Flicker Analysis and Case Studies - IEEE Entity Web ... · Flicker Analysis and Case Studies Jim Rossman, ... 150-hp head saw abruptly loaded up ... Case #1 – 200 hp Chipper Startup

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Flicker Analysis and Case Studies

Jim Rossman, P.E.Senior Manager of Power Quality

Gerald Johns, P.E.Senior Power Utilization Engineer

TVAAugust 2008

2

Voltage Drop Creating Visible Light FlickerVoltage Drop Creating Visible Light Flicker

Voltage Flicker Is:Voltage Drop as Seen by

OthersVisible With Incandescent

lights and some CFLsComplaints Normally From

Residential CustomersMuch lower in magnitude

than a fault related voltage sag – usually only a few volts on 120-V system

Noticeable at low levels and downright annoying at higher levels

Voltage Flicker Does Not:Normally does not cause

equipment downtimeDoes not damage other

folks equipment

3

Flicker is Perceived Voltage DropVoltage Drop is Graphically Shown Below

Drawing Copied from IEEE 141

Flicker is Perceived Voltage DropVoltage Drop is Graphically Shown Below

Drawing Copied from IEEE 141

Φ+Φ≅ sincos IXIRVdrop

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Per Unit Approach to Calculating FlickerPer Unit Approach to Calculating Flicker

100)1(%)1(%% XMVARswingRMWswingVdrop +

≅

Hand calculations often work best in percent on an MVA baseTVA uses 100-MVA as our base so the following is the same approach but written on a percent basis:

Example: Large motor draws 25-MW and 40-MVAR on startup. With a system Thevenin equivalent Of Z= 0.988% +j 7.170% (100-MVA base), What is the expected voltage swing on startup?

%1.3100

%)170.7(40%)988.0(25=

+≅

MVARMWVdrop

Φ+Φ≅ sincos IXIRVdrop

5

Perceived Voltage Drop in LightsGE Flicker Curves

Copied From IEEE 141

Perceived Voltage Drop in LightsGE Flicker Curves

Copied From IEEE 141

6

TVA Flicker CurveTVA Flicker Curve

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Flicker CurvesIEEE 141 and TVA

Flicker CurvesIEEE 141 and TVA

TVACurveInRed

8

Three Key Flicker ComponentsThree Key Flicker Components

Recipe for Complaints:1. Start with - Varying load/generation equipment2. Serve from a - High System Impedance3. Repeat variations until annoying

9

Component 1:Equipment with Load Swings Leading to

Possible Flicker Issues

Component 1:Equipment with Load Swings Leading to

Possible Flicker Issues

• Motors and Compressors– Rock Crushers– Saw Mills– Large Motors (Car Shredders, pumping systems)– HVAC systems

• Welders• Process ARC Furnaces• Process Induction Furnaces• Wind Generators• Others

10

Mitigation Systems Reducing Load SwingsMitigation Systems Reducing Load Swings

Dynamic Var Systems– Static Var Compensators– Dstatcom– Intellivar– Thyristor-Controlled Capacitor Systems

Motor Impact Reduction– Reduced Voltage Starters– Wound Rotor Motor Resistors– DC Motor Systems

Sequencing Multiple Welder SystemsArc Furnace Reactors

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Component 2:Impedance Issues Important to Flicker Critical

Point of Common Coupling (PCC) for Flicker Studies

Component 2:Impedance Issues Important to Flicker Critical

Point of Common Coupling (PCC) for Flicker Studies

+

161kVRMSLL /_0

AC1

RL+

PI1

1 2

69/13.2

20_MVA2

3

1

161/69/13

60_MVA

RL+

PI2

.287Ohm

ZZ_1

+

RL1

Transmission Sub-transmission Distribution Distribution Level Circuit Level Bus Level Circuit Level

My PCC Definition:Closest Interconnection Location Where Another Customer Can See The Voltage Drop From The Disturbing Load

12

Component 2:Series Impedance to PCC –

Shown in Percent (100-MVA Base)

Component 2:Series Impedance to PCC –

Shown in Percent (100-MVA Base)

+

161kVRMSLL /_0

AC2

RL+

PI3

+

RL3

RL+

PI4

+

RL4+

RL2

Distribution Circuit – 13-kV

Distribution Bus – 13-kV

Sub-transmission – 69-kV

Transmission – 161-kV

Possible PCC Interconnection

(30.47+j138.9)% – total to DD

(1.75+32.6)% – total to CC

(1.08+j12.6)% – total to BB

(0.70+j4.82)% – total to AA

% Series Circuit Impedance 100-MVA base

A B C D

Hopkinsville, KY Facility - Services Went From 13-kV to 161-kV

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Mitigation Approaches With Impedance Reductions

Mitigation Approaches With Impedance Reductions

Historical Solution to Flicker Problems – Reduce Impedance and percent voltage drop by Moving PCC upstream:

– General Distribution to Dedicated Distribution Feed– Dedicated Distribution Feed to Sub-transmission Feed– Sub-transmission Feed to Transmission Feed

Add Series Capacitors In Line

14

Component 3:Frequency of Voltage Variation Swings

Component 3:Frequency of Voltage Variation Swings

• Startup Related (once per season, month, week, day)– Pump Motors– Process Systems– Energizing Transformers

• Low Frequency Process cyclic (multiple times per day or hour)

– Air compressors– Refrigeration Compressors

• High Frequency Process cyclic (many times per hour of second)

– Rock crusher cycling– Shredders– Welders– Arc Furnaces

15

GE Flicker CurvesCopied From IEEE 519


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Drawbacks of IEEE 141/519 CurveDrawbacks of IEEE 141/519 Curve

280 300 320 340 360 380

116

117

118

119

120

121

122

123

124

125

126

seconds

RM

S V

olts

16:04:0203/13/2008Thursday

16:04:04 16:04:06 16:04:08 16:04:10

272.5

275.0

277.5

280.0

282.5

285.0

287.5

290.0

Volts

A Vrms (val)

230 230.5 231 231.5 232 232.5

119.99

119.995

120

120.005

120.01

seconds

RM

S v

olts

2530.5 2531 2531.5 2532 2532.5 2533 2533.5 2534 2534.5

270

272

274

276

278

280

282

284

286

288

seconds

RM

S V

olts

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IEEE 1453IEEE 1453

• Based on IEC 61000-4-15 (adopts the IEC standard).

• Provides specifications for the measurement of flicker based on IEC 61000-4-15.

• Provides recommended flicker limits on medium-voltage, high-voltage, and extra-high voltage systems based on IEC 61000-3-7.

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Advantages of using IEEE 1453 over IEEE 141/519 curvesAdvantages of using IEEE 1453 over IEEE 141/519 curves

• Measurement that directly represents flicker level in terms of human perception.

• Provides a way of measuring flicker when voltage fluctuation is anything but a rectangular change.

• Impact of modulations caused by modern solid-state converters (interharmonics) on voltage fluctuations taken into account.

• Can be incorporated into simulation models to provide future flicker estimates and the effectiveness of various flicker mitigation options.

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UIE/IEC FlickermeterUIE/IEC Flickermeter

First 4 blocks produce a signal that collectively represent:• Response of a lamp to a supply voltage variation.• Perception ability of the human eye• Memory tendency of the human brain.

Block 5 is a statistical calculation that emulates human irritability to the flicker level.

Figure Source: J.C. Gomez, M.M. Morcos, “Flicker Measurement and Light Effect”, Power Engineering Review, Nov. 2002.

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IEEE 1453 DefinitionsIEEE 1453 Definitions

• Pst – “A measure (statistical) of short-term perception of flicker obtained for a ten-minute interval. “

• Plt – “A measure (statistical) of long-term perception of flicker obtained for a two-hour period. This value is made up of 12 consecutive Pst values per the following formula.” - Necessary when duty cycle varies or multiple loads operating simultaneously.

N33

1

1Plt = PstNwhere N = The nunber of Pst readings.

jj=

×∑

N should be based on the duty cycle of the fluctuating load. If exact duty cycle is unknown, assume N=12 to represent 2 hours.

21

IEC FlickermeterIEC Flickermeter

• Pst of 1.0 represents a magnitude and frequency of voltage fluctuation that is generally considered to be objectionable.

• Measurement based on luminous fluctuation associated with 60-watt, 60-Hz 120-VAC or 50-Hz 240-VAC incandescent lamps.

22

Comparison of IEEE 141 and IEC Flickermeter CurvesComparison of IEEE 141 and IEC Flickermeter Curves

*1 dip = 2 changes

23

IEEE 1453 Recommended Flicker LevelsIEEE 1453 Recommended Flicker Levels

However, levels that are not objectionable may still be perceivable.

Represents the levels below which complaints are not generally received.

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1453 Statistical Guidelines1453 Statistical Guidelines

• As a general guideline, when designing, Pst and Plt should not exceed the planning levels more than 1% of the time (99% probability level), with a minimum assessment period of one week.

• IEEE 1453 recommends that Pst and Plt not exceed 1.0 pu 5% of the time in existing low voltage and medium voltage systems (95% probability level.

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Other Points To Note About FlickerOther Points To Note About Flicker

• People most sensitive to fluctuation frequency of 2 to 10 Hz with flicker visible up to 35 Hz.

• Any change in voltage 6.0 % or greater results in objectionable flicker, regardless of frequency. [1]

• Lower-wattage incandescent bulbs produce more flicker for a given change in voltage. At the same rated wattage, a 230-volt bulb will flicker more than a 120-volt bulb for a given change in voltage.

• Dimmers can exacerbate the flicker problem because flicker becomes more perceptible as baseline lumen levels are reduced.

• Fluorescent lamps typically flicker less for a given voltage input [2].

[1] R.Dugan, et al., Electrical Power Systems Quality, 2nd Ed., 2002.

[2]T.A. Short, Electric Power Distribution, 2005.

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EPRI Studies of Compact Fluorescent Lamp Gain FactorsEPRI Studies of Compact Fluorescent Lamp Gain Factors

The gainfactor is defined as the ratio of relative lightchanges to relative voltage changes.

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EPRI Studies of Linear T8 Fluorescent Lamp Gain FactorsEPRI Studies of Linear T8 Fluorescent Lamp Gain Factors

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How About a Break!

Lets Keep It to 15 Minutes – The Best is Yet to Come!

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Case #1 Sawmill on Rural FeederCase #1 Sawmill on Rural Feeder7.2/12.47 kV distribution source @ mill

Primary Z = 12.94 + j10.45 ohms

9.47 miles of 14.4/24.9 kV

3.76 miles of 7.2/12.47 kV

Flicker caused by load fluctuations as well as motor starts.

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14:49:30.012/17/2007

Monday

14:49:30.5 14:49:31.0 14:49:31.5 14:49:32.0 14:49:32.5

100

200

300

400

500

kW

TOT P(kW) (val)

300400500600700800

kVAR

TOT Q(kVAR)

255260265270275280

Vol

ts

A Vrms (val) B Vrms (val) C Vrms (val)

-1500

-500

500

1500

Am

ps

A I B I C I

Real power draw starts to increase due to increase load torque (large log), but then declines because of reduced speed.

Reactive power draw increases substantially due to extreme speed reduction.

Significant voltage reduction due to reactive power draw.

Event #1 – 150-hp head saw abruptly loaded up – data collected at utility metering point

Case #1 - Head-Saw Load Up – 9.6% Vdrop @ Mill Secondary and 6.6 % Vdrop On PrimaryCase #1 - Head-Saw Load Up – 9.6% Vdrop @ Mill Secondary and 6.6 % Vdrop On Primary

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12:22:5012/17/2007

Monday

12:22:52 12:22:54 12:22:56

300

500

700

900

1100

Am

ps

A Irms (val) B Irms (val) C Irms (val)

260265270275280285

Vol

ts


100

150

200

250

300

kW

TOT P(kW) (val)

300400500600700800

kVA

R

TOT Q(kVAR)

Softstart programmed to start motor @ 330 % FLA

Case #1 – 200 hp Chipper Startup w/softstart 7.5 % instantaneous Vdrop at Sawmill and app. 5 % corresponding drop at residenceCase #1 – 200 hp Chipper Startup w/softstart 7.5 % instantaneous Vdrop at Sawmill and app. 5 % corresponding drop at residence

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Initial 1-Week Pst ProfileInitial 1-Week Pst Profile

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Initial GoalsInitial Goals

• Reduce flicker Pst on utility system to < 1.0.• Reduction in voltage sags caused by sawmill

operations on utility system to no more than 2.0 percent.

• Mitigation mechanisms must not cause greater than 2.0 percent voltage rise on utility system.

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S & C’s AVC (Adaptive VarCompensator)

ABB’s DynaComp (Dynamic-VarCompensator

Examples of Products Providing Fast Reactive Power CompensationExamples of Products Providing Fast Reactive Power Compensation

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More Examples of Products Providing Fast Reactive Power CompensationMore Examples of Products Providing Fast Reactive Power Compensation

Eaton-CH Active Filter

Square-D Active Filter

Square-D Hybrid-VarCompensator

36

Case Study #1 – Examples of Motor Starts with AutoXFMR startersCase Study #1 – Examples of Motor Starts with AutoXFMR starters

12:17:5512/17/2007

Monday

12:18:00 12:18:05 12:18:10

260

265

270

275

280

285

290

Vol

ts


250

500

750

1000

Am

ps

A Irms (val) B Irms (val) C Irms (val)

Headsaw(150hp) w/67% tap

Edger (150hp) w/50 & 67% taps

37

Starter ModificationsStarter Modifications

Set all taps to 50% on all autotransformer starters.

Programmed 200hp softstart to start at 250 % of FLA.

After starter modifications, Max starting Vdrop on primary ~3%

38

Findings of Additional Recording at the SawmillFindings of Additional Recording at the Sawmill

Fluctuations were more frequent and of higher magnitude overall due to type of wood being sawed.

12:0005/12/2008

Monday

00:0005/13/2008

Tuesday

12:00 00:0005/14/2008Wednesday

12:00 00:0005/15/2008Thursday

12:00 00:0005/16/2008

Friday

012345

B VPst

0

200

400

600

kW

TOT P(kW) (val)

0200400600800

kVA

R

TOT Q(kVAR)

Dran-View 6.5.00 OEM Site License Tennessee Valley Authority

39

Case Study #1 – Sawmill on Rural FeederCase Study #1 – Sawmill on Rural Feeder

Worst-case primary fluctuation = 8%

40

Calculations - Converting 3.9 miles to 14.4/24.9 kV Calculations - Converting 3.9 miles to 14.4/24.9 kV

New worst-case primary fluctuation = 2.8%

41

Pst Calculations and Estimated Pst with Voltage ConversionPst Calculations and Estimated Pst with Voltage Conversion

06:0005/13/2008

Tuesday

08:00 10:00 12:00 14:00 16:00 18:00 20:00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

B VPst

Created with DranView 6.5.0

Residence

Sawmill

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Estimating Future Pst After Voltage ConversionEstimating Future Pst After Voltage Conversion

• Max Pst at residence for day shown = 1.34

• Corresponding Pst at sawmill secondary metering point = 1.74

• Typical ratio “every other interval” ~ 0.7-0.75

• Impedance Ratio =

• By converting last 3.76 miles to 14.4/24.9 kV

@

@

1.34 0.771.74

Max residence

Corresponding sawmill

PstPst

= =

_ _ _ Pr

_ _ _

0.1070 0.70.1535

To XFMR Sawmill imary

To XFMR Sawmill Secondary

ZZ

= =

_ _ _ Pr

_ _ _

0.0448 0.480.0933

To XFMR Sawmill imary

To XFMR Sawmill Secondary

ZZ

= =

With Impedance Ratio = 0.48 PstMax @ Residence Due to Sawmill Load = 0.84

43

Case Study #2a & #2b – Residential Air-Conditioning StartingCase Study #2a & #2b – Residential Air-Conditioning Starting

• Customer complaints at their worst have resulted in service drop/lateral changeout or possibly even transformer upsizing

• HVAC technicians often install “hard start” kits• On average, electric consumers understand

that flicker is simply going to occur when their A/C starts.

• Members sharing secondary conductors and sometimes transformer may result in one member seeing another member’s A/C startup.

44

A/C Starting Case Study #2aA/C Starting Case Study #2a

19:55:25.307/11/2007Wednesday

19:55:25.4 19:55:25.5 19:55:25.6 19:55:25.7

-150

-50

50

150

Vol

ts

A V

-150-100

050

150

Am

ps

A I

110.0112.5115.0117.5120.0

Vol

ts

A Vrms

20:09:57.307/11/2007Wednesday

20:09:57.4 20:09:57.5 20:09:57.6 20:09:57.7

-150

-50

50

150

Vol

ts

A V

-150-100-50

0

100150

Am

ps

A I C I

110.0112.5115.0117.5120.0

Vol

ts

A Vrms (val)

Before hard start installed

After hard start installed

45

Results of Using Hard Start DevicesResults of Using Hard Start Devices

• Hard start results in increased starting torque• Compressor accelerates to full speed more

quickly, thereby reducing startup duration• Magnitude of initial inrush current and voltage

drop still the same as before – capacitor provides phase shift but no voltage rise

46

Minimum Voltage Magnitude Profile and Corresponding Pst for A/C Startups Case StudyMinimum Voltage Magnitude Profile and Corresponding Pst for A/C Startups Case Study

Min Max 95% 99%AVrms 113.3 124.8 N/A N/AAVPst 0.06869 0.8114 0.7575 0.8114

20:0006/15/2008

Sunday

22:00 00:0006/16/2008

Monday

02:00 04:00 06:00

115.0

117.5

120.0

122.5

125.0

Vol

ts

A Vrms (min)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

A VPst

Flicker could be considered objectionable although Pst<1.0

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A/C Startup Case Study #2bA/C Startup Case Study #2b

• Customer complained about flickering lights, number of interruptions occurring, and damaged electronics.

• Distributor power-quality monitoring revealed nothing problematic.

• Distributor changed 50 kVA to 75 kVA transformer and concerns were not resolved.

• Relationship between customer and distributor was tense and customer wondered why the transformer had been changed out if no problem could be detected.

• HVAC technician told customer that the A/C unit needed a “booster” (hard-start kit).

48

A/C Startup Case #2b Power Quality Monitoring A/C Startup Case #2b Power Quality Monitoring

-400

-300

-200

-100

0

100

200

300

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

T ime (sec)

Switchbounce associated with the mercury-bulb thermostat resulted in multiple A/C starts

A/C unit starting current

49

Case Study - Raw Water Pumping Station – Original Design Case Study - Raw Water Pumping Station – Original Design

• Original study began in 2004– Design incorporated 1 pump driven by 1250 hp

4,160 V AC induction motor– Provision for additional pump installation– 4,160 VAC Electronic softstarter– 2,125 kVAr 2-stage capacitor bank switched

simultaneously on with motor (electromechanical contactor-switched)

– 1,800 kVAr switched off just as motor about to reach full speed

50

Original Design – Circuit CharacteristicsOriginal Design – Circuit Characteristics

• Fed from 161/69/12.47 sub off of 12.47-kV system

• App. 3.5 miles with 8 line sections of distribution line

• 12.47 kV to 4,160 V 2,500 kVA padmountXFMR

• 0.1 miles from riser pole to XFMR, but distributor wanted PCC to still be at primary terminals of XFMR

51

Original Objectives and ConstraintsOriginal Objectives and Constraints

• Determine if original design with both electronic softstartand simultaneously-switched cap bank:

– Result in less than 2.0 % voltage drop at PCC during motor start?

• Use softstart manufacturer’s stated inrush current values for calculations

• Perform calculations by hand and/or using steady-state type analysis program

52

Original Calculations from 2004-2005Original Calculations from 2004-2005

2.0 % limit exceeded but distributor willing to go to 3.0 % withunderstanding that pump not started more than once per week

53

2006 Design Changes2006 Design Changes

• Latest starter mfr/consultant analysis indicated voltage drop will exceed 4.0 percent at PCC during startup.

• New design called for 2 pumps operating simultaneously

• Increased runtime/# of startups• Customer contemplating generator because distributor

does not want to allow more than 3% fluctuation under any circumstances

54

Tm

ST

D EV4

+

1 6 1 k VR MSL L /_ 0? v

AC 1

s c opes c p 3

v(t)

p1sc

ope

scp4

scop

e

scp5

scop

esc

p6

rmso u tin

tr_ 1

rmso u tin

tr_ 2

rmso u tin

tr_ 3

s c opeSe c o n d a ry Vo lta tTra n s fo rme r

s c opes c p 8

s c opes c p 9

s c opes c p 1 0

rmso u tin

tr _ 4

s c opeMo to rN o 2 R MSC u r r e n t

+

7 |1 E1 5 |0

? i

SW 1

1 2

1 2 .4 7 /4 .1 6

Yg Yg _ n p 2

2 3

1

YgYg

D_n

p1

?

161/

12.4

7/69

+

? v

2 3

1

YgYg

D_n

p2

?16

1/12

.47/

69

+

?v

s c ope

Pr ima ry _ C u r r e n t_ A

i(t)

p3

v(t)

p2

rmso u tin

tr _ 9

rmso u tin

tr _ 1 0

rmso u tin

tr _ 1 1

s c opeC a d iz Su b Vo lta g e

s c opes c p 1 7

s c opes c p 1 8

s c opeSp e e d 2

rmso u tin

tr_ 5s c ope

Mo to r N o 1 R MSC u r re n t

f(u)1

Fm2

Fm3

f(u)

Fm1

+c SW 1

+c SW 3

+

C 1? i

2 7 6 u F

+

C 2? i

2 7 6 u F

+

C 3? i

2 7 6 u F

+

c SW 2

f(u)

1

Fm

f(u)

1

Fm6

rmso u tin

tr_ 1 2

s c opePr ima ry Vo lta g e a tTra n s fo r me r

s c opeSe c Vo ltD ro p a tTra n s fo rme r

s c opePr ima ry Vo ltD ro p a tTr a n s fo rme r

v ( t )p 4

f(u)1

Fm4

s c opeMo to rN o 2 Sp e e d

f(u)

Fm9

+c SW 4

+c SW 5

+

C 4? i

4 5 .9 8 u F

+

C 5? i

4 5 .9 8 u F

+

c SW 6

+

C 6? i

4 5 .9 8 u F

f(u)1

2

Fm7 P Q

s c opePF

c1 0 0 0 0

C 8

Tm_ 1

+

? v

+

C 7? i

4 5 .9 8 u F

rmso u tin

tr_ 6

s c ope

Pr ima ry _ C u r r e n t_ Brmso u tin

tr_ 7

s c ope

Pr ima ry _ C u r r e n t_ Crmso u tin

tr_ 8

f(u)1

Fm5 s c ope

Pe rc e n tVd r o p a tC a d iz Su b s ta tio n

AS MS

4 .1 6 0 k V1 2 5 0 h p

? m

ASM1Sp e e dia

AS MS

4 .1 6 0 k V1 2 5 0 h p

? m

ASM2Sp e e dia

BU S1

a

cba

BU S2

BU S2

BU S2

•EMTP used to simulate motor start using dedicated feed from substation

•Analysis of across-the-line start with and without simultaneous cap switching

55

With Cap Bank Switched - ResultsWith Cap Bank Switched - Results

Max 1.4 % drop during start at substation with caps

56

Without 1,800 kVAr Cap Bank Switched - ResultsWithout 1,800 kVAr Cap Bank Switched - Results

Max 1.7 % drop during start at substation without caps

57

Case Study #4 – Automotive Component Manufacturer with Welders (Reactive Power)Case Study #4 – Automotive Component Manufacturer with Welders (Reactive Power)

Estimated 400-kVAr swings per phase based on 1-minute max/avg/min data

58

Case Study #4 – Automotive Component Manufacturer with Welders (Real Power)Case Study #4 – Automotive Component Manufacturer with Welders (Real Power)

Estimated 200-kW swings per phase based on 1-minute max/avg/min data

59

Case Study #4 – Automotive Component Manufacturer with Welders (Voltage)Case Study #4 – Automotive Component Manufacturer with Welders (Voltage)

3 to 4.7-volt swings based on 1-minute max/avg/min data

60

Case Study #4 – Corresponding Pst on Bus Feeding Welders (Dirty Feed)Case Study #4 – Corresponding Pst on Bus Feeding Welders (Dirty Feed)

Generally, Max Pst ~ 1.5Due to voltage sag

61

Case Study #4 – Corresponding Pst on Bus Fed By Separate Transformer Bank (Clean Feed)Case Study #4 – Corresponding Pst on Bus Fed By Separate Transformer Bank (Clean Feed)

Generally, Max Pst ~ 0.5

62

Vdrop Calculation and Comparison of Welder Bus Pst to That of Separately Fed BusVdrop Calculation and Comparison of Welder Bus Pst to That of Separately Fed Bus

• Max Pst on welding bus = 1.5• Max Pst on separately fed bus = 0.5• Utility-supplied SCC = 4,127 A @ 7.2/12.47 kV• Welding bus XFMR %Z = 6 % • Assume X/R of utility circuit = 7 and X/R of XFMR = 12

32.0350111

350j363.111j16

Bus Welding to ZTotal ZSourceCommon

3.05.15.0

Pst Bus dingWelPst Bus Fedarately Sep

%4.4100

239)(111.31.220)(160.6 Drop %Voltage Expected

percent 239j20 base)MVA -100(on r ZTransforme

percent 3.111j16

1012470

73.1j25.0 Zbase,MVA 100On

ohms 73.125.0)))7(sin(tanj))7((cos(tan41277200

8

2 source

11

≈≈++

=

==

=+×++×

=

+=

+=+

=

+=+× −−

63

Case 5 – Wind Generation

64

Buffalo Mountain Wind Farm Generation -Flicker Case

Buffalo Mountain Wind Farm Generation -Flicker Case

TVA originally contacted for three small windmills to be fed from a local distributor’s 13-kV system. Occasionally during windmill startup, the distributor received flicker complaints. When the 15-1.8-MW units went in service, it was decided to serve the new load at 161-kV.

65

Aggregate Load Swings for 15-1.8-MW Wind Generators

Aggregate Load Swings for 15-1.8-MW Wind Generators

Voltage

MW

MVAR

66

Case 6 – Large Motor System

Evaluate Possibility ofServing a 3000-hp Wound Rotor Motor

Metal ShredderAt Two Possible Locations

– XXX 69-kV: Z1 = 23.989 + j 52.618%– YYY 161-kV: Z1 = 1.559 + j 9.048%

67

Characteristics of ShredderProvided by Vendor

Characteristics of ShredderProvided by Vendor

3 times per minuteShred Load Cycling

3.1-MVA swings at 78%p.f.

2.4-MW swing1.9-MVAR swing

68

Hand Calculation Used for Approximation and EMTP Model Used for More Exact Solution

Hand Calculation Used for Approximation and EMTP Model Used for More Exact Solution

Site XXX Hand Calculation:Z1 = 23.99 + j 56.6 % (100-MVA base)MVA swing = 2.4 + j1.9

%VDrop 2.4-MW (23.99)/100 + 1.9-MVAR (56.6)/100 = 1.65%

+

AC1

69kVRMSLL /_0

s3 s4

DEV1

MW_MVAR_MW_METER

Tm

Gain2

9.549297

scopeRPM

c

0.25

C2

c

1.0

C3

Timer

3/7

tmr1

c

2

C4

1

2

select

Sel1?s

+

2.5

R1+

0.0e+0m

R2

i(t) p1

scope

IArms_Corrected

SpeedTeg scope

Torque

+

184uF C1

ASMS R

N

4.16kV3000hp

ASM1

i(t) p2

outTACS type-66

rms meter

inDEV3

scope

IArms_Uncorrected

outTACS type-66

rms meter

inDEV5

+RL1

1 2DYg_1

69/4.16

v(t)

p3

outTACS type-66

rms meter

inDEV6

f(u)1Fm1

scopePercent_V

++-

sum1

+SW1

500ms|1E15|0

≅

Use EMTPModelingFor MoreExactSolution

69

EMTP Simulation ResultsVoltage Drops As Shredder Cycles

EMTP Simulation ResultsVoltage Drops As Shredder Cycles

XXX -69-kV1.75%

YYY – 161-kV0.3%

70

Applying Results to TVA Flicker Curve Shows YYY is OK and XXX is Not Recommended

Applying Results to TVA Flicker Curve Shows YYY is OK and XXX is Not Recommended

TVA

XXX 69-kV – Above Curve – Ruled Out

YYY 161- Below Curve - OK

71

Case 7

My Town Needs a Steel Rolling MillWhat do we need to do to allow us to run

this mill?Remote Community Fed at 46-Kv – Impedance to Substation - Z1 = 74.9 +j113.5%

At 26-kV Substation Transformer Secondary (PCC) - Z1=76.3 +j169.0%

72

Company Choose IntelliVar as Mitigation System

Company Choose IntelliVar as Mitigation System

Not actualInstallationBut ShowsAll Major Components

TransformersValvesFiltersControls

73

IntelliVAR System at 1500-KVARControls Not Working Properly

IntelliVAR System at 1500-KVARControls Not Working Properly

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

13 WedJun 2007

14 Thu 15 Fri

46kV - Pst Afrom 06/13/2007 to 06/15/2007

EPRI/Electrotek PQView®

Pst

A

Time

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

13 WedJun 2007

14 Thu 15 Fri

26kV - Pst Afrom 06/13/2007 to 06/15/2007


Pst

A

Time

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

13 WedJun 2007

14 Thu 15 Fri

26kV - P Totalfrom 06/13/2007 to 06/15/2007

EPRI/Electrotek PQView®Time

Min[P Total] (kW) Avg[P Total] (kW) Max[P Total] (kW)

-1000

-500

0

500

1000

1500

2000

2500

3000

3500

4000

13 WedJun 2007

14 Thu 15 Fri

26kV - Q Fund Allfrom 06/13/2007 to 06/15/2007


Min[Q Fund All] (kvar) Avg[Q Fund All] (kvar) Max[Q Fund All] (kvar)

PST(95) – 1.47

PST(95) – 1.17

74

IntelliVAR Sizing Doubled to 3000-KVARControl System Finally Tuned

IntelliVAR Sizing Doubled to 3000-KVARControl System Finally Tuned

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

24 ThuApr 2008

25 Fri 26 Sat

26kV - P Totalfrom 04/24/2008 to 04/26/2008


Min[P Total] (kW) Avg[P Total] (kW) Max[P Total] (kW)

-4000

-3500

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

24 ThuApr 2008

25 Fri 26 Sat

26kV - Q Fund Allfrom 04/24/2008 to 04/26/2008



0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

24 ThuApr 2008

25 Fri 26 Sat

26kV - Pst Afrom 04/24/2008 to 04/26/2008


Pst

A

Time

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

24 ThuApr 2008

25 Fri 26 Sat

46kV - Pst Afrom 04/24/2008 to 04/26/2008


Pst

A

Time

26-kV - PST(95) - 1.18

46-kV - PST(95) – 0.82

75

Before and After Intellivar ChangesBefore and After Intellivar Changes

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

24 ThuApr 2008

25 Fri 26 Sat

26kV - Pst Afrom 04/24/2008 to 04/26/2008


Pst

A

Time

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

13 WedJun 2007

14 Thu 15 Fri

26kV - Pst Afrom 06/13/2007 to 06/15/2007


Pst

A

Time

13600

13800

14000

14200

14400

14600

14800

15000

15200

15400

13 WedJun 2007

14 Thu 15 Fri

Kosciusko - Attala Steel 26kV Kosciusko - V RMS Afrom 06/13/2007 to 06/15/2007


Min[V RMS A] (V) Avg[V RMS A] (V) Max[V RMS A] (V)

13600

13800

14000

14200

14400

14600

14800

15000

15200

15400

24 ThuApr 2008

25 Fri 26 Sat

Kosciusko - Attala Steel 26kV Kosciusko - V RMS Afrom 04/24/2008 to 04/26/2008



PST(95) - 1.18 – Not Under 1.0But No Routine Complaints

76

Case 8

My Largest Industry Has Us in a Bad Situation Due to Flicker, What Are Our

Options?

77

Distributor Not Routinely Serving Any Customer From 46-kV Winding Due to Flicker Complaints

Distributor Not Routinely Serving Any Customer From 46-kV Winding Due to Flicker Complaints

T Equivalent

+

161kVRMSLL /_0

AC1+

PI1

+

RL1+

RL2

+

RL3

2

3

1

161/46/13

YgYgD_np1

+

RL4

Arc Furnace

DEV1

Arc Furnace

DEV2

Arc Furnace

DEV3

Other Customers Normally FedFrom 46-kV SystemDistributor Removed Them Due to Flicker Complaints

PCCIs LocatedWithinTransformerAt T EquivalentTie Point

Site Fed FromDedicated13-kV Winding161/46/13Transformer

78

PST Estimate – Traditional Hand CalculationPST Estimate – Traditional Hand Calculation

161-kV MVAsc at Sub – 1558 MVAsc or 3.85% at 60 MVA Base

161-kV:46-kV:13:kV Transformer Nameplate:Z161-46 = 9.7% at 60-MVA, Z161-13 = 5.8% at 21-MVA (16.57% at 60-MVA)Z46-13 = 2.1% at 21-MVA (6.0% at 60-MVA)Convert to T equivalentZ161 = ½ (9.7% +16.57%-6.0%) = 10.135% at 60 MVAZ46 = ½ (9.7% + 6.0% -16.57%) = -0.435% at 60 MVAZ13 = ½ (16.57%+6.0% -9.7%) = 6.435% at 60-MVA

PCC Includes TVA plus 161-kV portion of winding to 46/13-kV T pointPCC = 3.85% + 10.135% = 13.985% = 429-MVAsc

Estimated AF Swing = 2 x 4-MW = 8-MVA3 3Swing with 3 AF = x 8-MVA = 11.54-MVAsc for 3 units operating

46-kV Short Circuit Voltage Depression (SCVD) = 11.54/429 = 0.0269161-kV Short Circuit Voltage Depression (SCVD) = 11.54/1558 = 0.0074

46-kV PST Estimate = 0.0269 x KST = 0.0269 x 60 = 1.61

161-kV PST Estimate = 0.0074 x KST = 0.0074 x 60 = 0.44

79

Event #25 at 06/25/2007 08:10:30.067AVrms RMS and Waveform

Timeplot

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

A FDPst

06/12/2007 06/14/2007 06/16/2007 06/18/2007 06/20/2007 06/22/2007 06/24/2007 06/26/2007 06/28/2007

Event #1 at 05/23/2007 14:04:48.349AVrms RMS and Waveform

Timeplot

06/12/2007 06/14/2007 06/16/2007 06/18/2007 06/20/2007 06/22/2007 06/24/2007 06/26/2007 06/28/2007

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

A FDPst

161-kV PST (a phase)

46-kV PST (a phase)

161-kV Flicker0.44 per hand calc.

46-kV Flicker1.61 per hand calc.

PST Measurements of 46-kV and 161-kV Bus Confirm Hand Calculations - Target – PST Under 1.0

Moving to 161-kV Accomplishes This Objective

PST Measurements of 46-kV and 161-kV Bus Confirm Hand Calculations - Target – PST Under 1.0

Moving to 161-kV Accomplishes This ObjectivePST Measurements at 161-kV

PST Measurements at 46-kV - PCC

80

Option 1 – Add Transformer at SubstationUse Existing 13-kV Feed to Plant

Option 1 – Add Transformer at SubstationUse Existing 13-kV Feed to Plant

T Equivalent

+

161kVRMSLL /_0

AC1+

PI1

+

RL1+

RL2

+

RL3

2

3

1

161/46/13

YgYgD_np1

+

RL4

Arc Furnace

DEV1

Arc Furnace

DEV2

Arc Furnace

DEV3

1 2

161/13

DYg_1

Other Customers FedFrom 46-kV System

NewPCCAt161-kV Existing 13-kV LineDedicated 161:13-kV

Transformer at Sub

Remove PlantLoad FromExisting 3-windingTransformer

81

Move PCC Up to 161-kVOption 1 - Install Dedicated Transformer

Move PCC Up to 161-kVOption 1 - Install Dedicated Transformer

$1,742 Grand Total - New Transformer System

$124 Misc. cost not currently identified - 20% of cost (excluding transformer)

$123 $23 $100 Two-Step - 4.5 (4.0 effective) -MVAR Harmonic Filter1e

$20 $10 $10 Routing Existing 13-kV Wiring to New System 1d

$75 $25 $50 13-kV Distribution Breaker with relays1c

$400 $150 $250 161-kV SF-6 breaker w/ bay and relays1b

$1,000 $150 $850 New 16-MVA Transformer, oil containment, foundations, bus1a

TotalInstallEquip.

All cost below in $1000s

Move PCC up to 161-kV System at Substation1

Option

82

Option 2Build 161-kV Line to Plant Site and Add

Transformer at That Site

Option 2Build 161-kV Line to Plant Site and Add

Transformer at That Site

T Equivalent

+

161kVRMSLL /_0

AC1+

PI1

+

RL1+

RL2

+

RL3

2

3

1

161/46/13

YgYgD_np1

Arc Furnace

DEV1

Arc Furnace

DEV2

Arc Furnace

DEV3

1 2

161/13

DYg_1

+

PI2

NewPCCAt161-kV Dedicated 161:13-

kV Transformer at Plant

New 161-kV LineTo Plant Site


Remove PlantLoad FromExisting 3-windingTransformer

83

Move PCC to 161-kV Option 2 - Install Dedicated 161-13-kv Substation at

Plant Site

Move PCC to 161-kV Option 2 - Install Dedicated 161-13-kv Substation at

Plant Site

$1,683 Grand Total - Used Transformer System

$2,183 Grand Total - New Transformer System

$210 Misc. cost not currently identified - 20% of cost (excluding transformer)

$123 $23 $100 Two-Step - 4.5 (4.0 effective) -MVAR Harmonic Filter2f

$75 $25 $50 13-kV Distribution Breaker at Plant with relays2e

$125 $25 $100 161-kV Circuit Switcher at Plant with relays 2d

$400 161-kV Feed to Plant (existing row - big unknown ??)2c

$325 $75 $250 161-kV SF-6 breaker w/ bay and relays2b

$425 $75 $350 Used 18-MVA Transformer, oil containment, foundations, bus2a

$925 $75 $850 New 16-MVA Transformer, oil containment, foundations, bus2a

TotalInstallEquip.


Move PCC Up to 161-kV System at Plant2

Option

84

Option 3 - Install Quick, Dynamic VAR Correction and Harmonic Filter System at Plant Site

Option 3 - Install Quick, Dynamic VAR Correction and Harmonic Filter System at Plant Site

T Equivalent

+

161kVRMSLL /_0

AC1+

PI1

+

RL1+

RL2

+

RL3

2

3

1

161/46/13

YgYgD_np1

+

RL4

Arc Furnace

DEV1

Arc Furnace

DEV2

Arc Furnace

DEV3

3x1x

1 2 SVC

_1


Add Dynamic VarCorrection at PlantSite

No Transmission orDistribution SystemChanges Needed!

85

Fix Flicker at Plant 13-kV Bus Option 3 - Install Quick, Dynamic VAR Correction and

Harmonic Filter System at Plant Site

Fix Flicker at Plant 13-kV Bus Option 3 - Install Quick, Dynamic VAR Correction and

Harmonic Filter System at Plant Site

$1,370 Grand Total

$125 Misc. cost not currently identified - 10% of cost

$125 $25 $100 13-kV Switchgear Integrated Into Existing System3c

$145 $25 $120 Two Step - 6.6/6.3 (6.0 effective)-MVAR Harmonic Filter3b

$1,100 $100 $1,000 Install +10 /- 2-MVAR Var Compensator3a

TotalInstallEquip.


Install ABB Mincomp or S&C Purewave Dstatcom3

Option

86

Economic Summary:Installing Dynamic Var Compensation is Best Choice

Economic Summary:Installing Dynamic Var Compensation is Best Choice

2.9$1,370$479.4$415.0$31.6$32.8Option3

33.9$2,183$64.4$0$31.6$32.8Option2

27.0$1,742$64.4$0$31.6$32.8Option1

SimplePayback(years)

TotalCost

(1000s)

TotalSavings

(1000s)

ProductionProfitIncrease(1000s)

Electronic Equip.Savings(1000s)

Power FactorCorrectionSavings(1000s)

Option#

Option 1 – Transformer Isolation at Substation, filter at PlantOption 2 – Transformer Isolation at Plant, filter at PlantOption 3 – Install Filter/Dynamic VAR Compensation at Plant

87

Case 9

A Large Steel Mill Has an SVC, Why is it Creating More Flicker When On

Compared to When its Off?

Arc Furnace

DEV1

1 2

161/33

DY_1

+

10

R1

+0.804,2.3585Ohm

RL1

+

161kVRMSLL /_0

AC1+

0.285,4.004Ohm

RL2

IECFLickermeter

FLICKERMETER_PCC

1 2

33/0.7

DD_1

s3

Super_Voltmeter1

DEV2

PCC

88

Phase A Voltage(Max, Min, Avg)

Flicker SummaryPCC Monitor SiteWithout SVC/ FiltersPST(95) = 0.93

Base Case Without SVC System Operating2 Days

Base Case Without SVC System Operating2 Days

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

29 FriOct 2004

30 Sat 31 Sun

161PCC - Pst Afrom 10/29/2004 to 10/31/2004


Pst A

Time

89

Phase A Voltage(Max, Min, Avg)

Flicker SummaryPCC Monitor SiteWithout SVC/ FiltersPST(95) = 1.22

Base Case With SVC System Operating2 Days

Base Case With SVC System Operating2 Days

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

26 TueOct 2004

27 Wed 28 Thu

161PCC - Pst Afrom 10/26/2004 to 10/28/2004


Pst

A

Time

90

Flicker Reduced by Approximately 24% by Switching Off SVC/Filters

Flicker Reduced by Approximately 24% by Switching Off SVC/Filters

What is the reason for lower flicker levels with the SVC out of service?

Without SVC With SVC

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

29 FriOct 2004

30 Sat 31 Sun

161PCC - Pst Afrom 10/29/2004 to 10/31/2004


Pst

A

Time

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

26 TueOct 2004

27 Wed 28 Thu

161PCC - Pst Afrom 10/26/2004 to 10/28/2004


Pst

A

Time

PST (95) – 0.93 PST (95) – 1.22

91

Flicker SummaryPCC Monitor SiteWithout SVC/ Filters PST(95) = 1.86

Base Case With SVC System Operating -Weakened TVA System - 2 Days

Base Case With SVC System Operating -Weakened TVA System - 2 Days

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

9 SatFeb 2008

10 Sun 11 Mon

161PCC - Pst Afrom 02/09/2008 to 02/11/2008


Pst

A

Time

Complaints Ramped Up During This Period

92

Comparison of Voltage Swings at PCC Both With and Without SVC Operation

Comparison of Voltage Swings at PCC Both With and Without SVC Operation

ControlsOvershoot –One PossibilityForFlicker Swing

No SVC

SVC

93



Voltage Swing Possible By TCR Overshoot = 1.1%

94

Case 10

A Large Steel Mill Has an SVC and DC Electric Arc Furnace, Here is The Way

Things Should Operate!

95

EAF Operation with Great SVC Control PerformanceEAF Operation with Great SVC Control Performance

92000

92500

93000

93500

94000

94500

95000

95500

96000

96500

97000

3 TueJun 2008

3AM 6AM 9AM 12PM 3PM 6PM 9PM 4 Wed

161PCC- V RMS Afrom 06/03/2008 to 06/04/2008



0.05

0.10

0.15

0.20

0.25

0.30

0.35

3 TueJun 2008


161PCC- Pst Afrom 06/03/2008 to 06/04/2008


Pst A

Time

-30000

-25000

-20000

-15000

-10000

-5000

0

5000

10000

15000

20000

25000

30000

3 TueJun 2008


161PCC- Q Fund Allfrom 06/03/2008 to 06/04/2008



PST

VOLTAGE

REACTIVEPOWER

96

Questions/Comments

If not, then lets eat!!

Documents

Flicker Analysis and Case Studies - IEEE Entity Web ... · Flicker Analysis and Case Studies Jim Rossman, ... 150-hp head saw abruptly loaded up ... Case #1 – 200 hp Chipper Startup