voltsge sag

8/13/2019 voltsge sag

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Welcome


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Presented by-

Swagat pradhan

VOLTAGE SAG


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What is voltage sag?

A short-term decrease in voltage lasting anywhere

from milliseconds up to a few seconds.

It is a temporary drop below 90 percent of thenominal voltage level.

Usually caused by equipment start or nearby short

circuits on the utility system.


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Voltage Dip

It is the amount by

which the nominal

voltage declines.

In percentage

terms, this is 100-

Voltage Sag.


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Voltage sagsThree cases:

System under Type A sag voltage

Phase voltages during a type A sag


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System under Type C sag voltage

Phase voltages during a type

C sag


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System under Type D sag voltage

Phase voltages during a

type DRsag


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Where do voltage sags occur? Utility systems - Voltage sags can occur on utility

systems both at distribution voltages and

transmission voltages.

Inside industrial plants-Voltage sags are typically

caused by starting large motors or by electrical faults

inside the facility.


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Causes of voltage sag - Opening of reclosers and circuit breakers

Equipment failure

Bad weather Pollution

Construction activity

Animals and birds Vehicle problems

Industrial plants


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ultiphase sags Single phase sagsSingle phase sags
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Effect of voltage sag on adjustable speed drives

Decrease of DC busvoltage undersag

Line currents during sag

event

Case I: Three phase sag


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Case II : Sag due to phase-to-ground fault

Decrease of DC voltage under

different load conditions

Increase of load currents

under different load

conditions


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Case III :Sag due to phase-to-phase fault

Decrease of DC voltage under

sag

Line current during sag

event


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Sensitivity of equipment to voltage sags The voltages

experienced during a

voltage sag conditionwill depend on

equipment connection.

Different categories of

equipment havedifferent sensitivities to

voltage sag.

CBEMA operating voltage

envelope


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Voltage sag evaluation Build and maintain a

transmission line datatable for reference.

Determine area ofvulnerability.

Convert the data of thisarea to actual expected

events per months. Perform the calculations

for different voltage sagseverities.

Sag voltage magnitude


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The Solution

Equipment identification

Identify the voltage sags

Install metering

Record unplanned production stoppages

Choose a solution


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Voltage correction devices Traditional solutions

UPS solutions

Electronic voltage regulators

Pay back on sag correction investment


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Conclusion Voltage sags are becoming an increasing concerns for

process industries due to increasing automation.

Evaluation of fault performance of distribution andtransmission lines can be used to predict the voltage

sag performance at customer facility.

Sensitivity of industrial equipments to voltage sags

varies greatly.


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References IEEE paper , voltage sag in industrial system

,by G. Alonso Orcajo , J.M. Cano R.

IEEE paper , voltage sag analysis ,by Dr. S.Thiruvengadam.

Recommended practice on monitoring electric

power quality,IEEE December 1994.

Effect of voltage sags on adjustable-speed

drives: a critical evaluation and an approach to

improve performance IEEE Transactions on

Industry Applications, vol. 35.


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hank You

voltsge sag

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