SONA COLLEGE of TECHNOLOGY , SALEM-5
Department of Electrical & Electronics Engineering
January 2015
Issue 1
About EEE Department
CONTENTS
1
About EEE Department
2
Events
3
Faculty Achievements
4
Students Achievements
Harnessing electrical energy is the challenge for
electrical engineers. The power packed EEE department
inspires the budding Electrical Engineers with the
potent idea of constructing Generating Stations,
Transmission Lines and Distribution Systems at
economic rates and to design, test and supervise the
manufacture of Electrical and Electronic equipments
used in electrical utilities, buildings, automobiles, aircrafts, radar, navigation system and broadcast and
communication systems.
EVENTS
 Conduct Intra College Technical Symposium Techgrill
symposium on 30.9.2014.
IEEE
Department of Electrical and Electronics Engineers
Faculty Achievements
Arulmozhiyal R, Design of Topology for maximum energy efficient charge pumps as storage device
for renewable energy applications , JOURNAL OF CHEMICAL AND PHARMACEUTICAL
SCIENCES JCPHS, 4, 4, Page 266 - 269, 01-Dec-2014.
Arulmozhiyal R , An ANFIS powered Integrated System for Continuous Power for a Domestic Load
by Harnessing Maximum Energy from the Solar and wind Source , INTERNATIONAL JOURNAL
OF ADVANCEMENTS IN ELECTRONICS AND ELECTRICAL ENGINEERING, 3, 3, Page 67
–71,01-Aug-2014.
Student Achievements
P.Kathivel
III yr EEE
Classification of Electrical Power
One of the biggest industries in electrical engineering is power systems. It is the oldest
segment of our industry and has been around for over a century, yet not many people
know much about its inner workings besides electrical engineers in that field. However,
power sytems are something used every day of our lives, so it's important to understand
how they work.The power industry is comprised of three main areas: Generation,
Transmission, and Distribution. Generation, which happens to be my favorite part, is the
actual production of electricity through a number of ways, whether it is through coal and
propane or the relatively newer renewable sources such as solar and wind. Most
generation is done today through coal and propane, though it is starting to shift towards
renewable energy (thankfully).
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Transmission is the high voltage power line system (> 135KV normally) that transmits
the power from the generation source to the distribution system. The distribution system
converts the very high voltages down to lower, more usable voltages. The distribution
system is comprised mostly of 24KV and 12KV lines (varies by state/country) and also
includes the substations and transformers. The figure below shows a summary.
Generation
Generation can be a very tedious task due to electromagnetic fields. It is easy to generate
electricity using electrical motors (that’s another topic for another day), but it’s very
difficult to do it efficiently (more about this later). The real power is the power generated
by all the resistive elements in a power system (P, with unit of Watts), but the
other component of power that is not mentioned often is reactive power (Q, with units of
VARS). Reactive power is created when AC current and AC Voltage are not in phase.
AC voltage and currents can be thought of as sinusoidal wave forms. If you have an AC
voltage over a simple resistor, the current will stay in the same phase. If we pass the same
voltage over an inductor or capacitor, the current will be out of phase, as these two
devices require time to charge and discharge, unlike the resistor, which has no charge or
discharge time and only has a voltage drop and power loss. Specifically, an inductive
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circuit will cause the current to lag behind the voltage, and a capacitive circuit will cause
the current to lead the voltage. A diagram visually explaining this sometimes can be
easier to understand (E is the voltage waveform, I is the Current Waveform, and P is
power).
Equations
There are several useful and fundamental power equations that engineers and physicists
use. One is S=EI, where S is the apparent power (containing the real power in watts and
the reactive power in vars. The units for S are volt-amperes where E is the AC voltage
waveform and I* is the conjugate of the AC current waveform).
It's strange to think of current and voltage as having an angle, though it does simplify
things when you assume the voltage has an angle of 0, since the angles for the current and
voltage are in all practical terms relative anyhow. There are two ways to represent AC
voltages and currents: rectangular (or complex) form or polar (or phasor) form. This is
best explained in an example.
V=IR
This is the most well-known electrical formula, Ohms law, but here we replace R with Z
to account for the fact that most loads are not purely resistive, and have an “imaginary”
component to them. Z is known as the impedance.
V=10∠600
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Z=5+j5
Here we have the voltage in phasor form and the impedance in complex format. In
electrical engineering, we use j in place of the imaginary i, since i also means current.
The conversions between the two are rather simple.
From complex to phasor:
A+jBtoC∠theta
C=A2+B2−−−−−−−√
θ=tan−1(BA)
A=Ccos(θ)
B=Csin(θ)
From the given V and Z values, the current is calculated to be (phasor form):
I=VZ
I=1.414∠150
Power (Power as a form of Real Watts and Reactive VARs) calculations can be slightly
more complex. The *, as mentioned above, is the conjugate of the current.
S=VI∗=|V|2Z∗=I2Z
To obtain the conjugate of the current, you simply negate the angle in phasor form or
negate the imaginary coefficient in complex format. So the complex power here would be
14.14 < 75°. Complex power can also be represented in complex form as P+jQ-- as
we’ve mentioned before, P is the real power and Q is the reactive power. So applying the
same conversion from complex to phasor and vice versa, we can easily obtain
the following formulas
P=VIcos(θ)
Q=VIsin(θ)
P is the real power that consumers pay for, but why is reactive power such an important
thing in the power industry?
Like most businesses, the answer is cost. Simply put, when there is a net reactive power
loss in a system, it costs power plants more resources to output that power.
Mathematically put, when Q is not 0 (power factor is lagging or positive, can be positive
or negative), the magnitude of I is higher than if would be if Q is zero (power factor is
unity). Having to generate a higher
current magnitude can be very costly to a power plant.
Department of Electrical and Electronics Engineers
In the end, power plants and generating facilities are always trying to cancel out whatever
net value of Q is on the system. For most systems, the net Q on the systems tends to be
positive (lagging); this is because most loads on the system will tend to be inductive due
to motor loads think air-conditioning units and transformers, which are always present on
every system regardless of residential, commercial or industrial use. To offset this
mostly inductive load, utilities will install large switching capacitor banks on a
distribution and transmission system to help balance out. These banks will switch on and
off depending on their need at the time, usually they are switched on during peak load
usage times.
There is not a perfect system out there, as it is cost prohibitive. But generally power
factor for a system is kept above .95 for most areas. Visually, power plants are trying
to bring this power triangle to unity (a straight line).
There are many specializations in the power industry; this article only scratches the
surface. The technology is constantly changing and forcing engineers to think of new
ways to come up with solutions to the problems and challenges that it may bring. In
my opinion, the main challenges we face today are the effects of climate change and what
role the power industry plays in it, as well as emerging and newly developed countries
and their appetite for electric power. In this area, only one thing is certain: there will
always be a need for power engineers.
Department of Electrical & Electronics Engineers
News letter organizing Committee
Dr C. Easwarlal
Dr R.Shivakumar
A.Rajendran
Student team
N.Nivas
R.Dinesh Kumar
S.Subbiah
P.Kathivel
K.Preveen
M.vivek
Sona College of Technology,
Junction Main Road,
Salem - 636 005,
Tamilnadu, India.
Phone : 91 - 427 - 2443545, 4099999
Fax : 91 - 427 - 4099888.