Transient Stability Analysis of Multi-Source UHV 1200 kV Corridors Using RK4 with AVR and Governor Models

This paper presents a comprehensive transient stability analysis of a 1000 km, 8000 MW Ultra High Voltage (UHV) 1200 kV AC transmission corridor using fourth-order Runge-Kutta (RK4) integration combined with IEEE AC1A Automatic Voltage Regulator (AVR) and IEEEG1 Governor models. Four generation source types are evaluated: nuclear (H=5.0s), hydraulic Francis (H=5.5s), combined cycle gas turbine (H=3.5s), and renewable with synchronous compensator (H=1.8s). Results demonstrate that AVR+Governor action reduces maximum rotor angle deviation from 64.9° to 32.0° for renewable sources (+32.9° improvement), with all sources maintaining stability margins exceeding 80° above the critical angle of 145°. The Critical Clearing Time (CCT) ranges from 149.8 ms to 261.9 ms across all scenarios, well above the 83.3 ms breaker clearing time.