To buy a medium-voltage vacuum circuit breaker (VCB) from China, fix five ratings first — rated voltage, rated normal current, rated short-circuit breaking current, mechanism type and installation (indoor or outdoor) — then ask for type-test reports to IEC 62271-100 that match those exact ratings. Most problems with imported VCBs come from a mismatch between the breaker offered and the panel, network or protection scheme it has to serve, not from the vacuum interrupter itself.
What a vacuum circuit breaker does
A VCB interrupts load and fault current inside a sealed vacuum interrupter. When the contacts separate, the arc burns in metal vapour and goes out at the next current zero, because there is no gas to sustain it. Vacuum breakers are the usual choice for distribution networks from 3.6 kV to 40.5 kV, both as withdrawable units inside high-voltage switchgear and as fixed or pole-mounted outdoor units.
For the ranked list of Chinese manufacturers in this product group, see vacuum circuit breakers.
The ratings you must specify
A Chinese factory will quote quickly if your enquiry contains complete ratings. Leave any of these out and you will receive a "standard" model that may not suit your system.
| Parameter | Typical values offered | What to decide |
|---|---|---|
| Rated voltage (Ur) | 12 kV, 24 kV, 40.5 kV | Must be equal to or above the highest system voltage, not the nominal voltage |
| Rated normal current (Ir) | 630 A, 1250 A, 1600 A, 2000 A, 2500 A, 3150 A, 4000 A | Size for the feeder or incomer, allowing for ambient temperature and enclosure derating |
| Rated short-circuit breaking current (Isc) | 20 kA, 25 kA, 31.5 kA, 40 kA | Must exceed the prospective fault level at the point of installation |
| Short-time withstand duration | 3 s or 4 s | Match your protection clearing time and utility requirement |
| Rated peak withstand current | 2.5 × Isc (50 Hz) or 2.6 × Isc (60 Hz) | Confirm the frequency used in the test report |
| Rated frequency | 50 Hz or 60 Hz | 60 Hz markets need 60 Hz test evidence |
| Insulation level | Power-frequency and lightning-impulse withstand | Check against the values your utility or consultant specifies |
| Auxiliary voltage | 24–220 V DC or 110/230 V AC | Closing coil, tripping coil and motor must all match your station supply |
Note that "12 kV" in Chinese catalogues is the rated (maximum) voltage for an 11 kV or 10 kV network. A 33 kV network needs a 36 kV or 40.5 kV breaker.
Endurance classes in IEC 62271-100
IEC 62271-100 defines classes that describe how hard a breaker has been tested. Ask the supplier to state them, and check the test report confirms them.
- Mechanical endurance M1 or M2. M2 means the breaker passed an extended mechanical test (10,000 operations). Specify M2 for frequently switched feeders, capacitor banks or motors.
- Electrical endurance E1 or E2. E2 indicates extended electrical endurance and is normal for distribution breakers that will not be maintained often.
- Capacitive switching C1 or C2. C2 means a very low probability of restrike. Specify C2 if the breaker will switch capacitor banks or long cables.
Operating mechanism types
The mechanism closes and opens the contacts. Two families dominate Chinese production.
| Feature | Spring-operated mechanism | Permanent-magnet actuator |
|---|---|---|
| Principle | Motor charges a spring; spring energy closes the breaker | Magnetic latch holds position; coil pulses move the contacts |
| Moving parts | More components, needs periodic lubrication | Fewer parts, lower maintenance |
| Auto-reclose duty | Standard O–0.3 s–CO–180 s–CO available | Available, depends on capacitor charge design |
| Manual operation | Hand charging and manual close possible | Manual trip usually available; manual close limited |
| Field familiarity | Widely known by maintenance teams | Requires the supplier's controller and spares |
Spring mechanisms remain the safer default if your maintenance staff already know them. Magnetic actuators make sense for outdoor reclosers and sites with limited maintenance, provided you can secure spare controllers.
Indoor or outdoor
Indoor VCBs are built to fit a specific switchgear panel, either withdrawable (on a truck) or fixed. The critical point is interchangeability: the breaker's pole spacing, contact arms, interlocks and secondary plug must match the panel. If you are buying breakers separately from the switchgear, send the panel drawings, or buy the breaker and panel from one factory.
Outdoor VCBs are pole-mounted or ground-mounted, often with embedded poles in epoxy or silicone housings. Ask for the creepage distance, pollution class, UV resistance of the housing and the ingress protection of the mechanism box. For compact secondary distribution, also compare ring main units and prefabricated substations, which can integrate the breaker function.
Embedded poles and interrupters
Many Chinese VCBs use embedded poles, where the vacuum interrupter is cast into epoxy resin. This protects the interrupter from dust and humidity and reduces assembly errors. Ask:
- Who makes the vacuum interrupter, and is it in-house or bought in?
- What is the contact wear allowance, and how is it checked in the field?
- Is a vacuum integrity test method recommended for maintenance?
Specification checklist for your enquiry
Copy this list into your request for quotation:
- System nominal voltage, highest voltage, frequency and earthing method.
- Rated voltage, normal current, breaking current and short-time duration.
- Mechanism type, auxiliary voltages, and number of auxiliary contacts.
- Endurance classes (M, E, C) required.
- Indoor withdrawable, indoor fixed, or outdoor; panel model if retrofit.
- Operating sequence for auto-reclose, if any.
- Ambient temperature, altitude and pollution level of the site.
- Required routine tests and witness test arrangements.
- Protection relay, current transformers and surge arresters if supplied with the breaker.
- Spare parts for two years of operation and recommended tools.
What to check with a Chinese supplier
Before you pay a deposit, verify the company and the evidence:
- Type-test reports. Ask for full IEC 62271-100 type-test reports, not summary certificates. The ratings, model number and frequency in the report must match your order. Check which laboratory issued the report and whether it is accredited.
- Routine test records. Every breaker should leave the factory with its own routine test record: power-frequency withstand, main-circuit resistance, mechanical operation and timing.
- Factory or trader. Ask for the production address and a video or visit of the assembly line. A trader can be fine, but you should know who actually builds the breaker.
- Registered entity. Check the company name against its Unified Social Credit Code, the 18-character registration number every Chinese company holds.
- Quality system. ISO 9001 certification is a baseline; it does not replace type tests.
- Export references. Ask for projects in markets with similar grid conditions to yours.
Our category rankings score companies on data completeness, not product quality. The method is explained on the methodology page.
Common mistakes
- Ordering by nominal voltage (11 kV) instead of rated voltage (12 kV).
- Accepting a 50 Hz test report for a 60 Hz network.
- Ignoring altitude: above 1,000 m, insulation must be corrected.
Frequently asked questions
Which standard applies to medium-voltage vacuum circuit breakers?
IEC 62271-100 covers AC circuit breakers above 1 kV, and IEC 62271-1 sets the common specifications. Chinese national GB standards for VCBs are closely aligned with these IEC documents.
Is a 12 kV VCB suitable for an 11 kV network?
Yes. 12 kV is the rated maximum voltage for 10 kV and 11 kV systems. Confirm the insulation levels also meet your utility's specification.
What breaking current should I choose?
Choose a rated short-circuit breaking current above the calculated fault level at the installation point, with margin for future network growth. Your network study or utility should provide the fault level.
Can I buy only the breaker and fit it into existing switchgear?
It is possible, but the breaker must match the panel's dimensions, contacts, interlocks and secondary wiring. Send full panel drawings and ask the supplier to confirm interchangeability in writing.