Protection and control
Circuit breakers
Medium voltage breakers that interrupt network faults and low voltage air and moulded case breakers that protect boards and feeders, including replacements for existing panels.
At a glance
- Medium voltage standard
- IEC 62271-100AC circuit breakers above 1000 V
- Low voltage standard
- IEC 60947-2circuit breakers up to 1000 V AC or 1500 V DC
- Key ratings
- rated current and breaking capacitybreaking capacity set by the fault level
- Replacement
- retrofit or like for likecompatibility with the existing panel decides
A circuit breaker is specified by what it carries and what it must interrupt. The rated current comes from the circuit. The short circuit breaking capacity comes from the prospective fault level at the point of installation, which is why the transformer impedance and the upstream network matter to a breaker order.
At medium voltage, distribution breakers are specified by interrupting medium, vacuum or gas. Name the medium in the enquiry if the site standard requires one. At low voltage, air circuit breakers serve incomers and large feeders, and moulded case breakers serve smaller feeders. Replacing a breaker in an existing panel is its own discipline, because the new device has to fit the cradle, the interlocks and the secondary wiring of the old one, or be supplied as a retrofit designed for that panel.
What gets specified
| Parameter | Typical options | What decides it |
|---|---|---|
| Voltage level | Medium voltage or low voltage | The circuit |
| Rated current | In A | The load or transformer on the circuit |
| Short circuit breaking capacity | In kA | The prospective fault level |
| Interrupting technology | Vacuum at medium voltage; air or moulded case at low voltage | Voltage and duty |
| Mounting | Fixed or withdrawable | The panel and the maintenance approach |
| Operating mechanism and auxiliaries | Spring mechanism, motor, shunt trip, undervoltage release | Control and interlocking |
| Protection | Integral trip unit, or an external relay | Voltage level and scheme |
| Replacement type | New panel, like for like, or retrofit | The existing installation |
Typical options are the ones buyers most often specify. They are not a list of what is available, which is confirmed per enquiry.
Applicable standards
| Standard | What it covers |
|---|---|
| IEC 62271-100 | AC circuit breakers for three phase systems above 1000 V |
| IEC 62271-1 | Common specifications for AC switchgear and controlgear above 1000 V |
| IEC 60947-2 | Low voltage circuit breakers up to 1000 V AC or 1500 V DC |
The standard that applies is set by the specification and the destination market. Editions change, so the edition cited in a specification is confirmed in the quotation.
Documents normally requested
| Document | What it evidences |
|---|---|
| Technical datasheet | Ratings, functions and the variant offered |
| Type test report or certificate | The design has passed the tests of its standard |
| Dimensional drawing | Mounting, cut out and connection positions |
| Wiring or connection diagram | Terminals, auxiliary supply and communication |
| Settings and configuration files | Where a device is supplied preconfigured |
| Manual | Installation, commissioning and operation |
Where a device replaces an existing one, the nameplate, model and firmware of the existing device are the most useful documents to send.
What we need to quote accurately
| 01 | Device type and the system voltage it serves |
| 02 | Rated current and the short circuit breaking or withstand values required |
| 03 | The protection scheme and functions needed, and the scheme it must integrate with |
| 04 | Auxiliary supply voltage and communication protocol |
| 05 | Whether this replaces an existing device, with its nameplate or model if known |
| 06 | Quantity, destination, required delivery date and acceptable condition |
| 07 | For a replacement: panel manufacturer and type, and whether the breaker is fixed or withdrawable |
Delivery and logistics
Devices are lighter to move than transformers and switchboards, but compatibility is the harder part of the delivery. A replacement breaker has to fit the existing panel, a relay has to fit the cut out and the scheme, and a firmware or communication mismatch can make a correct device unusable on the day.
Delivery dates are stated in each quotation for the specific item offered. We do not publish a general lead time.
Related
Request a quote for this equipment
Send the rating, the voltage and the destination, or submit the specification, drawing or nameplate. Anything missing is raised before it reaches a supplier.