INTRODUCING CableGuardian.

The first platform to offer proactive monitoring, detection and location of both insulation and conductor faults on live low voltage ungrounded power distribution systems.

CableGuardian Explained.

Find out how CableGuardian is being used around the country to monitor and diagnose faults on rail network electrical systems. Helping to keep the trains running!.


The CableGuardian system consists of multiple sensor units distributed across principal supply points (PSPs) and functional supply points (FSPs) each measuring multiple electrical parameters and communicating via a secure internet connection to a cloud-hosted data storage and analytics system. This system analyses the sensor data, providing continuous monitoring of the live system and indicating the location of any cable or conductor faults without the need to down-power the system, reducing the frequency and duration of trackside fault-finding campaigns.

CableGuardian provides monitoring at a cable section level, as defined in NR/L2/SIGELP/27725, breaking away from the traditional limitations of insulation monitoring devices which offer only a single insulation resistance measurement for the complete circuit or, at best, feeder level monitoring. Additionally CableGuardian’s capability for continuous monitoring of both the cable insulation and the copper or aluminium cores offers a technological alternative to the intrusive periodic cable testing requirements of NR/L2/SIGELP/50000.


CableGuardian meets the Tier 1, Tier 2 and Tier 3 cable monitoring requirements of NR/L2/SIGELP/27725.

Tier 3 Fault Monitoring:
A single CableGuardian in the PSP monitors all connected feeders and returns the IR value of the complete system.

Tier 2 Fault Monitoring:
The IR of each feeder is monitored individually from the PSP. IR faults can be attributed to an individual feeder.

Tier 1 Fault Monitoring:
Multiple CableGuardian units are installed on each feeder. The measurements from each CableGuardian unit are sent to the analytics package which resolves for the IR of each cable section between adjacent CableGuardian units. Each CableGuardian unit monitors for open circuits or short circuits and reports the results to the analytics package. Results from multiple units can be resolved to indicate the location of the conductor fault.


BS7671 (IET Wiring Regulations) requires that periodic inspection of electrical installations is performed. This has resulted in the periodic manual cable testing of Signalling Power Supply (SPS) systems described in NR/L2/SIGELP/50000. CableGuardian offers an advanced technological solution providing a real, effective and non-intrusive alternative to the current manual periodic cable testing.

CableGuardian offers a number of advantages over manual cable testing:

  • In addition to the cables, CableGuardian monitors and tests all of the components connected to the system (e.g. transformers, connectors, switches, bus bars, etc). These components may have inherent insulation faults of their own which are undisclosed by the traditional manual cable testing methods.
  • CableGuardian continuously monitors and tests the system whilst it is powered rather than having to switch off the system to perform the traditional manual cable testing.
  • CableGuardian provides continuous 24/7 IR monitoring and trending plus core-core open/short circuit monitoring rather than a snapshot single measurement in time.
  • CableGuardian is non-intrusive, requiring no disconnection of cables or other equipment to perform its measurements, resulting in less trackside excursions and “boots on ballast”. This also eliminates the risk of faults being introduced when the cables are reconnected.
  • CableGuardian permits a move from a frequency based inspection regime to one driven by actual asset condition and performance.


How does CableGuardian compare to other cable monitoring products?

  • CableGuardian is the only system trialled by Network Rail offering Tier 1 compliance to Network Rail Insulation Monitoring Device standard NR/L2/SIGELP/27725, providing cable monitoring at a sub-network cable section level.
  • CableGuardian is unique in offering cable insulation monitoring and conductor monitoring in a single platform for continuous monitoring of live systems.
  • CableGuardian is the only product available incorporating SSTDR for live conductor monitoring.

Learn More.

The Underlying Technologies.