121438521 Power Quality
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Transcript of 121438521 Power Quality
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POWER QUALITY
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UNIT - I
INTRODUCTION TO POWER QUALITY
Terms and definitions – Overloading – Under
voltage – Sustained interruption-Sags and
Swells –Waveform distortion – Total Harmonic
Distortion (THD) – Computer Business
Equipment Manufacturers Associations
(CBEMA) curve.
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ENERGY• ENERGY CAN NEITHER BE CREATED NOR BE
DESTROYED BUT IT CAN BE CONVERTED FROM ONE FORM TO ANOTHER FORM.
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ELECTRICAL ENERGY
• GENERATION OF ELECTRICAL
ENERGY IS NOTHING BUT THE
CONVERSION OF VARIOUS OTHER
FORMS OF ENERGY INTO AN
ELECTRICAL ENERGY.
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WIND POWER PLANT
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HYDRO POWER PLANT
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SOLAR POWER PLANT
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THERMAL POWER PLANT
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ELECTRICAL POWER SYSTEM
• FLOW OF ELECTRICAL POWER FROM THE GENERATING STATION TO THE CONSUMER
1. GENERATING STATION
2. TRANSMISSION
3. DISTRIBUTION
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POWER QUALITY = VOLTAGE QUALITY
“ Any Power Problem manifested in Voltage,
Current, (or) frequency deviations that results
in failure (or) mis-operation of customer
equipment ”.
It is related to hardware, software (or) control
system malfunctions.
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WHY WE ARE CONCERNED ABOUT POWER QUALITY ?
The Main reasons behind the growing concern about PQ are:
• North American industries lose Tens-of-Billions of Dollars
every year in downtime due to power quality problems.
(Electrical Business Magazine)
• Load non-linearities in rising and is expected to reach 50 to
70% in the year 2005 (Electric Power Research Institute)
[Computers, UPS, fax machines, printers, fluorescent lighting,
ASD, industrial rectifiers, DC drives, arc welders, etc).
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WHY WE ARE CONCERNED ABOUT POWER QUALITY ?
• Economic impacts on utilities, their customers, and suppliers of load equipment.
• Meeting Customer Expectations
• Customers :
1. Industrial
2. Domestic
3. Commercial
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POWER QUALITY ISSUE AND PROBLEMS
Power Quality issues can be roughly broken into a number of sub-categories:
Harmonics (sub, super and inter-harmonics); Voltage swells, sags, fluctuations, flicker, and
transients Voltage magnitude and frequency deviation,
voltage imbalance (3ph sys.) Hot grounding loops and ground potential rise
(GPR)–Safety & Fire Hazards Monitoring and measurement.
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BLOCK DIAGRAM GENERATION
TRANSMISSION & DISTRIBUTION
CUSTOMERS
INDUSTRIAL CUSTOMERS
RESIDENTIAL CUSTOMERS
COMMERCIAL CUSTOMERS
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TRANSIENTS
• Used in the analysis of power system variations to denote an event that is undesirable and momentary in nature.
• Classified in to 2 categories(i) Impulsive Transient(ii) Oscillatory Transient
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TYPES OF TRANSIENTS
IMPULSIVE TRANSIENT• It is a sudden, non-power
frequency change in the steady state condition of voltage, current (or) both that is unidirectional in polarity.
• They are normally characterized by their rise and decay times, which can also be revealed by their spectral content.
OSCILLATORY TRANSIENT• It is a sudden, non-power
frequency change in the steady state condition of voltage, current or both, that includes both positive & negative polarity.
• Example :Capacitor Bank
Energization.
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OVERVOLTAGE• An overvoltage is an increase in the r.m.s. ac
voltage greater than 110 % at the power frequency for a duration longer than 1 min.
• It is a result of load switching.Eg : Switching OFF a Large load
Energizing a capacitor bank
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UNDERVOLTAGE
• An undervoltage is a decrease in the rms ac voltage to less than 90 % at the power frequency for a duration longer than 1 min.
Example : Load Switching Capacitor Bank Switching off
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INTERRUPTIONS
An interruption occurs when the supply voltage or load current decreases to less than 1p.u for a period of time not exceeding 1 min.
It can be the result of power system faults, equipment failures and control malfunctions.
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VOLTAGE SAG
• A sag is a decrease to between 0.1 and 0.9 p.u in r.m.s voltage or current at the power frequency for durations from 0.5 cycle to 1 min.
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VOLTAGE SAG
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VOLTAGE SWELL• A swell is defined as an increase 1.1 and 1.8
p.u in r.m.s voltage or current at the power frequency for durations from 0.5 cycle to 1 min.
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VOLTAGE IMBALANCE
• Also called Voltage Unbalance• Maximum deviation from the average of the
three phase voltages (or) currents.
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SYSTEM MODEL
Converter Type Arc Type Dynamic Cyclical Ripple Inrush Temporal Motorized on/off SMPS ASD Saturation Type
NonlinearLoad
NLL
R s L sV s V L
YF(s)
on/off orPWM
Load Bus
ElectricUtility
Transformer
System+Transformer+FeederElectric
Equivalent(Plant) Load
Switched/ModulatedPower Filter or Static
Capacitor Compensator
i s
ControlSignals
SmartController
*V s
Ps
SMPFDifferent
Topologies
Nonlinear Load (NLL)
* Smart-controllers arebased on specified control
objectives
eight designs(Dr. A.M. Sharaf) YF (TAF, C-Type, HPDF, Special Topology)
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TOTAL HARMONIC DISTORTION
• The ratio of the root mean square of the harmonic content to the r.m.s value of the fundamental quantity expressed as a percent of the fundamental.
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TOTAL HARMONIC DISTORTION
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WAVEFORM DISTORTION
• Steady-state deviation from an ideal sine wave of power frequency principally characterized by the spectral content of the deviation.
• 5 types of waveform distortion1. DC offset2. Harmonics3. Inter-Harmonics4. Notching5. Noise
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WAVEFORM DISTORTION TYPES
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ITI CURVE• ITI Curve ---- Information Technology
Industry Council Curve
• A set of curves published by ITI representing the withstand capabilities of computers connected to power systems in terms of magnitude and duration of the voltage disturbance.
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CBEMA CURVE
• CBEMA ---- Computer Business Equipment Manufacturers Association.
• A set of curves representing the withstand capabilities of computers in terms of the magnitude and duration of the voltage disturbance.
• Standard for measuring the performance of all types of equipment and power systems.
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CBEMA CURVE
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