π Case Study
Naval Base San Diego Island Microgrid Protection Retrofit
Legacy overcurrent relays failed to coordinate during low-voltage ride-through events; false tripping during grid-support mode transitions
ποΈ Project Overview
US Navy microgrid integrating 4.2 MW solar PV, 3.5 MWh BESS, and diesel backup on isolated island infrastructure
π― Challenge
Legacy overcurrent relays failed to coordinate during low-voltage ride-through events; false tripping during grid-support mode transitions
π§ Design Approach
Deployed adaptive IEDs with synchrophasor-triggered logic, reconfigured zone boundaries using real-time SCR estimation, and integrated anti-islanding delay compensation into TCC curves
π Key Calculations
SCR-based Fault Current Scaling Factor
I_sc_actual = I_sc_rated Γ (V_pcc / V_nom)^2 Γ SCR
Result: 0.42 pu
Corrects relay sensitivity for voltage sag conditions
π Results
99.98% protection reliability over 18-month monitoring; eliminated nuisance trips; achieved IEEE 1547-2018 Category III complianceπ‘ Lessons Learned
- β’SCR must be dynamically updatedβnot assumed static
- β’TCC curves require dynamic time-multiplier adjustment based on IBR operating mode
β Key Takeaways
- 1SCR must be dynamically updatedβnot assumed static
- 2TCC curves require dynamic time-multiplier adjustment based on IBR operating mode