Short-circuit mitigation
Start with the over-dutied buses and breakers, the fault type, and the study assumptions that produced them.
Preferred action order
- Confirm the duty is real: machine subtransient data, motor contribution, pre-fault voltage assumption, fault type (three-phase vs single-line-to-ground), and the X/R used for asymmetry — over-duty findings are often data findings.
- Apply operational fixes first: split buses, open bus-tie or loop points, and re-dispatch nearby generation where switching alone relieves the duty.
- Add impedance on the offending paths: series reactors or higher-impedance transformer choices for new connections.
- Screen fault-current limiters where switching and impedance are not enough.
- Recommend breaker replacement or uprating as the planning fix, with an interim operating guide until installed.
Working rules
- Check maximum (all-sources-in) and minimum (credible outage) fault cases — protection settings need the minimum, breaker duty needs the maximum.
- Single-line-to-ground duty can exceed three-phase duty near grounded transformer banks; do not screen on three-phase faults alone.
- Bus splitting changes power-flow transfer paths and N-1 performance; re-run the contingency screen after any topology fix and route findings to
contingency-mitigation. - Keep the protection engineer in the loop: any fix that changes fault levels changes relay reach.
Deliver
- The over-dutied equipment, its rating basis, and the computed duty.
- The mitigation sequence tried, from switching to reinforcement.
- The residual duty margin and any protection re-coordination still required.
