Effect of surface fluorination on space charge behavior at LDPE/EPDM interface

Joints and terminations in polymer insulated HVDC cable system have been identified as weak points with much higher failure probability than the cable itself. This is mainly due to space charge accumulation at interfaces between different insulating materials. According to the Maxwell-Wagner-Sillars polarization theory, the accumulation of interfacial charge depends on conductivity and permittivity mismatch. Fluorination had been reported as a surface modification method of polymer dielectrics, which may lead to remarkable increase in permittivity and conductivity, thus could be a possible way to reduce space charge at the insulation interface of cable and its accessory. This paper presents the results of pulsed electro-acoustic (PEA) measurement of space charge distribution in LDPE/EPDM double-layer sample subjected to a DC field. Original and fluorinated LDPE layer were both used to study the effect of surface fluorination on space charge behavior at LDPE/EPDM interface. The results show that a significant amount of space charge accumulated at the interface of the original-LDPE/EPDM sample. And the property of the interfacial charge changed a lot after the LDPE layer is surface fluorinated.