T&D How

Cable Injection

Discuss this Video 1

Ben
on Aug 27, 2016

During the presentation the commentator explains that a low voltage TDR detects faults and the beginnings of abrasions in the insulation which supposedly is what cable injection can repair. The commentator also states that the fluid will fix faults and abrasions in the insulation. These comments are commonly reported in the industry but they are incorrect on several points. In addition, it is surprising to see the injection team is performing a high potential test on the aged cable system. This is a known risk factor for future failure.

TDR can not detect insulation faults (failures) or defects. That would require an insulation assessment like a factory comparable PD test. What a high resolution TDR can detect is broken concentric neutral wires due to corrosion or mechanical damage. I think this maybe what the commentator meant to say.

Injection can not fix any existing insulation defects, including insulation faults and abrasions. Large scale studies have shown that potential failure producing defects existing before injecting will be present after injection. What the silicone based fluid can do is is react with water and address the stress enhancing effects of areas of lossy XLPE insulation that is more commonly referred to as a water tree. Although water trees don't fail cable, in some special circumstances, they can initiate an electrical tree that might grow over time to eventually fail the cable system.

I hope these comments will help prevent the propagation of a few common misunderstandings in our industry and make this video of more value to future viewers.

Kind regards,

Ben Lanz

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