
Substation Fault Analysis Assistant
Diagnose substation faults from relay data and waveforms to pinpoint root causes
What You Can Do
You can rapidly reconstruct fault sequences, identify relay coordination failures, and diagnose protective system misoperations by organizing complex data streams into structured investigative narratives. The skill guides you through methodical analysis of relay timing, fault current magnitudes, equipment condition logs, and SCADA telemetry to generate root cause reports and actionable mitigation recommendations for substation engineers and stakeholders.
Features
organize protective relay operation timelines to verify coordination and identify nuisance trips or delayed operations
systematically determine phase-to-phase, phase-to-ground, or three-phase fault characteristics from waveform and relay data
correlate relay misoperations, transient overvoltages, harmonic distortion, and equipment condition to pinpoint failure mechanisms
forensic review of transformer and line differential schemes to detect sensitivity or security issues
reconstruct fault location and impedance measurements to validate relay reach and coordination
connect relay operation sequences to transformer oil breakdown, breaker contact wear, and cable insulation failure patterns
produce organized technical reports suitable for regulatory filings, stakeholder communication, and engineering review
flag missing oscillograph records, incomplete SCADA logs, or ambiguous relay timestamps requiring clarification from field crews
Example Output
Example 1: Nuisance Trip Investigation
Input: Relay data showing 138 kV distance relay operated at 0.52s during light load condition; oscillography shows 2.1 kA fault current; no visible faults on line patrol.
Output:
- Fault Type: Phase-A-to-ground (transient)
- Likely Cause: Capacitive coupling from adjacent 345 kV line during switching operation
- Root Cause: Distance relay reach set to 1.8x line impedance; transient overvoltage briefly exceeded pickup voltage
- Recommendation: Reduce reach to 1.5x; implement transient blocking logic for sub-cycle events
Example 2: Transformer Differential Misoperation
Input: 115/12 kV transformer differential relay operated at 0.18s during external 12 kV fault; CT saturation suspected; oil sample shows breakdown products.
Output:
- Relay Operation: Differential current 1,240 A vs. restraint current 890 A (margin = 1.39x, below 2x threshold)
- Root Cause: Secondary CT on 12 kV side saturated during high external fault current; magnetizing inrush current bled into differential circuit
- Equipment Impact: Transformer winding insulation exposed to 0.18s fault duration; oil analysis confirms thermal stress
- Recommendation: Upgrade CT to 2.5 VA burden; add inrush restraint logic; schedule winding moisture analysis
Example 3: Coordination Failure Report
Input: Feeder relay operated at 0.42s (backup); main line relay failed to operate; 4,200 A three-phase fault on 34.5 kV line.
Output:
- Fault Location: 3.8 km from substation (within primary protection zone)
- Primary Relay Status: Non-responsive; CT fuse blown on phase B
- Coordination Impact: Feeder protection correctly assumed backup role; coordination preserved but equipment damage extended
- Root Cause: CT fuse undersized for in-rush transients during motor starting 2 hours prior
- Recommendation: Install 200A fuses (upgrade from 150A); implement differential protection as independent backup scheme
What's Included
- SKILL.md instruction file: core diagnostic framework and investigative workflow
- Relay sequence worksheet: timeline template for logging protective relay operations with timestamps and operating currents
- Fault analysis checklist: systematic questions for distance protection, differential protection, and overcurrent schemes
- Equipment damage correlation matrix: guide linking relay operation sequences to transformer, breaker, and cable failure modes
- Root cause report template: structured narrative format for regulatory filings and stakeholder communication
Who It's For
- Substation engineers — diagnosing protective relay misoperations and equipment failures during fault incidents
- Relay engineers — forensic analysis of protective scheme coordination and relay setting validation
- Distribution system operators — rapid fault investigation to restore service and prevent cascading outages
- Asset management teams — post-mortem analysis of transformer, breaker, and cable damage to inform maintenance and replacement strategies
- Regulatory compliance officers — incident investigation documentation for NERC standards, state utility commissions, and insurance claims
Best For
- Protective relay misoperation investigation and nuisance trip root cause analysis
- Post-fault equipment damage assessment and failure mode correlation
- Relay coordination verification for distance, differential, and overcurrent schemes
- Fault sequence reconstruction from incomplete oscillography or SCADA data
- Technical incident reporting for regulatory agencies and stakeholder communication







