) Transient faults are common reasons for bayonet style fuses to blow on underground transformers.
False
19) Vectors can only be drawn vertically or horizontally.
False
2) Aluminum links or straps are used to make the connections on a transformer terminal board.
False
2) OSHA has nothing to say about how you hook up and lift a load.
False
2) There will be no current present in a transformer unless there is a load connected to the secondary.
False
2-2-9 Transformer: Completely SelfProtected 1) The secondary breaker of a CSP protects it from high voltage surges.
False
20) When installing a longterm paralleled transformer, the coils must be in series.
False
21) In a longterm, paralleled transformer situation, if one transformer fuse opens, the customer continues to be served normally at 120\240.
False
23) A Potential Transformer is safe because it is not used to measure high voltage.
False
23)The ratio of the transformer does not matter when making a polarity test. The voltmeter will always show plus or minus 12 volts.
False
3) A transformer will not backfeed until it is mounted on a pole.
False
3) CSP transformers do not have an internal primary fuse and rely on a pole mounted openlink fuse for protection.
False
5) Backfeed will only occur on a transformer if full secondary voltage is applied from X 1 to X 3 .
False
7) The KVA rating of a transformer decreases 3% for each degree below 30°C.
False
7) The voltage ratios are not important when connecting two transformers.
False
9) Phase position and phase sequence (rotation) are usually established at the point of service to the customer.
False
9) Singlephase transformer polarity is established similar to that of a battery. Once energized, there is a permanent north and south pole.
False
13) The H 2 terminal on a single bushing transformer is solidly connected to the __?__ of the tank.
Inside
9) The H 2 terminal on a single bushing transformer is solidly connected to the __?__ of the tank.
Inside
25) A current transformer should have its __?__ shortcircuited while being installed, or while connected in a circuit with no meter connected to the secondary.
Secondary
6) Indicate the polarity of the following transformer: 13,800 volt, 75kVA
Subtractive
7) Indicate the polarity of the following transformer: 14,400 volt, 500kVA
Subtractive
8) Indicate the polarity of the following transformer: 67,000 volt, 167kVA
Subtractive
17) Any transformers that are paralleled must be __?__ as paralleled.
Tagged
10) A __?__ fuse reduces nuisance fuse blowing from transient faults.
Tlink
18) On a transformer with Basket Terminals, copper leads should be inserted from the __?__.
Top
2-2-6 Transformer Operation 1) The principle by which a(n) __?__ induces voltage from one winding to another is known as electromagnetic induction.
Transformer
10) A dual voltage transformer is made to operate on one of two different primary voltages.
True
10) The voltage ratio of a transformer is the effective voltage of the primary to the potential voltage of the secondary.
True
11) Fuse size and speed are specified by the utility.
True
11) Industry standards for phase rotation are ABC and CBA in a counterclockwise direction.
True
11) Two secondary bushings are to be used on a transformer when the secondary coils are connected in parallel.
True
14) The primary fuse link of a CSP will operate at 8 to 14 times the normal current.
True
16) It is not a recommended practice to use a CSP as part of a bank of transformers.
True
18) The emergency handle is sealed so it cannot be operated unless the seal is cut.
True
18) Vectors represent physical quantities.
True
2-2-13 Conducting Transformer Load Checks 1) A load test taken with a clip on ammeter and a voltmeter will tell you if a transformer is overloaded at the time of the test.
True
26) The angle of the vectors for a given transformer is the same from the primary to the secondary.
True
26) With the secondary open, if a CT is energized, the high voltage may puncture the insulation and cause personal injury.
True
5) In a Delta configuration, the pointed plus end of one arrow (vector) makes contact with the negative tail of the next arrow.
True
6) A distribution transformer may have its secondary coils connected in series or parallel.
True
6) The voltage change from primary to secondary is governed by the ratio of turns in the primary coil to the turns in the secondary coil.
True
6) When paralleling transformers, both transformers must be connected to the same phases on the primary and on the secondary.
True
7) One advantage of completing a vector drawing of a threephase bank prior to physically building it is it will be built in a logical fashion.
True
8) A transformer can carry more current in January than in June.
True
8) Alley Cat, Bad Dog is a good way to remember how the secondary leads are connected when connecting a 120\240 volt transformer for full capacity at 120 volts.
True
14) The rating of a surge arrestor is specified at __?__ voltage as the circuit.
a slightly higher
11) A balanced load on a transformer is when __?__.
both phase to neutral leads have the same load
4) When a maximeter is clamped around an energized conductor, never __?__.
change taps on the meter
14) One factor that affects the mass that may be attached to a pole is the __?__.
class of the pole itself
24) Potential vectors will always point away from the __?__.
common point
9) If you have installed several 120volt security lights and need the total capacity of the transformer, you should __?__.
connect the coils in parallel
15) Heat in a transformer core is generated because of the __?__ of molecules.
constant reversal
16) Once you have established a __?__ for vectoring, you must maintain it throughout a vectoring exercise.
convention
10) The coil leads B and C emerge above the oil level in the __?__ position.
crossed
7) Of the three ratios governing transformer operation __?__ is in the reverse order to the other two.
current
17)A(n) __?__ installed in series with a fuse cutout can protect a worker when energizing a defective transformer.
current limiting fuse
22) External damage to a transformer tank may include __?__.
damaged bushings, leaking oil, and a bulged tank
6) In a Delta configuration, if a plusminus combination comes in contact with another Plusminus combination, a(n) __?__ will result.
dead short
3) If taps are available on the high voltage coil, the transformer must be __?__ before changing taps.
deenergized
6) Before operating the tap changing switch on a distribution transformer, it must be __?__.
deenergized from all sources of energy
2-2-5 Transformer Information Characteristics 1) On a transformer nameplate, an X between the primary numbers means __?__.
either voltage is available but not at the same time
18) The use of PCBs in transformer oil was declared a(n) __?__ by the EPA in the 1970s.
environmental hazard
5) Maximeters record the __?__ during the time of the test.
highest load
19) One requirement of the 1996 Migratory Bird Treaty Act regarding new transformer installations to protect birds from electrocution is to __?__.
install bushing covers
11) The __?__ tells how to connect a transformer for the voltage involved.
nameplate
20) Paint discoloration on an overhead transformer may be a sign of __?__.
overheating
10) If a singlebushing transformer has only one ground and the ground is broken, the tank may become energized at __?__.
primary voltage
20) The length of a vector line is __?__ the magnitude of the vector quantity.
proportional to
19) A broken signal light may be a source of __?__.
radio noise
12)You can get 480 volts out of two 120\240volt transformers by __?__.
removing the grounding straps, connecting the secondary in series, and paralleling the primary side
2) One of the two internal components which protects a CSP transformer is the __?__.
secondary breaker
11) Installing a transformer over a hot secondary with the leads installed __?__.
should never be done
8) The emergency control handle on a CSP transformer should be used as a __?__.
temporary fix to an overload situation
2-2-10 Installing Transformers 1) The proper way to hang a small distribution transformer when power equipment is not available is __?__.
to use rope blocks, pole jib, and block
12) A properly sized fuse should be installed in a cutout to protect the __?__.
transformer and the system
18) Singlephase transformers can be paralleled for increased capacity in the following manner, __?__.
transformers can be connected across insulated secondary breakers
2) The most common reason for a cutout being open is a(n) __?__.
transient fault
19) Distribution transformers normally have one primary coil and __?__ secondary coil(s).
two
3) A transformer rating of 120\240 shows that there is\are __?__.
two secondary coils
9) A transformer fuse is coordinated so it will isolate a transformer before __?__.
upstream protection opens the primary circuit
11) Transformer bushings are manufactured using a __?__ process.
wet
14) How can the primary turns of a distribution transformer be changed?
with a tap changing switch
22) Since transformers have no moving parts, their efficiency is always 100%.
False
22) If a vector is drawn to represent 480 volts and is scaled where ¼" equals 12 volts, the line will be __?__ inches long.
10
23) When a three phase current unbalance exceeds __?__%, a test for voltage unbalance should be performed.
10
8) When paralleling transformers, the voltmeter must read zero or not over __?__ volts.
10
16) The tap setting must always be set at __?__ before a distribution transformer is put into service.
100%
15) The secondary amperage available on a 25kVA transformer at 240 volts is __?__ amps.
104
7) Voltage indicators only indicate that voltage is present but do not indicate the __?__ voltage.
Actual
10) Distribution transformers are generally manufactured with __?__ polarity.
Additive
4) Indicate the polarity of the following transformer: 7,200 volt, 15kVA
Additive
3) When drawing the primary and secondary of a threepot transformer bank using vectors, the lines which make up the secondary are always at the same __?__ as the lines representing the primary.
angle
18) If a primary fuse blows on a paralleled transformer, the other transformer will __?__.
backfeed the one with the blown fuse
25) Most digital multimeter displays include a(n) __?__ to show changes and trends in a circuit.
bar graph
14) A company specifies the __?__ and __?__ of a fuse to be used in a transformer.
size\speed
2) More heat flows out of a transformer windings if __?__ or __?__ wire is used in the coils.
square, rectangular
5) The red light on a CSP __?__ after the load decreases.
stays on
18) A transformer may be either a __?__ or a __?__, depending on its use.
step up, step down
3) According to industry standards, all distribution transformers above 200kVA and\or 8,600 volts are __?__.
subtractive
3) The primary fuse in a CSP protects the __?__ from an internal fault.
system
7) A transformer with reduced insulation at H 2 must have H 2 tied to the __?__.
system neutral
2) CSP transformers can be equipped with a __?__ to adjust the secondary voltage.
tap changer
33) Extra care must be provided to digital test instruments because their movements are susceptible to damage from shock.
False
7) The Babylonian calendar consisted of 360 days. This led to fractions such as 1\60 which are still used in astronomy and for the minutes and seconds of the day.
True
38) Electrical Warning
White with Bolt
12) Normal types of losses concerning electrical transformers are __?__.
Correct copper and core
12) The warning signal word used to indicate a high voltage location and conditions that could result in death or serious personal injury from an electrical shock if proper precautions are not taken is __?__.
Electrical
39) Explosion Warning
Explosion one
10) Core type transformers are best suited for low voltage and high currents.
False
14) Of the three things which govern the strength of a transformers electromagnetic field, the ease with which the core can be magnetized is not one of them.
False
17) Digital test instruments are less susceptible to noise than analog test instruments.
False
17) The primary coil of a transformer is always a high voltage winding.
False
24) Most analog multimeters do not have calibrated scales that correspond to the different selector switch settings.
False
26) Grounding is the connection of all exposed, noncurrent carrying metal parts to the neutral conductor.
False
3) AC current is current in a circuit that flows in one direction only.
False
3) Impedance is the combination of resistance and current.
False
3) The best insulation for transformer coils is cotton.
False
30) Clothing made of synthetic materials, such as rayon, are the only type that are to be worn when working with energized electrical circuits.
False
6) Weight is often used as a standard because it is universally constant, regardless of latitude.
False
20) For maximum safety, personal protective equipment and safety requirements for test instrument procedures must be followed, as specified in __?__, which is one of several standards.
NFPA 70E
4) The meter was defined as 1\10,000,000 of the distance of the meridian passing through __?__ from the North Pole to the equator.
Paris
15) Only a meter marked __?__ can be used when taking a measurement on a circuit that includes solid state components that distort the shape of AC sine waves.
RMS
11) An ohmmeter is a test instrument that measures __?__, the opposition to the flow of electrons in a circuit.
Resistance
17) __?__ leakage current is current that flows from areas on conductors where insulation has been removed to allow electrical connections.
Surface
8) A voltage indicator needs to only be near a voltage source to indicate the presence of voltage.
True
6) A test light is a test instrument with a bulb that is connected to two leads to give a visual indication when __?__ is present in a circuit.
Voltage
25) Never touch any part of an electrical shock victims body when it is in contact with the circuit. When the circuit cannot be turned off, use any __?__ device to free the victim.
nonconducting
15) Of the three things which govern the strength of a transformers electromagnetic field, the amount of current flowing and the __?__ are two of them.
number of turns in the winding
2) Ohms law cannot be used directly on AC circuits because __?__.
reactance and resistance oppose current flow
4) All transformer connections, single and threephase, are based on the voltage and current rules for __?__ and __?__ circuits.
series, parallel
2-2-1 Introduction to Test Instruments 1) All other units of measure are defined and compared to the four basic measurements of length, __?__.
weight, time, and temperature
13) A transformer that is energized but not loaded can draw as much as __?__ % of the current taken in by a loaded transformer of the same size.
5
12) The higher the resistance in a circuit, the higher the current flow through the circuit.
False