Power Quality Issues and Improvement

1. POWER QUALITY ISSUES & IMPROVEMENT

2. AN OVERVIEW : TOPICS COVERED
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3. DEFINITION
• The IEEE defines POWER QUALITY as the ability of a system or an equipment to function
satisfactorily in its electromagnetic environment without introducing intolerable
electromagnetic disturbances to anything in that environment.
Power quality is often defined as the electrical network's or the grid's ability to
supply a clean and stable power supply.
In other words, power quality ideally creates a perfect power supply that is always
available, has a pure noise-free sinusoidal wave shape, and is always within voltage
and frequency tolerances.
Power Quality mainly deals with
Continuity of the supply.
Quality” of the voltage.

4. Where:

5. Why is Power Quality Important?
 Low power quality contributes to high energy cost and rising
energy and production disturbances.
 Voltage sag and swell can cause sensitive equipment to fail,
shutdown and create a large current unbalance.
 Reliability: Uninterrupted power supply to the service sectors.
 The performance of electronic devices (semiconductor devices)
is directly linked to the power quality level.
Hence, power quality provides a good platform to deal with all
these problems.

6. Common Behavior of Electrical Disturbances

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CAUSES OF POWER QUALITY PROBLEMS
A. Internal causes :
i. About 80% of Power Quality problems originate within a industrial facility.
ii. Due to large equipment start or shut down, improper wiring and
grounding, overloaded circuits or harmonics.
B. External causes :
i. About 20% of Power Quality problems originate within the utility
transmission and distribution system.
ii. Due to lightning strikes, equipment failure, weather conditions etc.

8. 1. Voltage sag (or dip)
Description: A decrease of the normal voltage level between 10 and 90% of the nominal
rms voltage at the power frequency, for durations of 0,5 cycle to 1 minute.
Causes: Faults on the transmission or distribution. Faults in consumer’s installation.
Connection of heavy loads and start-up of large motors.
Consequences: Malfunction of microprocessor-based control systems. Tripping of
contactors and electromechanical relays. Disconnection of electric rotating machines.
2. Very short interruptions Description: Total interruption of electrical supply for duration from few milliseconds to
one or two seconds.
Causes: Mainly due to the opening and automatic recloser of relays. The main fault
causes are insulation failure, lightning and insulator flashover.
Consequences: Tripping of protection devices.
3. Long interruptions Description: Total interruption of electrical supply for duration greater than 1 to 2 seconds
Causes: Equipment failure in the power system network, storms, fire, human error, failure of
protection devices.
Consequences: Stoppage of all equipment.
POWER QUALITY DISTURBANCES

9. 4. Voltage spike Description: Very fast variation of the voltage value for durations from a several microseconds to
few milliseconds. These variations may reach thousands of volts, even in low voltage.
Causes: Lightning, switching of lines or power factor correction capacitors, disconnection of
heavy loads.
Consequences: Destruction of components (particularly electronic components) and of
insulation materials, electromagnetic interference.
5. Voltage swell Description: Momentary increase of the voltage, at the power frequency, outside the normal
tolerances, with duration of more than one cycle and typically less than a few seconds.
Causes: Start/stop of heavy loads, badly dimensioned power sources, badly regulated
transformers (mainly during off-peak hours).
Consequences: Data loss, flickering of lighting and screens, stoppage or damage of sensitive
equipment, if the voltage values are too high.
6. Harmonic distortion
Description: Voltage or current waveforms having frequencies that are multiples of power-
system frequency.
Causes: All non-linear loads, such as power electronics equipment, SMPS, data processing
equipment.
Consequences: Increased probability in occurrence of resonance, overload in 3-phase
systems, overheating of all cables and equipment, electromagnetic interference with
communication systems.

10. HARMONIC DISTORTION

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BROWNOUTS
A brownout is a steady lower voltage state causes glitches, data loss and equipment failure.
An example of a brownout is what happens during peak electrical demand in the summer, when
utilities can’t always meet the requirements and must lower the voltage to limit maximum
power.
Possible Solutions are using Voltage Regulators, Uninterruptable Power Supplies, and Power
Conditioners.
BLACKOUTS
A power failure or blackout is a zero-voltage condition that lasts for more than two cycles. It
may be caused by tripping a circuit breaker, power distribution failure or utility power failure. A
blackout can cause data loss or corruption and equipment damage.

13. Power Quality Issues – SolutionTree

14. POWER QUALITY MONITORING
 It is a multi-level approach to identifying, analyzing and correcting power quality
problems.
 Helps to identify the cause of power system disturbances.
 Helps to identify problem conditions before they actually cause interruptions or
disturbances.
 Objectives for power quality monitoring are generally classified into:
1. Proactive approach
 Intended to study the system performance.
 Helps to understand and thus match the system performance with customer needs.
2. Reactive approach
 Intended to study a specific problem.
 Performs short term monitoring at different loads.

15. SCHEMATIC PQ MONITORING

16. BENEFITS OF POWER QUALITY
MONITORING
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1. Ensures power system reliability.
2. Identify the source of disturbance.
3. Helps in the preventive and predictive maintenance.
4. Evaluation of incoming electrical supply and distribution to determine if power
quality disturbances are impacting.
5. Reduction of energy costs and avoid hazards.
6. Allows to identify the most sensitive equipment and install power conditioning
systems wherever necessary.

17. Methods to solve PQ issues
 TRANSIENTVOLTAGE SUPPRESSOR – For Overvoltage
A TVS consists of an array of devices that are designed to react to
sudden or momentary overvoltage conditions. It consists of a
metal oxide varistor or a Zener diode) that limits excessive line
voltage and conduct any excess impulse energy to ground
FILTERS- For Noise and harmonics
 Noise filters are used to avoid unwanted frequency current or
voltage signals (noise) from reaching sensitive equipment.
 Harmonic filters are used to reduce undesirable harmonics.
Voltage Regulator – For consistent voltage supply
It maintains a nearly constant output voltage during large
variations in input voltage.

18.  DynamicVoltage Restorer- ForVoltage sag
A dynamic voltage restorer (DVR) acts like a voltage source
connected in series with the load. It injects additional energy to
the circuit whenever necessary.
 StaticVAR compensator- For power factor correction
Static VAR compensators (SVC) use a combination of capacitors
and reactors to regulate the voltage quickly.
 IsolationTransformers – For sensitive loads
Isolation transformers are used to isolate sensitive loads from
transients and noise deriving from the mains.

19. CONCLUSION
1. The mitigation of all the power quality related issues leads to the economic operation of
the power system.
2. A technically sound quality of power will be supplied to all the equipment, thereby
leading to their smooth operation and ensuring a long life for them.
3. The elimination of harmonics and other issues leads to the proper operation of the
system, thereby eliminating the unwanted vibrations and keeping the system stable.
4. The reactive power is balanced at an acceptable and affordable cost and thus, the
system efficiency improves.
5. The power factor is improved; this leads to a heavy savage in the costs of electricity bills.
6. Above all, the problem of power pollution is eliminated.

20. OUTCOMES
 OUTCOME ‘F’
F1. IEEE CODE OF CONDUCT
F2. IEEE CODE OF ETHICS
 OUTCOME ‘H’
H1. Awareness of global effect of product : There is a global need for power quality
improvement with the increase in population & power demand.
H2. Understanding of economic factor: If power quality is not checked and the standards
are not maintained properly, then it can lead to great economic loss for power
generating companies.
H3. Understanding of environmental effects : PQ maintaining equipment are eco-
friendly.

21.  OUTCOME ‘I’
I1: Gather relevant technical and scientific information
I2: Ability to identify retrieving and organization info
I3: To engage in lifelong learning: NEED FOR FUTURE RESEARCH
OUTCOME ‘J’
J1-Describes contemporary issues in modern global contexts
J2- Distinguishes contemporary issues in modern global contexts
J3- Evaluates contemporary issues in modern global contexts by representing a contemporary
technical case study
OUTCOMES

22. REFERENCES
I. Math H.J. Bollen, Understanding power quality problems: voltage sags and interruptions, IEEE Press,
New Delhi.
II. Domijan, A. Heydt, G.T., Meliopoulos, A.P.S., Venkata, S.S., West, S., “Directions of research on electric
power quality,” IEEE Transactions on Power Delivery, Vol. 8, pp. 429-436, 1993.
III. Anurag Agarwal, Sanjiv Kumar, Sajid Ali, “A Research Review of Power Quality Problems in Electrical
Power System”. MIT International Journal of Electrical and Instrumentation Engineering, Vol. 2(2), pp.
88-93, 2012.
IV. Power Quality Problems and New Solutions by A. de Almeida, L. Moreira. J. Delgado.
V. ALEXANDER KUSKO and MARC.C.THOMPSON.(2007).Power Quality in Electrical Systems. New York :
McGraw-Hill.
VI. IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems,
ANSVIEEE Standard 519, 2008