Circuit breaker and cable coordination context
A guide to keeping cable candidate, fault current and protective-device assumptions aligned before Australian protection review.
Coordination record purpose
Cable and protective-device decisions should not live in separate silos. Cable current-carrying capacity, voltage drop, fault current, clearing time, breaking capacity and I2t withstand can all affect the same project record.
This guide keeps the record aligned. It does not perform a manufacturer coordination study.
Workflow
- Record the cable candidate and current-carrying-capacity source.
- Record the protective-device type and data source.
- Prepare fault current from loop or source data.
- Review I2t withstand where fault duty and clearing time matter.
- Stop for manufacturer curves or engineering review when coordination is the actual question.
Coordination table
| Area | Calculator or source | What must stay aligned |
|---|---|---|
| Cable candidate | Cable-size calculator | Metric label, material and source data |
| Voltage drop | Voltage-drop calculator | Route length and conductor data |
| Fault current | Loop or short-circuit calculator | Location and voltage basis |
| Thermal withstand | I2t calculator | Fault current, time and conductor role |
| Device rating | Manufacturer/project source | Breaking capacity and clearing behaviour |
Boundaries
- Do not treat cable sizing as complete without protection context.
- Do not treat public worksheets as selectivity studies.
- Do not mix device data from another product family.
- Do not hide manufacturer requirements behind calculator output.