The Electrical Distribution System

Summary

This 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

• 🏢 The electrical distribution system is crucial for delivering power throughout a building, starting from the utility company's supply.
• ⚡ Transformers play a key role in stepping down high voltages from the utility to safer, usable levels within buildings.
• 🔌 Oil-filled transformers are used for stepping down voltages and are typically located outside due to fire risk.
• 🛠 Switchgear is the starting point of the electrical distribution system inside a facility, containing switches and breakers for managing power flow.
• 🔵 The function of a bus bar is to distribute voltage within the switchgear, similar to how wires in conduit distribute power.
• 🔄 Draw out breakers in switchgear allow for easy maintenance and are designed for specific circuit amp ratings.
• 🏗 Bus ducts are used for larger amp ratings and contain bus bars within a metal enclosure, facilitating power distribution.
• 🏥 Automatic transfer switches ensure continuity of power by switching to an emergency generator in case of utility power interruptions.
• 🔋 Battery banks provide temporary power in critical facilities until the generator supplies the correct voltage after a power failure.
• 🔧 Motor control centers (MCCs) distribute power to electric motors used in various machinery and equipment within a facility.
• 💻 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

00:00

🔌 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.

05:02

🏢 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.

10:02

🛠 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.

Keywords

💡Electrical Distribution System

An electrical distribution system is a network of electrical components that transmits power from a central source to various loads within a building or area. In the video, this system is central to the narrative as it illustrates how power is distributed from the utility company to different parts of a building, starting from the utility pole and ending at the end-user devices.

💡Transformer

A transformer is a device that changes the voltage levels of electrical power. In the video, transformers are used to step down high voltage from the utility company to a lower, safer voltage for use within the building. The script mentions oil-filled transformers and dry transformers, highlighting their different cooling methods.

💡Voltage

Voltage is the electric potential difference between two points. The script discusses how transformers step down voltage from 13,800 volts to 4,160 volts and then to 480 volts, which is crucial for the safe and efficient distribution of electricity within the building.

💡Ampere (Amperage)

Amperage, or current, is the flow of electric charge. The video explains the inverse relationship between voltage and amperage, where an increase in voltage results in a decrease in amperage, and vice versa. This is exemplified by the different wire sizes carrying different voltage levels.

💡Three-Phase System

A three-phase system is an electrical power system with three sequentially displaced alternating currents. The video describes how the incoming power to the transformer is a three-phase system, with three windings corresponding to each phase, which is a common method for distributing power in industrial settings.

💡Junction Box

A junction box is an enclosure that houses electrical connections. In the context of the video, the junction box on the high or primary side of an oil transformer receives the incoming power and directs it to the transformer windings, playing a critical role in the distribution process.

💡Switch Gear

Switch gear refers to the equipment used to control, protect, and switch electrical circuits. The video describes switch gear as the beginning of the electrical distribution system inside the facility, receiving power from the transformer and directing it to various sections for further distribution.

💡Bus Bar

A bus bar is a conductive bar, usually made of copper or aluminum, used to distribute electrical power within switch gear or other electrical equipment. The script mentions bus bars carrying voltage through the switch gear to energize each section, highlighting their role in the distribution process.

💡Draw Out Breaker

A draw out breaker is a large disconnect switch with a specific amp rating for a circuit. The video explains that these breakers are mounted on casters for easy removal, which is important for maintenance and repair of the electrical distribution system.

💡Bus Duct

Bus duct is a metal enclosure that houses bus bars, designed to handle larger amperage ratings than conduit. The script describes bus ducts rising vertically through the building, distributing power to different floors and electrical rooms, which is essential for the efficient distribution of power in larger facilities.

💡Automatic Transfer Switch (ATS)

An automatic transfer switch is a device that switches between two power sources, such as a utility power and an emergency generator. The video explains how ATS ensures continuous power supply in critical facilities by switching to the generator in case of a utility power interruption, which is crucial for maintaining operations in data centers and hospitals.

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

[Music]

[Applause]

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]

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

[Music]