Creeping breakdown caused by metal particles on the silicone rubber/XLPE interface of prefabricated cable joints often happens. Study on the development process of such insulation defect-led partial discharge (PD) can serve as a basis for the assessment of its severity level. In this paper, metal particles are sandwiched on the rubber/XLPE interface of a 35 kV prefabricated cable joint to simulate a creeping defect.