kee okt13 ipapic 3

8/17/2019 KEE Okt13 IPapic 3

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1

Course

Power Quality - 3

Ljubljana, Slovenia

2013/14

Prof. dr. Igor Papič

[email protected]

Harmonics - design of power

factor correction devices

Content

1st day 2nd day 3rd day 4th day 5th day

Session 1

Introduction toPower Quality

• what is PQ• economic value• responsibilities

Harmonics –definitions

• calculations• non-linear loads• harmonic

sequences

Harmonics - designof power factorcorrection devices

• resonance points• filter design

Flicker case study

• calculation offlicker spreadingin radial network

• variation ofnetworkparameters

Interruptions

• definitions• reliability indices• improving

reliability

Session 2

Basic terms and

definitions

• voltage quality• continuity of

supply

• commercialquality

Propagation ofharmonics

• sources• consequences• cancellation

Flicker - basicterms

• voltage variation• flicker frequency• sources• flickermeter

Voltage sags –definitions

• characteristics• types• causes

Consequences ofinadequate powerquality

• voltage quality• interruptions• costs

Session 3

PQ standards

• EN 50 160• other standards• limit values

Harmonics -resonances innetwork

• parallelresonance

• series resonance

Flicker spreading

• radial network• mashed network• simulation• examples

Propagation ofvoltage sags

• transformerconnections

• equipmentsensitivity

• mitigation

Moderncompensationdevices

• active and hybridcompensators

• series and shuntcompensators

Session 4

PQ monitoring

• measurements• PQ analyzers• data analyses

Harmonics casestudy

• calculation offrequencyimpedancecharacteristics

Flicker mitigation

• system solutions – networkenforcement

• compensation

Other voltagevariations

• unbalance• voltage

transients

• overvoltages

Conclusions

• PQ improvementand costs

• definition ofoptimal solutions

Power Quality, Ljubljana, 2013/143


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2

Design of PFC devices

• influence of impedance change – compensator impedance varies with the number of used

compensation s tages (crossing of resonance points)

– network impedance change has large influence onfrequency response

– load impedance has minor influence on frequencyresponse

• detuned filter – series connection of inductor and capacitor

– resonance frequency is below the characteristic harmonic(141 Hz, 225 Hz)

– good response under different operating conditions


Influence of network impedance change

• frequency impedance characteristics

– data for calculation of one supply transformer 20/0,4 kV

(two transformer in previous case)

– short-circuit voltage

– rated power

– rated voltage

– ratio R / X

%13,4= scu

kV4,0kV;20 == LV MV U U

4/1)/( =TR X R

MVA63,0x1=nS




– calculation of parameters of one supply transformer 20/0,4 kV

TRTRTR

TR

TR sc

n

NN TR

TR

sc

n

LV TR

L f j R f j Z

X R

X Ru

S

U R

X R

u

S

U L

π π

π

2)2(

m54,2)/(1

)/(

100

μH4,32)/(1

1

100100

2

2

2

2

+=

Ω=+

=

=+

=



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3



– harmonic sourceis on the network

side

• impedancecharacteristics

as a functionof frequency

• one supplytransformer

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100





side


as a function

of frequency

• two supplytransformers(previous case)

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100





side


as a functionof number ofused

compensationstages


0 0.2 0.4 0.6 0.8 10.01

0.1

1

10



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4


• frequency impedance characteristics – harmonic source

is on the networkside

• impedancecharacteristicsas a functionof number ofusedcompensationstages

• two supplytransformers(previous case) 0 0.2 0.4 0.6 0.8 10.01

0.1

1

10

Power Quality, Ljubljana, 2013/14 10



– harmonic sourceis on the load

side


as a function

of frequency


0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1





side



• two supplytransformers(previous case)

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1



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side


as a functionof number ofusedcompensationstages


0 0.2 0.4 0.6 0.8 10.01

0.1

1




is on the loadside

• impedancecharacteristicsas a functionof number ofusedcompensationstages

• two supplytransformers(previous case) 0 0.2 0.4 0.6 0.8 10.01

0.1

1


Detuned filter


– equivalent circuit with detuned filter



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7

Detuned filter


– calculation of parameters of detuned filter

• detuned filter

f

f f f

f f

fL f fC

f

f

C f j L f j R f j Z

R R

X RC X RC

R

π π π

π π

2

12)2(

m10)Hz225( ;m15)Hz141(

)/(502)/(502

1

++=

Ω=Ω=

⋅⋅⋅+⋅⋅⋅

=


Detuned filter


– voltage harmonic source is on the network side


Detuned filter


– harmonic source is on the network side

• impedance from the network side


)2(Z)(Zvalueabsolute

)(Z

1

)(Z

1

1)(Z)(Z)(Z

11

1

f j j

j j

j j j

f L

TRSC

π ω

ω ω

ω ω ω

=→

+

++=



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Detuned filter – frequency response



side



• filter resonancefrequency is141 Hz

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100





side


as a function

of frequency

• filter resonancefrequency is225Hz

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100



0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100


is on the networkside

• impedancecharacteristicsas a functionof frequency





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side



• comparison withclassicalcompensator

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1

10

100


Detuned filter


– current harmonic source is on the load side


Detuned filter


– harmonic source is on the load side

• impedance from the load side

• parallel resonance

)2(Z)(Zvalueabsolute

)(Z)(Z

1

)(Z

1

)(Z

1

1)(Z

22

2

f j j

j j j j

j

TRSC f L

π ω

ω ω ω ω

ω

=→

+

++

=



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side




0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1





side


as a function

of frequency

• filter resonancefrequency is225Hz

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1




is on the loadside

• impedancecharacteristicsas a functionof frequency



0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1



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side



• comparison withclassicalcompensator

0 1 00 200 300 400 500 600 7 00 800 900 100 01 .10

3

0.01

0.1

1


Flicker - basic terms

Content


Session 1





sequences



Flicker case study



Interruptions


reliability

Session 2

Basic terms and

definitions


supply










Session 3

PQ standards





Flicker spreading





• mitigation




Session 4

PQ monitoring


Harmonics casestudy


Flicker mitigation


• compensation



transients

• overvoltages

Conclusions





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What is flicker?


Flicker frequency – case 1

• What is the frequency of flicker?

– assume sinusoidal modulation

– what signal does represent flicker with frequency 3 Hz


Flicker frequency – case 2

– or



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What is the frequency of flicker

– case 1

– case 2

t mt V t v f ω ω coscos)( 0 += Hz3 Hz500 == f f f

t t mV t v f 0cos)cos1()( ω ω +=

⎥⎦

⎤⎢⎣

⎡−+++= t

mt

mt V t v f f )cos(

2)cos(

2cos)( 000 ω ω ω ω ω

Hz47 Hz53 Hz50 000 =−=+= f f f f f f f


Causes of flicker

– loads drawing

large and highly

variable currents

– arc furnaces

installations

• voltage 20 kV

time (s)


Causes of flicker

– steel rolling mils

– induction motors

starting

V o l t a g e ( % )



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Causes of flicker

– welding machines

– motor drives with cycloconverters

• simulation results (interharmonics)

time


Causes of flicker

– wind farms in distributed production

– switching of capacitor banks

– households

• pumps, refrigerators, air conditioning, washing

machines, drills

• devices with heavy-start motors

– …


Flicker evaluation

• flicker meter

– IEC 61000-4-15: Electromagnetic compatibility (EMC) -Part 4: Testing and measurements techniques - Section

15: Flickermeter - Functional and design specifications

– flicker severity – intensity of flicker annoyance defined

by the UIE-IEC flicker measuring method and evaluated

by short and long term severity



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Flicker evaluation

• flicker meter

– short term severity Pst – measured over a period of 10minutes

– long term severity Plt – calculated from a sequence of

12 P st values over a two hour interval, according to the

following expression:

3

12

1

3

st

lt12

∑== i

i P

P


Flicker evaluation

– comparison between P lt and P st


Scheme of a flicker meter

inputvoltageadaptor

demodulator

weighting filter

BLOCK 1 BLOCK 2 BLOCK 3 BLOCK 4 BLOCK 5

squaringand

smoothing

dB

35

0

0,05

-3

-60

Hz

rangeselector

∆U / U ( % )

X

P P st and P lt

calculationof

P st and

P lt

statisticalevaluation

voltage

mesurement

simulation of lamp-eye-brain response

Hz8,8

1

0



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Scheme of a flicker meter

• Block 1 – Input voltage adaptor and calibration checkingcircuit

– signal generator for calibration and checking

– voltage adapting circuit that scales the input signal to areference per-unit level

• Block 2 – Square law demodulator

– the input to the flicker meter is the relative voltage variation

– the modulated wave must be extracted from carrier (50 or 69Hz)

– quadratic demodulator simulates the behavior of a lamp


Scheme of a flickermeter

• Block 3 and 4 – Weighting filters, squaring and smoothing

– block 3 is composed of a cascade of two filters and a measuringrange selector

– first filter eliminates the dc and double mains frequency ripplecomponents of the demodulator

– second filter is weighting filter block that simulates thefrequency response of a coiled filament gas-filled lamp (60 W ,

230 V) combined with a human visual system – block 4 is composed of a squaring multiplier and a first order

low-pass filter

– the human flicker sensation via lamp, eye and brain issimulated by the combined non-linear response of blocks

2, 3 and 4


Scheme of a flickermeter

• Block 5 – On-line statistical analysis

– the statistical classifier models human irritability in the presenceof flicker stimulation

– it provides the statistical information required to calculate short-term flicker severity Pst (observation period is 10 minutes)

– smoothed percentil values

– i.e. P 0.1 – the level exceeded by only 0.1 % of the observationperiod (10 minutes)

s50s10s3s11,0st 08,028,00657,00525,00314,0 P P P P P P ⋅+⋅+⋅+⋅+⋅=



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Flicker value

• required magnitude of voltage fluctuation for sinusoidal andrectangular modulation to get the flicker vale P = 1

• the response function

is based on perceptibility

threshold found at each

frequency by 50 % ofthe persons tested


Flicker value

• multiple fluctuating loads may be impacting the same

network

• aggregateP st value calculation from N loads

– m = 4 coordinated loads to avoid coincident fluctuations

– m = 3 likelihood of coincident fluctuations is small

– m = 2 likelihood of coincident stochastic noise is likely

– m = 1 likelihood of coincident fluctuations is small

m

N

i

m

i P P ∑=

=1

stst


Compatibility and planning levels

• graphical representation of flicker levels

– planning level is usualy less than planning level

– compatibility level may be exceed 5% of the evaluation

period



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– compatibility levels

– EN 50160 gives

higher value for P lt

(1.0, 95 % value)

– planning levels

quantity

compatibility levels for

MV and LV networks(IEC/TR3 61000-3-7)

P st 1.0

P lt 0.8

quantity

planning levels

(IEC/TR3 61000-3-7)

MV HV

P st 0.9 0.8

P lt 0.7 0.6



• required short-circuit power in the point of

common coupling PCC

– primarily depends on nominal power of a supply

transformer of disturbing load

– S sc = (90÷160)·S tr [MVA]

– empirical and statistical evaluation


Flicker spreading


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Content


Session 1





sequences



Flicker case study



Interruptions


reliability

Session 2

Basic terms anddefinitions


supply










Session 3

PQ standards





Flicker spreading





• mitigation




Session 4

PQ monitoring


Harmonics casestudy


Flicker mitigation


• compensation



transients

• overvoltages

Conclusions




Flicker spreading

• calculation of voltage variation

– dynamic load

X·I

φ

θ

R·I

U 1

U 2

I

I

U 1 U 2

R, X

P, Q

ϕ ϕ sincoscos 21 ⋅⋅+⋅⋅+=⋅ I X I RU ΘU

ϕ ϕ sincos21 ⋅⋅+⋅⋅=− I X I RU U

1cos ≈Θ


Flicker spreading

• relative voltage variation

2

2

22

2

21 sincos

U

I U X I U R

U

U U ϕ ϕ ⋅⋅⋅+⋅⋅⋅=

−

2

nn U

Q X P R

U

U ⋅+⋅=

Δ

sc

2

nn S

Q

U

Q X

U

U =

⋅≈

Δ



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Flicker spreading

• relative voltage variation

– active and reactive power variations of an arc furnace


Flicker spreading

• flicker level decreases in the direction from the

disturbing load towards supply source

• flicker level practically does not change in a radial

direction from the disturbing load where are no

supply sources

• flicker reduction on transformers


Flicker spreading

• transfer coefficient of flicker in a radial network

between point A and P (disturbing load)

• calculation in a mashed network is more complex

– use of simulation tools

( )( )PA

st

stAP

P

P TC =

A P

P



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Flicker spreading

• flicker spreading in a radial network

– case A A P

P

A P

P

Z A Z AP

( ) ( ) ( )APA

A

stAPstst PPA

Z Z

Z P TC P P

+⋅=⋅=


Flicker spreading

• flicker spreading in radial network

– case B

A P

P

B

( ) ( ) ( ) ( )P1PPB ststBPstst P P TC P P =⋅=⋅=


Flicker spreading


– case C

A B

P

P

( ) ( ) ( )BPABA

ABA

stBPstst PPB Z Z Z

Z Z P TC P P

++

+⋅=⋅=



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Flicker spreading


– case D

A P

P B

( ) ( ) ( )

( ) ( ) APstAPst

BAAPstBPstst

P1P

PPB

TC P TC P

TC TC P TC P P

⋅=⋅⋅=

=⋅⋅=⋅=


Simulation of flicker spreading

• steady-state calculation – model of transmission system

– switch on/off of the load – change of voltage magnitudes – injection of load current

• dynamic simulations – model of transmission system

– model of arc furnace

– model of flicker meter – Influence of generator voltage controllers – models of compensation devices

• calibration of simulation model wit measurements results

• calculation of flicker levels for all buses


Flicker spreading

• flicker spreading in mashed network

– load flow method

– two states of s disturbing load (0,1)

– calculation of relative voltage drops

– calculation of transfer coefficients

2

,1,0

,1,0

x x

x x

x

x x

V V

V V

V

V v

+

−=

Δ=Δ

j

iij

v

vkv

Δ

Δ=



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Flicker spreading

• flicker spreading

in mashed

network

– load flow method

– comparison with

measurements

– variation of load


Flicker spreading

• flicker spreading in mashed network

– current injection method

11 1N 1

2

AAA A

N-1

N1 NN N

Y . . . . . Y0

. . . .

. . . .0

. Y .

. . . .0

. . . .

Y . . . . . Y0

V

V

V I

V

V

⎡ ⎤⎡ ⎤⎡ ⎤⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥

= ⋅ ⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥⎢ ⎥

⎣ ⎦ ⎣ ⎦ ⎣ ⎦

M

M

M

M)(

)(

j

iij

V

V kv

ℜ

ℜ=

IYV 1−=


Flicker spreading

• flicker spreading

in mashed

network

– current injectionmethod

– comparison withmeasurements

– variation of

injected current



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Flicker spreading

• flicker spreading through transformers

– in a radial direction from the disturbing load towardslower voltage levels (first approximation is value 1)

– transfer coefficient of flicker from EHV to HV level is

approximately 0.8

– transfer coefficient of flicker from HV to MV level is

approximately 0.9 (worst case)

– transfer coefficient of flicker from MV to LV level is

approximately 1


Example of flicker spreading analysis

• measurement campaign in Slovenian transmissionnetwork – 31 locations

– analysis of measurement results

• simulation of flicker spreading – network model

– calibration of the model wit measurement results – simulation of flicker spreading in all nodes

– present situation

– future situation (2020)

– analysis of compensation measures


Flicker measurement locations



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Flicker measurement results (SIST EN 50160)

flicker level (P lt)

95 % values

locationvoltagelevel (kV)

L1 L2 L3

RTP Jeklarna Jesenice 110 7,41 7,50 7,85RTP Železarna Ravne 110 2,87 2,80 2,68RTP Lipa 110 1,62 1,48 1,57RTP Okroglo 110 1,256 1,331 1,415RTP Zlato polje 110 1,25 1,33 1,41

RTP Kleče 110 0,85 0,87 0,92RTP Beričevo 110 0,74 0,69 0,80

RTP Lj Center 110 0,79 0,80 0,85

RTP Šiška 110 0,92 0,95 1,02

RTP Logatec 110 0,90 0,94 1,00

RTP Slovenj Gradec 110 1,47 1,44 1,33RTP Podlog 110 0,82 0,76 0,79RTP Pekre 110 0,60 0,62 0,56

RTP Maribor 110 0,50 0,51 0,48RTP Ljutomer 110 0,50 0,52 0,53



flicker level (P lt)95 % values

locationvoltagelevel (kV)

L1 L2 L3

RTP Ljutomer 110 0,50 0,52 0,53

RTP Rače 110 0,60 0,52 0,51

RTP Laško 110 0,81 0,75 0,78

RTP Hudo 110 0,72 0,88 0,75

RTP Kočevje 110 0,81 1,98 0,87

RTP Divača 110 0,39 0,40 0,56

RTP Vrtojba 110 0,30 0,31 0,44

RTP Tolmin 110 0,40 0,37 0,41

RTP Koper 110 0,63 0,61 0,65RTP Beričevo 220 0,56 0,58 0,60

RTP Podlog 220 0,34 0,35 0,41RTP Kleče 220 0,56 0,58 0,60

RTP Beričevo 400 0,59 0,59 0,60RTP Podlog 400 0,41 0,42 0,46RTP Okroglo 400 0,74 0,74 0,74

RTP Krško 400 0,27 0,23 0,59



• arc furnace 40 MVA

• short and long term flicker level at 110 kV



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• arc furnace 40 MVA

• long term flicker level and current at 110 kV - correlation



• network node – different configurations

• cumulative flicker levels – determination of 95 % value


Measurement results at 110 kV level

voltage (kV) current (A)

time (s)time (s)



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Measurement results at 20 kV level

voltage (kV) current (A)

time (s) time (s)


Measurement results

• arc furnace 40

MVA

• voltage at 110 kV


• current at 20 kV


Measurement results

• arc furnace 40MVA



• current at 20 kV



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Measurement results

• arc furnace 40MVA

• correlation between the flicker level at 110 kV and 20 kV

0

1

2

3

4

5

6

0 5 10 15 20 25

Pst Jeklarna Ravne UHP 20 kV

P s t J e k l a r n a R a v n e 1 1 0 k V


Flicker spreading simulation

• analysis of flicker spreading in the Slovenian

power system (three arc furnaces)

– present situation – summation law m = 2.7

12%

17%

20%

51%

Plt>1,5 1


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Flicker spreading simulation for the year

2020



– results for the year 2020

5%

19%

27%

49%

P lt >1 ,5 1


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Content


Session 1





sequences



Flicker case study



Interruptions


reliability

Session 2

Basic terms anddefinitions


supply










Session 3

PQ standards





Flicker spreading





• mitigation




Session 4

PQ monitoring


Harmonics casestudy


Flicker mitigation


• compensation



transients

• overvoltages

Conclusions




Flicker mitigation

• system enforcement – increased short-circuit power

• electrical separation of disturbing loads – disconnectedsubstation busbars

• compensation measures – series reactor – Static Var Compensator – SVC – Static Compensator - StatCom

• elimination of flicker sources – power reduction of disturbing

loads (if possible)• lighting technology

– fluorescent lamps are considered to be less sensitive to voltageflicker than incandescent lamps

– ban of incandescent lamps due to energy savings reasons


System enforcement

• increased short-circuit power will

reduce flicker

level

– new parallellines

– additionaltransformers

– connection tothe highervoltage level

line disconnection



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32

Separation of disturbing loads

• electrical separation of disturbing loads – disconnectedsubstation busbars

P lt =3,03P lt =0,47

P lt =0,71P lt =0,71

TR 412400/110kV

TR 411400/110kV

Okroglo 110 kV »ostali «

Okroglo110 kV

»sunkovit «

Okroglo 400 kV

P lt =5,31

TR412400/110 kV

TR411400/110 kV

Okroglo 110 kV

Okroglo 400 kV

P lt =1,13

P lt = 3,44

P lt =1,13

P lt =0,52

RTPJeklarnasunkovit odjem

RTPJeklarnasunkovitodjem



• electrical separation of

disturbing loads

– connected substation

busbars

– arc furnace is supplied

by two transformers inparallel



• electrical separation ofdisturbing loads

– disconnected substation

busbars

– arc furnace is suppliedby one transformers



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Compensation measures

• series reactor

– for minor flicker level reductionin the point of common coupling

– redistribution of flicker level

– influences the operation of arc

furnace

arc

series

reactors



• Static Var Compensator – SVC – flicker and reactive power

compensation

– controllable shunt connected reactance

– TCR – Thyristor Controlled Reactor isthe main element

– reactive compensation current is a

function of voltage – flicker reduction factor is up to 2

– reliable – good operationalexperiences

– small operational losses



• Static Var Compensator – SVC

– single-line diagram

– TCR

– fixed capacitors andfilters



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34



– voltage profile improvement with SVC




– arc furnace performance improvement with SVC



• Static Var Compensator SVC

– practical applications



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35


• Static Compensator - StatCom – flicker and reactive power

compensation

– controllable source of reactivecurrent

– Voltage Sources Converter - VSCis the main element

– employs GTO thyristors or IGBTs

– flicker reduction factor is up to 5

– not a lot of operationalexperiences

– higher operational lossescompared to SVC



• Static Compensator -

StatCom

– single-line diagram

– VSC

– fixed capacitors

(tuned filters)



• Static Compensator – StatCom

– voltage profile improvement with StatCom

– increased power of arc furnace



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– substantial flicker level reduction




– comparison of the arc furnace currents with thecompensated grid currents




– first StatCom application for flicker mitigation – Hagfors,Sweden (ABB commercial name SVC Light)



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37

Analysis of compensation measures



– present situation – no compensation measures

12%

17%

20%

51%

Plt>1,5 1


38/38

Analysis of compensation measures



– only arc furnace C is compensated (series reactor)12%

14%

21%

53%

Plt >1 ,5 1

kee okt13 ipapic 3

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