Vacuum Interrupters for Medium...

03571_Vacuum Interrupters 22.10.1999 12:49 Uhr Seite 2

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C M Y CM MY CY CMY K

Vacuum Interrupters for Medium Voltage


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Today, vacuum as an arcextinguishing medium pro-vides the most cost-effectivesolution for medium-voltagecircuit-breakers.

Siemens vacuum interruptersconvince in respect of relia-bility, long service life and fullyenvironmentally friendly mate-rials used for and during pro-duction process.Decades of experience, con-tinuos research and develop-ment as well as latest pro-duction technology andupdated quality conceptsmakes Siemens superior invacuum technology.

The high reliability of our

vacuum interrupters are

based on all common

designs:

• The arc chamber that actsas a vapour shield: During the switching process, ametal vapour arc occurs between the contacts andis extinguished at current zero. The small amount ofmetal vapour that is not redistributed over the contact pieces condenseson the arc chamber wall. The arc chamber protects the inside of the ceramic housing against the effectof the metal vapour, whichwould reduce the insulation.

Reliable, Maintenance-Free and Environmentally Friendly

• One contact is fixed tothe ceramic housing. The other is a moving contact connected to the housing via bellows.

• The metal bellows forms the vacuum-tight connection between the moving contact and the interrupter housing, thus allowing the moving contact to perform its stroke. The stroke is a function of the rated voltageof the vacuum interrupter.

• The insulators are made ofmetallized aluminum oxideceramics.

• All connections, whether metal-to-metal or metal-to-ceramics, are brazed in vacuum ovens and there-fore provide a vacuum sealfor life.

Long service life means

• up to 30,000 interruptions with rated current;

• high short-circuit breaking operations(average of 50 times);

• mechanical operations ofup to 2 million(e.g. contactor interrupters).

The vacuum interrupters aremanufactured in an environ-mentally friendly productionprocess, using only materialsfor the interrupters which caneasily be disposed afterusage.

Selected materials, minimalwear and contact erosionensure that the vacuum inter-rupter is maintenance-freefor its entire life and makesfor maximum availability.

Va c u u m I n t e r r u p t e r s

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Switching Duties

Loads with high

switching rate

The use of vacuum interrup-ters is an especially economicproposition in cases whereloads have to be switchedfrequently (e.g. motors, arcfurnaces, reactive powercompensating coils and capac-itors). This is because theyare capable of switching ratednormal current up to 30,000times.

Capacitive currents

Unloaded cables, overheadlines and capacitor banks areswitched off without voltagesurges because Siemens va-cuum interrupters are capableof interrupting capacitive cir-cuits without restrike. Evenwhere the contact gap issmall, dielectric recovery isremarkable. In numeroustests, currents of up to 1000 Aat 36 kV were reliably inter-rupted without restrike. Thecapacitive currents switchedin test laboratories are limitedby the capacitors installed,and operating experience hasshown that even greater ca-pacitive currents can be relia-bly switched. Even parallelingof capacitors poses no prob-lems.

Short-circuit currents

Siemens vacuum circuit-breakers switch short-circuitcurrents of up to 80 kA. Thearcing times are less than15 ms, even at the highestcurrents. These short arcingtimes and the minimal arcvoltage keep energy conver-sion in the break to a mini-mum. Consequently, thebreakers are suitable not onlyfor the usual O-0.3s-CO auto-reclosure cycle, but also formultiple auto-reclosures.An O-0.3s-CO-15s-CO-15s-CO-15s-CO duty cycle wascarried out successfully(up to 31.5 kA).

Small inductive currents

Magnetizing currents ofunloaded transformers areinterrupted without unduevoltage surges building up,because the chopping currentof Siemens vacuum interrup-ters is below 5 A. In numer-ous tests it was shown that

the overvoltagefactor k was lessthan 3.1 at 12 kVand less than2.2 at 24 kV.

NXACT

vacuum

circuit-breaker

module

Horizontal

installation of

vacuum

interupters

High power

vacuum

circuit-breaker

Traction

vacuum

circuit-breaker


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Compact and Economical Concept for the Low Range of Rating


Single ceramic housing

interrupters with copper

flanges were developed

with the creation of a

compact circuit-breaker

and switchgear assembly

design as well as con-

tactors and load breakers

uppermost in mind.

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Versatile Standard Concept for all Voltage Levels


With their two-element ceramic

housing and internal

copper arc chamber, the

interrupters are a convincing

concept for both industry

and power supply utilities.

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The High-End Solutionfor up to 40.5 kV or High Short-Circuit Ratings


The interrupters with a

two-element ceramic housing

and external copper arc

chamber were specially

developed for requirements

on the 36-kV level and

for short-circuit ratings

≥ 50 kA – e.g. generator

circuit-breakers, as well

as for traction systems

with 16 2/3 Hz.

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Arc Quenching


When an arc is quenched, itare the contacts (the primecomponents of a vacuum in-terrupter) that must meet thehighest demands in terms of:

• High short-circuit breakingcapacity;

• High dielectric strength;

• Minimal chopping current;

• Minimal contact erosion;

• Minimal contact resistance.

The requirements have allbeen met to optimum effect,in both technical and econo-mic terms, as a result of basicresearch in our laboratories,development of suitable ma-terials (including the contactgeometry) and state-of-the-art manufacturing technology.

High dielectric strength

On opening of the contact,the current to be interruptedproduces a metal vapour arcdischarge and continues flow-ing through the plasma untilthe next current zero. The arcis extinguished in the vicinityof the current zero, and themetal vapour loses its con-ductivity within a few micro-seconds.

The dielectric strength of thebreak is thus reestablishedvery quickly. The steady-statepressure in a vacuum interup-ter is less than 10-9 bar. Con-tact clearances of between6 and 20 mm suffice thereforeto produce a high dielectricstrength.

Minimal chopping current

Below a certain minimum cur-rent, the metal vapour arc isinterrupted prior to the naturalcurrent zero. In inductive cir-cuits this chopping currentmust therefore be as low aspossible in order to preventthe build-up of impermissiblyhigh voltage surges.The magnitude of the chop-ping current depends largelyon the contact material used.Optimized chromium copperkeeps the chopping currentbelow 5 A.

High breaking current

Two contact geometry vari-ants are used in Siemensvacuum interrupters.

Radial magnetic field contact:With this contact, the arc re-mains diffuse up to currentsof 10 kA (instantaneous val-ue). Higher currents flowthrough a constricted arc.

Local overheating of the con-tacts must be avoided. Anadditional radial magnetic fieldproduces a force which drivesthe arc around the contactarcing rings. In this way, thecontact erosion occurring inthe arc root is distributed overthe full arcing ring area.

With axial magnetic field con-tacts, short-circuit currents ofup to 80 kA can be reliablyhandled.

The axial magnetic field al-lows a diffuse arc even wherethe current intensity is high.The disc-shaped contact sur-faces are uniformly stressedover their full area.Both the radial and axialmagnetic fields are producedby special current paths pro-vided in the contacts underthe surface.

Minimal contact erosion

The metal vapour plasma ofthe vacuum arc is highly con-ductive. The arc voltage (only20 V to 200 V) and the energyconversion in the break arelikewise minimal. The highconductivity, in conjunctionwith the minimal energy con-version and short arcing timesare the reasons for the mini-mal contact erosion and thelong electrical service life ofthe vacuum interrupters.

Minimal contact resistance

In a vacuum, the contact sur-faces are free of impuritiesand pollution layers. Highlyconductive materials areused. This ensures minimalcontact resistance. Betweenthe two outer terminations ofan interrupter the figure isbetween 8 and 15 µ Ω. Heatlosses are correspondinglylow.

Current distributionof a diffuse arc

Axial magnetic field contact

Contact piececonstructionB: Contact carrierC: Contact disc CrCu

Current pathand directionof a constricted arc

Radial magnetic field contact

ContactconstructionA: Arcing ring:Contact material CrCuB: Contact carrier

Diffuse high current discharge(i=60 kA)(Axial magnetic field contact)

Arc formations with radial andaxial magnetic field contacts

Diffuse arc prior to current zero(i=10 kA)(Axial magnetic field contact)

Constricted arc(i=40 kA)(Radial magnetic field contact)

Diffuse arc prior to current zero(i=2 kA)(Radial magnetic field contact)

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B

C

B

C

A

B

A

B


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Supply Program

Ratedvoltage

kV

7.2

Rated light-ning impulsewithstandvoltagekV

Rated powerfrequencywithstandvoltagekV

Ratedshort-circuitbreakingcapacitykA

Ratedshort-circuitmakingcapacitykA

Rated current and interrupter type

630 A 1250 A 1600 A 2000 A

60 20 12.5 31.5 VS 7000116 40 VS 1202020 50 VS 1202525 63 VS 1203131.5 8040 10050 125

80 200

V

12 75 28 32.8 VS 1201213.116 40 VS 1202020 50 VS 1202525 63 VS 1203131.5 80 V40 10050 125

80 20015 95 36 20 50

V25 6331.5 8040 10050 12563 160

17.5 95 38 20 50V25 63

31.5 8040 10063 160

24 125 50 VS 24016

V

36** 170** 70 16 4020 50

V25 63VS 30029 / VS31.5 80

V40 100

V

VS25016*/ VS 25005

800 A

VS 25005

63 160

63 160

80 200

16 4020 5025 6331.5 8040 100

80 200

Ratedvoltage

kV7.27.21224

RatedlightningimpulsewithstandvoltagekV60607595

RatedpowerfrequencywithstandvoltagekV 20 20 30 50

Ratedcurrent

A400400400800

Max.breakingcurrent

kA3.23.23.23.6

Max.makingcurrent

kA4444.5

Number ofoperatingcycles atratedcurrent

1.0 ·106

0.25 ·106

0.5 ·106

0.5 ·106

Interruptertype

VS 7202VS 7203VS 12003VS 24001

Dimension

diameterin mm

lengthin mm

75606868

134115160190

8

Vacuum circuit-breaker interrupters (50 to 60 Hz)

Vacuum contactor interrupters (50 to 60 Hz)


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* With the use of aninsulating covering

** Higher values on request


Design A Design B Design C

l

d

l

d

l

d

2500 A 3150 A 4000 A

VS 15100VS 15050

VS 17080

VS 17005

VS 17005VS 15100VS 15050

VS 10047

VS 17005VS 15100

VS 10047

VS 17005

VS 10047

VS 25007

VS 36025/ VSG 36031*

VS 30040

VS 30040

VS 15050

VS 15100

VS 10047

VS 17080

VS 17080

VS 17080

Type Design Diameterd (mm)

LengthI (mm)

VSG 36031

9

VS 70001

VS 12012

VS 12020

VS 12025

VS 12031

VS 24016

VS 17005

VS 15100

VS 25016

VS 25005

VS 25007

VS 36025

VS 15050

VS 10047

VS 17080

VS 30029

VS 30040

A

A

A

A

A

B

B

B

B

B

B

B

C

C

C

C

C

C

68

68

68

76

85

96

100

125

100

110

116

116

135

138

125

156

123

138

124

124

144

187

219

284

219

255

219

284

315

326

368

379

315

379

494

494

Interrupters to ANSI Standard

Interrupters to Chinese Standard

Load break switch

Recloser

Transformer tap changer

Traction systems (16 2/3 Hz)

Installation under gas and oil pressure

Special applications

Dimensions (in mm) Illustrations of principle


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Quality assurance

This starts at the very drawingboard, since this is where de-signs and jointing methods

are selected, with aview to eliminatingsources of faults inmanufacture. The var-rious manufacturingprocess stages aredevised in close

cooperation between produc-tion and development depart-ments, with safety and easeof handling in mind as well asthe technical requirements.

Material testing

This is of particular signifcance,due to the special materialsused. The technical data ofthe materials agreed with oursuppliers are subject to verytight tolerance ranges, adher-ence to which is checked onevery consignment delivered.Extensive qualitative andquantitative gas analyses en-sure that only fully satisfactorymaterials are processed.

Quality Assured by Sophisticated Testing

Vacuum tightness

A special internal pressuremeasuring process has beendeveloped to test for leakageeven after the interrupter hasbeen sealed. In a stationarymeasuring facility, anelectrical and a magneticfield are superimposedin such a way thatfree electrons ionizeany residual gasmolecules andproduce ameasuring currentthat varies as a functionof the pressure. All interrup-ters are stored in argon andthen tested by means of thisprocess; they are released forshipment only if a leakagerate of up to 10 -17 bar x l/s isnot exceeded. This amountsto a storage time of 20 yearswithout any loss in quality.Time compression methodscan be used to verify such astatement.

To this end, circuit-breakerinterrupters were stored for5000 hrs at 300 °C. It wassubsequently verified thatno inadmissible rise inpressure had occurred.

Powerto the

Siemens Aktiengesellschaft Subject to change without prior notice Order No. E50001-U229-A117-X-7600Printed in GermanyDispo-Stelle 3040061D6089 Ra/EK 101374 PA 10991.

Siemens AGPower Transmission andDistribution GroupMedium Voltage DivisionP.O. Box 32 20D-91050 Erlangen

www.ev.siemens.de

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