impact of harmonics on modern buildings

8/13/2019 Impact of Harmonics on Modern Buildings

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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??

impact of harmonics on modern buildings

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