Fluid-Filled Cable Leak Detection

Fluid-Filled Cable Leak Detection

Taking care of the UK’s legacy cable

Across the UK, many energy distribution and transmission network operators rely upon legacy fluid-filled cable systems. 

 

These legacy systems have proved their reliability over the years because of ongoing maintenance programmes but fluid leaks can occur, resulting from metal sheath fatigue, external corrosion or third-party damage. 

 

Locating these fluid leaks has been long winded and cumbersome, often involving de-energising the circuit, excavation, and then freezing it with liquid nitrogen to isolate the section. Traditionally an iterative process, this process would need to be repeated many times before the final source leak was found. At Prysmian, we developed a better solution.

What is PFT Solutions?

PFT (perfluorocarbon tracers)  are specialist compounds with excellent insulation properties, which we add to the cable fluid in minute quantities at cable system entry points. Where the cable system is damaged, the PFT compound, carried with the cable fluid, leaks and permeates the local environment. We then use our highly sensitive and sophisticated PFT equipment to detect the tracer compound and identify the source of the leak, and the repair can begin. 

 

We have developed proprietary methods of combining PFTs with cable fluid which we introduce into the cable system with no detriment to the flow or its insulation performance. We also continue to manufacture HV cable accessories for fluid-filled cable systems which can easily be deployed to site.

Injection

PFT circuit tagging can be carried out with or without the need for circuit outage and we have developed technical solutions to overcome the range of cable designs and hydraulic parameters. 

 

PFT technology has the following advantages: 

Vulnerable cable systems with significant environmental impacts should a fluid leak occur, can be pre-tagged as part of a normal maintenance programme. This means that should a leak occur, it can be located, isolated and repaired as soon as possible and reduce outage risks. 

Cable systems with on-going small leaks can be tagged during an outage period and leak detection can take place whilst the system is still energised. 

Prysmian uses a modern alkylbenzene fluid to replace existing cable fluid and provide greater biodegradability and less risk to the environment. Modern alkylbenzene cable fluid also has superior electrical qualities and greatly improved gas absorption properties.

Detection

Prysmian developed its own advanced mobile laboratory to detect background levels of perfluorocarbons in the environment. We collect samples of air along the cable route and compare it with background concentration results. The concentration of PFT in the air surrounding the leak is incredibly low, typically 40 to 100 parts per million however, our specialist equipment can detect these low levels of perfluorocarbon above the background and locate the leak.

 

The Prysmian PFT Solutions mobile lab gives real-time results. We can collect the sample and deliver results in as little as 90 seconds. This increases system performance by reducing time and resources to identify the leak. It avoids traditional methods that require air sample tubes couriered to specialist laboratories where results can take one to two weeks.