Medium Voltage Vacuum Circuit Breakers
SF₆-free vacuum switching from the 15 kV class to the 38 kV class
The vacuum circuit breaker is the interrupting element your medium voltage switchgear is built around. Choose it badly and you inherit nuisance trips, long outage windows and a spare-parts problem that outlives the panel. Atlas Energy supplies breakers for 12, 17.5, 24 and 36 kV systems (the 15, 27 and 38 kV ANSI classes) in fixed and withdrawable construction, so retrofits and new builds draw on the same platform.
Interruption is by vacuum, with no SF₆ to report, recover or refill. Rated current runs from 630 A to 4,000 A and short-circuit breaking from 20 kA to 45 kA, with peak making current to 100 kA and short-time withstand for 4 s at all but the 45 kA rating. Main circuit resistance is held to ≤25 µΩ per phase at 2,500 A and above. Mechanical endurance is 10,000 to 20,000 operations, and the motor charges the mechanism in under 15 s on a 24, 110 or 220 V AC or DC control supply.
Why it matters
No SF₆ anywhere in the interrupter, so the breaker stays outside greenhouse-gas handling and reporting obligations for the life of the panel.
One platform spans 630 A through 4,000 A and 20 kA through 45 kA, which keeps a mixed substation on a single spare-parts list.
Fixed and withdrawable versions share the same interrupter, so a draw-out retrofit does not force a second qualification exercise.
Main circuit resistance of ≤25 µΩ per phase at 2,500 A and above holds contact heating down where feeder loading is highest.
Closing in under 100 ms and opening in under 50 ms keeps clearing times inside the coordination margins your relays are already set to.
Ratings
Voltage class: 12 kV · 17.5 kV · 24 kV · 36 kV (15 / 27 / 38 kV ANSI classes)
Rated current: 630 · 800 · 1,250 · 1,600 · 2,000 · 2,500 · 3,150 · 4,000 A
Short-circuit breaking: 20 · 21.5 · 25 · 31.5 · 40 · 45 kA
Short-time withstand: Rated value for 4 s (1 s at the 45 kA rating)
Peak / making current: 50 · 63 · 80 · 100 kA
Power-frequency withstand (1 min): 42 kV (12/17.5 kV, 48 kV across isolating distance); 65 kV (24 kV, 79 kV across gap)
Lightning impulse (BIL): 75 kV (12 kV) · 95 kV (17.5 kV) · 125 kV (24 kV) · 170 kV (36 kV)
Operating sequence: O-0.3s-CO-180s-CO (O-180s-CO-180s-CO at 40 kA)
Mechanical endurance: 10,000 – 20,000 operations
Short-circuit operations: 20–30 at rated breaking current
Closing / opening time: <100 ms / <50 ms
Contact gap: 10 ±1 mm (12/17.5 kV), 11 ±1 mm (24 kV); over-travel 3.5 ±0.5 mm
Main circuit resistance: ≤50 µΩ (630 A) · ≤45 µΩ (1,250 A) · ≤35 µΩ (1,600–2,000 A) · ≤25 µΩ (≥2,500 A) per phase
Control voltage: 24 / 110 / 220 V AC or DC; motor charging <15 s
Capacitor switching: Single bank 630 A; back-to-back 400 A
Construction: Fixed or withdrawable (draw-out); SF₆-free vacuum interruption
Cubicle widths: 650 / 800 / 1,000 mm
Extended range
Trip and close accessories: Shunt open/close and lock-out coils; indirect overcurrent trip release
Anti-pumping: Anti-pumping relay
Interlocking: Shaft and opening mechanical interlocks
Secondary connection: 46-pin secondary connector
Signalling: Energy-storage micro-switches and auxiliary contacts
Standards
ANSI/IEEE C37.06 · C37.09 rating and test correspondence
IEC 62271-100
Applications
MV switchgear panels and ring main units
Utility and industrial distribution substations
Capacitor bank switching
Motor and feeder protection
Questions engineers ask
Which ANSI voltage classes do these vacuum circuit breakers cover?Rated voltages are 12, 17.5, 24 and 36 kV, corresponding to the 15, 27 and 38 kV ANSI classes. Lightning impulse withstand is 75 kV at 12 kV, 95 kV at 17.5 kV, 125 kV at 24 kV and 170 kV at 36 kV. Rating and test correspondence follows ANSI/IEEE C37.06 and C37.09 alongside IEC 62271-100.
Can the breaker be supplied as a draw-out unit for existing switchgear?Yes. Both fixed and withdrawable construction are available, with cubicle widths of 650, 800 and 1,000 mm. The withdrawable version carries a 46-pin secondary connector, shaft and opening mechanical interlocks, and energy-storage micro-switches, so racking and position signalling behave the way your panel logic already expects.
Technical documentation
Download HVEX 17.5 kV Vacuum Circuit Breaker datasheet (English, PDF)
