Space charge characterization in aged LDPE amalgamated insulation regions from underwater telecommunication systems

The requirement of insertion of optical amplifier units and joints, into lo ng-distance submarine telecommunication systems, results in regions of the polymeric insulation which have to be reinstated, using injection molding t echniques. These techniques introduce internal amalgamated interfaces, whic h subsequently can be the sites of possible electrical insulation failure i n the system. Studies [1-3] have proposed that the increased risk of failur e is associated with the development of stress enhancing space charge at th ese interfaces. This paper reports on space charge measurements, (using the pulsed electroacoustic (PEA) technique [4]), from microtomed thin film sam ples taken from the interface region of typical system joints which have un dergone accelerated aging tests under a de voltage at room temperature. The space charge distributions obtained for the samples are discussed with ref erence to the underlying mechanisms of both the bulk low density polyethyle ne (LDPE) and the surface (LDPE /electrode interface). The effect of varyin g the electrode material (i.e. Au and Al) is discussed with reference to pr eviously published data. Finally the effects of long term aging on space ch arge accumulation within LDFE are considered briefly.