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Energy Scene of Indiaon 31st March 2009
Target 231069 MW Target achieved 140366 MW
Upto 1969 11990 MW
Net Capacity 128376 MW
Aux. Power Consumption 6%
Plant load factor 2008-09 77.19%
Net Capacity available 93148 MW
T&D losses 30%
Net power available to Consumer 65203 MW
Source: All India Electricity Ststistics, Central Electricity Authorities
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Energy Efficiency
Steps
Decrease the load keeping output same
Increase the efficiency without affecting the
output
Result
Increase in the usage of non linear loadswhich generate harmonics.
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What is harmonics?
It is a virus.
It is a pollution
Heat generating element It reduces efficiency
Unwelcome guest
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Electronic ballast
An electronics ballast consumes 0.53 amperesfundamental current while it generates 0.46 amperesthird order zero sequence current (87% of fundamental)
Magnetic Ballast (Normal) =9 watts Magnetic Ballast (Low loss) =5.5 watts
Electronic Ballast are available with 30% THD (as perIS). They are also available with 10% THD as per
European stsndards. Total consumption with 36 watttubelight is 36 watt as the tubelight consumes 33 wattsand balance 3 watt is consumed by ballast.
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Non linear load
The presence of equipment generating
harmonics is evident from the following
data from US: Content of non linear loads in 1960 = 5% of total load
Content of non linear loads in 1990 = 30% of total load
Content of non linear loads in 2000 = 60% of total load
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Harmon ic Generat ion
Vh = h x hI Z
IhZ source
Hhthharmonic voltageVh
Ih
Zh
Hhthharmonic current
Hthharmonic
Where: (Ohms Law)
Hsystem impedance for h
Vthd1
Z1 Z2 Z3 Z4 Z5 Z6
Vthd2 Vthd3 Vthd4
VthdLoad
VthdSource
Vthd5 Vthd6
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Power Factor
With the harmonics in picture, the overall
power factor of the installation dips.
Problem no 1: power factor
Problem no 2: harmonics
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Reasons
Electronic Switching Power Supplies
Arcing Devices
Ferromagnetic Devices Appliances
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Electronic Switching Power Supplies
Personal computers
Laptop
UPS
Solid State Rectifier Electronic Process Control Equipment, PLC etc
Lighting Ballast, Dimmers
Reduced Voltage Motor Controller
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Arcing Devices
Discharge Lighting fluorescent, sodium,
mercury, CFL.
Arc Furnaces
Welding Equipment
Traction Equipment
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Ferromagnetic Devices
Transformer operating near saturation level
Magnetic Ballast ( Saturated Iron Core)
Induction Heating Equipment
Chokes
Motors
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Appliances
TV
Fax machine
Photo copy machine
Printer
Microwave Oven
Air Conditioner.
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Classification
Zero sequence harmonics.
Positive sequence harmonics.
Negative sequence harmonics.
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Effect on motor
Zero sequence harmonics - it does not rotate the
motor. It only heats the motor. These are called
triplen harmonics ( 3rd, 9th, 15th)
Positive sequence harmonics it rotate themotor forward.(7th , 13th, 19th.)
Negative sequence harmonics - it rotate the
motor backwards. (5th, 11th, 17th.)
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Problems with harmonics:
High neutral ground voltage
High peak phase current
High average phase current
High total harmonic distortion of the current High total harmonic distortion of the voltage
High transformer losses
High system losses
Telephone interference factor
Increases apparatus vibration
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Limits of current harmonics
Ratio of Short circuit
current/Full load
current
Harmonic Range Limit of % of
fundamental
Less than 20 Odd no. less than 11 4%
20 to 50 Odd no. less than 11 7%
More than 1000 Odd no. less than 35 1.4%
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Transformer capacity
K-Factor transformers are designed to be
operated fully loaded with any harmonic load
having a K-Factor equal to or less than its K-
Rating Additional thermal capacity to tolerate the
heating effects of the harmonic currents
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Example
First case
Normal transformer i.e. K1 rated
Copper losses for a transformer = 2000 watts
A normal transformer will dissipate no load losses + copper losses+ stray losses which will be much less than 100 watts
Second case
K 20 rated transformer
Copper losses for a transformer = 2000 watts
Stray Losses = 100 watts
Total losses shall be no load loss+copper loss+stray loss of 100wattsX20 i.e. 4000 watts in addition to no load loss.
K1 rated transformer is not designed for this amount of dissipation ofheat
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Solutions
Phase shifting is one of the technique to eliminate the
harmonics.
Use of Active and Passive Filters
Isolate the harmonic pollution device on a separatecircuit / feeder
Neutral to be at least twice the size of phase conductor.
ACB / MCCB to be selected having oversizes neutral
Ask equipment suppliers to design equipment with lowercontent of harmonics.
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K factor of the transformer
There are different amounts of harmonic currents
produced. The term for the total amount of harmonic
current present is called THD. Since this value has a
wide range, there needs to be an appropriate way to size
the K-rated transformer to the load. This is where K-factor comes in
K varies from 1 to 50.
The higher the K-factor, the more heat from harmonic
currents the transformer is able to handle.
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Recommended ratings of K
Non-Linear Load K-rating Incidental electronic equipment representing
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Thank you
Questions??
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