comet powerpoint template - university of texas at austin · by nicola gariboldi “high voltage...

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C O M E T 2 0 1 7W E L C O M E T O A

T E C H N I C A L P A P E R P R E S E N T A T I O N

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B y N i c o l a G a r i b o l d i

“High Voltage Circuit Breakers”

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A B O U T T H E A U T H O RA B O U T T H E A U T H O R

• Master Electrical engineer - Politecnico of Milan

• Since July 2017 in Qualitrol as Technical Application Specialist

• 23 years in ABB

o 3 years Surge Arrester development

o 12 years High Voltage Circuit breaker development

o 5 years in GIS and Circuit breaker testing

o 3 years in Short Circuit Laboratory

• Member of CIGRE, IEC, IEEE

B R I E F B I O

N I C O L A G A R I B O L D IT e c h n i c a l A p p l i c a t i o n S p e c i a l i s t

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A B S T R A C TS U M M A R Y

O V E R V I E W &

What is a Circuit Breaker?

Why do we need it?

Technology

Fault clearing basics

Wear

L E A R N M O R E

Oil Circuit Breaker designed in 1901

by JOSEPH N. KELMAN

40 kV – 300A

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CLOSE position Ideal conductor

I

W h a t i s a C i r c u i t B r e a k e r ?

Electrical device connecting two grids

• Carrying Nominal & Fault current

• Isolating the grids & wistanding the

voltage

• Switching On & Off Nominal and

Fault current

Grid 1 Grid 2

Grid 1 Grid 2

OPEN position Ideal insulator

Grid 1 Grid 2

Operation Making and Breaking capability

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Disconnector ?

Safety

• Guarantee the grid isolation

• Higher insulation between contact

than to ground

• BEFORE and AFTER the circuit

breaker

• Visible Galvanic Separation

disconnector Circuit breaker disconnector

Grid 2Grid 1

• Disconnector• Circuit breaker• Disconnector

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Disconnector ?

Visible Galvanic Separation

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Disconnector ?

Withstanding Voltage

- Visible gap

Carrying current

- Nominal & Fault

NO Clearing capability

- also very small

we need a Circuit Breaker

Substation 500 kV Eldorado Boulder City, Nevada.Disconnector trying to clear reactive current of ~ 100A

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L o a d a n d F a u l t c u r r e n t

Nominal current

- l imited mainly by LOAD impedence

- Power factor ~ 1

Voltage drop ~ 5-10%

- short circuit impedance

ZscG

I

ZLoad

Usc ULoadUg

Loadsc

g

nZZ

UII

scLoad Z10..20Z

Ug 5%..10%IZU scsc

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L o a d a n d F a u l t c u r r e n t

FAULT condition

- Load is short circuited

Current limited by grid impedance

- ~ 10 .. 20 In

Short circuit condition

scLoad Z10..20Z

n

sc

g

sc I10..20Z

UII

UgIZU scscsc

Loadsc

g

ZZ

UI

ZscGI

ZLoad

UscUg

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F a u l t c u r r e n t

Grid impedence highly inductive

- R is low to l imit the l ine losses

- L is geometry dependent

Phase shift Voltage - Current

- ~ 90°

- Current Zero Voltage Max

Stored magnetic energy

-1

2𝐿𝐼2

- Transient effect

U

U

II

U

~90°

U

I

L

R

Z

t @50Hz @60Hz

[ms] [°el] [°el]

45 86.0 86.6

60 87.0 87.5

75 87.6 88.0

120 88.5 88.7

133 88.6 88.9f

R

L

R

L

t

t

2

tan

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Fau l t I n i t i a t i onAt Current ZERO ~ at voltage PEAK

- Current is already at steady state value

- NO current transient

Y O U R A B S T R A C T M E S S A G E

tt

rms etIi(t) 00 sinsin2 0cos2 tUu(t) rms

90~0

-3

-2

-1

0

1

2

3

-0.04 -0.02 0 0.02 0.04 0.06 0.08time [s]

U

I_dc

I_symm

I

0

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Fau l t I n i t i a t i on

~ at voltage ZERO

- Current should “jump” to max value (90deg)

- Transient DC component superimposed

- Condition for MAX peak for every L/R


tt

rms etIi(t) 00 sinsin2 0cos2 tUu(t) rms

00

𝑰𝒑𝒆𝒂𝒌 = 𝟐. 𝟓 − 𝟐. 𝟕 𝑰𝒓𝒎𝒔

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Three phase

- Voltage & Current are shifted 120 °el

- Fault initiation is a stochastic event

- Asymmetrical current will happen in one or the other phase


120°Ur [p.u.] Ir [kA] Is [kA] It [kA]

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S h o r t c i r c u i t c u r r e n tE l e c t r o - d y n a m i c s t r e s s

Proportional to

- square values of current

- instant value

Max peak = 2.5 – 2.74 I rms

- 𝜏 =𝐿

𝑅...45 – 133 ms

- Frequency

Fault current ~20 times nominal current

Mechanical stress ~ 1000 times higher

𝑭 = 𝑩𝟏 × 𝑰𝟐𝒍 =𝝁𝟎𝑰𝟏𝟐𝝅𝒅

𝑰𝟐

(𝐼1 = 𝐼2 )

𝑭 = 𝒌𝑰𝟐

Current peak 𝑰𝒑𝒆𝒂𝒌 (f, t)=

•2.5 Irms (50Hz, t = 45 ms)

•2.6 Irms (60Hz, t = 45 ms)

•2.7 Irms (t > 45 ms, frequency independent)

•2.74 Irms (Generator breakers IEEE C37.123, t = 133 ms )

Ipeak

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S h o r t c i r c u i t c u r r e n tT h e r m a l s t r e s s

Joule effect

- R: resistance of the current path

- Max temperature proportional to

injected energy

Proportional to

- Effective current value

- Current duration 1 or 3 sec.

Fault current ~20 times nominal current

Thermal stress ~ 400 times higher

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1sec

Short circui current 1 sec

Current duration

TT

Joule dttiRdttiRE0

2

0

2 )()(

2)( tiRPJoule

specific let-through energy (or I2T)

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C o n s e q u e n c e s o f D y n a m i c & T h e r m a l s t r e s s

F a u l t C u r r e n t

A company is an association or

collection of individuals, whether

natural persons, legal persons.

C O N C L U S I O N 1


E l e c t r o - d y n a m i c T h e r m a l B o t h

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C i r c u i t B r e a k e r

Interrupter

- Contacts to close and open

- Quenching / insulating medium

Operating mechanism

- Operates the contact with defined speed

Insulators / bushings

- Insulate from ground

- Between terminals

OperatingMechanism

U

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C i r c u i t B r e a k e r

Three phase system

- 3 phases

- 3 Poles

- 1 or 3 operating mechanism

U3U2

U1

OperatingMechanism

U

OperatingMechanism

U

OperatingMechanism

U

Pole

Circuit breaker

Interrupter

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P o l e

For very high voltage ( > 300kV)

very often Two or more interrupts in

series

To improve the voltage distribution

Grading Capacitors can be used

- 500 – 2000 pF to every chamber

- NOT always used

OperatingMechanism

U ~ 50% U~ 50% U

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C i r c u i t B r e a k e r t e c h n o l o g y

Quenching medium

- Oil

- Air Blast

- Vacuum

- SF6

1910 1995

1955 1985

1950 1980

1965

Minimum Oil

Bulk Oil

Vacuum

Single Pressure SF6

1965

Air Blast

Dual Pressure SF6

1955 1980

20 30 40 50 60 70 80 90 00

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O i l





C O N C L U S I O N 2Bulk Oil circuit breakers

• Developed ~1910

• Technology, discontinued ~ 1995

• Still in service


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O i l





C O N C L U S I O N 2Minimum Oil circuit breakers

- Developed ~1955

- Technology, discontinued ~1985

- Still in service


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A i r b l a s t






Air blast circuit breakers

- Developed ~1950

- Technology, discontinued ~1980

- Still in service


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V a c u u m





C O N C L U S I O N 2Vacuum circuit breakers

- Developed ~1965

- Very common in medium voltage

- Available up to 145 kV


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S F 6





C O N C L U S I O N 2Sulfur hexafluoride (SF6) circuit breakers

- Developed ~1965

- Predominant technology for High Voltage

- Alternatives are now available

• Dielectric strength 3 times than air

• Density ~ 6 times than air

• Condensation temperature @ 6 bar: –31.8 °C

• High affinity for electrons


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Live Tank

- Insulating tank

- At Grid potential

- Support insulator

- Typical Europe

U

SupportInsulator

Dead Tank

- ALU Tank at GROUND potential

- 2 Bushings per pole are needed

- Lower center of gravity (earthquake)

- Typical USA

Bushings

T a n k

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Operating Mechanism

- It moves the contacts of the interrupter

with the needed velocity

- Typical operating time 15 - 40 ms

- Typical operating velocity 3 - 12 m/s

- Typical stored energy 300 - 8000 J

Interrupter

- It clears & makes the current

- Contact distance to withstand the voltage

- Typical contact stroke 80 - 200 mm

OperatingMechanism

Interrupter

stro

ke

time

CLOSE position

OPEN position

Opening speedClosing speed

Travel curve


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Gang operated Circuit Breaker

1 operating mechanism for 3 poles

Single Pole operated Circuit Breaker

1 operating mechanism per every pole

Linkage

Op. Mech

O p e r a t i n g M e c h a n i s m

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O p e r a t i n g M e c h a n i s m

Spring

- ~ 51% breakers in service. Trend increasing

Hydraulic

- ~ 26% breakers in service. Trend decreasing

Pneumatic

- ~ 22% breakers in service.

- Oldest technology almost discontinued

Motor drive or magnetic actuator

- < 1% breakers in service.

CIGRE survey 2004 -2007

CIGRE survey 1988 -1991

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Norma l cond i t i on

- Circuit breaker close

- Load current

- U load = Ugrid ~ Us

Y O U R A B S T R A C T M E S S A G EUloadUgridUs

I

F a u l t c l e a r i n g b a s i c s

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Fau l t

- Short circuit current

- U load = Ugrid = 0 (short circuit)

- Us = I Zsc

Y O U R A B S T R A C T M E S S A G EUloadUgridUs

I


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Tr i p s i gna l

- Sent by protection system

- Minimum reaction time = half period

- 8.3 ms @ 60Hz, 10 ms @ 50Hz

- Circuit breaker starts opening

UloadUgridUs

I


Trip signal

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Con tac t

Sepa ra t i on

- Arc burns between contacts

- Current flows through the contact gap

- Arc voltage << System voltage

- U load = Ugrid ~ 0 (arc voltage)

UloadUgridUs

I


Trip signal Contact Separation

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Cur ren t C lea red

- At Current Zero

- Load side of the grid isolated

- Source side voltage can go back to System value

- Transient Recovery voltage charging stray capacitance

UloadUgridUs

I


Trip signal Contact Separation

Current Zero

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G A S c i r c u i t b r e a k e r g e o m e t r y

Movement

CLOSE OPEN

Contact Gap

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Stationary arcing contact (Copper –Tungsten)

Main nozzle (PTFE) Aux nozzle (PTFE)

Moving arcing contact (Copper –Tungsten)

Heating Channel

Exhaust tube (steel)

Moving main contact (silver plated Copper)

refilling valve

Heating volume

Puffer volume

Intermediate valve

Stationary main contact (silver plated Copper)

SF6 @ 6 bar

G A S c i r c u i t b r e a k e r g e o m e t r y

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Stationary main contact (silver plated Copper)

Stationary arcing contact (Copper –Tungsten)

Main nozzle (PTFE) Aux nozzle (PTFE)

Moving arcing contact (Copper –Tungsten)

Heating Channel

Exhaust tube (steel)

Moving main contact (silver plated Copper)

Puffer volume Heating volume

SF6 @ 6 bar

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time

N o L o a d O p e n i n g1 - Close

2 – Contact separation

5 – Open

1

5

2

C o n t a c t s

Travel curve

Coil current

Opening

time

3

4

3

4

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time

O p e n i n g w i t h c u r r e n t

1 - Close

2 – Contact separation

5 – Open

1

3

2

3 – High Current

Current Zero

4

5

Opening

timeArcing

time

Clearing time

C o n t a c t s

Travel curve

Coil current

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IC u r r e n t C l e a r i n g

S u m m a r y

• ARC between arcing contacts insulating medium turns into plasma

• The Arc Voltage is TOO low to influence the current.

• The breaker is mechanically OPEN, but electrically CLOSE

I t c a n o n l y h a p p e n a t c u r r e n t Z e r o

• The interrupter is designed the BLOW “fresh” gas in the arc region

• The Cooling Power is enough to turn Plasma back into dielectric medium

• The current STOPS flowing

T h e r m a l p h a s e @ C u r r e n t Z e r o

• The recovery voltage appears across the contacts with a transient

• The Transient Recovery Voltage causes Dielectric Stress

• Contact distance and gas density have to be enough to withstand it

D i e l e c t r i c P h a s e – j u s t A F T E R c u r r e n t Z e r o

• Plasma turned back into dielectric medium

• Contact Distance & Density high enough to withstand the Recovery Voltage

• .... If this is NOT the case the breaker has to wait the NEXT Current ZERO

I n t e r r u p t i o n i s s u c c e s s f u lthermal phase

dielectric phase

~ 100-1000 us

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I n t e r r u p t i n g w i n d o w

- Shortest t ime between:o Contact Separat ion

o Cleared current zero .

Minimum arcing time

- If CS moves closer to Current Zero o Clear ing condi t ions are not fu l f i l led

o Pressure bu i ld up no t enough

o Contac t d is tance a t cu r ren t ze ro too sma l l

- The breaker wil l NOT clear and it has to

wait for the NEXT Current Zero

Maximum arcing time

- Any other clearing condition is within the

Min and Max arcing time

Tarc max

dt = 18°

Tarc min

Tarc max = Tarc min + 180° -dt

Contact Separation

43C O M E T 2 0 1 7I n t e r r u p t i n g w i n d o w ( s i n g l e p h a s e s y s t e m )

Minimum arcing time

Maximum arcing time

Minimum arcing time

Maximum arcing time

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Medium arcing time

Maximum arcing time

tarc

tarc

tarc

Minimum arcing time

S h o t s e q u e n c e s i n g l e p h a s e t e s t

mst 10min

mst

dT

Ttt

1911010

3602

max

minmax

mstt

tmed 5.142

maxmin

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Current interruption = arc

two main wearing effects

• Nozzle ablation

• Contact erosion

W e a r

Nozzle ablation

Contact erosion

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Arc energy sublimates PTFE material

The PTFE gas contributes to interruption

- Pressure build up

- High electron affinity

Ablation nozzle geometrical changes:

Higher distance from arc to PTFE surface

Less energy abortion Less PTFE vapours

Bigger cross section:

Lower pressure build up

Less thermal clearing capabil i ty

N o z z l e A b l a t i o n

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TWO contact systems

Main for nominal current (~ 30uohm)

Arcing for interruption (~ 300uohm)

CommutationTime

-Current from Main to Arcing contacts

-Arc voltage between main contacts ~ 20 V

-~ 1.. 3 ms depending from:- Current Ampl i tude

- Resis tance of two contact systems

-Contact overlap is needed

Erosion earlier contact separation

If commutation is not over fatal failure

C o n t a c t E r o s i o n & C o m m u t a t i o n

Contact erosion = earlier contact separation

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P A P E R Q & AC O M E T | C O L L A B O R A T E | S H A R E

K N O W L E D G E | P R O G R E S S

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+ 4 1 7 9 5 9 3 0 8 5 3 n g a r i b o l d i @ q u a l i t r o l c o r p . c o m N i c o l a G a r i b o l d i

NICOLA GARIBOLDI

.

Qualitrol Technical Application Special ist

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comet powerpoint template - university of texas at austin · by nicola gariboldi “high voltage...

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