Submitted To:

Mr. Dwarka Prasad

Associate Professor

EE Department

Submitted By:

Ishan Tiwari

B.Tech, VIII sem

10ELDEE021

• Abstract

• Introduction

• Definition of Power Quality (PQ)

• Importance of PQ

• Problems related to PQ

• Cost of PQ problems

• Solutions of PQ problems

• Conclusion

• References

In this seminar, the importance of good Power Quality (PQ) and its

main problems are presented with their associated causes and

consequences. The economic impacts associated with PQ are

characterized. Finally, some solutions to mitigate the PQ problems

are presented.

• Power Quality (PQ) related issues are of most concern

nowadays.

• Due to non-linearity of loads there is a disturbance in

voltage waveforms.

• These loads are electronic equipments, adjustable speed

drives, PLCs etc.

• Money factor also comes in play with power quality.

• When a disturbance occurs, huge financial losses may

happen, with the consequent loss of productivity and

competitiveness.

• The most critical areas are the continuous

process industries and the information technology services.

• Any deviation from a perfect sinusoidal waveform that can

result in failure or mis-operation of customer equipment

• Quality of the Current and voltage provided to the customers

-Providing customers with a clean sinusoidal waveforms at 50

Hz without sags or spikes.

-Providing power to allow sensitive electronic equipment operate

reliably.

• Proliferation of highly sensitive computerized equipment places

more stringent demands on PQ

-Semiconductor industry

-Computers and computer-related businesses

-Variable-speed drives or robots

-Programmable logic controllers

• Electronic equipment results in more PQ problems

• Deregulation of power industry creates more competitive

market

• Impact

-One cycle interruption makes a silicon device worthless

-Five minutes shut down of a chip fabrication plant causes delay

from a day to a week

- One second of power outage makes ecommerce sites lose

millions of dollars worth of business

Voltage sags

Major causes: faults, starting of large loads, and brown-out

recovery

Major consequences: shorts, accelerated aging, loss of data or

stability, process interrupt, etc.

Capacitor switching transients

Major causes: a power factor correction method

Major consequences: insulation breakdown or spark over,

semiconductor device damage, shorts, accelerated aging, loss of

data or stability

Harmonics

Major causes: power electronic equipment, arcing, transformer

saturation

Major consequences: equipment overheating, high voltage/current,

protective device operations

Lightning transients

Major causes: lightning strikes

Major consequences:

insulation breakdown or spark

over, semiconductor device

damage, shorts, accelerated

aging, loss of data or stability

High impedance faults

(One of the-most difficult power system protection

problems)

Major causes: fallen conductors, trees (fail to establish a

permanent return path)

Major consequences: fire, threats to personal safety High

Impedance Fault (RMS)

Noise

Description: Superimposing of high frequency signals on the

waveform of the power-system frequency.

Causes: Electromagnetic interferences provoked by Hertzian

waves such as microwaves, television diffusion,

and radiation due to welding machines, arc furnaces, and

electronic equipment

Consequences: Disturbances on sensitive electronic equipment,

usually not destructive. May cause data loss

and data processing errors.

The costs related to a PQ disturbance can be divided in:

• Direct cost

•Indirect Cost

• Non- material inconvenience

The mitigation of PQ problems may take place at different

levels

Transmission DistributionDistribution resources

Power quality

interface

End-use devices

Power Quality

Events

Assured grid

adequacy

Develop

advanced

distributed

resources

Develop

codes and

standards

Develop

enhanced

interface

devices

Make end-

use devices

less sensitive

• Many PQ problems have origin in the transmission or distribution

grid.

• Proper transmission and distribution grid, with adequate planning

and maintenance, is essential to minimize the occurrence of PQ

problems.

• Use of distributed energy resources (DER) has increased

substantially due of their potential to provide increased

reliability.

• Includes distributed generation and energy storage systems.

• Energy storage systems, also known as restoring

technologies,

• It is used to provide the electric loads with ride-through

capability in poor PQ environment.

Fig – Restoring technologies principle

Fig – Working principle of an energy storage

system.

• Electrochemical battery

• Flywheels

• Super capacitors

•Superconducting Magnetic Energy Storage (SMES)

• It is an electromechanical device that couples a rotating

electric machine (motor/generator) with a rotating mass to

store energy for short durations.

•Traditional flywheel rotors are constructed of steel and have

speed of few thousand rpm whereas advance ones are made up

of carbon fiber and have speed of 40,000 to 60,000 rpm

•They provide power during a period between power supply

failure and the start of a back up generator (diesel)

Fig – A Flywheel

• Ultra capacitors are DC energy sources

•must be interfaced to the electric grid

with a static power conditioner

• provides power during short duration

interruptions or voltage sags.

• medium size capacitors are available

commercially, large size capacitors are

still in development. Capacity is 50 to

60 J/g

Fig. 9 – Electric double layer

super capacitor

•Dynamic Voltage Restorer

•Transient Voltage Surge suppressors (TVSS)

•Constant Voltage Transformers

•Noise Filters

•Isolation Transformers

•Static VAR Compensators

•Harmonic Filters

• Designing the equipment to be less sensitive to disturbances is

usually the most cost effective measure to prevent PQ problems.

• Adding a capacitor with a larger capacity to power supplies,

using cables with larger neutral conductors, de-rating

transformers and adjusting under voltage relays,

are measures that could be taken by manufacturers to reduce the

sensitivity of equipment to PQ problems

The availability of electric power with high quality is

crucial for the running of the modern society. 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 prevent PQ

problems.

• A. de Almeida, L. Moreira. J. Delgado ISR “Power Quality Problems and

New Solutions”–Department of Electrical and Computer Engineering,

University of Coimbra, Pólo II, 3030-290, Coimbra (Portugal)

• P.V.Chopade Member IEEE, V, A. Bugade LMISTE, D.G.Bharadwaj. “ A

step towards securing energy for the future. Ensuring Power Quality and

Reliability”. National Conference @ IIT Roorkee

• Dr. Kurt Schipman, Dr. François Delincé “The importance of good

Power Quality”, ABB Power Quality Products, Belgium

• Surya Santoso,” Power Quality Requirements for Reliability: Towards

`Perfect’Power Quality”, University of Texas at Austin