Unsa Ang Moadto Kung Mawala Ang Bakuwahan Sa Isang Vacuum Circuit Breaker? Ipahayag Ang Totoong Resulta Sa Pagsubok

Unsa ang Mga Mabangha Kini nga Moadto Sa Pagkawaswas Ug Ang Vacuum Interrupter Mawaswas?

Kon ang vacuum interrupter mawaswas sa iyang vacuum, ang sumala nga mga operasyonal nga scenario ang dapat isipon:

• Ang pagbukas sa mga contact

• Ang pagbutang sa operasyon

• Nagoperasyon normal nga isara

• Pagbukas ug pag-interrupt sa normal nga kuryente

• Pagbukas ug pag-interrupt sa fault current

Ang mga kasong a, b, ug c adunay relatyibong simple. Sa matang nga situwasyon, wala ang sistema mahimong maapektuhan sa pagkawaswas sa vacuum.

Pero ang mga kasong d ug e nanginahanglan og dugang diskusyon.

Isip paagi, kon ang usa ka three-phase feeder vacuum circuit breaker mawaswas sa usa ka pole. Kon ang load nga gisilbi sa defective breaker adunay delta-connected (ungrounded) load, ang switching operations wala mahimong magresulta sa failure. Sa esensya, wala gyud na. Ang duha ka healthy phases (e.g., Phase 1 ug Phase 2) makapugos sa pag-interrupt sa circuit, ug ang kuryente sa faulty phase (Phase 3) natural nga mogawas.

Ang uban nga situwasyon ang mag-adto kon grounded ang load. Sa matang nga kasong, ang pag-interrupt sa duha ka healthy phases wala makapugos sa pagdagan sa kuryente sa faulty phase. Usa ka arc nagpadayon sa Phase 3 ug walay maoy mogawas niini, ug ang kuryente magpadayon hangtud ang backup protection magoperasyon. Ang resulta karaniwan nga catastrophic damage sa breaker.

Tungod kay ang vacuum circuit breakers sa 3–15 kV range gamiton sa grounded systems, kami mi nag-investigate sa epekto sa failed interrupter sa aming laboratoryo ngadto sa una nga tuig. Gitubagon namin ang usa ka vacuum interrupter sa atmospheric pressure ("flattened" it) ug gitubagon ang breaker sa full short-circuit interruption test.

As predicted, ang "flat" interrupter failed to clear the fault in the affected phase and was destroyed. The laboratory backup breaker successfully cleared the fault.

Human sa test, ang breaker gi remove gikan sa switchgear cell. Heavily sooted pero mechanical intact. Smoke ug soot gi clean gikan sa breaker ug switchgear, ang faulty unit gi replace, ug ang breaker gi reinserted sa compartment. Later that same day, another short-circuit test was performed—successfully. Years of subsequent field experience have confirmed the findings from these laboratory tests.

One of our customers, a major chemical company, experienced isolated failures on similar circuit configurations (one with an air-magnetic breaker, one with a vacuum breaker) at two different facilities in different countries. Both shared a common circuit configuration and failure mode: a tie circuit where the power sources on either side of the breaker were out of synchronism, applying nearly twice the rated voltage across the contact gap. This caused breaker failure.

These failures resulted from application conditions violating ANSI/IEEE guidelines and far exceeding the breaker’s design ratings. They do not indicate a design flaw. However, the extent of damage is instructive:

• In the air-magnetic breaker case, the unit’s enclosure ruptured violently. Adjacent switchgear cells on both sides suffered extensive damage, requiring major reconstruction. The breaker was a total loss.

• In the vacuum breaker case, the failure was significantly less violent. The faulty vacuum interrupter was replaced, arc byproducts (soot) were cleaned from the breaker and compartment, and the system was returned to service.

Our extensive laboratory testing, where we routinely push vacuum interrupters to their limits, supports these real-world results.

Recently, several high-power tests were conducted in our lab to evaluate interruption attempts using "leaking" vacuum interrupters. A small hole (~3 mm diameter) was drilled into the interrupter housing to simulate vacuum loss. Results were revealing:

• A 1,310 A normal current (rated continuous current: 1,250 A) was 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 were ejected, the breaker did not explode, and only the 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 occurred. Glowing particles were ejected from the hole, but no mechanical components or adjacent breakers were damaged. All damage was 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 are extremely low. Vacuum loss is no longer a significant concern.

In the early 1960s, vacuum interrupters were prone to leaks—this was a major issue. Early designs used brazed or welded joints between dissimilar materials, with no organic materials. Handcrafting was common, especially with borosilicate glass insulators, which couldn’t withstand high temperatures.

Today, machine welding and batch induction furnace brazing are used with extremely strict process controls. The only moving part inside a vacuum interrupter is the copper contact, connected to the end plate via a welded stainless steel bellows. Since both ends of the bellows are welded, the failure rate of this moving seal is exceptionally low—demonstrating the high reliability of modern vacuum circuit breakers.

In fact, the MTTF (Mean Time To Failure) of modern vacuum interrupters is now estimated at 57,000 years.

Customer concerns about vacuum loss were valid in the 1960s, when vacuum breakers were new to power applications. At that time, vacuum interrupters often leaked, and surge issues were common. Only one company offered vacuum breakers, and reports indicated numerous problems.

By the mid-1970s, European-developed vacuum interrupters—like modern Siemens designs—differed fundamentally from 1960s models in materials and process control. Copper-bismuth contacts were more surge-prone than today’s chromium-copper alloys. Hand-built interrupters were more prone to leaks than today’s precision-manufactured units.

Today, rigorous process control and automation have eliminated most human variability. As a result, modern vacuum interrupters offer long service life, and the dielectric stress they impose on connected equipment is no worse than that of traditional air-magnetic or oil circuit breakers.