Eaton W-VACi, VCP-W, VCP-WG and Magnum Breakers

What it is and where it is used

Eaton makes medium-voltage vacuum power circuit breakers in two lines. The Eaton VCP-W is its withdrawable circuit breaker for ANSI metal-clad switchgear, widely installed in industry, with the VCP-WG version for generator circuits. The W-VACi is its solid-insulation circuit breaker for the IEC market; in existing switchgear the W-VAC, from the same line, is also found. In low voltage, the brand’s power circuit breaker is the Magnum DS.

They are found at the outgoing feeders, transformers, motors and generators of industrial plants, data centers, oil and gas, mining and power plants. For the principle, see medium-voltage vacuum circuit breaker.

Variants: VCP-W, VCP-WG, W-VACi, W-VAC and Magnum DS

The voltage, continuous current and breaking current depend on the frame and the order code; the nameplate governs.

Main characteristics

• Vacuum interruption in sealed bottles; see vacuum integrity test.
• Spring mechanism with charging motor, closing and opening coils and auxiliary contacts; see circuit breaker operating mechanism.
• Withdrawable in ANSI (VCP-W) and IEC (W-VACi) switchgear, with test and disconnected positions and interlocks; see withdrawable truck and switchgear interlocks.
• Generator circuit breaker (VCP-WG) with ratings for the demands of that circuit, such as the asymmetry of the fault current near the generator.

Communications and integration

The circuit breaker does not communicate by itself: its states reach the switchgear relay through auxiliary contacts, and from there SCADA over IEC 61850, DNP3 or Modbus. In Eaton switchgear it is common to find the brand’s own protective relays. See circuit breaker auxiliary contacts and medium-voltage switchgear.

Frequently asked technical questions

• Eaton VCP-W manual: Eaton publishes instruction books and spare parts lists by frame and voltage; there are several generations of the VCP-W.
• VCP-W breaker that will not go into the switchgear: the frame, voltage and current must match the switchgear; the coded interlocks prevent inserting the wrong one.
• The circuit breaker does not close: it is usually the spring not charged, the coil, the anti-pump relay or the truck out of position; see circuit breaker control cabinet.
• VCP-WG instead of a VCP-W at a generator output: the generator circuit breaker has ratings for the asymmetrical fault current and the transient voltage specific to that circuit; one is not replaced by the other without review.
• ANSI and IEC standards: a VCP-W and a W-VACi are not interchangeable; they correspond to different standards and switchgear.
• Replacing old air-magnetic circuit breakers: vacuum replacement circuit breakers exist for existing switchgear; the change requires a review of the switchgear and the circuits.

What the VCP-W instruction book says

The data in this section come from Eaton’s instruction book for VCP-W circuit breakers (3A74374H04, I.B. 32-255-1J, March 2013). It is the general document; the one for your unit depends on the frame, the voltage and the year of manufacture.

Families within the VCP-W

The book covers several versions of the same horizontal withdrawable circuit breaker, designed for VacClad-W metal-clad switchgear and tested to ANSI and IEC:

• VCP-W: standard version up to 15 kV and also at 27 kV.
• VCPW-SE: version for special environments, up to 27 kV.
• VCPW-ND: narrow version for 5 kV, intended for sites where space does not allow the standard 36-inch-wide switchgear.
• VCP-WC: extra-capacity version, from 5 to 27 kV.
• VCP-WG and VCP-WGC: generator versions; the WGC is designed for high altitude.
• VCP-W (K=1) and VCP-WXC: later generations up to 15 kV, with constant breaking current up to the maximum voltage.

There are also rating tables in IEC up to 17.5 and 24 kV and in GB for China. A VCP-W with an IEC table is not interchangeable with an ANSI one even if the frame looks similar.

How to read the type designation

In the book, a row of the table carries the designation 150VCP-W63 (1500). It is of the 13.8 kV class, with 63 kA breaking current and 1,500 MVA in parentheses. Its continuous currents are 1,200, 2,000 and 3,000 A, and its maximum voltage is 15 kV, with 36 kV power frequency and 95 kV impulse withstand. The number after the W is the breaking current in the new designations and the MVA class in the old ones; the conversion is the usual one: 1.73 × 13.8 kV × 63 kA gives about 1,500 MVA. Before ordering a spare part, read the full designation on the nameplate and not just “VCP-W”.

Timing and operating duty

For the VCP-W up to 15 kV, the book gives an opening time of 30 to 45 ms, a closing time of 45 to 60 ms, a reclosing time of 18 cycles (300 ms) and an operating duty of CO-15 s-CO. An optional interrupting time of 3 cycles exists; the standard for the row cited is 5 cycles. For 27 kV, the book gives 33 to 55 ms for opening and 50 to 60 ms for closing. These are catalog values to compare with the times measured in the operating time test; the factory protocol of your unit governs.

Vacuum interrupters and contact wear

The VCP-W uses vacuum interrupters with copper-chromium petal contacts, in which the arc rotates under its own magnetic force to avoid heavy wear. The book describes an erosion indicator: a green mark on the moving stem that must be visible with the circuit breaker closed, and when erosion reaches 1/8 of an inch the complete vacuum interrupter is replaced. It also describes a charging spring indicator and control of the contact travel (“wipe”). The book also includes the vacuum integrity test; see vacuum integrity test. The book further includes the map of the mechanism’s lubrication points, which is followed as written.

What to verify when replacing or rebuilding

• Frame, voltage and current of the switchgear must match those of the circuit breaker; the coded interlocks prevent inserting the wrong one, as described in withdrawable truck and interlocks.
• Replacement circuit breaker in an old switchgear: check the control circuit taps, the coil and motor voltage, and the auxiliary contacts of the switchgear (MOC and TOC) before inserting.
• Generator: a standard VCP-W is not installed in place of a VCP-WG; the asymmetry of the fault current near the generator requires the ratings of the generator circuit breaker standard, IEEE C37.013.
• Relay and trip: after any circuit breaker change the complete trip chain is checked; see circuit breaker control cabinet.

How we help

At Tiza Group we do not sell circuit breakers. We test and commission Eaton circuit breakers and those of any brand: operating times, contact resistance, insulation, vacuum, coils and mechanism, and we verify the switchgear control and protection circuits, in Colombia or elsewhere on request. See circuit breaker testing within testing and commissioning. If you are going to modernize old switchgear, we design the change under engineering design and studies. Write to us through the contact page.

Related guides

• Medium-voltage vacuum circuit breaker
• Medium-voltage switchgear
• Low-voltage open circuit breakers
• Vacuum integrity test
• Withdrawable truck and switchgear interlocks
• ABB VD4, VD4 evo, VM1 and HD4 vacuum circuit breaker

References

• IEEE C37.04 and C37.06, ratings of AC circuit breakers.
• IEEE C37.013, generator circuit breakers.
• IEC 62271-100, alternating-current circuit-breakers for high voltage.
• Eaton, W-VACi and VCP-WG product pages, generator circuit breaker brochure, VCP-WRG instruction book and VCP-W price and spare parts list.

Frequently asked questions