The Electrical Distribution System
Summary
TLDRThis educational video script offers an in-depth virtual tour of an electrical distribution system in a building. It starts with the utility company supplying high voltage, which is stepped down by transformers to meet various electrical demands. The script explains the function of components like oil transformers, switchgear, bus ducts, and motor control centers. It also touches on emergency power systems with automatic transfer switches and battery banks, ensuring uninterrupted power supply in critical facilities.
Takeaways
- ๐ข The electrical distribution system is crucial for delivering power throughout a building, starting from the utility company's supply.
- โก Transformers play a key role in stepping down high voltages from the utility to safer, usable levels within buildings.
- ๐ Oil-filled transformers are used for stepping down voltages and are typically located outside due to fire risk.
- ๐ Switchgear is the starting point of the electrical distribution system inside a facility, containing switches and breakers for managing power flow.
- ๐ต The function of a bus bar is to distribute voltage within the switchgear, similar to how wires in conduit distribute power.
- ๐ Draw out breakers in switchgear allow for easy maintenance and are designed for specific circuit amp ratings.
- ๐ Bus ducts are used for larger amp ratings and contain bus bars within a metal enclosure, facilitating power distribution.
- ๐ฅ Automatic transfer switches ensure continuity of power by switching to an emergency generator in case of utility power interruptions.
- ๐ Battery banks provide temporary power in critical facilities until the generator supplies the correct voltage after a power failure.
- ๐ง Motor control centers (MCCs) distribute power to electric motors used in various machinery and equipment within a facility.
- ๐ป Power distribution units (PDUs) in data centers and computer rooms provide clean power to computer servers and network equipment.
Q & A
What is the purpose of the electrical distribution system described in the script?
-The electrical distribution system described in the script is designed to distribute electrical power throughout a building by stepping down voltage from the utility company and distributing it to various components and systems within the facility.
What is the primary function of a transformer?
-A transformer's primary function is to step down high voltage from the utility company to a lower, safer voltage suitable for use within a building.
Why are the incoming wires carrying 4,160 volts smaller than the wires carrying 480 volts?
-The incoming wires carrying 4,160 volts are smaller than those carrying 480 volts because, as voltage is lowered, the amperage increases, which generates more heat and requires larger wires to handle the higher current.
What role does the oil in an oil transformer play?
-The oil in an oil transformer is used for cooling the core. It is filled with non-conductive oil, typically mineral oil, which helps dissipate heat through the conduction process.
Why are oil transformers often located outside the facility?
-Oil transformers are often located outside the facility due to the high fire risk they pose. They are placed on a concrete pad to help contain any potential fire.
What is switchgear and where is it typically located?
-Switchgear is the beginning of the electrical distribution system inside a facility. It is typically located in an electrical room and is made up of several sections containing switches and/or breakers.
What is the purpose of a draw-out breaker in switchgear?
-A draw-out breaker in switchgear is a large disconnect switch with a designated amp rating for a specific circuit. It allows for easy removal for maintenance and repair.
What is the difference between a distribution switchboard, a distribution panel, and a branch circuit breaker panel?
-The difference between a distribution switchboard, a distribution panel, and a branch circuit breaker panel lies in their amperage ratings. A distribution switchboard has an amp rating between 1,201 and 1,999, a distribution panel has a rating of 401 to 1,200, and a branch circuit breaker panel has a rating equal to or less than 400 amps.
How does a dry transformer differ from an oil transformer?
-A dry transformer differs from an oil transformer in that it uses air for cooling instead of oil. It is generally used to step down 600 volts or less.
What is the role of an automatic transfer switch in an electrical distribution system?
-An automatic transfer switch monitors the incoming power from the utility. If there is an interruption, it sends a signal to start an emergency generator and switches over to emergency power once the generator reaches the desired voltage level.
What is the purpose of a battery bank in an electrical distribution system?
-A battery bank in an electrical distribution system provides power until the generator is able to supply the correct voltage in case of a power interruption, ensuring uninterrupted power supply in critical facilities like data centers and hospitals.
Outlines
๐ Understanding Electrical Distribution Systems
This paragraph introduces the concept of electrical distribution systems in buildings. It explains the process of power distribution starting from the utility company supplying 13,800 volts to a pole in the parking lot. Three transformers step down this voltage to 4,160 volts, which is then transferred to an oil transformer via underground copper wires encased in conduit. The oil transformer further steps down the voltage to 480 volts using its three-phase system. The paragraph also discusses the physical aspects of transformers, such as the need for larger wires at lower voltages due to increased amperage and heat generation. It also touches on the cooling mechanisms of oil transformers, which use mineral oil and convection for cooling, and are typically located outside facilities due to fire risks. The narrative then moves to the switch gear, which is the starting point of the internal electrical distribution system, consisting of sections with switches or breakers that distribute power throughout the building.
๐ข Components of Electrical Distribution Inside Facilities
The second paragraph delves into the components found inside facilities that are part of the electrical distribution system. It starts with the switch gear, which receives power from the oil transformer and is protected by fuses connected to a bus bar. The bus bar, made of copper or aluminum, distributes voltage to different sections of the switch gear. The paragraph discusses draw out breakers, which are large disconnect switches with specific amp ratings for circuits, and their maintenance. It also mentions the concept of spare breakers for future expansion. The narrative continues with the explanation of bus duct, which is used to handle larger amperage ratings and is connected to various electrical components like breaker panels and transformers. The paragraph also distinguishes between different types of panels based on their amperage ratings: distribution switchboard (1,201 to 1,999 amps), distribution panel (401 to 1,200 amps), and branch circuit breaker panel (400 amps or less). Additionally, it contrasts oil and dry transformers, with the latter using air for cooling. The paragraph concludes with a discussion on automatic transfer switches that monitor utility power and switch to emergency generators in case of interruptions, ensuring uninterrupted power supply, especially critical in facilities like data centers and hospitals.
๐ Specialized Electrical Equipment for Power Distribution
The final paragraph focuses on specialized equipment used in electrical distribution systems, such as motor control centers (MCCs), which are composed of sections with buckets assigned to specific motors. Each bucket contains components like disconnect switches, breakers, and control devices like computer logic boards or PLCs. The paragraph highlights the role of disconnect switches and breakers in protecting motors from excessive power and the combination motor starters that include manual start/stop and auto/manual modes. An example of a sump pump is given to illustrate how these components work in practice. The paragraph also discusses power distribution units (PDUs) found in data centers and computer rooms, which provide clean power to computer servers through circuit breaker panels and transformers. The narrative concludes with a general overview of the variability in electrical distribution system layouts across different facilities, emphasizing the importance of understanding the flow of power from the incoming source to the various components and their locations within the facility.
Mindmap
Keywords
๐กElectrical Distribution System
๐กTransformer
๐กVoltage
๐กAmpere (Amperage)
๐กThree-Phase System
๐กJunction Box
๐กSwitch Gear
๐กBus Bar
๐กDraw Out Breaker
๐กBus Duct
๐กAutomatic Transfer Switch (ATS)
Highlights
Electrical power distribution system explained
Utility company supplies 13,800 volts
Transformers step down voltage from 13,800 to 4,160 volts
Copper wires encased in conduit transfer voltage underground
Oil Transformers explained and their cooling process
Three-phase system and its voltage step-down process
Amperage increases when voltage is lowered
Switch gear as the beginning of the electrical distribution system inside the facility
Main breaker or fuses protect downstream electrical equipment
Draw out breaker for easy maintenance and repair
Bus duct for handling larger amp ratings
Different types of electrical panels based on amperage rating
Dry Transformers use air for cooling instead of oil
Automatic transfer switch for emergency power
Battery bank provides power until the generator supplies the correct voltage
Electric motors and their distribution through motor control centers
Combination motor starter with start/stop and auto/manual switches
Power distribution units (PDUs) in data centers
Disconnect switch for specific voltages and amperages
Unique layout of electrical distribution system for each facility
Transcripts
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in this course we will take you on a
virtual tour to see how electrical power
is distributed throughout a building
this is defined as the electrical
distribution
system these systems are uniquely
comprised of a variety of electrical
components to meet specific electrical
demands you will learn the function of
each of these electrical components and
how it relates to the total operation of
an electrical distribution system in our
example we begin with the utility
company supplying 13,800 volts from the
road to a utility pole in the parking
lot at the top of this pole you see
three Transformers these Transformers
will step down the 13,800 volt to 4,160
volts this voltage is transferred down
the pole through copper wires that are
encased in
conduit this conduit travels underground
and enters the oil Transformer on the
high or primary side of its junction
box let's look at how the oil
Transformer works the junction box
receives the incoming power on the high
or primary side it enters the transform
warmer through insulated copper
connectors notice there are three wires
this is our three-phase system there are
three windings one for each of the wires
or phases the wires are connected to the
top of the
windings the windings in this
Transformer will step down the voltage
to 480 volts notice that the incoming
wires that are carrying the 4,60 volts
are smaller than the wires at the bottom
carrying 480 Vols this this is because
the amperage increases when the voltage
is lowered and vice
versa higher amperage generates more
heat and requires larger wires wires
connecting to the bottom of each winding
will then return to the low or secondary
side of the junction box from here the
wires will pass through conduit and
travel underground to switch gear for
further
distribution the oil in an oil
Transformer is used for cooling the core
is filled with non-conductive oil in
most cases mineral oil is used traveling
through fins cools this oil which
utilizes the conduction process usually
there are no pumps in smaller oil
Transformers in addition to fins some
larger oil Transformers will have
exterior fans with thermostats that blow
additional cool air over the
fins oil Transformers are placed on a
concrete pad and almost always located
outside the facility this is in part due
to a high fire
risk what is switch gear it's the
beginning of the electrical distribution
system inside the facility located in an
electrical room it is made up of several
sections containing switches and or
Breakers the first section receives the
incoming power from the oil
Transformer the wires are connected to a
main breaker or in this example they are
attached to fuses the fuses are connect
connected to bus bar bus bar is either
made up of copper or
aluminum the voltage travels through the
bus bar to each section of connected
switch gear energizing each
section here in our example we have
switch gear that is rated at 2,000 amps
it consists of five sections connected
together as you can see section one
contains the incoming voltage connected
to the main fuses these main fuses
protect the downstream electrical
equipment within the switch gear from
exceeding 2,000 amps in the event that
more than 2,000 amps are drawn these
fuses will open and disconnect
voltage section two and three both
contain a draw out breaker a draw out
breaker is a large disconnect switch
that has a designated amp rating for a
specific circuit these Breakers are
large and heavy which require them to be
on casters which run on tracks this
allows easy removal for maintenance and
repair
pairs you can see the draw out breaker
in section two is connected to the bus
bar that is traveling up into bus duct
section three of the switch gear
contains the second draw out breaker you
can see that the bus bar connecting to
this breaker is not attached to anything
this is a spare breaker designed for
future expansion of the
facility section four contains six
molded case circuit breakers these
Breakers have a lower amp rating than
draw out Breakers and are not as heavy
this allows them to be directly bolted
to the bus bar remember all Breakers
have the same function they are to
disconnect voltage when amperage exceeds
its maximum
rating the fifth and final section of
this switch gear is empty with a solid
or blank panel cover this could be a
spare section for future expansion a
blank front does not necessarily imply
that the section is a spare it is
important to ask what is the function of
this section
and is there something in there that
needs to be
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tested our draw out breaker in section
two is connected to bus duct bus duct is
a rectangular or Square metal enclosure
containing bus bar its purpose is the
same as electrical wire in conduit but
is able to handle larger amp ratings bus
duct is made up of 10t sections plugs or
connectors are spaced every 2 or 3 feet
for the purpose of attaching fused
disconnect safety switches which can
then Supply voltage to designated areas
in our example facility you see the bus
duck Rising vertically to the roof it
passes through an electrical room on
each floor these rooms generally house
breaker panels one or more Transformers
and or disconnect switches power is then
distributed throughout the
floor the bus duck reaches the roof to
supply power to HVAC systems through a
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disconnect a distribution switchboard a
distribution panel and a branch circuit
breaker panel all have the same
functionality they can contain many
circuit breakers Distributing voltage to
all areas of the facility what
differentiates them from each other is
their amperage rating distribution
switchboard is an electrical p panel
with an amp rating between
1,21 and
1,999 a distribution panel has an aage
rating of 401 to
1,200 a branch circuit breaker panel has
an aage rating that is equal to or less
than 400 amps
the dry Transformer has the same
function as an oil Transformer it steps
down voltage the difference is that the
dry Transformer uses air for cooling
instead of oil as the Transformer heats
the air inside cool air is pulled in at
the bottom heat rises through a natural
convection process and exits from the
top dried Transformers generally are
used to step down 600 volts or less
please note that Transformers can be
used to step up voltage or maintain a
certain voltage in most cases
Transformers are used to step down
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voltage an automatic transfer switch
monitors the incoming power from the
utility if there is an interruption it
will send a signal to start an emergency
generator once the generator reaches a
desired voltage level the ATS will
switch over to the emergency power there
is a slight interruption in power from
the time the ATS switches over to the
generator from the utility power in
facilities such as data centers and
hospitals where uninterrupted power is
very important a battery bank is in
place to provide Power until the
generator is able to supply the correct
voltage once the power from the utility
is restored the automatic transfer
switch will automatically switch back to
normal Power this emergency power
generally feeds specific circuits in
some cases it may Supply the entire
facility but this is not the norm in
larger facilities with higher emergency
demands you may find several generators
along with several automatic transfer
switches auxiliary power is also stored
in a battery Bank a battery bank is
located in a designated room with
battery racks that house batteries that
are connected together they are being
charg 24 hours a day these batteries are
connected together to provide a specific
voltage for a certain period of
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time almost every facility there are
electric motors Motors are used in pumps
Machinery conveyors elevators and the
list is endless in order to distribute
power to Motors the electrical
distribution system has motor control
centers or
mcc's these mcc's are made up of series
of sections each section contains
buckets each bucket is assigned to a
specific
motor a MCC bucket contains many things
to operate the motor there can be
Computer Logic boards or
plc's Transformers contactors and other
control devices to operate the motor for
the purpose of electrical distribution
we only need to focus on a few
components that relate specifically to
the
electrical each bucket has a disconnect
switch and a breaker the breaker is
designed to trip if the power exceeds
the recommended setting the disconnect
switch is there to manually turn off the
power to the
motor there is also a combination motor
star these consist of the same
disconnect switch and breaker but also
has two other features it has a start
stop switch to manually turn the motor
on and off it also has a handoff auto
switch when this switch is in the auto
mode it allows another source to control
the motor a good good example of this
would be a sump pump a float switch that
is switched on by Rising water will
control the sump pump the motor will be
turned off when water levels go down and
reset the float switch to the off
position when this switch is in the hand
position the motor is always
on power distribution units or pdus are
found in data centers and computer rooms
each of these units contain one or more
circuit breaker panels and a Transformer
they provide clean power to computer
servers a disconnect switch is nothing
more than a switch designed for specific
vages and amperages there are many
different types and sizes some
disconnects have fuses in
them the electrical distribution system
will have a unique layout for each
individual facility you will not always
find every type of electrical component
that we reviewed or the same
configurations in every electrical
distribution system that you examine as
well the key to identifying each layout
is to begin at the incoming power source
and identify each component and location
as it distributes electrical power
through the facility
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