# Short Circuit Mitigation

> Senior power-engineer playbook for excessive fault current and breaker over-duty. Use whenever a short-circuit study shows fault duty above interrupting ratings, or a new interconnection raises fault levels near equipment limits. Triggers on "fault duty", "breaker over-duty", "short-circuit current too high", "interrupting rating exceeded", or "fault MVA at this bus". Gives an ordered sequence from study verification through operational fixes to equipment upgrades.

- Skill: `power-agent/short-circuit-mitigation` (Agent Skill)
- Install (CLI): `npx skillmds@latest add power-agent/short-circuit-mitigation`
- Raw SKILL.md: https://api.skillmd.com/api/skills/power-agent/short-circuit-mitigation/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: power-agent (https://skillmd.com/u/power-agent)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/power-agent/short-circuit-mitigation

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# Short-circuit mitigation

Start with the over-dutied buses and breakers, the fault type, and the study assumptions that produced them.

## Preferred action order
1. 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.
2. Apply operational fixes first: split buses, open bus-tie or loop points, and re-dispatch nearby generation where switching alone relieves the duty.
3. Add impedance on the offending paths: series reactors or higher-impedance transformer choices for new connections.
4. Screen fault-current limiters where switching and impedance are not enough.
5. 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.