Space charge and interface reliability in underwater telecommunications systems

The insertion of repeater units into submarine telecommunication systems requires the reinstatement of the insulation integrity through injection moulding. This technique introduces internal interfaces into the insulation which are known to pose a major threat to the insulation reliability. Recent work has implied that the risk of failure is associated with the development of electric stress enhancement due to space charge in the interface region. Here we report the results of a study of insulation mouldings aged for 34000 hours at an elevated voltage. Microtomed sections have been taken from the moulding and their susceptibility to space charge trapping investigated by the PEA technique. Space-charge distributions in the microtomed sections have been monitored during further ageing in an attempt to correlate short breakdown times with stress enhancement