power quality unit 1

8/19/2019 Power Quality Unit 1

1/76


2/76

Course ObjectiveCourse Objective

To know the various powerquality phenomenon, their originand monitoring and mitigation

methods.

To know the efects o various

power quality phenomenon invarious equipmentsworkingcondition.


3/76

POWER QUALITYPOWER QUALITY

Maintaining a sinusoidal waveformof bus voltages!urrents at ratedvoltage!urrent and fre"uen!#$

T%e waveform of ele!tri! &ower atgeneration stage is &urel# sinusoidaland free from an# distortion$


4/76

'owever( t%ere are man#

devi!es t%at distort t%ewaveform$

T%ese distortions ma#

&ro&agate all over t%e ele!tri!alnetwor)$


5/76

Modern Utilit# *#stem


6/76

Modern Utilit# *#stem+Modern Utilit# *#stem+ ,eregulation,eregulation

Inde&endent *#stem O&erator

,istributed generations

Wind Energ# *olar Energ# -o+generation &lants

Load as -ustomer ,emand


7/76

-AU*E* O. POWER QUALITY,ETERIORATIO/

0$ /atural !auses1

• .aults or lig%ting stri)es on

transmission lines or distributionfeeders

• .alling of trees or bran!%es on

distribution feeders duringstorm# !onditions( e"ui&mentfailure et!$


8/76

2$ ,ue to /on+linear loads 3E"ui&ment4 ortransmission line feeder o&eration1

• Transformer energisation• -a&a!itor or feeder swit!%ing• Power ele!troni! loads 3UP*( A*,(

!onverters et!$4• Ar! furna!es and indu!tion %eating

s#stems• *wit!%ing on or off of large loads

et!$


9/76

*OUR-E* O. POWER QUALITY PRO5LEM*

0$ Load e"ui&ment and !om&onents

-onverters( Pulse modulated loads( Ma!%ine drives(Ar! furna!es( -om&uters( UP*( Television sets

.luores!ent and ot%er gas dis!%arge lig%ting

-ertain !om&onents w%i!% em&lo# magneti! !ir!uits2$ *ubs#stems of t%e transmission and distribution

s#stem

6rounding s#stems( resonant s#stems


10/76


11/76


12/76

Power Qualit# 7 8oltage Qualit#

T%e utilit# !an onl# !ontrol t%e"ualit# of t%e voltage9 it %as no!ontrol over t%e !urrents t%at&arti!ular loads mig%t draw$

T%erefore( t%e standards in t%e&ower "ualit# area are devoted tomaintaining t%e su&&l# voltage

wit%in !ertain limits$


13/76

6enerators ma# &rovide a near+

&erfe!t sine wave voltage( t%e!urrent &assing t%roug% t%eim&edan!e of t%e s#stem !an !ause

a variet# of disturban!es to t%evoltage$ .or e:am&le(

0$ -urrent resulting from a s%ort!ir!uit !auses t%e voltage to sag or

disa&&ear !om&letel#$

Load !urrent !%anged due to variet# of disturban!e


14/76

2$ -urrents from lig%tning stro)es&assing t%roug% t%e &ower s#stem

!ause %ig%+im&ulse voltages t%atfre"uentl# flas% over insulation andlead to ot%er &%enomena( su!% as s%ort

!ir!uits$

;$ ,istorted !urrents from %armoni!+

&rodu!ing loads also distort t%e voltageas t%e# &ass t%roug% t%e s#stemim&edan!e$ T%us a distorted voltage is

&resented to ot%er end users$


15/76

In!reased !on!ern about t%e "ualit# ofele!tri! &ower all utilit# !ustomers$

Utilit# !ustomers + alwa#s want toin!rease &rodu!tivit#Manufa!turers + want faster(

more &rodu!tive( more effi!ientma!%iner#Utilities+ en!ourage t%is effort

be!ause it %el&s t%eir !ustomersbe!ome more &rofitable


16/76

E:am&le for Linear loadsE:am&le for Linear loads


17/76

E:am&le for /onlinear loadsE:am&le for /onlinear loads

E l f l l d d


18/76

E:am&le for /onlinear loads+ !ontd$(E:am&le for /onlinear loads+ !ontd$(


19/76

T#&i!al PQ ProblemsT#&i!al PQ Problems


20/76

PQ ProblemsPQ Problems


21/76

-lassifi!ation of &ower "ualit#a!!ording to t%e sour!e

-onvertersMagneti! !ir!uit non linearit#Ar! furna!e or b# t%e wave

s%a&e of t%e signal su!% as%armoni!s( .li!)er or b# t%e

fre"uen!# s&e!trum 3radio

fre"uen!# interferen!e4$


22/76

*#n!%ronous &%enomena

s#n!%ronism wit% A$- waveform at&ower fre"uen!#$

/on+*#n!%ronous &%enomena$

PQ P%enomenon !%ara!teri


23/76

%# l ifi l t ti h i t th


24/76

Conducted low-frequency phenomena

Harmonics, interharmonics

Signal systems (power line carrier)

Voltage fluctuations (flicker)

Voltage dips and interruptionsVoltage imbalance (unbalance)

Power frequency variations

nduced low!frequency voltages

"# in ac networks

Radiated low-frequency phenomena

$agnetic fields%lectric fields

Conducted high-frequency phenomena

nduced continuous!wave (#&) voltages or currents

'nidirectional transients

scillatory transients

Radiated high-frequency phenomena

$agnetic fields

%lectric fields

%lectromagnetic fields #ontinuous waves

ransients

Electrostatic discharge phenomena (ESD)

Nuclear electromagnetic pulse (NEM)

%# classifies electromagnetic phenomena into the groups


25/76


26/76

Power Qualit# P%enomenaT#&es( -%ara!teristi!s(

and t%eir Origin


27/76

0$Transients

It !an be !lassified into two!ategories(

0$Im&ulsive

2$Os!illator#


28/76

Im&ulsive transient It is a sudden( non=&ower fre"uen!#

!%ange in t%e stead#+state !onditionof voltage( !urrent( or bot%$

It is unidire!tional in &olarit# 3&rimaril# eit%er &ositive or negative4$

Im&ulsive transients are normall#!%ara!teri


29/76

.or e:am&le(

0$2>?@+se!(2@@@+volt384 im&ulsive transient nominall# risesfrom


30/76


31/76

Os!illator# Transient

It is a sudden( non=&ower fre"uen!#!%ange in t%e stead#+state !onditionof voltage( !urrent( or bot%$

It in!ludes bot% &ositive andnegative &olarit# values$

It !onsists of a voltage or !urrentw%ose instantaneous value !%anges

&olarit# ra&idl#$

d d l


32/76

It is des!ribed b# its s&e!tral!ontent 3&redominate fre"uen!#4(

duration( and magnitude$

T%e s&e!tral !ontent sub!lasses

defined are

'ig%MediumLow fre"uen!#

'. P i . t


33/76

'.1 Primar# .re" !om&onent B?@@)%< mesd in Mi!ro*e! duration +Lo!al s#s res&onse to Im&ulsiveTransient

Med .re"1 Primar# .re"

!om&onent ?+?@@)%< mesd in Mi!ro*e!duration + 5a!)+to+ba!) !a&a!itor

energi


34/76

0$Med$Os!illator# Transientdue to !a&a!itor swit!%ingdue to -able swit!%ing

2 L . d b )


35/76

2$Low .re" Os!$transient due to !a&a!itor ban)energi


36/76

;$Low .re" Os!$transient due to ferroresonan!e inTransformer

scillatory transients with principal frequencies less than *++ H can also be

found on the distribution system-

hese are generally associated with ferroresonance and transformerenergiation-

*'ORT ,URATIO/ 8ARIATIO/*


37/76

*'ORT ,URATIO/ 8ARIATIO/*Ea!% t#&e of variation !an be designated as(

0$Instantaneous(2$Momentar#(

;$Tem&orar#( de&ending on its duration interru&tions( sag and swell are !ommon for all F $

-AU*E*

0$.ault !onditions2$T%e energi


38/76

Interru&tionInterru&tion

An interru&tion o!!urs w%en t%e su&&l#voltage or load !urrent de!reases to lesst%an @$0 &u for a &eriod of time note:!eeding 0 min$

-auses of Interru&tion-auses of Interru&tionresult of &ower s#stem faults

e"ui&ment failure and !ontrol s#stemmalfun!tion

I/TERRUPTIO/ = !ontd


39/76

I/TERRUPTIO/ = !ontd$(

T%e interru&tions are measured b# t%eir durationsin!e t%e voltage magnitude is alwa#s less t%an 0@&er!ent of nominal$

T%e duration of an interru&tion due to a fault ont%e utilit# s#stem is determined b# t%e o&erating

time of utilit# &rote!tive devi!es$

Instantaneous re!losing generall# will limit t%einterru&tion !aused b# a non&ermanent fault to lesst%an ;@ !#!les$


40/76

,ela#ed re!losing of t%e &rote!tive devi!e ma#

!ause a momentar# or tem&orar# interru&tion$T%e duration of an interru&tion due to e"ui&mentmalfun!tions or loose !onne!tions !an be irregular$

.igure s%ows su!% a momentar# interru&tion duringw%i!% voltage on one &%ase sags to about 2@ &er!entfor about ; !#!les and t%en dro&s to


41/76

Tem&orar# interru&tion due to fault

*ags 3di&s4


42/76

*ags 3di&s4

A sag is a de!rease in rms voltage or !urrent

between @$0 to @$H &u at rated &ower fre"uen!# fordurations from @$? !#!le to 0 min$

-auses of 8oltage sags –

Asso!iated wit% s#stem faults–Energi


43/76

E:am&le1 voltage sag t%at !an be asso!iated wit% asingle+ line+to+ground 3*L64 fault on anot%er feederfrom t%e same substation$

E:am&le1+ 8oltage sag due to large motor


44/76

E:am&le1+ 8oltage sag due to large motorstarting$ An indu!tion motor will draw to 0@times its full load !urrent during start+u&$

•In t%is !ase( t%e voltage sags immediatel# to G@ &er!ent and t%en graduall#returns to normal in about ; s$• /ote t%e differen!e in time frame between t%is and sags due to utilit#s#stem faults$

*wells


45/76

*wells•A swell is defined as an in!rease in rms voltage or!urrent from 0$0 to 0$G &u at rated &ower fre"uen!#

for durations from @$? !#!le to 0 min$

•*wells are !%ara!teri


46/76

-auses of 8oltage *well

+Asso!iated wit% s#stem faults–

Energi


47/76

8oltage *well due to *ingle line to 6round fault

Long+,uration 8oltage 8ariations


48/76

Long+,uration 8oltage 8ariations

Long+duration variations en!om&assroot+mean+s"uare 3rms4 deviations at&ower fre"uen!ies for longer t%an 0

min$ It !an beOvervoltagesundervoltages$*ustained interru&tion

O8ER8OLTA6E


49/76

O8ER8OLTA6E

In!rease in t%e rms a! voltage greater t%an00@ &er!ent at t%e &ower fre"uen!# for a

duration longer t%an 0 min$

-AU*E*

0$load swit!%ing 3e$g$( swit!%ingoff a largeload or energi


50/76

Overvoltages and undervoltages

generall# are not t%e result of s#stemfaults( but are !aused b# loadvariations on t%e s#stem and s#stem

swit!%ing o&erations$

Long+duration variations are t#&i!all#

dis&la#ed as &lots of rms voltageversus time$

U/,ER8OLTA6E


51/76

U/,ER8OLTA6E

,e!rease in t%e rms a! voltage to less t%anH@ &er!ent at t%e &ower fre"uen!# for a

duration longer t%an 0 min$0$load swit!%ing 3e$g$( swit!%ing on a largeload or overloading4

2$ ,ue to fault on t%e lines-AU*E*

0$A load swit!%ing on or a !a&a!itor ban)

swit!%ing off !an !ause an under voltageuntil voltage regulation e"ui&ment ont%e s#stem !an bring t%e voltage ba!)to wit%in toleran!es$2$Overloaded !ir!uits !an result in

undervoltages

*U*TAI/E, I/TERRUPTIO/


52/76

W%en t%e su&&l# voltage %as been


53/76

8oltage Imbalan!e 3voltage unbalan!e 4

•8oltage imbalan!e 3or unbalan!e4 is defined as t%e ratioof t%e negative or


54/76

8oltage Imbalan!e underunbalan!ed load !ondition

Waveform ,istortion


55/76

Waveform ,istortionIt is defined as a stead#+state deviation from anideal sine wave of &ower fre"uen!# &rin!i&all#

!%ara!teri


56/76

T%e &resen!e of a d! voltage or !urrent in an a!&ower s#stem is termed d! offset$

'ARMO/I-*• 'armoni!s are sinusoidal voltages or !urrents %avingfre"uen!ies t%at are integer multi&les of t%efre"uen!# at w%i!% t%e su&&l# s#stem is designed too&erate$

•IEEE *tandard ?0H+0HH2 &rovides guidelines for%armoni! !urrent and voltage distortion levels ondistribution and transmission !ir!uits$

•Periodi!all# distorted waveforms !an be


57/76

Periodi!all# distorted waveforms !an bede!om&osed into a sum of t%e fundamentalfre"uen!# and t%e %armoni!s$

• 'armoni! distortion originates in t%e

nonlinear !%ara!teristi!s of devi!es and loadson t%e &ower s#stem$

•'armoni! distortion levels are des!ribed b#t%e !om&lete %armoni! s&e!trum wit%magnitudes and &%ase angles of ea!% individual

%armoni! !om&onent$

•Total %armoni! distortion 3T',4 as a measure of


58/76

Total %armoni! distortion 3T',4( as a measure oft%e effe!tive value of %armoni! distortion$

•T', + used to !%ara!teri


59/76

T t l ' i di t ti 3T',4


60/76

•Total 'armoni! distortion 3T',4

•IEEE ?0H sets limits on total %armoni!

distortion 3T',4 for t%e utilit# side of t%emeter

•Utilit# is res&onsible for t%e voltagedistortion at t%e &oint of !ommon !ou&ling3P--4 between t%e utilit# and t%e end user$

•Total %armoni! distortion is a wa# toevaluate t%e voltage distortion effe!ts ofinKe!ting %armoni! !urrents into t%e utilit#s

s#stem$

Total 'armoni! distortion 3T',4 7


61/76

Total 'armoni! distortion 3T',4 7•3RM* of t%e %armoni! !ontent RM* value of t%efundamental4 0@@•Total %armoni! distortion 3T',4 is a term used todes!ribe t%e net deviation of a nonlinear waveformfrom ideal sine waveform !%ara!teristi!s$

E:am&le1 .ind t%e total %armoni! distortion of


62/76

E:am&le1 .ind t%e total %armoni! distortion ofa voltage waveform wit% t%e following%armoni! fre"uen!# ma)e u&1

.undamental 7 8 0 7 00N 8

;rd %armoni! 7 8 ; 7 N 8

?t% %armoni! 7 8 ? 7 2 8t% %armoni! 7 8 7 0$? 8

Ht% %armoni! 7 8 H 7 0 8

T', 7 3N$G200N4 0@@ 7N$2;J

Total ,emand ,istortion 3T,,4


63/76

3 4•IEEE ?0H sets limits total demand distortion3T,,4 for t%e end+user side of t%e meter$

•3RM* of t%e %armoni! !urrent RM* valueof Ma:imum ,emand Load -urrent 4 0@@

•E:&ressed as a &er!ent of rated load!urrent$

•T,, deals wit% evaluating t%e !urrentdistortions !aused b# %armoni! !urrents in t%eend+user fa!ilities$

Total ,emand ,istortion 3T,,4 !ontd


64/76

Total ,emand ,istortion 3T,,4+ !ontd$(

I/TER'ARMO/I-*


65/76

I/TER'ARMO/I-*

8oltages or !urrents %aving fre"uen!# !om&onentst%at are non+integer multi&les of t%e fundamental

fre"uen!#$

*our!es of Inter%armoni! Waveform ,istortion

•

*tati! fre"uen!# !onverters•-#!lo!onverters

•Indu!tion furna!es

•Ar!ing devi!es

/OT-'


66/76

/OT-'

/ot!%ing is a &eriodi! voltage disturban!e !aused b#t%e normal o&eration of &ower ele!troni! devi!es

w%en !urrent is !ommutated from one &%ase toanot%er

/OI*E


67/76

/OI*E

/oise is defined as unwanted ele!tri!al signals wit%broadband s&e!tral !ontent lower t%an 2@@ )'<

su&erim&osed u&on t%e &ower s#stem voltage or!urrent in &%ase !ondu!tors( or found on neutral!ondu!tors or signal lines$

*OUR-E*

Power ele!troni! devi!es( -ontrol !ir!uits( Ar!inge"ui&ment( Loads wit% solid+state re!tifiers( and*wit!%ing &ower su&&lies$

8OLTA6E .LU-TUATIO/ 38OLTA6E


68/76

8OLTA6E .LU-TUATIO/ 38OLTA6E.LI-QER 4

• 8oltage flu!tuations are s#stemati!variations of t%e voltage envelo&e or a seriesof random voltage !%anges( t%e magnitude ofw%i!% does not normall# e:!eed t%e voltage

ranges s&e!ified b# A/*I -GN$0 of @$H to0$0 &u$•*OUR-E•Loads t%at !an e:%ibit !ontinuous( ra&idvariations in t%e load !urrent magnitude !an!ause voltage variations t%at are oftenreferred to as fli!)er$


69/76

Power .re"uen!# 8ariations


70/76

" #

Power fre"uen!# variations are defined as t%edeviation of t%e &ower s#stem fundamental fre"uen!#

from it s&e!ified nominal value$


71/76

-5EMA -urve


72/76

•A set of !urves re&resenting t%e wit%standing

!a&abilities of !om&uters in terms of t%e magnitudeand duration of t%e voltage disturban!e$

•,evelo&ed b# t%e -om&uter 5usiness E"ui&ment

Manufa!turers Asso!iation 3-5EMA4


73/76

•T%e a:es re&resent magnitude and duration of t%e


74/76

& gevent$

•Points below t%e envelo&e are &resumed to !ause t%eload to dro& out due to la!) of energ#$

•Points above t%e envelo&e are &resumed to !auseot%er malfun!tions su!% as insulation failure( overvoltage tri&( and over e:!itation$

ITI- -urve


75/76

ITI- -urve•A set of !urves &ublis%ed b# t%e InformationTe!%nolog# Industr# -oun!il 3ITI-4 re&resenting t%e

wit%stand !a&abilities of !om&uters !onne!ted to02@+8 &ower s#stems in terms of t%e magnitude andduration of t%e voltage disturban!e$

• T%e ITI- !urve re&la!es t%e !urves originall#develo&ed b# t%e ITIs &rede!essor organi


76/76

power quality unit 1

Documents