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Presented by:

IndrajeetIndrajeetIndrajeetIndrajeet PrasadPrasadPrasadPrasad

Content:

• WHAT IS POWER QUALITY

• PQ PROBLEMS

• DESCRIPTION OF PQ PROBLEMS

• SOURCES OF PQ PROBLEMS• SOURCES OF PQ PROBLEMS

• MAJOR PQ PROBLEMS

• HOW THEY AFFECT

• HOW TO MONITOR

• BENEFITS OF PQ MONITORING

• CONCLUSION

• REFERENCE

WHAT IS POWER QUALITY ?

The term Power quality is used to describe the extent ofvariation of the voltage, current and frequency on thepower system. The variation of voltage and current caneither be in terms of magnitude or waveformshape/distortion.shape/distortion.

WHAT IS POWER QUALITY MONITORING ?

The best way to detect and diagnose the problems inelectrical power system is called Power qualitymonitoring.

POWER QUALITY PROBLEMS:

• 1.Disturbance

I. Voltage sag

II. Voltage interruption

III. Voltage swellIII. Voltage swell

IV. Transient

V. Voltage notch

• 2.Imbalance

• 3.Distortion

• 4.Voltage fluctuation

• 5.Voltage flickering

DESCRIPTION:

• 1.DISTURBANCES

A DISTURBANCE IS DEFINED AS THE TEMPORARY DEVIATION

FROM THE STEADY STATE WAVEFORM.FROM THE STEADY STATE WAVEFORM.

• VOLTAGE SAG

Reduction in voltage magnitude for a short period of time.

• VOLTAGE INTERRUPTION

Voltage sag with 100% reduction in amplitude.

• VOLTAGE SWELL

Increase in RMS voltage or current at the power frequency between 1.1

to 1.9 per unit for a duration of 8milisec to 1min.

• TRANSIENT

Voltage disturbance shorter than sag/swell and are caused by sudden

changes in power system.

• VOLTAGE NOTCH

Periodic transient occurring within each cycle.

• 2.IMBALANCE

A SITUATION IN WHICH VOLTAGE,FREQUENCY AND PHASE ALL ARE DIFFERENT.

• 3. DISTORTION

IT IS GENERALLY EXPRESSED IN TERMS OF HARMONICS WHICH ARE SINUSOIDAL IT IS GENERALLY EXPRESSED IN TERMS OF HARMONICS WHICH ARE SINUSOIDAL

VOLTAGES OR CURRENTS HAVING FREQUENCY THAT ARE INTEGER MULTIPLE OF THE

FREQUENCY AT WHICH THE SUPPLY SYSTEM IS DESIGNED TO OPERATE.

• 4.VOLTAGE FLUCTUATION

THE RAPID CHANGE IN VOLTAGE MAGNITUDE IN THE ALLOWABLE LIMIT I.E., 95% TO 105%.

• 5.VOLTAGE FLICKERING

THE COLOUR OCCURING WHEN THE FREQUENCY OF VARIATION OF LIGHT FLUX LIES

BETWEEN FEW HERTZ AND FUSION FREQUENCY.

PQ is a Business Problem:

Power Quality issues cause business problems

such as:

– Lost productivity, idle people and equipment

– Lost orders, good will, customers and profits

– Lost transactions and orders not being processed

– Revenue and accounting problems

– Customer and/or management dissatisfaction

– Overtime required to make up for lost work time

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PQ Problems are Expensive

– Berkeley Lab Study Estimates $80 Billion Annual Cost of Power Interruptions … Research News, Berkeley Lab, February 2, 2005

– $50 billon per year in the USA is lost as a results of power quality breakdowns …. Bank of America Report

– A manufacturing company lost more than $3 million one day last summer in Silicon Valley when the “lights went out.” … New York Times January 2000

– “A voltage sag in a paper mill can waste a whole day of production - $250,000 loss” … Business Week, June 17,, 1996

– Half of all computer problems and one-third of all data loss can be traced back to the power line … Contingency Planning Research, LAN Times

Who is Affected?

• High Cost Facilities

o Semiconductor plants

o Pharmaceuticals

o Data centerso Data centers

• Medium Cost Facilities

o Automotive manufacturing

o Glass plants

o Plastics & Chemicals

o Textiles

Sources of PQ Problems:

Utility Sources

– Lightning

– PF Correction Equipment

– Faults

Internal Sources

• Individual Loads –Lighting, Elevators, Coolers, HVAC

• Uninterruptible Power Supplies – Faults

– Switching • Variable Frequency Drives

• Battery Chargers

• Large Motors During Startup

• Electronic Dimming Systems

• Lighting Ballasts (esp. Electronic)

• Arc Welders, and Other Arc Devices

• Medical Equipment, e.g. MRIs and X-Ray Machines

• Office Equipment and Computers

• Wiring

Major PQ Problems:

Spikes, 7%

Outages, 6%

Sags, 56%Swells, 31%

Swells

System fault conditions

Switching on a large capacitor bank

Switching off a large load

Sags (Dips)

Associated with system faults

Switching of heavy loads

Starting of large motors

HOW DO THEY AFFECT YOU:

• Motors stall

• Computers crash

• Production is affected

• Equipment damaged• Equipment damaged

• Product spoilage

• ‘The lights go out’

How To Monitor:

POWER QUALITY PROBLEM SOLUTION

VOLTAGE SAG UPS,DVR,CVT

VOLTAGE INTERRUPTION UPS

VOLTAGE SWELL UPS,POWER CONDITIONERVOLTAGE SWELL UPS,POWER CONDITIONER

TRANSIENT SVC

VOLTAGE NOTCH SNUBBER CKT

IMBALANCE PROTECTION SCHEME

DISTORTION SERIES & SHUNT ACTIVE FILTER

VOLTAGE FLUCTUATION SVC

VOLTAGE FLICKERING VOLTAGE UNBALANCED RELAY

BENEFITS OF POWER QUALITY MONITORING:

Direct Benefits / Technical Benefits• – Energy Savings

• – Release of blocked capacity

• – Reduced temperature rise• – Reduced temperature rise

• – Increased reliability / Life of equipment (e.g. Transformer, Motors, capacitors...)

• – Reduced mal-function of equipment (e.g. Drives, Relays, Meters)

Indirect / Regulatory Benefits• – Penalty savings / Incentives (e.g. Demand charges)

• – Tax benefits

• – Compliance to standards & Regulations

Conclusion:

• DISTURBANCES PLACE ALL BUSINESSES AT RISK BOTH

IN TERMS OF FINANCIAL LOSSES AND ENERGY

EFFICIENCY SO THEY SHOULD BE TAKEN SERIOUSLY.EFFICIENCY SO THEY SHOULD BE TAKEN SERIOUSLY.

• POWER QUALITY MONITORING IS VERY ESSENTIAL TO

GET AN UNINTERRUPTABLE AND EFFICIENT POWER

SUPPLY.

References:

• UNDERSTANDING POWER QUALITY PROBLEMS – VOLTAGE SAGS &INTERRUPTIONS, MATH H J BOLLEN, IEEE PRESS.

• AN INTEGRATED APPROACH TO POWER QUALITY IMPROVEMENT, R VENKATESH & S R KANNAN, - ET POWER TECH .VENKATESH & S R KANNAN, - ET POWER TECH .

• SOLUTIONS TO THE POWER QUALITY PROBLEM, PROF. RAY ARNOLD,IEE POWER ENGINEERING JOURNAL, APRIL 2001

• POWER QUALITY ISSUES A DISTRIBUTION COMPANY PERSPECTIVE,IEE POWER ENGINEERING JOURNAL, APRIL 2001

• MONITORING POWER FOR THE FUTURE, AFROZ K. KHAN, IEEPOWER ENGINEERING JOURNAL, APRIL 2001