Power quality disturbances

Guided By :-
Dr. Bhagabat Panda
Presented By :-
Manas Kumar Patro
Regd No. –
1501109287
Mahesh Panigrahi
Regd No. -

CONTENTS:-
Introduction to Power Quality
Power Quality Definition
Causes Of Power Quality Problems
Power Quality Disturbances
Solutions For Power Quality Problems
Conclusion
References

INTRODUCTION:
-
• The aim of power system is to supply electrical energy or
power to customers.
• Non linear loads, utility switching and fault clearing produce
disturbances that affect the quality of this delivered power.
• Power quality means the quality of the normal voltage
supplied to our homes, factories, etc.
• It is based on the extent of variation of the voltage and
current waveforms from the ideal pure sinusoidal waveforms
of fundamental frequency.

POWER QUALITY DEFINITION
• Power Quality is the set of parameters defining the
properties of the power supply as delivered to the user in
normal operating conditions , in terms of the continuity of
voltage and voltage characteristics.
• As per IEEE 100 Authoritative Dictionary of IEEE Standard
Terms, Power Quality is defined as `The concept of
powering and grounding electronic equipment in a manner
that is suitable to the operation of that equipment and
compatible with the premise wiring system and other
connected equipments’.

CAUSES OF POWER QUALITY
PROBLEMS
• Difficult to point an exact cause for a specific
problem.
• Power quality problems are broadly classified as two
categories :
1.Internal Causes
2.External Causes

• 1.Internal causes
i)About 80% of Power Quality problems originate within a
business facility.
ii)Due to large equipments start or shut down, improper wiring
and grounding, overloaded circuits or harmonics.
• 2.External causes
i)About 20% of Power Quality problems originate within the
utility transmission and distribution system.
ii)Due to lightning strikes, equipments failure , weather
conditions etc.

POWER QUALITY DISTURBANCES:-
• Power Quality disturbances can be divided into 2 basic
categories:
• 1.Steady-state variations
• 2.Events
1.Steady-state variations:-Small deviations from the desired
voltage or current values.
i)voltage fluctuations
ii)voltage unbalance
iii)harmonic distortion
iv)high frequency voltage noise

2.Events:-Significant sudden deviations of voltage or current
from the nominal or ideal wave shape.
i)interruptions
ii)voltage sag
iii)voltage swell
iv)transients

1.I) VOLTAGE FLUCTUATION
• Due to variations of total load of a distribution system, action
of
transformer tap changers, switching of capacitor banks, etc.
• If the variations are large enough or in a certain critical
frequency range, it can affect the performance of the
equipment.
Fig.:-Voltage Fluctuation

1. ) VOLTAGE UNBALANCE
• A voltage variation in a three-phase system in which the
three
voltage magnitudes or the phase angle differences between
them
are not equal.
Causes: Large single-phase loads, incorrect distribution of
all
single-phase loads by the three phases of the system.
Consequences: The most affected loads are three-phase
induction
machines.1.iii) HARMONIC DISTORTION
• Non-fundamental frequency components are called harmonics.
• Deviation of voltage and current waveforms from the ideal pure
sinusoidal waveforms of fundamental frequency.
• Causes:
Classic sources
Modern Sources

1.IV) HIGH FREQUENCY VOLTAGE NOISE
• Non periodic high frequency components in supply voltage.
• Caused mainly due to arc welding or operation of electrical
motor.
• Analysis needed only if it leads to some problem with power
system or end user equipments.
.

2.I) INTERRUPTIONS
• Supply interruption occurs when voltage at supply terminals is
close to zero.
• Normally initiated by faults which subsequently trigger protection
measures.
• Based on the duration, interruptions are
subdivided into:
1. Sustained interruptions
2. Temporary interruptions
3. Momentary interruptions
2.ii) VOLTAGE SAG
• Decrease in the RMS value of the
voltage, ranging from a half cycle to
few
seconds(less than 1 minute).

Cont.….
• Referred to as ‘under voltage’, if continues for longer duration.
• Causes:
1)Faults on the transmission or distribution networks.
2)Connection of heavy loads.
• Consequences:
1)Malfunction of microprocessor base control systems.
2)Loss of efficiency in electrical rotating machines.
2.iii) VOLTAGE SWELL
Momentary increase of the voltage, at
the
power frequency, outside the normal
tolerances with duration of more than 1
cycle, and typically less than 1 minute.

VOLTAGE SWELL(CONT.):
• Referred to as ‘over voltage', if continues for longer
duration.
• Causes:
1)Start and stop of heavy loads.
2)poorly regulated transformers
• Consequences:
1)Flickering of lighting and screens.
2)Damage of sensitive equipments.

2.IV)TRANSIENTS
• Sub cycle disturbances of very short duration that vary greatly
in magnitude.
• Mainly subdivided into:
1)Impulsive transient, where there is a large deviation of the
waveform for a very short duration in one direction, followed
possibly by a couple of smaller transients in both directions.
2)Oscillatory transient, where there is a ringing signal or
oscillation following the initial transient.

SOLUTIONS FOR POWER QUALITY PROBLEMS

• Grid Adequacy
• Distributed Resources – Energy Storage Systems
• Distributed Resources – Distributed Generation
• Enhanced Interface Devices
• Develop Codes and Standards

1.Distributed Generation
The most common solution is the combination of
electrochemical batteries UPS and a diesel genset. At
present, the integration of a flywheel and a diesel
genset in a single unit is also becoming a popular
solution, offered by many manufacturers.

2.DISTRIBUTED RESOURCES – ENERGY STORAGE
SYSTEMS
• Restoring technologies
Energy storage systems, also known as restoring technologies,
are used to provide the electric loads with ride-through
capability in poor PQ environmentFlywheels
Electromechanical device that couples a
rotating electric
machine(motor/generator) with a rotating
mass to store energy for short durations.

SUPER
CAPACITORS
• New technology applied to capacitors
• High power density
• Long life and non-toxic
Superconducting Magnetic Energy
Storage (SMES)
Energy is stored in the magnetic field of a coil
made of superconductor material.
• High power density
• Very fast response
• Very expensive (on development)

3.CODES AND STANDARDS
• Need to regulate:
• the minimum PQ level that utilities have to provide to
consumers, and
• the immunity level that equipment should have.4.Enhanced Interface Devices
A.Dynamic Voltage Restorer
B. Transient Voltage Surge suppressors (TVSS)
C. Noise Filters
D.Static VAR Compensators
E. Harmonic Filters
5.Make End-use Devices Less
SensitiveSome measures to increase equipment immunity:
-Add a capacitor with larger capacity to power supplies
– Use cables with larger neutral conductors

CONCLUSION
• The availability of electric power with high quality is crucial for
the running of the modern society. If some sectors are satisfied
with the quality of the power provided by utilities, some others
are more demanding . To avoid the huge losses related to PQ
problems, the most demanding consumers must take action to
prevent the problems. Among the various measures, selection
of less sensitive equipment can play an important role. When
even the most robust equipment is affected, then other
measures must be taken, such as installation of restoring
technologies, distributed generation or an interface device to
avoid PQ problems.

REFERENCES
• Roger C. Dugan , Surya Santoso , H. Wayne Beaty and MARK F.
McGRANGHAN.(2013).Electrical Power Systems Quality.3rd edition McGraw-Hill
Education.
• ALEXANDER KUSKO and MARC.C.THOMPSON.(2007).Power Quality in Electrical
Systems .New York : Mc Graw-Hill.
• D.SAXENA,K.S.VERMA and S.N.SINGH.(2010).Power Quality Even Classification : an
Overview and Key Issues . International Journal of Engineering , Science and
Technology.2(3),pp.186-199.
• ALEXANDER KUSKO and MARC.C.THOMPSON.(2007).Power Quality in Electrical
Systems . New York : Mc Graw-Hill.
• M. Bollen, “Understanding Power Quality Problems – Voltage Sags and
Interruptions”, IEEE Press Series on Power Engineering – John Wiley and Sons,
Piscataway, USA (2000).

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