Effect of pressure and temperature on interfacial breakdown between two dielectric surfaces

Breakdown experiments were performed on slices of EPDM rubber pressed one against the other. To achieve this, an experimental jig was designed so as to induce breakdown between the two slices, longitudinally along their interface. Effects of interfacial pressure and of the presence of silicone grease at the interface are taken into account. Breakdown voltages are given for AC measurements. The authors illustrate how deformations, due to high-temperature operation, can occur in a cable joint. A relationship is also established between this deformation and the joint interfacial pressure, which in turns affects the interfacial dielectric strength. It is concluded that the dielectric strength of an EPDM/EPDM interface is greatly affected by the interfacial pressure. Moreover, the presence of silicone grease both improves (at low pressure) and limits, even if the interfacial pressure is increased (above 50 kPa), the dielectric strength of EPDM/EPDM interfaces