Method and device for detecting liquid fuel leakage in a gas turbine system combustion assembly

A method of detecting liquid fuel leakage in a gas turbine system combustion assembly (1) provided with a combustion chamber (2) having a plurality of diffusion nozzles (15) and a feed circuit (3), which feeds liquid fuel to the combustion chamber (2) and comprises a diffusion section (19) for supplying the diffusion nozzles (15), includes: - sealing the diffusion nozzle (15) of each burner assembly (5); - feeding a pressurized test fluid along the diffusion section (19); - checking for test fluid leakage along the diffusion section (19).