TEPCO Power Grid, Incorporated is seeking technology that can inspect and diagnose water intrusion non-destructively from the outside, as there are cases of water intrusion into the interior from around underground cable connections.
In the past, cable surveys were handled in the following manner: external inspection ⇒ confirmation of defective parts ⇒ dismantling survey (power outage work) ⇒ confirmation of internal flooding ⇒ restoration (in the same manner as before dismantling).
They are looking for a technology that can determine flooding from the outside in a non-destructive manner (internal diagnosis technology that requires dismantling the intermediate connection is not applicable).
Overview of the technology sought:
We are looking for a technology that can diagnose water ingress into high-voltage (66kV) underground power cables from the outside (water droplets in the gaps between copper wires and tapes, water soaked into cloth tape, etc.) without dismantling the intermediate cable connections, etc.
Cable Structure Diagram:
The cross-sectional view of the cable is shown below. Flooding occurs at the joints and reaches the inside of the water shield layer, reaching the outer conductive layer and degrading the insulation. A technology is needed to externally confirm the presence of water inside the cable.
The above cable is further covered with heat-shrinkable tubing consisting of resin, aluminum film, and adhesive layers from the outside. (The green sheet in the lower left photo)