We have had an extremely high success rate from the very start of the project, and it is now the most important tool used for cable fluid leak detection across our entire network,” said Paul Capp, occupier duties manager, National Grid. “PFT Technology has enabled our success in dramatically shortening repair time, lowering costs, and reducing fluid loss into the environment.


High voltage transmission cables contain pressurized dielectric fluid

  • Fluid provides electrical isolation between cables and the ground
  • Leaks are difficult to locate and expensive to repair

Traditional leak location and repair is expensive, time-consuming and inefficient 

  • Cable is excavated at its midpoint; fluid is frozen and pressure is measured to determine leak direction
  • Can require up to four freezes (or more) to isolate leak point
  • Cable must be taken out of service to effect repairs; leaks often seal up
  • Major cable outage can run $500K - $1MM per day of outage
  • Leakage of fluid continues even when cable is out of service

PFTtech leak detection system is fast, efficient and environmentally-friendly

  • System involves injecting (“tagging”) minute amounts of perfluorocarbon (PFT) tracer element into the dielectric fluid of a high-voltage cable
  • Tracer remains in the fluid until a leak occurs; then converts to gas and reaches ground level
  • At the surface, sophisticated detectors pick up the PFT at 1 part per quadrillion (1:1,000,000,000,000,000) concentration to locate the leak
  • System has a 99% success rate over 10 years in three countries
  • Leaks can be located in pre-tagged cable in as little as 24 hours, within a few feet, while the cable is still in service, without the need for multiple excavations 

PFT TECH Environmental Leadership

  • PFT tracer system is environmentally friendly

  • PFT tracer element used at levels documented to be safe

  • Proven safe over 20 years of use

  • Environmentally-approved tracer element (extremely low levels used)

  • Proprietary instrumentation is 10x more sensitive than commercially available

  • Able to detect tracer element above ground at 1 part per quadrillion (1:1,000,000,000,000,000)

  • Preventing cable fluid leaks is beneficial to the environment

  • PFT Tech ensures fluid leaks are at a minimum

  • Up to 35% of fluid leaks occur in environmentally-sensitive areas

Traditional techniques for locating cable fluid leaks are challenging, time-

consuming and can typically only be carried out under outage conditions. To isolate a leak in a typical section of buried cable, a repair crew excavates the pipe at its midway point, freezes its dielectric fluid, and monitors the oil pressure to determine on which side of the freeze the leak is located. The crew then creates another freeze point halfway to the cable end, and continues the process until they locate the leak.

However, when the cable is taken out of service and cools down, the fluid leak will often seal up, making it impossible to locate. Also, even during the freeze, which can last a week or more, the cable will remain under pressure and continue to leak fluid, even when it is out of service. Taking a major transmission line out of service can cost a utility as much as $500K to $1 million per day that the cable is out.

With PFTtech’s leak detection system, on the other hand, it takes just one to five days to tag a circuit with the tracer and less than twenty-four hours to find a leak. Power to the cable does not have to be shut down for the leak search, and if a cable is pre-tagged (PFTtech’s tracer has previously been injected into the line) then the total time to leak detection is less than twenty-four hours.

The PFTtech process is not only faster, safer and cost effective, but it also helps protect the environment since it dramatically reduces cable fluid loss and eliminates the need for freeze pits and the use of liquid nitrogen. Furthermore, the process limits the frequency and duration of scheduled outages; this, in turn, enables utility companies to minimize the inconvenience to the public by reducing road closures and also reduces potential accidental damage to other buried services during repairs. Finally, and perhaps most important, by eliminating cable leaks PFTtech allows utilities to extend the life of the cable and manage their assets much more cost effectively. Consequently, for utilities that employ PFTtech, the savings are significant.