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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
http://4.bp.blogspot.com/-t8f-LjnZXEk/TbOmzBUuXwI/AAAAAAAAAHU/gjvDIeGxbYo/s1600/Interruption-after-a-Voltage-Sag.jpghttp://4.bp.blogspot.com/-t8f-LjnZXEk/TbOmzBUuXwI/AAAAAAAAAHU/gjvDIeGxbYo/s1600/Interruption-after-a-Voltage-Sag.jpg8/13/2019 voltsge sag
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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