ENGINEERING UTILITIES 1
LECTURE 1
Prepared by:
ENGR. JUDE DAVID T. BADAL
TOPICS
• Basic Electrical Terms, Theories, and Units
• Basic Electrical Devices/Equipment
• Energy Calculation
• Cost of Operation of Electrical Equipment
• Types of Building System Voltage
• Distribution Equipment
LEARNING OUTCOMES
• Be able to familiarize basic electrical terminologies, theories, and
devices/equipment
• Be able to calculate energy and cost of operation of electrical
equipment
• Be able to distinguish types of building system voltage and
distribution equipment
BASIC TERMS, THEORIES, AND UNITS
Electric Charge – is carried by the electrons and proton within an atom.
Electrons carry negative charge, while protons carry positive charge.
The SI unit of electric charge is coulomb. One electron of proton has a
charge of 1.6 x 10-19 coulomb.
Note: Copper is used as a universal reference conductor. 1 cubic
centimeters of copper has 8.5 x 1022 free electrons.
V=1cm3
1cm
1cm
1cm
BASIC TERMS, THEORIES, AND UNITS
Free Electrons – are electrons which are not attached to a specific atom
and its free to move. It is sometime called as conduction electrons.
Example: Solve the number of free electrons in a copper conductor
having a diameter of 1.6 mm and a length of 10 m.
Note: 1.6 mm = 0.16 cm; 10 m = 1000 cm
2
3
3
3
BASIC TERMS, THEORIES, AND UNITS
TRY TO SOLVE THIS!
The number of free electron in a given copper bus bar is known to be
4.18 x 1024 electrons. If the bus bar has a cross section of 0.5 inch by
0.6 inch, how long is the bus bar?
ANSWER: 10 inches
BASIC TERMS, THEORIES, AND UNITS
Electric Current – rate of electron movement or electron flow in a given
material. The SI unit of current is coulomb per second or commonly
called ampere.
I = current flow, in amperes (A)
Q = total charge moving, in coulombs (C)
t = time occurrence, in seconds (s)
BASIC TERMS, THEORIES, AND UNITS
Example: If a current of 2 A flows through a point in a wire for 30
seconds, how many coulombs pass through the point in the wire?
TRY TO SOLVE THIS!
A current of 4 A is flowing in a wire. How many electrons are flowing per
second through the wire?
ANSWER: 2.5 x 1019 electrons/second
BASIC TERMS, THEORIES, AND UNITS
Electromotive Force (emf or voltage) – the energy provided by a cell
or battery or a generator per coulomb of charge passing through it. The
SI unit of emf is joule per coulomb or commonly called volt.
E = emf or voltage, in volts (V)
W = energy, in joules (J)
Q = charge, in coulombs (C)
BASIC TERMS, THEORIES, AND UNITS
Example: What quantity of charge must be delivered by a battery with a
potential difference of 100 V to do 500 J of work?
TRY TO SOLVE THIS!
An energy equal to 136 J is expended in moving 8.5 x 1018 electrons from one
point to another in an electric circuit. What potential difference does this
create between the two points?
ANSWER: 100 volts
BASIC TERMS, THEORIES, AND UNITS
Electric Energy and Power
Electric energy is a form of energy used to run or operate various electrical devices. Standard unit of
electrical energy is joule or kilojoule. The other common units are kilowatt-hour and megawatt-hour.
Electric power is the rate of consuming the electric energy. Standard unit of electrical power is watt
(bigger units are kilowatt and megawatt).
W = electric energy, in joules (J)
P = electric power, in watts (W)
I = current, in amperes (A)
E = emf or voltage, in volts (V)
t = time, in seconds (s)
BASIC TERMS, THEORIES, AND UNITS
Example: A radio receiver draws 0.9 A at 110 V. If the set is used 3 hours per
day, how much energy does it consume in 10 days?
TRY TO SOLVE THIS!
An electric heater takes 1.2 kWh in 30 min at 120 volts. What is the current
input to the heater?
ANSWER: 20 amperes
BASIC TERMS, THEORIES, AND UNITS
Electric Resistance – property of a material to oppose or resist the electron
flow. The SI unit is ohm.
Current
Resistance
Note: The resistance of a conductor varies directly as the length and inversely
to the cross-sectional area.
R = resistance of the given conductor, in ohms (Ω)
ρ = resistivity of the given conductor, (Ω-m)
L = length of the given conductor, in meter (m)
A = cross-sectional area of the conductor, (m2)
BASIC TERMS, THEORIES, AND UNITS
Resistance
ohm
ohm
Resistivity
ohm-m
ohm-CM/ft
Length
m
ft
Area
m2
CM
BASIC TERMS, THEORIES, AND UNITS
Specific resistance or resistivity of a material is the resistance offered by
1 m length of the material having a cross-sectional area of 1 m2.
At 20˚C, the resistivity of annealed copper wire is,
−8
Note: If not specified, a copper wire is assumed an annealed copper
wire and at 20˚C conditions.
BASIC TERMS, THEORIES, AND UNITS
Circular Mil (CM) – is an old unit in specifying the cross-section area of
a wire. It is equal to the area of a circle having a diameter of 1 mil.
1mil
A = d2
A = cross-section area of the wire, in cmils (CM)
d = diameter of the wire, in mils
Note: 1 inch = 1000 mils; 1 MCM = 1000 CM
BASIC TERMS, THEORIES, AND UNITS
Relation between a Circular Mil and a Square Mil
1mil
1mil
A = 1 circular mil
1mil
A = 1 sq. mil
BASIC TERMS, THEORIES, AND UNITS
Example: A 400,000-cir-mil cable is composed of 37 strands. What is
the diameter, in mils, of each strand?
BASIC TERMS, THEORIES, AND UNITS
TRY TO SOLVE THIS!
A bus bar has cross-section of 0.5 inch by 0.6 inch. Determine its crosssectional area in circular mils?
ANSWER: 381,972 circular mils
BASIC TERMS, THEORIES, AND UNITS
Example: What length of wire of diameter 0.315 mm will be required to
construct a coil of resistance 10 ohms, if the specific resistance of the
wire is 49 μΩ-cm?
2
BASIC TERMS, THEORIES, AND UNITS
Example: A standard copper wire is 0.064 inch in diameter. What is the
resistance of 1000 ft of this wire at 20˚C?
BASIC TERMS, THEORIES, AND UNITS
TRY TO SOLVE THIS!
Solve the resistance of a 564 m long aluminum conductor of cross
section 40 mm by 20 mm. Resistivity of aluminum is 2.826 x 10-8 Ω-m.
ANSWER: 0.02 ohm
BASIC TERMS, THEORIES, AND UNITS
Electric Circuit – is a continuous and closed path of an electric current.
An electric circuit consists of electric devices, a source of electricity and
wires that are connected with the help of a switch.
BASIC TERMS, THEORIES, AND UNITS
Ohm’s Law – it states that the current drawn by an electric load is
directly proportional to the voltage across the load and inversely
proportional to the electrical resistance of the load.
I = current, in amperes (A)
V = emf or voltage, in volts (V)
R = resistance, in ohms (Ω)
BASIC TERMS, THEORIES, AND UNITS
Example: An electric iron draws 2.5 A at 230 V. Determine its
resistance?
TRY TO SOLVE THIS!
A nichrome heating coil takes 30 A when a voltage of 120 V is applied.
Determine the resistance of the coil.
ANSWER: 4 ohms
BASIC TERMS, THEORIES, AND UNITS
TRY TO SOLVE THIS!
Solve the resistance of a 564 m long aluminum conductor of cross
section 40 mm by 20 mm. Resistivity of aluminum is 2.826 x 10-8 Ω-m.
ANSWER: 0.02 ohm
BASIC TERMS, THEORIES, AND UNITS
Electric Power Efficiency - is defined as the ratio of the output power
divided by the input power.
% Efficiency = efficiency, in percent (%)
Pout = useful power output, in watts (W)
Pin = total electrical power consumed or input, in watts (W)
BASIC TERMS, THEORIES, AND UNITS
Example: What is the efficiency when 5 J is supplied to a buzzer and 2
J is transferred into sound energy?
TRY TO SOLVE THIS!
What is the efficiency when 120 J is supplied to a toaster and 50 J of
energy is transferred into heat?
ANSWER: 41.67%
BASIC ELECTRICAL DEVICES/EQUIPMENT
BASIC ELECTRICAL DEVICES/EQUIPMENT
BASIC ELECTRICAL DEVICES/EQUIPMENT
Reading Assignment:
https://www.electricaltechnology.org/2014/01/basic-electrical-engineering-tools.html
ENERGY CALCULATION
Electric Energy
Electric energy is a form of energy used to run or operate various
electrical devices. Standard unit of electrical energy is joule or kilojoule.
The other common units are kilowatt-hour and megawatt-hour.
W = electric energy, in joules (J)
P = electric power, in watts (W)
t = time, in seconds (s)
ENERGY CALCULATION
Example: A television set draws 0.5 A at 120 V. If the set is used 3
hours per day, how much energy does it consume in 10 days?
COST OF OPERATION IN ELECTRICAL
EQUIPMENT/DEVICES
Using the Previous Example: The total energy that a television set
consumed in 10 days is 1.8 kWh. If the cost per kWh is Php 9.72, how
much would it cost?
Php 9.72 – rate/cost per kWh, in Pesos (Php)
COST OF OPERATION IN ELECTRICAL
EQUIPMENT/DEVICES
For a detailed or step-by-step example, please watch the YouTube
Video in the link provided below.
https://www.youtube.com/watch?v=nnsl-lIihdM
BUILDING SYSTEM VOLTAGE
Overview: The Structure of Electric Power Systems in the Philippines
Generation
Transmission
Distribution
End-users
BUILDING SYSTEM VOLTAGE
Overview: The Structure of Electric Power Systems in the Philippines
BUILDING SYSTEM VOLTAGE
ANSI C84.1-2011 Electric Power Systems and
Equipment — Voltage Ratings (60 Hertz)
System Voltage Classes
3.1 Low Voltage (LV): A class of nominal system
voltages 1000 volts or less.
3.2 Medium Voltage (MV): A class of nominal system
voltages greater than 1000 volts and less than 100 kV.
3.3 High Voltage (HV): A class of nominal system
voltages equal to or greater than 100 kV and equal to or
less than 230 kV.
3.4 Extra-High Voltage (EHV): A class of nominal
system voltages greater than 230 kV but less than 1000
kV.
3.5 Ultra-High Voltage (UHV): A class of nominal
system voltages equal to or greater than 1000 kV.
BUILDING SYSTEM VOLTAGE
In Section 1.10.3.5(c) of the
Philippine Electrical Code (PEC), it
is mentioned that:
Where the voltage exceeds 600
volts, nominal, permanent and
conspicuous warning signs shall
be provided, reading as follows:
DANGER — HIGH VOLTAGE —
KEEP OUT
BUILDING SYSTEM VOLTAGE
Power Distribution in Small Buildings
Small commercial or residential buildings have a very simple power
distribution system. The utility will own the transformer, which will sit on
a pad outside the building or will be attached to a utility pole. The
transformer reduces the voltage from 13.8kV down to 120/240 or
120/208 volts and then passes the electricity to a meter, which is owned
by the utility and keeps a record of power consumption.
BUILDING SYSTEM VOLTAGE
BUILDING SYSTEM VOLTAGE
After leaving the meter, the power is transmitted into the building at
which point all wiring, panels, and devices are the property of the
building owner. Wires transfer the electricity from the meter to a panel
board, which is generally located in the basement or garage of a house.
In small commercial buildings, the panel may be located in a utility
closet. The panel board will have a main service breaker and a series of
circuit breakers, which control the flow of power to various circuits in the
building. Each branch circuit will serve a device (some appliances
require heavy loads) or a number of devices like convenience outlets or
lights.
BUILDING SYSTEM VOLTAGE
Power Distribution in Large Buildings
Large buildings have a much higher electrical load than small buildings; therefore,
the electrical equipment must be larger and more robust. Large building owners will
also purchase electricity at high voltages (in the US, 13.8kV) because it comes at a
cheaper rate. In this case, the owner will provide and maintain their own step-down
transformer, which lowers the voltage to a more usable level (in the US, 480/277
volts). This transformer can be mounted on a pad outside the building or in a
transformer room inside the building.
The electricity is then transmitted to switchgear. The role of the switchgear is to
distribute electricity safely and efficiently to the various electrical closets throughout
the building. The equipment has numerous safety features including circuit breakers,
which allow power to be disrupted downstream - this may occur due to a fault or
problem, but it can also be done intentionally to allow technicians to work on specific
branches of the power system.
BUILDING SYSTEM VOLTAGE
BUILDING SYSTEM VOLTAGE
It should be noted that very large buildings or buildings with complex electrical systems may
have multiple transformers, which may feed multiple pieces of switchgear.
The electricity will leave the switchgear and travel along a primary feeder or bus. The bus or
feeder is a heavy gauge conductor that is capable of carrying high amperage current
throughout a building safely and efficiently. The bus or feeder is tapped as needed and a
conductor is run to an electric closet, which serves a zone or floor of a building.
Each electrical closet will have another step-down transformer - in the US, this will drop the
power from 480/277 volts to 120 volts for convenience outlets. That transformer will feed a
branch panel, which controls a series of branch circuits that cover a portion of the building.
Each branch circuit covers a subset of the electrical needs of the area - for instance: lighting,
convenience outlets to a series of rooms, or electricity to a piece of equipment.
DISTRIBUTION EQUIPMENT
Distribution Equipment
1. Distribution Transformer
A distribution transformer or service
transformer is a transformer that
provides the final voltage
transformation in the electric power
distribution system, stepping down the
voltage used in the distribution lines to
the level used by the customer.
The distribution transformer is a main
and largest equipment of distribution
substation.
DISTRIBUTION EQUIPMENT
2. Circuit Breaker
The circuit breaker is an equipment which
automatically cut off power supply of the
system when any fault or short circuit
occurs in the system. It detect and isolate
faults within a fraction of a second thereby
minimizing the damage at the point where
the fault has occurred.
The circuit breakers are specially designed
to interrupt the very high fault currents,
which may be ten or more times the normal
operating currents.
DISTRIBUTION EQUIPMENT
3. Lightning Arrester
Lightning arrester is a most important
protective device of distribution
substation to protect valuable
equipment as well as working
personnel. It arrests and discharges
over voltage to earth during lightning
strokes. These are installed between
line and earth near equipment.
DISTRIBUTION EQUIPMENT
4. Air Break Switch / Isolator
Air break switches are used to isolate
equipment for maintenance and also for
transfer of load from one bus to another.
Lay-out of substation depends upon type
of Air break switches.
These switches are of two types viz.
vertical break type or horizontal break type.
Horizontal break type normally occupies
more space than the vertical break type.
DISTRIBUTION EQUIPMENT
5. Insulator
The main function of an insulator is to
insulate live conductor or equipment at
different voltages with reference to the
ground structures as well as provide
mechanical support.
Provision of adequate insulation in a
substation is of primary importance
from the point of view of reliability of
supply and safety of personnel.
DISTRIBUTION EQUIPMENT
6. Busbar
The busbar is a conductor used to connect two and
more equipment located side-by-side when the
currents are very high. These are usually
rectangular, sometimes tubular, bare copper bars
supported on insulators. The outdoor busbars are
either of the rigid type or of the strain type.
In the rigid type, pipes are used for making
connections among the various equipment. The
strain type busbars are an overhead system of
wires strung between two supporting structures and
supported strain type insulators. Since the busbars
are rigid, the clearances remain constant.
DISTRIBUTION EQUIPMENT
7. Capacitor Bank
It is a series parallel combination of
capacitors required to improve power
factor of the system. They act as
reactive power generators, and provide
the needed reactive power to
accomplish active power in the circuit.
This reduces the amount of reactive
power, and thus total power (kVA) or
the demand.
DISTRIBUTION EQUIPMENT
8. Distribution Panel Board
Distribution panel board consists of
MCCBs, control equipment, meters and
relays are housed in the control room.
The panel frame shall be connected to
the earth grid by an earthing conductor.
A rubber mat of prescribed size and
quality shall lay in front of panel.
END OF LECTURE 1