Design of dynamic and thermal stability test system for UHV switchgear based on 330kV grid power supply

Abstract

To meet the low-voltage, high-current, and long-duration requirements of thermal and dynamic stability tests for UHV disconnectors and earthing switches, this paper proposes a two-stage step-down test system powered by a 330 kV grid. The system employs a 12.5 MVA transformer (330 kV/35 kV) and a 90 MVA short-time-rated low-voltage high-current transformer (35 kV/0.206–0.824 kV). A seven-level binary reactor (0–254 Ω, 2 Ω step) enables continuous impedance matching, a phase-selective synchronous closing device (±3.6° accuracy) suppresses DC components within 20%, and a 35 kV/31.5 kA circuit breaker performs centralized interruption. A unified low-voltage-side impedance model is established and all operating conditions are quantitatively verified. Tests on a GW45–800 kV disconnector (170 kA/0.3 s peak, 63.3 kA/2 s short-time) show excellent agreement with calculations, confirming system practicality.