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Power Quality

PresentedbyB.Nagaraju

S.Vijayasree

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Introduction

Over the last thirty years or so, the amount of equipmentcontaining electronics has increased dramatically. Such equipment

can both cause and be affected by electromagnetic disturbances.A

disturbance that affects a process control computer in a large

industrial complex could easily result in shutdown of the processAt the other end of the scale, a domestic user of a PC has to re-boot

the PC due to a transient voltage dip, causing annoyance to thatand other similarly affected users.

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What is a Quality Power?

There can be completely different definitions for powerquality, depending on ones frame of reference.For example

a utility may define power quality as reliability and showstatistics demonstrating that its system is 99.98 percentreliable

A perfect power supply would be one that is alwaysavailable, always with in voltage and frequency toleranceand has a pure noise free sinesoidal wave shape.

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CLASSIFICATION OF POWERSYSTEM

DISTURBANCES

1. Voltage dips2. Over and under voltage

3. Harmonics4. Voltage fluctuation5. Transients

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Voltage dips

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Over and under voltageEquipment failures may immediately result in the caseof severe over voltages, but more likely is accelerateddegradation leading to premature failure withoutobvious cause.

Excessive network loading, loss of generation,incorrectly set transformer taps and voltageregulator malfunctions, cause under voltage.

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Harmonics

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REMEDIAL MEASURES

There are many methods available for correcting PowerQuality problems.Brief details of each method are givenbelow, but it is emphasised that the solution adopted will betailored specifically to the problem and site.

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UPS Systems

The former eliminates all problems due to voltagesurges/spikes/dips and interruptions while the latterpasses some of the disturbance through, until the

supply is transferred from the normal source to theUPS.

A UPS system consists of the following:

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EXAMPLE

Investigation of Harmonic Pollution Problems on anIndustrial Plant

An industrial plant was suffering Power Quality problems, and

harmonic pollution was suspected as the cause. A PowerQuality meter was installed at various parts of the network todetermine the extent of the problem and the equipmentcausing the problem.Confirmation of the pollution as beingdue to harmonics was readily obtained

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Conclusion

This centers objective must be towards work withindustry to improve the quality and reliability ofthe electricity supply to industrial, commercialand domestic users.