Breaking capacity
The largest that a protective device can interrupt safely under its stated conditions. If the available fault exceeds that rating, the device may fail while trying to clear a . Selection compares the device rating with the fault current possible at its point in the installation.
Using Breaking capacity in context
Updated
A distinction worth remembering
Breaking capacity is the fault current a device can interrupt under its specified conditions. It is not its normal load-current rating, so the two numbers must not be used interchangeably.
Questions to take further
- How can I revise Breaking capacity beyond the definition?
- Explain what Breaking capacity describes, compare it with a related term and use it in a topic question. State any assumptions and what evidence you would need before applying the idea to real work.
Sources
- HSE: electrical safety questions — Isolation, competence and precautions before electrical work.
- IET: current BS 7671 edition and updates — BS 7671:2018+A4:2026 and the main subject areas updated by Amendment 4.
Where Breaking capacity fits in the learning path
The Installation section covers these units:
- Wiring Systems & Enclosures
- Cable Selection & Circuit Design
- Earthing, Bonding & Consumer Units
Curriculum mapping: C&G 2365 Units 203/204/305.
See this section in the full curriculum
This section is on the Plus path. Lesson availability depends on content review and your learning path.
Read, practise, return
1. Read it in context
- UK Fuse TypesInstallation
- MCB Types B, C and DInstallation
- Prospective Fault CurrentTesting & Inspection
2. Try recalling, then explore practice
Use the memory prompt below to connect the vocabulary.
- Inspection & Testing — quiz previewPlus · Testing & Inspection
3. Return to the meaning
After reading or practising, explain the idea in your own words, then check what you remembered.
Recall a related term
Which term fits this definition? Say it to yourself, then reveal it. This is a memory prompt, with no score or saved result.
The current that could flow at a point if a fault of negligible impedance occurred there. Assessment considers the relevant short-circuit and earth-fault conditions. Protective devices must have adequate breaking capacity, or a verified coordinated arrangement with upstream protection, for the fault current at their location.
Compare related terms
Open a meaning to compare its role with Breaking capacity, or follow its full entry.
PFC — Prospective Fault Current
The current that could flow at a point if a fault of negligible impedance occurred there. Assessment considers the relevant short-circuit and earth-fault conditions. Protective devices must have adequate breaking capacity, or a verified coordinated arrangement with upstream protection, for the fault current at their location.
Read the PFC entryPSCC — Prospective Short-Circuit Current
The current that could flow through a short circuit of negligible impedance between live conductors at a particular point. The possible fault arrangements differ between single-phase and three-phase supplies. It is assessed alongside prospective earth-fault current when choosing protective equipment; it is not the current drawn by a load in normal service.
Read the PSCC entryShort circuit
A short circuit is an unintended connection of very low impedance between points that should have a voltage difference, such as line and neutral. It bypasses the intended load and can allow a large current to flow, limited by the supply and circuit impedance. It differs from an overload caused by too many loads. PSCC describes the current that could flow in such a fault, rather than a current flowing in normal use.
Read the Short circuit entryA definition is a start. Using it in a real question is where it sticks.