Patent ID: 8601858

Claim:
A method for testing a mechanical integrity of an insulating layer covering a conductor in a cable, a longitudinal void being defined inside the insulating layer in a region of the conductor, comprising the steps of: blocking a first end of the insulating layer; injecting a compressed gas at a second end of the insulating layer remote from the first end thereof so that the gas enters and travels the longitudinal void inside the insulating layer towards the first end thereof; measuring a gas pressure inside the insulating layer at least near the second end thereof; stopping injection of the compressed gas after a predetermined injection time period; monitoring a variation of the gas pressure inside the insulating layer during a diagnostic time window succeeding to a transitional time period following the stopping of the injection and during which a pressure wave travels along the longitudinal void; measuring a travel time of the pressure wave to reach the first end of the insulating layer from an initial injection of the compressed gas at the second end of the insulating layer; determining a pneumatic impedance of the cable based on the travel time; and determining integrity of the insulating layer based on the variation of the gas pressure during the diagnostic time window and the pneumatic impedance.