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The circuit type in which voltage drops across the resistors and amperage stays the same.
Series
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The circuit type in which voltage remains the same, but amperage drops across the resistors.
Parallel
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Which of the two basic types of circuits is preferred because it is reliable?
Parallel
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Anything that is connected across two _______ is said to be in series.
points of different potential
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Anything that is connected in series will have current flow through it unless the _______ is sufficient to prevent it.
resistance
-
When individually viewing regulators, reclosers, sectionalizers, and switches and how they are connected to the line, what type of circuit do they form?
Series
-
For what type of circuit does the current rule, I total = I1 = I2 = I3 apply?
Series
-
For what type of circuit does the resistance rule, R total = R1 + R2 + R3 apply?
Series
-
The total resistance in a series circuit is equal to the sum of the values of the ____________ connected in the circuit.
individual resistors
-
For what type of circuit does the voltage rule, E total = E1 + E2 + E3 apply?
Series
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In a series circuit, the sum of all the ______ drops across all the resistors must equal the ______ applied to the circuit.
-
For what type of circuit does the power rule, P total = P1 + P2 + P3 apply?
All circuits.
-
A parallel circuit with only one branch is a _____ circuit.
series
-
A transformer is essentially a machine with ______________.
no moving parts
-
An electrical device that converts voltage either from high voltage to low voltage, or low voltage to high voltage.
Transformer
-
Will a transformer work on a DC circuit?
No
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The source side is known as the _______.
Primary side
-
The load side or customer side is known as the ___________.
Secondary side
-
What is the most widely used apparatus in the electrical utility industry?
Transformer
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A pole mounted transformer is physically attached to the pole using ______.
hanger bolts
-
What are the three types of underground tranformers?
- Pad-mounted
- Vault
- Submersible
-
A pad-mounted tranformer is generally placed on a ________ pad or a _______ pad on the ground.
-
The primary side is sometimes called the _______ side and the secondary side is sometimes called the _______ side.
-
The points of termination on an overhead transformer where the conductors attach.
Bushings
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What type of transformer would have an H1 and where would you find it?
- Overhead.
- On the top left side as you face the transformer.
-
X2 is also known as the _________ or __________.
-
On an additive transformer, how would the secondary bushings be labeled from left to right?
X3, X2, X1
-
On a subtractive transformer, how would the secondary bushings be labeled from left to right?
X1, X2, X3
-
The primary side of a pad-mounted transformer is on the ______ side.
Left
-
On a single phase pad mounted transformer, how are the primary bushings labeled?
-
On a 3-phase pad-mounted transformer, how are the primary bushings labeled?
-
The device used to both energize and de-energize the secondary or low voltage side of a pad-mounted transformer.
Bayonet fuse.
-
What does KVA stand for?
kilo-volt-amperes
-
What is another term for KVA?
Kilowatt rating
-
Generally and average sized home will draw ______ watts at peak load.
6,000
-
A large home will draw around ___________ watts at peak load.
15,000
-
When transformers are banked together, how do you determine the KVA rating of the bank.
The sum of the KVA ratings of the individual transformers.
-
What are the two main types of overhead transformers?
-
What does CSP stand for?
Completely self protected
-
With a conventional overhead transformer, what two purposes does the fused cutout switch serve?
- To energize and de-energize the transformer.
- To protect it from fault currents.
-
What three protective devices does a CSP transformer have that a conventional one does not?
- Internal current limiting fuse (primary fuse)
- Internal circuit breaker
- Lightning arrestor attached externally
-
What are two external indicators on a CSP transformer that should enable you to identify it from a conventional transformer?
- Secondary breaker switch
- Lightning arrestor
-
What does the internal circuit breaker do on a CSP transformer?
It energizes and de-energizes the secondary side of the transformer.
-
The type of transformer that has an overhead conductor for it's primary source of feed.
Pole mounted
-
The type of transformer that has an underground conductor as it's primary source of feed?
- pad-mounted
- also submersible or vault
-
What are the three main internal components of a transformer?
- Core
- windings
- insulating fluid
-
At what psi will the pressure relief valve let off pressure?
10 psi
-
What does the core do?
The core concentrates the magnetic lines of flux, which substantially improves the transformers efficiency.
-
What is the core made up of?
Thin laminations of grain-oriented silicon steel which are coated with an insulating material.
-
The construction of the core can have a significant impact on the _____ losses of the transformer.
Watt
-
What are the two configurations of transformer cores and describe them.
- Wound type core, a square ring.
- Shell type core, two squares resembling a blocky numeral 8.
-
What is the wound type core generally used for?
Distribution transformers
-
What is the special type of steel that has been recently utilized to further reduce the losses within the core?
amorphous steel
-
What is the most popular material used for windings due to it's low resistance and superb conductivity?
copper
-
Which windings generally have smaller sized wire?
Primary
-
What shapes of windings are used?
round or rectangular ribbon shaped
-
Why are winding conductors coated with insulation?
To keep the turns from shorting out.
-
Inside the transformer, the secondary windings are tagged, what two tags would be connected to X2?
-
Plays a critical role in cooling and insulating the core and coil assembly.
Insulating fluid
-
The term describing the process where the hot oil rises and is forced to the outside walls of the tank. As it cools it sinks and continues circulating.
Convection
-
Where would you find the KVA rating of a transformer?
Stenciled on the can and on the name plate.
-
What is the insulating oil?
General it is some form of mineral oil.
-
Can insulating oil be flammable under certain conditions?
Yes
-
What does the acronym PCB stand for?
Polychlorinated Biphenyls
-
In what type of insulating fluid would you find PCB's?
askarel
-
Allows gasses that result from the breakdown of impurities in the insulating oil to escape to atmosphere.
Pressure relief valve
-
On CSP transformers, the component that isolates and protects the transformer from internal faults.
Internal fuse
-
On CSP transformers, the component intended to disconnect the hot legs in the event of an overload or short circuit on the secondary side.
Internal secondary breaker
-
Which type of transformer has an internal fuse that is operated externally?
Pad-mounted, bayonet fuse
-
What should you do before removing a bayonet fuse?
Bleed off the internal pressure.
-
A transformer in it's simplest form is nothing more than _____________ placed very close to each other but not touching.
two coils of wire
-
What can be done to maximize induction and obtain higher voltages?
Place the windings around an iron core.
-
Where are step-up generators generally found?
Generation substations
-
How do you figure the turns ratio of a transformer?
Divide the primary voltage rating (the smaller or sometimes only number in the primary portion of the nameplate) by the secondary voltage rating (X1 to X3 reading, the larger or sometimes only number in the secondary portion of the nameplate) and then add :1 to the number.
-
How do you determine if a transformer is additive or subtractive?
- Read the nameplate.
- If the KVA rating is 200 or smaller, AND the primary rating is 8660 volts or smaller, it is additive. All others are subtractive.
- If X1 is on the left, it is subtractive. If X1 is on the right, it is additive.
-
How is the polarity of a transformer determined?
The direction the secondary coil is wrapped in relation to the primary coil.
-
The direction of current flow through the two coils of a transformer.
Polarity
-
When is knowing the polarity of a transformer very important to know?
When banking or paralleling transformers.
-
What is the most important part of a transformer?
The nameplate, without it the transformer is no good.
-
Prior to installing a transformer, linemen refer to the nameplate for what four pieces of information?
- Ensuring that the desired primary voltage is chosen.
- Ensure that the desired secondary voltage is chosen.
- Ensure the impedances are within +- 10% if banking or paralleling.
- Determine the weight of the transformer for rigging purposes.
-
What is the purpose of the nameplate of a transformer?
Provides technical information that can be used to safely store, transport, install, maintain, and inventory the unit.
-
Where is the nameplate generally found on an overhead transformer?
On or near the lower mounting bracket.
-
Where is the nameplate generally found on pad-mounted transformers?
Inside the door or on the face.
-
A depiction of the primary and secondary coils and their relationship.
Schematic
-
Total opposition to current flow caused by resistance and inductive reactance.
Impedance
-
The unique number assigned to each transformer in a companies inventory.
Serial number
-
What are the seven pieces of information found on a nameplate that are the most important to a lineman?
- Weight
- Voltage ratings
- KVA
- Serial number
- Polarity
- Impedance
- Schematic
-
What markings indicate the impedance on a transformers nameplate?
%Z
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