PRESENTED BY:ABHILASH MAHAPATRA REGN: 1201294142GUIDED BY Dr.

CONTENTSWHAT IS POWER QUALITYPOWER QUALITY PROBLEMSSteady State Voltage SwellVoltage SagInterruptionHarmonicsVoltage fluctuationPower frequency variationLong duration voltage variationOver voltageUnder voltagePOWER QUALITY SOLUTIONS D-STATCOMDVR Dynamic Voltage Restorer

CONCLUSIONREFERENCES

POWER QUALITYIEEE1100 defines power quality as the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment.Any deviation from perfect sinusoidal waveform that can result in failure or misoperation of customer equipment.Providing customers with clean sinusoidal waveforms at 50 Hz without sags or spikes.Providing power to allow sensitive electronic equipment to operate reliably.

Why PQ is important?Proliferation of highly sensitive computerized equipment places more stringent demands on PQSemiconductor industryComputers and related businessVariable-Speed Drives / RobotsProgrammable logic controllersElectronic equipment results in more PQ problems

Power Quality DisturbancesShort duration voltage variation Voltage SwellVoltage SagInterruptionHarmonicsVoltage fluctuationPower frequency variationLong duration voltage variationUnder voltageOver voltage

PQ disturbances & effectsVoltage Swellas an increase in rms voltage between 1.1 and 1.8 p.u. at the power frequency for the duration 0.5 cycles to 1 min. Causesystem faultsswitching off large loadsEffectsFlickering of lighting and screens.Stoppage and damage of sensitive equipments if the voltage values are too high.loss of data/stability

PQ disturbances & effectsVoltage Sagas an decrease in rms voltage between 0.1 and 0.9 p.u. at the power frequency for the duration 0.5 cycles to 1 min. Causefaultsconnection of large loads

EffectsTripping of contactors and electromechanical relays.Loss of data/stabilityProcess Interruption

InterruptionAn interruption occurs when the supply voltage or load current decreases to less than 0.1pu for a period of time not exceeding 1 min.CAUSES : power system faults equipment failure control malfunctionEFFECTS: Tripping of protecting device loss of information

Waveform Distortion:Harmonics: sinusoidal voltages or currents having frequencies that are integral multiples of the fundamental frequency . Method of characterizing:Harmonic distortionTotal harmonic distortion

Causes: Nonlinear loads Impacts: Mal operation of sensitive equipment fuse blowingTelephone interference

Voltage Fluctuation (flicker): The impact of the voltage fluctuation on lamps such that they are perceived to flicker by the human eye. This is due to loads which exhibit continuous, rapid variations in the load current, particularly the reactive component.Causes Arc furnaces Frequent start/sop of motorImpactsLighting flicker Maloperation of sensitive loads

The deviation of the power system fundamental frequency from its specified nominal value (e.g., 50 or 60 Hz).

Causes:Poor speed regulations of local generation Faults on the bulk power system Large block of load being disconnected Disconnecting a large source of generation Impact :Equipment Failure Frequency Variation

Long Duration Voltage variationUnder voltage: Decrease in the rms value of the voltage to less than90% at the power frequency for a duration longer than one minute.Over voltage: Increase in the rms value of the voltage to greater than 110% at the power frequency for a duration longer than one minute.causes:Switching on/off a large load.Capacitor bank switching off/on.

POWER QUALITY SOLUTIONSD-STATCOM:A D-STATCOM (Distribution Static Compensator), consists of a two-level Voltage Source Converter (VSC), a dc energy storage device, a coupling transformer connected in shunt to the distribution network through a coupling transformer. The VSC connected in shunt with the ac systemcan be used for up to three quite distinct purposes:

1. Voltage regulation and compensation of reactive power;2. Correction of power factor; and3. Elimination of current harmonics.

D-STATCOM

DVR Dynamic Voltage Restorer

In the event of a voltage dip, the power electronic converter injects the appropriate voltage required into the supply bus to compensate for the sag. It effectively acts as a buffer to the load and prevents unacceptable disturbances.A DVR would typically have sufficient energy storage capacity to compensate a 50 per cent three-phase voltage dip for up to 10 cycles, the period normally required for fault clearance. Capacitors serve as the energy storage device.

Harmonic FiltersA harmonic filter usually consists of a capacitor which is connected in series with a reactor. The components are dimensioned to create a series resonance circuit for a required frequency. A harmonic filter works like a short circuit at one or more specified frequencies.

UNINTERRUPTED POWER SUPPLY(UPS)

ON LINE UPS

OFF LINE UPS

HYBRID UPS

UPS

CONCLUSION Power quality problems can not be altogether eliminated from system operation but perfect analysis of system will give exact type and depth of problems. Using these results required corrective measures must be decided and implemented which will lead to minimization power quality disturbances and perfect operation of power system.

REFERENCES

POWER QUALITY ANALYSIS AND MITIGATION BY U.C.CHARLESUSING ACTIVE POWER FILTER TO IMPROVE POWER QUALITY BY LUIS A MORAN AND JUAN W. DIXONPOWER QUALITY PROBLEMS AND NEW SOLUTION BY A. de Almeida, L. Moreira , J. DelgadoBOOKSELECTRICAL POWER SYSTEMS QUALITY BY Roger C. Dugan/Mark F. McGranaghanSurya Santoso/H. Wayne Beaty

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