چی دیت کاته وەکووی ڤێکیووم سیرکیت برێکەر لە ڤێکیوومدا بڕووبکات؟ نەتایەکانی ئامادەی خۆراکەوەی باشکەنراون
Vacuum Interrupterê Şûrçavê Li Benda Vekirîna Vacuuma?
Eger vacuum interrupterê şûrçavê li benda vacuuma bigire, an jî pêşkeftên operasyonan dehê dîsa hesab bikin:
Contacts opening
Closing operation
Closed and operating normally
Opening and interrupting normal current
Opening and interrupting a fault current
Amûrên a, b û c hêsan derbas. Li vê amûran, sistemê yê bijêr nayê têkiliyê li ser biyayışê vacuuma.
Lê, amûrên d û e dihê zêde dîsazkirin.
Begere ku birka circuit breaker ê three-phase feeder vacuum ê vacuuma li polek din bigire. Eger barka ku ji boya breakerê reşeyê delta-connected (ungrounded) ye, operasyonên switching ne hatine destnîşan biafirîne. Di navbera ya, tu ne heye. Dua phasek çêk (mînace Phase 1 û Phase 2) barkirina circuitê beser kirin, û girra phasek çewt (Phase 3) bete derbas bibe.
Di amûreku grounded loads de, şitê din dike. Li vê amûre, barkirina dua phasek çêk nayê gerrê girra phasek çewt bêtir. Arcê di Phase 3 de dikare wekheva, û ev gerr heta backup protection îşe bike. Neticê hêsan herêmserî çewtî ye ku breakerê werdikîne.
Ji ber ku vacuum circuit breakers ê di demîna 3–15 kV de hatine barkerbûn li ser sistemas grounded, piştî sedsan salan me li ser test laboratory ê hatine xweşkirin cuhê yên ku interrupterê têkildar be. Me bi sef wêjî vacuum interrupter ê li ser presura atmosferî ("flattened") ve hatine qebûl kirin, û li ser breakerê testên full short-circuit interruption hatine bişindandin.
Wek ku pêşdîtin, "flat" interrupterê nayê guherandîna çewtiya phasek çewt bêtir û werdikîne. Laboratory backup breakerê bi serkeftî guherandîna çewt bêtir.
Piştî test, breakerê ji switchgear cell ê hatine rakin. Wekheviya sootê dike, lê makînikî intact. Smoke û soot hatine saz kirin ji breaker û switchgear, unita çewt hatine vegerîn, û breaker ê bi serkeftî hatine darîn di kompartimenta de. Piştî roja yekem, testên yekem short-circuit bi serkeftî hatine bişindandin. Sedsanan sala dawîn hatine destnîşan ku testên laboratory ê bi serkeftî hatine xweşkirin.
Yekan lêkolînên me, ku company ê chemical major e, hatine kevekên çewtî li ser configurationên circuitê tevahî (yek bi air-magnetic breaker, yek bi vacuum breaker) di du facliyên jîyan de. Her du wekheviya configurationa circuitê û modey ê çewtî: tie circuit ku power sources li ser yek ji her du tara ya breaker ê out of synchronism, nearly twice the rated voltage across the contact gap. Ev hatine breaker failure.
Ev kevekan hatine ji application conditions ku ANSI/IEEE guidelines û far away from breaker’s design ratings. Ev nayê destnîşan ku flawa design e. Lê, extant of damage instructive ye:
Li amûre air-magnetic breaker, enclosure ê unita hatine rupîn violent. Adjacent switchgear cells li ser her du tara hatine damage extensive, requiring major reconstruction. Breaker total loss.
Li amûre vacuum breaker, failure less violent. Vacuum interrupter ê faulty hatine vegerîn, arc byproducts (soot) hatine saz kirin ji breaker û compartment, û system returned to service.
Extensive laboratory testing me, ku routine push vacuum interrupters to their limits, supports these real-world results.
Dawîn, several high-power tests conducted in our lab to evaluate interruption attempts using "leaking" vacuum interrupters. A small hole (~3 mm diameter) drilled into the interrupter housing to simulate vacuum loss. Results revealing:
A 1,310 A normal current (rated continuous current: 1,250 A) interrupted by one pole of a vacuum breaker. Current flowed through the "faulty" breaker for 2.06 seconds before the lab backup breaker cleared the fault. No parts ejected, breaker did not explode, only paint on the interrupter housing blistered. No other damage occurred.
A second pole of the same breaker attempted to interrupt 25 kA (rated breaking current: 25 kA). The arc lasted 0.60 seconds before the lab breaker cleared the fault. The arc burned a hole through the side of the interrupter housing. No explosion or flying debris. Glowing particles ejected from the hole, but no mechanical components or adjacent breakers damaged. All damage confined to the failed interrupter.
These tests confirm that the consequences of a vacuum interrupter failure are significantly less severe compared to failures in other interrupting technologies.
But the real question is not what happens when it fails, but how likely is it to fail?
Vacuum interrupter failure rates extremely low. Vacuum loss no longer significant concern.
In early 1960s, vacuum interrupters prone to leaks—major issue. Early designs used brazed or welded joints between dissimilar materials, no organic materials. Handcrafting common, especially borosilicate glass insulators, couldn’t withstand high temperatures.
Today, machine welding and batch induction furnace brazing used with extremely strict process controls. Only moving part inside vacuum interrupter copper contact, connected to end plate via welded stainless steel bellows. Since both ends of bellows welded, failure rate of this moving seal exceptionally low—demonstrating high reliability of modern vacuum circuit breakers.
In fact, MTTF (Mean Time To Failure) of modern vacuum interrupters now estimated at 57,000 years.
Customer concerns about vacuum loss valid in 1960s, when vacuum breakers new to power applications. At that time, vacuum interrupters often leaked, surge issues common. Only one company offered vacuum breakers, reports indicated numerous problems.
By mid-1970s, European-developed vacuum interrupters—like modern Siemens designs—fundamentally different from 1960s models in materials and process control. Copper-bismuth contacts more surge-prone than today’s chromium-copper alloys. Hand-built interrupters more prone to leaks than today’s precision-manufactured units.
Today, rigorous process control and automation eliminated most human variability. As result, modern vacuum interrupters offer long service life, dielectric stress they impose on connected equipment no worse than traditional air-magnetic or oil circuit breakers.
