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During a fault event, whether due to vandalism, theft, cable degradation, vermin damage, or water ingress, the analytics package can send an alert to the maintenance team via email, text, or automated phone call.


The CableGuardian units are the “eyes and ears” of the monitoring system. The unit is installed as part of a kit with the necessary measurement coil harness, power cable and communications antenna (if using cellular communications).

The unit can be powered from a domestic supply at 240V or 110V but it can also take its power from the 650V line being monitored, with the appropriate power cable being supplied by us depending on the option chosen. “Solid” or “split” measurement coil options are available.

Solid cores are used when the system can be down-powered to install the equipment. The split core can be installed around a live 650V cable. A second, smaller, split measurement coil is connected around a single core within the 650V cable to measure the line current. A functional earth connection is required for the CableGuardian unit to measure correctly. Note that this is not a protective earth as the unit is fully Class II certified.


The number of units depends on the Tier of monitoring as defined in NR/L2/SIGELP/27725 that is required by the asset owner and further for Tier 1 systems it also depends on the feeder layout and resolution of fault location desired. The more units installed in a Tier 1 system the better the resolution of Insulation resistance measurements. A unit in each location case will provide complete cable section level monitoring.

In a Tier 3 installation a single CableGuardian unit monitors all electrically connected feeders from a PSP. A Tier 2 system requires a single CableGuardian unit for each feeder. For a Tier 1 installation the maximum number of units required is equal to the number of location cases on all feeders in the same electrical circuit plus a unit for each feeder at the PSP, however complete cable monitoring is generally achievable without installing a unit in each location case. Please contact us with your system information and we will be happy to provide a CableGuardian system proposal to meet your individual requirements.


During a fault event alarms are enunciated to users via easily accessible notification options, including the web portal, email, SMS text message and automated telephone voice message. The alarm levels and methods of alert are all configured to meet the customer requirements when Viper carry out the system engineering and can be altered at any time upon request.

Alarms can be set to meet the general requirements of Network Rail Flight Engineers while avoiding spurious anomalies, for example an alarm can be enunciated if the system IR drops below a prescribed level for a continuous period longer than 4 hours (rather than alarming for a single short anomalous drop below the same level).

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