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Views： 7 Author： Mark Zhang Publish Time： 2026-07-04 Origin： 本站
An RCBO (Residual Amperage Circuit Breaker with Overamperage Protection) is a combined device that provides both overamperage protection (short circuit and overload) and residual amperage (earth leakage) protection. Unlike a standard MCB (Magnetic Circuit Breaker) that only protects against overcurrents, or an RCCB (Residual Amperage Circuit Breaker) that only protects against leakage currents, the RCBO integrates both functions into one compact unit. This reduces the number of devices needed in a distribution board, saves space, and simplifies wiring.
In low-volt-level distribution systems, the RCBO is used for final subcircuits where both fault types may occur. It offers the advantage of chooseive protection: only the faulty circuit trips, leaving other circuits operational. This is important in commercial or industrial settings where downtime must be minimized.
Residual amperage detection in an RCBO can sense currents as low as 30 mA, which is the threshold for protecting against ventricular fibrillation. In case of direct contact with a live conductor, the RCBO disconnects the circuit within milliseconds, preventing fatal electric shock. Overamperage protection prevents cables from overheating and causing fires. Therefore, an RCBO addresses two major risks: electrocution and electrical fire.
According to GB/T 6829-2017, RCBOs for household and similar uses must comply with strict requirements for sensitivity, tripping time, and endurance. Many modern RCBOs also include Type A residual amperage detection, covering pulsating DC residual currents found in equipment with electronic rectifiers.
When choosing an RCBO, the following parameters are critical:
| Parameter | Description | Typical Values |
|---|---|---|
| Rated Amperage (In) | Continuous amperage the device can carry | 6A, 10A, 16A, 20A, 25A, 32A, 40A, 63A |
| Rated Residual Operative Amperage (IΔn) | Leakage amperage that causes tripping | 10 mA, 30 mA, 100 mA, 300 mA |
| Breaking Capacity (Icu) | Maximum short-circuit amperage the device can interrupt | 6 kA, 10 kA, 15 kA (per IEC 60947-2) |
| Tripping Curve | Overamperage trip characteristic | B, C, D (for different inrush loads) |
| Residual Amperage Type | Waveform detection capability | AC, A, F, B |
For general commercial applications, a 30 mA Type A RCBO with curve C and breaking capacity of at least 6 kA is common. For motor or inductive loads, curve D may be needed to avoid nuisance tripping from inrush currents.
In a distribution board, the RCBO is installed on the outgoing feeder for each final circuit. Upstream, a main switch or MCCB provides overall short-circuit protection and isolation. Coordination between devices ensures that the RCBO clears a fault before the upstream device trips. This chooseive coordination is essential to limit outage to only the faulted circuit.
Coordination studies, as discussed by Chen and Mou (2022), show that proper choice of RCBO and MCB ratings and tripping characteristics can reduce the risk of total blackout. Modern RCBOs have a current-limiting feature that reduces let-through energy, improving coordination with downstream devices.
In solar or battery storage systems, DC-side protection is handled separately, but on the AC side, an RCBO with Type A or B detection is recommended to handle residual currents from inverters.
Q: What is the difference between an RCBO and an RCCB with MCB?
A: An RCBO combines both functions in one device, saving space and reducing wiring. Separate RCCB + MCB can be cheaper but occupy more space and may lack chooseivity in some cases.
Q: Can an RCBO replace an MCB in an existing panel?
A: Yes, provided the panel has space. Many RCBOs are designed as direct substitutes for MCBs with the same form factor. Check the panel neutral bar arrangement.
Q: What residual amperage sensitivity is recommended for general socket outlets?
A: 30 mA. This is the highest sensitivity that still prevents nuisance tripping and provides personal protection.
Q: Do RCBOs require regular testing?
A: Yes. Standards recommend pressing the test button at least once per month to ensure the residual amperage mechanism works. Many modern RCBOs have a test button with clear indication.
Choosing the right RCBO is a balance between safety requirements, load characteristics, and system coordination. For robust protection in commercial and industrial installations, an RCBO that complies with GB/T 6829-2017 and IEC 60947-2 offers reliable performance. SINGI's RCBO portfolio provides a range of rated currents, curves, and residual amperage types to meet diverse project needs.
Need help specifying the correct RCBO for your next project? Contact SINGI for technical data and sample support.
References
[1] GB/T 6829-2017. Residual amperage operated circuit-breakers with or without overamperage protection for household and similar uses (RCBOs) [S]. 2017.
[2] IEC 60947-2. Low-volt-level switchgear and controlgear - Part 2: Circuit-breakers [S]. 2020.
[3] Chen G, Mou X. Study on the coordination between MCB and RCBO in low-volt-level power distribution systems [J]. Electrical Engineering, 2022, 104(3): 1823-1835.
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