📋 Case Study
Refinery 13.8 kV Switchgear Arc Flash Mitigation Upgrade
Existing 13.8 kV metal-clad switchgear exceeded 40 cal/cm² incident energy; no ZSI or arc-resistant design
🏗️ Project Overview
Major Gulf Coast refinery electrical system modernization
🎯 Challenge
Existing 13.8 kV metal-clad switchgear exceeded 40 cal/cm² incident energy; no ZSI or arc-resistant design
🔧 Design Approach
Integrated zone-selective interlocking with SEL-751 relays, arc-resistant retrofit, and AFRM implementation
📐 Design Diagram
AI-generated project design illustration
📐 Key Calculations
Pre-Mitigation IE
IEEE 1584-2018 Eq. 4.8
Result: 62.3 cal/cm²
Required Category 4 PPE (40+ cal/cm²)
Post-ZSI Trip Time
Relay coordination study + arc duration modeling
Result: 0.08 s
Reduced IE by 78%
AFB Reduction
IE ∝ t × d⁻²
Result: From 182 cm → 61 cm
Expanded safe work zone
📊 Results
Incident energy reduced from 62.3 → 13.7 cal/cm²; eliminated Category 4 PPE requirement; achieved full AFRM compliance across 92 MCCs💡 Lessons Learned
- •ZSI must be validated under minimum arc current conditions
- •Arc-resistant gear requires UL 1558 Type 2 certification
- •AFRM procedures require documented lockout/tagout integration
✅ Key Takeaways
- 1ZSI must be validated under minimum arc current conditions
- 2Arc-resistant gear requires UL 1558 Type 2 certification
- 3AFRM procedures require documented lockout/tagout integration