The marine environmental conditions

in which the offshore wind turbine generators operate

were investigated. Specimens for modeling the stator insulation system of 5 MW/3 kV offshore wind turbine generator were prepared to conduct the simulated marine environment tests

concerning changing temperature

steady damp and heat air

and continuous salty mist

in order to investigate the insulation system of the wind turbine generator.The specimens’ breakdown voltage and the non-destructive characteristic parameters

such as dissipation factor and insulation resistance

were measured during and after the tests to evaluate the marine environment endurance of the insulation system. Test results show that

although micro-cracks appeared between the winding insulation and the core to let brine or damp permeate into the inner surface of the core slot during the environment test

the insulation system of the specimens exhibits excellent marine environment endurance due to the electrical shielding effect of the semi-conductive slot coating.