Download - Vacuum Interrupters for Medium Voltage
03571_Vacuum Interrupters 22.10.1999 12:49 Uhr Seite 2
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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
Va c u u m I n t e r r u p t e r s
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Compact and Economical Concept for the Low Range of Rating
Va c u u m I n t e r r u p t e r s
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
Va c u u m I n t e r r u p t e r s
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
Va c u u m I n t e r r u p t e r s
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
Va c u u m I n t e r r u p t e r s
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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Va c u u m I n t e r r u p t e r s
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
Va c u u m I n t e r r u p t e r s
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