1. ECE-611 Transient in Power System, Spring 2016, NJIT, New Jersey, USA
Different Types of Power Problems
Chintan H. Patel
ECE Department
New Jersey Institute of Technology, New Jersey, USA
cp327@njit.edu
Abstract — Technological world these days has become
dependent upon the electrical power. The mystery of the
equipment failure, data corruption, software and hardware
failure, home utility, small and large scale buisness are the
result of problematic power supply. In these discussion I am
going to describe the most common and routine power
disturbances, and the factors that cause these problems,
how do they affect the equipment, whether it is a
commercial or residential and how to safeguard those
equipment, using the IEEE standards for describing the
power problems and it’s quality.
Keywords— Transients, Interruptions, Waveform Distortion,
Voltage Fluctuations, Sag & Swell, Solutions of Power Problems
I. INTRODUCTION
The need of the electrical power has curiously
increased as our technological world is advancing, as off the
continuous supply of the electrical power. Almost all the
countries, make the commercial power available throughout the
nation by running long grids, interconnecting numerous power
generating stations to the loads. Through these grids the
national needs of the electrical power such as residential,
lighting, heating, air conditioning, along with the critical
supplies to the government bodies, industrial, financial,
commercial, medical, and communication sector. Commercial
power is the much necessity to enable present modern world to
function in a busy and smooth pace.
These days the intelligent technologies have taken a
valuable place in our houses and in many sector off the nation.
These intelligent systems need a power which is free of
interruption and disturbance. But still there are consequences of
large scale power incidents at brief intervals. A study few years
back in USA shows that Industrial an Digital Business firm lose
$45.7 billion every year due to power interruptions, and across
all the business sectors the loss is around $104 billion to $164
billion. Origin of the power problems in the in the commercial
power grid, due to it’s thousands of miles of transmission lines,
is also subject to weather conditions which causes switching
incidents. Power problems are also caused due to the local
facilities due to various number of situations such as startup
loads, faulty distribution, typical electrical noise.
In this paper, we are going to discuss firstly about
what we look at the power, then the problems of the powers and
the last but not the least the solutions to these power problems.
These can be done by using the IEEE standards and various data
collected over the years.
II. HOW WE LOOK AT POWER?
Electricity is an electromagnetic phenomenon at the
wall outlet. Commercial power is provided as an alternating
current (AC), which is a silent, seemingly limitless source of
energy generated at power stations, boosted by transformers
and transported few hundred miles to any location in region.
Smooth AC power is to reliable operation of the sophisticated
systems that we are dependent on. An oscilloscope allows us to
see what the energy looks like. In these world, the commercial
ac power appears as a smooth, symmetrical sine wave, varying
either at 50 or 60 cycles every second (known as Hertz-Hz)
depending on the part of the world you are in. The following
figure 1 shows an AC sine wave that would appear on the
oscilloscope.
Figure 1. sine wave representation on oscilloscope
The sinusoidal wave here represents a voltage
changing from a positive value to a negative value, 60 times

2. per second. When this flowing shape changes size, shape and
symmetry, frequency, or develops impulses, ringing, or drops
to zero, disturbance occurs in power. These ideal sine wave
representation will be shown along the examples of the paper
for all the categories of the power problems.
III. IEEE STANDARDS
The IEEE standards 1100-2005 has addressed
the problem of ambiguity in terminology presents a collection
of consensus best practices for the powering and grounding of
electronic equipment used in commercial and industrial
applications. The other IEEE Standards 1159-2009 addresses
the practice encompasses the monitoring of electrical
characteristics of single-phase and polyphase ac power systems.
It includes consistent descriptions of conducted
electromagnetic phenomena occurring on power systems. This
recommended practice describes nominal conditions and
deviations from these nominal conditions that may originate
within the source of supply or load equipment or may originate
from interactions between the source and the load. Some of
these terms are: (i) Blackout, (ii) Bump, (iii) Power Surge,
(iv) Clean Power, (v) Surge, (vi) Outage, (vii) Dirty Power,
(viii) Glitch, (ix) Spike.
IV. POWER AND IT’S PROBLEMS
Being able to talk effectively about power previously,
the difference between an interruption and oscillatory transients
or some other type of transient, will make an immense
difference while making buying decisions on power corrective
devices. Due to such a mistake would create an expensive
consequences when connected with a wrong power corrective
device, not purchased according to your needs, which would
lead to downtime, lost wages or even damage the equipment.
The following are the defined power quality
disturbances categorized by IEEE have been organized on the
basis of the wave shape in this paper.
1. Transients
2. Interruptions
3. Sag & Under-voltage
4. Swell & Overvoltage
5. Waveform Distortion
6. Frequency Variations
7. Voltage Fluctuations
This paper will conform these categories through details
from different journal and standards and graphics, which would
be able to clarify the differences between the individual power
quality disturbances.
1) Transients: This is potentially the most damaging
type of power disturbance. Basically transient falls
into two subcategories.
i. Impulsive
ii. Oscillatory
 Impulsive:
Impulsive transients occur due to the
sudden high peak events that take place which in-turn raise the
voltage and/or current levels in both positive or negative
direction. These types of the transient events can be further
categorized by the speed at which they click in (slow, medium
and fast). Impulsive transients usually are fast events. For
example, a 5 ns rise time from a steady state electrostatic
discharge of a short time duration. Following image and graph
shows the positive impulsive transients event
Figure 2 positive transient event
The impulsive transient is most people are referring to
when they say that they have experienced a surge or a spike.
The impulsive transient is also sometimes referred to as bump,
glitches, power surge, and spike have been used to describe
impulsive transient.
The reasons for the impulsive transients include
lightning, poor grounding, switching of inductive loads, utility
fault, electrostatic discharge. The results of these causes of
transients can range from loss of data from Data centers,
physical damage to equipment. In all of these, lightning is the
worst and most damaging.
As the power is transmitted over the lines to different
regions in open thru heavy lines, so when lightning occurs, due
to the electric flux created the around the high transmission
lines the lightning gets attracted towards it and that damages the
high voltage lines because of very large charge of the lightning.
These clicks an idea that what is lightning and how it is formed?
Lightning is formed by a buildup charge between the
clouds and the earth, or in between clouds. Clouds acquire
charge or at least become polarized, so that of the electric fields
of the considerable strength are created within the cloud and
between the cloud and adjacent masses, such as earth and other
clouds.

3. When these fields become excessive, to the extent that the
dielectric of the intervening space can no longer support the
electric stress, a breakdown of lightning flash occurs. This is
usually a high current discharge that we are all familiar with.
These effectively close a giant switch between the cloud and the
power line or the adjacent earth.
Physical Phenomenon of lightning
There is constant turnmoil inside a thundercloud. Its
shape changes continuously, developing a tower of
“thunderhead”. Fierce updraft occurs within the cloud and
downdrafts occur near the surface, in which the updraft is
responsible for the charge separation within the cloud which
leads to the creation of large electric fields within and around
the clouds and ultimately electric breakdown occurs.
Mechanism of Lightning
In a theory of creation of lightning, raindrops come into
action, when they fall down they get polarized in the
atmosphere, where the top has the positive charge and the
bottom becomes negatively charged, which has the path same
as the direction of the electric field
Another theory of creation of lightning depends on the
breaking of the water droplets. When they break they acquire
positive charge and in this process the negative charge is
imparted into the air around in the atmosphere. The figure
below demonstrates this theory
Figure-3 Hypothetical case of a cloud with a positive charge in the upper part,
a negative charge in the lower part, and a small region of positive charge near
the base. [1]
For the power circuits the basic transient is lumped up by
the parameters R, L and, C. Wiring and secondary loads have
resistance. Transformers and length conductors have
inductance, while capacitance is the form of the windings of the
transformers, dielectrics between the conductors, and physical
capacitors are added to the circuit
Under the transient conditions, specially under the
abnormal fault conditions, the inductance and the capacitance
can react to a sudden change in the current or the voltage,
causing a very large spikes in the voltage or current. This is
more oftenly seen under an unloaded condition.
The basic circuits for the R, L and C circuits are shown below:
Figure 4 (a) and (b)- Thumbprints of the simple RLC circuits
The voltage transient can also be generated in the local
utility by other means of transients such as Switching and
Ferroresonance. The power utilities need to minimize or
eliminate the effects of such faults and the transients, so that the
consumer’s equipment are not damaged.
Two of the most viable protection methods when it comes
to impulsive transients pertain to the elimination of the potential
electrostatic discharge or the sudden impulse increase in the
voltage or current. For these the use of surge suppression
devices (which is popularly known as transient voltage surge
suppressor: TVSS or surge protective device: SPD).
The electrostatic discharge can arc off to ground off your
finger without damaging us, beyond any surprise, while it is
more than enough to cause an entire computer motherboard to
come at a complete stop and never to work again. In the data
centers, printed circuit board manufacturing facilities or any
similar environment where the PCB’s are exposed to human
handling, it is important to dissipate the potential for the ESD.
For example in any proper data center environment involves air
conditioning of the air in the room, these air conditioning not
only cools the air but also to remove the heat from the data
center equipment, but also adjust the amount of moisture in the
air. While keeping the humidity in the air between 40-55%, will
help in decreasing the potential of the ESD to occur. You’ve
probably experienced how humidity affects ESD potential if
you’ve ever been through a winter when a few drags of your
socks across the carpet cause a tremendous arc to jump from
your finger unexpectedly to the doorknob you were reaching
for, or expectedly if you were aiming for someone’s ear. The
other things we experience in the PCB environment or any
small computer repair business is to keep the human body
grounded. This includes wrist straps, antistatic mats and
desktops, and antistatic footwear. Most of the equipment are
connected to a wire which leads to the ground facility, which
keeps the people safe from the electric shock and also dissipates
possible ESD to ground.
Surge Protective Device are in use since a long time.
These devices are still in use with the utility systems, as well as
devices with larger facilities larger facilities, data centers, small
business and home use. There has been an improvement in these
SPD’s over the year with the improvement in the metal oxide
varistor (MOV) technology. MOV technology allows for an
consistent suppression of the impulsive transient, swells and

4. other high voltage conditions, which are combined with the
thermal tripping devices such as circuit breakers, thermistors,
as well as other components such as gas tubes and thyristors.
For some of the appliances the SPD circuits are in-built, for
example the computer power supplies with in-built suppression
ability. They are more oftenly used to provide surge
suppression and emergency battery power should interrupt, or
when the power level is not safe and outside of the controllable
condition or safe power conditions.
 Oscillatory:
Oscillatory transient is a phenomenon
where we see a sudden change in the steady state condition of
the signal’s voltage, current or both the positive and the
negative signal, oscillating at the natural frequency. In simple
terms, the transient usually decay to zero within the cycle.
These transients occur when someone turn off an
inductive or capacitive load, such as a motor or a capacitor
bank. An oscillatory transient results because the load resists
the change. This is similar to that of suddenly turning off the
rapidly flowing faucet and we hear a hammering noise in the
pipes. The flowing water resists the change and the fluid
equivalent to that of the oscillatory transient that occurs.
For example, when we turn on the spinning motor, it act
briefly as a generator as it powers down, thereby producing
electricity and sending it through the electrical distribution. As
a long electrical distribution system acts as an oscillator when
the power is switched on or off, because all the circuits have
some inherent inductance and distributed capacitance that
briefly energies in a decaying form. When the oscillatory
transient appear on an energized circuit, usually because of the
utility switching operations, they can be quite disruptive to
electronic equipment.
The following figure 5 shows a typical low frequency
oscillatory transient attribute to capacitor banks which are
energized.
Figure 5 waveform of the oscillation in the capacitor banks
The most common and recognized problem associated
with the capacitor switching and its oscillatory transient is the
tripping of the adjustable speed drives (ASD’s). The relatively
slow transient cause a rise in the dc link voltage, which causes
the drive to trip off-line with an indication of over-voltage.
The common solution to these capacitor tripping is the
installation of the line reactors or the chokes that dampens the
oscillatory transient to a manageable level. These reactors can
be installed ahead of the drives or the DC link and are available
as a standard feature or as an option on most of the ASD’s.
Another solution to these oscillatory transient is the zero
crossing switch. When a sine wave arc descends and reaches
the zero level, this is called zero crossing as shown in the figure
6. A transient caused by the capacitor switching will have a
greater magnitude the farther the switching occurs away from
the zero crossing time of the sine wave. These zero crossing
switch will solve the problem by monitoring the sine wave to
make sure that the capacitor switching occurs as close as
possible to the zero crossing timing of the sine wave.
Figure 6 Zero crossing in a sine wave.
The UPS and the SPD systems are also effective in
reducing the harm that the oscillatory transients can cause,
especially between common data processing equipment such as
computers in a network. Though they cannot prevent the
intersystem occurrences of the oscillatory transients that a zero
crossing switch and a choke type device can prevent on
specialized equipment, such as the manufacturing floor
machining and their control system.
2) Interruptions:
The complete loss of the power supply
voltage or the load current is known as an interruption in terms
of power problems. Interruptions are categorized depending on
their duration such as instantaneous, momentary, temporary, or
sustained. The following example defines the types of the
interruptions category and the figure 7 below it shows an
example of interruption.
a. Instantaneous: 0.5 to 30 cycles
b. Momentary: 30 cycles to 2 second
c. Temporary: 2 seconds to 2 minutes
d. Sustained: greater than 2 minutes
Figure 7 example of the Interruption
The cause of the interruption can vary, but the result of
some type of the electrical supply grid damage, such as
lightning strokes, animals, trees, vehicle accidents, destructive
weather, equipment failure, or a basic circuit breaker tripping.
When the utility infrastructure is designed to automatically
compensate for many of these problems stated above, it is not
impeccable.

5. The most common example of what can cause
interruptions in commercial power system utility protective
devices, such as automatic circuit reclosers. Reclosers
determine the length of the time for most of the interruptions,
depending on the nature of the fault. Reclosers are the devices
used by the utility companies to sense the rise in the current
from a short circuit in the utility infrastructure, and to shut off
the supply power when this occurs. The recloser will, after a set
time bring power back on line, in an attempt to burn off the
material creating the short circuit. You have also experienced
an interruption if you have ever seen all the power in your house
go out, just to have everything come back on a few minutes later
while you’re breaking out the candles. The power go out in your
house, even if it lasts all night, may be only an inconvenience,
but it can cause great expense.
An interruption, whether it is instantaneous, momentary,
temporary, or sustained, can cause disruption, damage, and
downtime, from the home user up to the industrial user. A
home, or a small business computer user, could lose valuable
data when the information is corrupted from the loss of power
in the equipment. More detrimental loss can be sustained by the
industrial customer due to the interruptions. Many industrial
processes count on the constant motion of certain mechanical
components. When these components shutdown suddenly from
an interruption, it can cause equipment damage, ruination of the
product, as well as the cost associated with the downtime,
cleanup, and restart. For example, in an yarn manufacturing
company while the yarn is being produced and there is
interruption in the power so the machine stops suddenly and the
yarn roll break out which in turn causes out excessive waste and
downtime. As for consistency yarn must be extruded at certain
speed for a good quality of end product.
The solution against the interruptions vary, both in
effectiveness and cost. The first effort should go into
eliminating or reducing the likelihood of the potential problems.
Good design and the maintenance of the utility systems are, of
coarse, essential. This is also to the industrial customer’s system
design, which is often as extensive and vulnerable as the utility
system.
Once the potential for the problems is reduced, additional
equipment or design methods are needed to allow the
customer’s equipment or process to ride-through, or restart after
unavoidable interruptions. The most common mitigating
devices employed are the uninterruptible power supply (UPS),
motor generator, and the use of the system design techniques
that take the advantages of the reductant systems and the energy
storage. When the power goes out, these forms of alternative
power can take over and can reduce the damage that is caused
by the interruption. The recent advances in the switch
technology have allowed for the standby energy storage system
to be utilized in less than half the cycle as soon as the
interruptions occurs.
The term “sustained interruption” can be explained as in
a commercial utility system where automatic protective
devices, because of the natures fault, cannot bring back the
power back online, and manual intervention is needed. This
terminology can be explained by the situation rather than using
the simple term of the power outage. The term outage generally
refers to the state of a component in the system that has failed
to function as it was expected to function (IEEE Std C37.100-
1992). It is probably safe to say that you are experiencing a
sustained interruption if the power has been off for more than 2
minutes, and you see utility trucks appear shortly after to repair
utility lines outside.
3) Sag & Under-voltage:
The reduction of the AC voltage
at a given frequency for the duration of 0.5 cycles to 1 minute
of time is known as SAG. Sag are usually caused by the systems
faults, and are also often the result of switching on loads with
the heavy startup current. Common causes of the sags includes
starting large loads, and remote fault clearing performed by the
utility equipment. Similarly, starting of the large motors inside
of the industrial facility can result in a significant voltage drop
(sag). A motor can draw six times its normal running current,
or more, while starting. Creating a large sudden electrical load
such as this will likely cause a significant voltage drop to the
rest of the circuit it resides on. Imagine that all the water outlets
in your house are turned on while you are having a shower. The
pressure of the water in your shower would for surely drop. As
a solution to this problem there might be another water heater
as a backup which is dedicated to the same shower line. The
same problem is true for the electronic circuits with large
startup loads that can create a large inrush current draw.
Figure 8 Example of SAG
While the most effective solution is adding a dedicated
circuit for the large startup loads, which might not be practical
or economical, specially if the whole facility has a myriad of
large startup loads. Other solutions to that of the large startup
loads include alternative power starting sources that do not load
the rest of the electrical infrastructure at the startup of the motor,
such as reduced voltage starters, with either autotransformers,
or self-delta configurations. A solid state type of soft starter is
also available which is effective at reducing the voltage sag at
the startup of the motor. Recently the adjustable speed drivers
(ASD’s) which may vary the speed of the motor I respective of
the load, this have been use in the industries to control the
process more efficiently and economically.
As mentioned in the interruption, the attempt of the
utility infrastructure to clear remote faults can cause problems
for the end users. When this problem is more evident it is seen
as an interruption. The techniques used as the solution for the
interruption, same can also be used to address the sag: the UPS
equipment, motor generators, and the system design techniques.
However the damage caused by the sag sometimes is not
apparent until it is seen overtime. While still in the infant time
some industrial processes provide sag analysis as a value-added
service to their customers. A sag analysis can now be performed
to determine that at what sag level the equipment can work

6.  Under-voltage:
It is the result of the long term that
creates the problem of the sag. The term “brownout” has
been commonly used to describe this problem, and has
been supersede by the term under-voltage. Brownout is
ambiguous in that it also refers to commercial power
delivery strategy during the periods of high demand.
Under-voltage can create overheating of the motor, and can
lead to the failure of the non-linear loads such as computer
power supplies. The solution for the sags also are applied
the that of the under-voltages. However, a UPS with the
ability to adjust voltage using an inverter first before using
the battery power will prevent the need to replace of the
UPS batteries as often.
Figure 9 Example of Under-voltage
4) Swell & Overvoltage:
When there is an increase in
the AC voltage for the duration of 0.5 cycles to 1 minute of time
is known as swell. It is the reverse of sag. For the swells to occur
the reasons like high impedance neutral connections, sudden
change in load regulations, and a single-phase fault on a three -
phase system are the most common.
The result of the swell can lead to data errors, flickering
of light, degradation of electrical contacts, semiconductor
damage in electronic equipment, or insulation degradation.
Figure 10 Example of Swell
The solutions for the swell are much similar to that of sag,
such as power line conditioners, UPS systems, and
ferroresonant control transformers. Unlike sag, swell may not
be apparent until their results are seen. Having a UPS or a power
conditioning devices that also monitor and log the incoming
power events will help us to measure when and, how often the
events of swell occur.
 Overvoltage:
Overvoltage on a long term can create
the problem of swell. It can also be thought of an extended
swell. The phenomenon of over voltage is common in the area
where the supply transformer tap settings are set incorrectly and
the load have been reduced. This is common in the seasonal
regions where the communities reduce the power during the off
season and the output is set for the high usage part of the season
and high power is still supplied even though there is no need of
high power. It is likely putting your thumb over the end of the
garden hose. The pressure increases because the hole where the
water comes out has been made smaller, even though the
amount of water coming out of the hose is the same as before.
The over-voltage conditions can create high current drawing
conditions and can cause unnecessary tripping of the
downstream circuit breaker, as well as overheating and putting
the stress on the equipment. Thus over-voltage can be compared
to that of the constant swell.
Figure 11 Example of Over-voltage
The solutions to prevent the over-voltage are the same by using
the UPS or conditioning equipment that works for swell and
also work for the over-voltage. But if the incoming power at
your facility is constantly in an overvoltage condition then the
utility power at your facility needs a check as well. The results
of the over-voltage is almost similar to that of the swell. But as
over-voltage is more constant than that of swell, excessive heat
might dissipate out of the equipment which is a proper
indication of over-voltage. Equipment which suddenly start
dissipating more heat than it is suppose too is due to the stress
induced by over-voltage. This is detrimental in tightly packed
data centers, equipment placed in such a place where there is
less space available for the discharge of heat and can cause the
equipment to heat up more and cause over voltage or circuit
breakage due to excessive heating.
5) Waveform Distortion:
The change in the waveform
of the power which is being transmitted or delivered to an
particular equipment. There are five primary types of waveform
distortion.
i. DC offset
ii. Harmonics
iii. Inter-harmonics
iv. Notching
v. Noise

7. DC Offset:
The direct current (DC) can be induced into an AC
distribution system, often due to the failure of the rectifiers
within many of the AC to DC conversion technology that have
been in the proliferated modern equipment. DC can traverse the
AC power system and can add some unwanted current to the
device that is already operating at the level at which they are
rated to operate. This can also cause overheating and saturation
of the transformer due to the circulating DC currents. When a
transformer saturates, it not only gets hot, but also is unable to
deliver full power to the load which it is suppose too deliver at
the output, and the subsequent waveform distortion can create
further instability in the electronic load equipment. The
example of the DC offset is shown in the waveform below:
Figure 12 Example of DC Offset voltage
The solution to the DC offset voltage is to replace the faulty
equipment that is the source of the problem. Having the very
modular, user replaceable, equipment that can be very much
useful in increasing the ease to resolve the DC Offset problems
caused by the faulty instruments, but they can be in a need of
an specialized repair labor which could even save money and
resolve the problem.
Harmonics:
Harmonic distortion is the corruption of the
fundamental frequency of the sine wave that are the multiples
of the fundamentals. For example 180Hz is the 3rd
harmonics of
the 60 Hz fundamental frequency. The symptoms of the
harmonic distortion include overheated transformers, neutral
conductors, and other electrical distribution equipment, as well
as the tripping of the circuit breaker and the loss of the
synchronization on the timing circuits that are dependent upon
a clean sine wave trigger at the zero cross-over voltage/ point.
Harmonic distortion is a significant problem with the IT
equipment in the past due to the nature of the switch mode
power supplies. These non-linear loads and many capacitive
design, instead of drawing the current over each full half cycle,
does “sip” some power at the positive and the negative peak of
the voltage wave. The return current, due to its short nature
combines with the neutral and all other return forms from the
SMPS using each of the three- phase in the typical distribution
system. Instead of subtracting the pulsed neutral current they
add up togather, creating a very high neutral current, almost
1.73 times that off the maximum phase current. An overload
neutral can lead to extremely high voltage on the legs of the
distribution system, leading to heavy damage to the attached
equipment. At the same time, the load of SMPS are drawn at
it’s peak voltage of the half cycle, which often leads to
transformer saturation and consequent overheating, other load
contributing to this problem are the variable speed motor drives,
lighting ballasts and large legacy UPS systems. The methods
use to mitigate this problem have included in over-sizing the
neutral conductors, installing K-rated transformers, and the
harmonic filters.
Figure 13 Typical Harmonic Waveform Distortion
Inter-harmonics:
They are a type of a waveform distortion
that are usually the result of a signal imposed on the supply
voltage by the electrical equipment such as the static frequency
converters, induction motors and the arcing devices. Cyclo-
converters (used in large scale industries), create some of the
most significant inter-harmonic supply power problems. These
device transform the supply voltage into the AC voltage of a
frequency lower or higher than that of the supply frequency.
The most noticeable effect of the inter-harmonic is the visual
flickering of the display and the incandescent light, as well as
the possible heat and communication interference.
Figure 14 Inter-Harmonic Waveform Distortion
The solution to that of the inter-harmonic waveform distortion
is by including the filters to the circuit, UPS systems, and the
line conditioners.
Notching:
This is periodic voltage disturbance caused by the
electronic devices, such as variable speed drives, light dimmers,
and the arc welders under normal operation. This problem could
be described as a transient impulse problem, but because the
notches are periodic over each half cycle, so notching is
considered a waveform distortion problem. The usual
consequences seen in notching are system halts, data losses, and
transmission problems.
By moving the load away from the equipment causing
the problem is one of the solution to notching. UPS and the

8. equipment filter are also viable solution for the equipment that
cannot be relocated.
Figure 15 Notching
Noise:
The unwanted voltage or current that are imposed on
the power system voltage of the current voltage is known as
noise. Noise can be generated by any means such as power
electronic devices, control circuits, arc welders, switching
power supplies, radio transmission and many more. Poorly
grounded sites make the system more susceptible malfunction,
long- term component failure hard disk failure, and the distorted
video display.
Figure 16 Noise
There many different ways of controlling the noise and
sometimes it is very much necessary to use different types of
techniques together at the same time in order to achieve a
desired result. Some of the methods to solve to suppress the
noise are:
 Isolate the load via UPS
 Install a grounded, shielded isolation transformer
 Relocate the load away from the interference source
 Install noise filters
 Cable shielding
One of the most common problem is the corruption the data due
to the generation of the EMI (electromagnetic interference) or
RFI (radio frequency interference, which creates the inductance
around the data carrying cable. The solution to this particular
problem involves moving the data carrying devices away from
the EMI/RFI sources, or to provide additional shielding to these
kind of devices to nullify the effect of the EMI/RFI.
6) Voltage Fluctuations:
As the fundamentals of the
voltage fluctuations are different from that of the rest of the
waveform, they are considered an totally independent category.
A voltage fluctuation is a systematic variation of the voltage
waveform or a series of random voltage changes, of small
dimensions, around 95 to 105% of nominal at a low frequency,
which is generally below 25Hz.
Figure 17 Example of Voltage Fluctuation
Any load which has a significant current variation can
cause voltage fluctuations. Arc furnaces are the most common
cause of voltage fluctuation on the transmission and distribution
system. One of the example for voltage fluctuation is the
flickering of incandescent lamps.
The solution to these is by removing the offending load,
relocating the sensitive equipment, or installing power line
conditioning or the UPS devices.
7) Frequency Variations:
This is a very rare occurring
transient in the utility power systems, especially the systems are
interconnected via a power grid. Where sites have dedicated
standby generators or poor power infrastructure, frequency
variation is often seen if the power generator is heavily loaded.
Generally the modern day equipment are frequency tolerant,
and are generally not affected by minor shifts in the local
generator frequency. The devices which are affected by the
frequency variations are any kind of motor devices or the
devices which are sensitive to the input power. Due to the
frequency variation that occur in the input power of the motor
may vary the working of the motor by making it run faster or
slower to match the frequency of the input power, which causes
the motor to run inefficiently which ends up in adding extra heat
and degeneration of the motor due to fluctuation in the speed of
the motor or excessive drawing of current
Figure 18 Example of Frequency Fluctuation
The solution to the frequency variation is just that all the
power generation sources causing this have to assessed,
repaired, corrected, or replaced
Voltage Imbalance:
This is not included in the type of
waveform distortion, as it is much needed to be aware about the

9. voltage imbalances while we are accessing the power quality
problems and the merit discussion in this paper. These problems
are generally caused by external utility supply, the common
source of the voltage imbalance is internal, and can be caused
by the facility loads. The voltage imbalance is often seen in the
Three-phase power distribution system where one leg is
supplying power to the single phase equipment, while the
system is supplying power to the three phase load. To access
the state of the voltage imbalance in the three phase network is
to take the difference between the highest and the lowest
voltages in the supply, which should not vary by more than 4%
of the lowest supply voltage in that particular network
V. CONCLUSION
The use of the electrical equipment in the day to day life
from home applications to large scale industries the awareness
of the power quality and the effects that are caused on the
electrical equipment has quiet increased over the time. The
modern world is greatly moving towards the use of equipment
that run on the small microprocessors that are very sensitive to
even a small variation in the input power. These
microprocessors can control an fast automatic assembly in
many of the manufacturing or factories, which can face
downtime due to the problems created by the power. The
economical solutions to these power problems are upto certain
limit, according to there definitions and the needs from the
described phenomenon.
The solutions which are mentioned in this paper if taken
in consideration can save your equipment from getting
damaged or blown out.
REFERANCES
1. A. Greenwood, “Electrical Transients in Power
Systems,” Second Edition, 1991, John Wiley & Sons,
Inc.
2. White Paper 18, The Seven Types of Power Problems,
by Joseph Seymour.
3. Ron A. Adams, Power Quality: A Utility Perspective,
AEE Technical Conference Paper,October, 1996.
4. Wayne L. Stebbins, Power Distortion: A User's
Perspective on the Selection and Application of
Mitigation Equipment and Techniques, IEEE Textile
Industry Technical Conference, Paper, May, 1996.
5. IEEE Recommended Practice for Powering and
Grounding Sensitive Electronic Equipment (IEEE
Green Book), IEEE Std. 1100-1992.
6. Transient and Surge- Protection Consid, paper, By
Don Gies