Seismic performance simulation and safety evaluation of 72.5 kV GIS for offshore wind power

Abstract

Offshore wind power facilities operate in near-sea environments where GIS equipment must withstand both marine wind loads and seismic forces. While existing national standards focus primarily on seismic resistance studies for land-based GIS systems, specialized detailed seismic analysis literature tailored to offshore wind conditions involving 72.5 kV GIS remains scarce. Identifying vulnerable components under combined wind-seismic loads proves challenging due to the lack of empirical formulas. This study employs a full-scale finite element model developed using ANSYS for a dedicated 72.5 kV GIS system designed for offshore applications, incorporating equipment self-weight, 0.5 MPa internal gas pressure, and 10 m/s offshore wind loads. Following GB13540-2009 and GB50009-2001 specifications, modal and spectral analyses were conducted using a multi-scenario seismic response spectrum method with a 5% damping ratio (0.5 g horizontally and 0.25 g vertically). The analysis identified the first 30 natural frequencies (15.763–53.389 Hz), exceeding the national standard limit of 35 Hz. Stress distribution maps and deformation profiles under coupled wind-seismic loads revealed that frame sides and cylinder flanges constitute critical seismic weak zones. The main structure meets offshore wind power seismic design requirements, with structural optimization recommendations provided for identified vulnerabilities, offering valuable simulation insights for seismic-resistant design and equipment selection of similar offshore GIS systems.