A Line Insulation/Isolation Monitor (LIM) that monitors the insulation resistance, capacitance and electrical integrity of subsea electrical umbilicals and distribution systems with ungrounded AC / DC pairs with working voltages up to 1000V.


Line Insulation resistance monitoring is an industry accepted and recognised method of measuring the effects of water ingress into and around the umbilical electrical conductors. Electrical integrity monitoring is usually included on the topside facility at the input to the umbilical electrical conductors.

It is important to be able to monitor the integrity of the electrical conductors from when they are first installed.  Degradation trending needs to be possible independently of the actual IR. Accuracy and repeat-ability of the sensing solution is key.


The V-LIM Line Insulation Monitor can be readily integrated into topsides equipment either as part of a new development or retrofitted to existing installations. The V-LIM accurately monitors the insulation resistance, voltage, current and the polarisation index of the umbilical and subsea equipment with high accuracies. Insulation resistance is measured down to less than 1KOhm and up to 10GOhm. The data gathered by the V-LIM can be used to analyse the rate of deterioration of the electrical insulation resistance in the system and further to estimate when the electrical insulation resistance is likely to result in system failure (electrical analysis required to determine system limits). The V-LIM data can also be interpreted to indicate if the failure has occurred in the bulk insulation of the umbilical conductors.

Key Benefits

  • Continuous monitoring provides real-time trending.
  • When combined with Viper Subsea's LIMBO analysis time to failure predictions can be made.
  • Interface modules allow for easy replacement of legacy equipment.
  • Determine fault locations when combined with the use of the V-SLIM and V-NET systems.
  • Compatible with V-LIFE technology.

Key facts

  • Provides accurate insulation resistance measurements down to <1KOhm
  • Can be used on both AC and DC floating earth power systems up to 1000V
  • Implements the V-NET system to link up with V-SLIM's for complete line monitoring and fault locating
  • Compatible with powerline signalling system
  • Can measure resistance, capacitance and polarisation index of the umbilical cable
  • The V-LIFE cable lifetime extender system can be incorporated