It is well known that the most common subsea electrical failure is as a result of water ingress into cables and connectors with degraded insulation. Failure of insulation resistance (IR) in a seawater environment can lead to complete failure of the copper conductors in a cable and potentially an unplanned production outage.
Most power modules that supply subsea production controls equipment require an insulation monitoring device (IMD) or Line Insulation Monitor (LIM) to ensure the system is safe to operate. Viper Innovation’s research has shown that the measurement current being driven by any IMD results in copper loss at the wetted surface of the conductor at any points where the insulation is degraded. It can be concluded that the action of this mandatory safety device in a cable which is submerged in seawater will cause some damage to the copper conductors. All is not lost, however, thanks to Viper Innovation’s V-LIM product.
The V-LIM has been designed with copper loss in mind. It automatically adjusts the measurement signal applied in low IR conditions to significantly reduce the rate of copper loss compared with competing IMDs on the market.
The logical first step to protect subsea cables from copper loss is to ensure that a V-LIM is installed in each topside’s power module. But what further actions can be taken?
Historically there have been two schools of thought on how to deal with IR faults; monitor and leave until failure or replace equipment until the faults are found. What if there was a third option?
Viper Innovations’ V-LIFE technology is an innovative software activated function of the topsides-located V-LIM. It initiates an electrokinetic and electrochemical process within the damaged cable. The application of V-LIFE blocks any pores in the insulation with a precipitate, thereby removing the seawater electrolyte and increasing insulation resistance often more than 100-fold. As a result, the leakage current decreases and any copper loss is dramatically reduced.
If V-LIFE can be used to increase the IR to 30MΩ from an assumed starting point of 30KΩ, then the rate of copper loss will be reduced by a factor of 15.
Therefore, besides replacing failed cables and umbilicals, the solution to mitigate copper corrosion in degraded subsea cables and extend the life of the subsea electrical infrastructure is to activate V-LIFE on the Viper V-LIM.