Introduction Power Quality Problems Power Quality Measurement Devices Power Quality Terminology Power Quality Standards Unbundled Power Quality Services Power Quality Monitoring Benefits of Power Quality Conclusion References

1. POWER QUALITY
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2. Index
 Introduction
 Power Quality Problems
 Power Quality Measurement Devices
 Power Quality Terminology
 Power Quality Standards
 Unbundled Power Quality Services
 Power Quality Monitoring
 Benefits of Power Quality
 Conclusion
 References
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3. WHAT IS POWER QUALITY….?
 Power Quality means to have a perfect power supply.
 A perfect power supply would be one that is always
available, always within voltage and frequency
tolerances, and has a pure noise free sinusoidal wave
shape.
 It is a set of electrical boundaries that allows equipment
to function in its intended manner without significant loss
of performance or life expectancy.
 According to IEEE, the concept of powering and
grounding sensitive electronic equipment in a manner
suitable for the equipment.
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4. Notching
Voltage
Transients
Harmonic
Distortion
Power
Quality
Problem
Interruption
Voltage
Swells &
sags
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5. Power quality problems
 Voltage sags: Voltage sag is decrease in voltage to
between 10 and 90% of nominal voltage for one-half cycle
to one minute .They can be generated both internally and
externally from an end users facility.
 Voltage swells: Voltage swells are increase in voltage
above 110% of nominal for one-half cycle to one minute.
Although swells occur infrequently when compared to
sags, they can cause equipment malfunction and
premature wear.
 Harmonics: Harmonics are a recurring distortion of the
waveform that can be caused by various devices including
variable frequency drives, non-linear power supplies etc.
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6. Power quality problems
 Transients: Transients are very short duration (sub-
cycle) events of varying amplitude.
 Interruptions: When the voltage drops below 10% of its
nominal value it is called an interruption or a blackout.
Interruptions have three classifications: momentary,
temporary and sustained.
 Notching: It is a disturbance of opposite polarity to the
normal voltage waveform (which is subtracted from the
normal waveform) lasting for less than one-half cycle.
Notching is frequently caused by malfunctioning
electronic switches or power conditioners.
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7. Power quality problems
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8. Power Quality
Measurement Devices
Oscilloscopes
Data
Loggers
and Chart
Recorders
Harmonic
Analyzer
Transient
Disturbance
Analyzer
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9. POWER QUALITY TERMINOLOGY
 Distortion — Qualitative term indicating the deviation of
a periodic wave from its ideal waveform characteristics.
 Distortion factor —Ratio of the RMS of the harmonic
content of a periodic wave to the RMS of the
fundamental content of the wave, expressed as a
percent. This is also known as the total harmonic
distortion (THD)
 Flicker — Variation of input voltage sufficient in duration
to allow visual observation of a change in electric light
source intensity. Quantitatively, flicker may be expressed
as the change in voltage over nominal expressed as a
percent. For example, if the voltage at a 120-V circuit
increases to 125 V and then drops to 117 V, the flicker,f,
is calculated as
f= 100×(125 – 117)/120 = 6.66%.
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10. POWER QUALITY TERMINOLOGY
 Linear loads —Electrical load which in
steady-state operation presents essentially
constant impedance to the power source
throughout the cycle of applied voltage.
 Nonlinear load —Electrical load that draws
currents discontinuously or whose impedance
varies during each cycle of the input AC
voltage waveform.
 Impulse —Traditionally used to indicate a
short duration overvoltage event with certain
rise and fall characteristics. Standards have
moved toward including the term impulse in
the category of transients
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11. POWER QUALITY STANDARDS IN INDIA
Indian government electricity regulatory authorities use
reliability indices (developed by IEEE) such as:
 System Average Interruption Duration Index (SAIDI)
SAIDI is the average duration of interruptions per consumers
during the year. It is the ratio of the annual duration of
interruptions (sustained) to the number of consumers. If
duration is specified in minutes, SAIDI is given as consumer
minutes.
SAIDI = Total duration of sustained interruptions in a year /
total number of consumers
 System Average Interruption Frequency Index (SAIFI)
SAIFI is the average number of sustained interruptions per
consumer during the year. It is the ratio of the annual number
of interruptions to the number of consumers.
SAIFI = (Total number of sustained interruptions in a year) /
(Total number of consumers)
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12. POWER QUALITY STANDARDS IN INDIA
 Consumer Average Interruption Duration Index
(CAIDI)
CAIDI is the average duration of an interruption,
calculated based on the total number of sustained
interruptions in a year. It is the ratio of the total duration
of interruptions to the total number of interruptions
during the year.
CAIDI = Total duration of sustained interruptions in a
year/total number of interruptions.
It can also be seen that CAIDI = SAIDI/SAIFI
 Electricity Supply Monitoring Initiative (ESMI) executes
basic monitoring of supply continuity and voltage levels
at ordinary consumer locations, in order to get an idea of
the actual situation in the field and to increase the
accountability of electricity utilities. The first three ESMI
data loggers were installed in Pune City.
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13. IEEE POWER QUALITY STANDARDS
 IEEE 644 : Standard Procedure for Measurement of
Power Frequency Electric and Magnetic Fields from AC
Power Lines.
 IEEE 518 : Guide for the Installation of Electrical
Equipment to Minimize Electrical Noise Inputs to
Controllers from External Sources.
 IEEE 519 : Recommended Practices and Requirements
for Harmonic Control in Electrical Power Systems
 IEEE 1100 : Recommended Practice for Powering and
Grounding Sensitive Electronic Equipment
 IEEE 1159 : Recommended Practice for Monitoring
Electric Power Quality
 IEEE 141 : Recommended Practice for Electric Power
Distribution for Industrial Plants
 And many more….
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14. UNBUNDLED POWER QUALITY SERVICES
 The unbundling of power quality services,
defined as permitting several levels of
power quality at a differentiated cost, is a
business concept that achieves its
potential in the presence of technologies
that can provide specific customers with
more than one level of power quality.
 The result of the process will lead to fully
integrated and distributed power
systems—FRIENDS.
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15. Features of friends
 Flexibility in power system
 Reliability of power supply
 Multimenu services to allow customers to
select the type of power provided and other
services offered by the electric utility
 Load leveling and energy conservation
 New automatic generation control
methodologies
 Voltage regulation functions
 Fault current-limiting functions
 Prevention of sags, swells, and harmonics
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16. QUALITY CONTROL CENTERS
 One of the most important characteristics of FRIENDS is
that QCC as a power quality control facility is installed
very closely to customers in order to supply several
qualities of power and enables customers to choose the
quality of power.
 The QCCs play a vital role in the operation of FRIENDS,
such as:
 Flexible change in system configuration
 Multiple menu services for customers (unbundled
services)
 Information management (information processing and
data exchange centers)
 Monitoring and controlling power flow by interchange of
information between QCCs so that the system can
operate in the most effective and economical way
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17. POWER QUALITY MONITORING
 Monitoring system provide information about the
quality of the power and the causes of power
system disturbances, but it can identify problem
conditions throughout the system before they
cause widespread customer complaints,
equipment malfunctions, and even equipment
failures.
 Database management PQ software, equipped
with statistical analysis and plotting tools and
wrapped in a user-friendly interface. It consists of
two major components, the Power Quality Data
Manager and the Power Quality Data Analyzer.
 Internet-based power quality monitoring
system for remote power quality inspecting and
analyzing.
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18. BENEFITS OF POWER QUALITY
 Economic impact
 Equipment reliability
 Environment
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19. Conclusion
 The concept of power quality is a qualitative
one for which mathematical expressions are
not absolutely necessary to develop a basic
understanding of the issues.Thus the main
objective of this study is to improve the quality
and reliability of the electricity supply to
industrial, commercial and domestic users.
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20. References
 A Technical note of Understanding on Power Quality” by
V.J.Gosbell, Technical Director, Integral Energy Power
Quality Center.[1]
 Math H.J.Bollen "Understanding Power Quality
Problems", IEEE
 K.Tsuji, K.Nara, J.Hasegawq and T.Oyama, "Flexible,
Reliable and Intelligent Electric Energy Delivery System:
Concepts and Perspective", Proceedings of the
American Power Conference,Vol.1, pp.504-511, April 6-
8, 1999, Chicago Illinois.
 Method of Measuring Power Quality and Development
of Monitor Device by Shuying Yang, IEEE.
 “Power quality monitoring” by Erich Gunther (electrotek
concepts)
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21. THANKS
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