📋 Case Study

110 kV Substation Expansion Study

Voltage drop exceeding 5% at downstream feeders; insufficient reactive support during peak summer load

🏗️ Project Overview

Expansion of regional 110 kV GIS substation serving growing urban load center

🎯 Challenge

Voltage drop exceeding 5% at downstream feeders; insufficient reactive support during peak summer load

🔧 Design Approach

Integrated VAR compensation via 12 MVAR STATCOM + revised tap settings on 110/33 kV transformers; updated Y-Bus with new feeder impedances

📐 Design Diagram

AI-generated project design illustration

📐 Key Calculations

Voltage Profile Sensitivity (dV/dQ)

∂V_i/∂Q_j = Re(Y⁻¹)_ij

Result: -0.018 p.u./MVAR

Guided STATCOM placement at weakest bus (Bus #42)

Transformer Tap Optimization

V_out = V_in × (N_tap / N_nom)

Result: 1.025 pu tap ratio selected

Restored 33 kV bus voltage to 1.002 p.u. under peak load

📊 Results

Voltage deviation reduced from −6.2% to +0.8%; transformer loading decreased by 14%; STATCOM utilization < 65% across all scenarios

💡 Lessons Learned

• •STATCOM location must be validated using Q-V curves—not just voltage magnitude
• •Tap scheduling requires co-optimization with capacitor banks

✅ Key Takeaways

• 1STATCOM location must be validated using Q-V curves—not just voltage magnitude
• 2Tap scheduling requires co-optimization with capacitor banks