Early identification of faults on rail signalling power systems driven by new standards

Jon Lawson

Tony Edwards looks at how increasing demands for more effective identification of faults is shaping more sensitive and responsive monitoring

Every day rail maintenance crews face the challenge of ensuring that the power systems for operating signalling systems are free from faults to ensure that there is no interruption of service.

Faults inevitably occur due to a natural degradation of the infrastructure or other common causes such as rodent damage or water ingress.

The maintenance teams are set targets to rectify those faults – but they can only be achieved by deploying technology which helps them to identify earlier and more accurately where those faults are occurring.

The ideal scenario is technology which gives them early warning of faults which are not yet critical – providing a breathing space to plan and deliver predictive and preventative maintenance solutions.

The new standard for those products from June 2017 is detailed in the Network Rail Level 2 Product Specification: Insulation Monitoring and Fault Location Systems for use on Signalling Power Systems.

It sets out Network Rail’s vision for Insulation Monitoring Devices (IMDs) and Insulation Fault Location Systems (IFLS) comprising their system requirements, network monitoring architectures, and IMD and IFLS capabilities along with requirements for portable models, and the integration of devices with Network Rail’s Intelligent Infrastructure systems.

The document explains that the changes are designed to drive the development of new technology to provide additional parameters, for example capacitance to assess the safety of the Signalling Power System and further reduce the risk of electric shock.

It also states that it wants to improve detection of signalling power cable failure before it interrupts a power supply leading to loss of signalling, and improve the ability to pinpoint the position of faults to drive reductions in time and the disruption caused by signalling power cable faults.

Network Rail believes better monitoring will ultimately drive reductions in OPEX and CAPEX costs, enable the deployment of alternatives to more expensive auto reconfiguration systems, and extend the life of existing cables and networks.

Bender UK is currently the only UK supplier with approved products to meet this requirement and the company has worked closely with its principal contacts at Network Rail to shape the development of the technology to meet the new standards.

One of the key requirements is the need for enhanced sensitivity to narrow down the area where a fault is occurring.  Bender has responded with the new upgraded RS4 integrated insulation monitoring and earth fault location system.

It is more sensitive that the widely deployed RS3 and enables ‘first fault’ location (100 kilo ohms) before the fault becomes critical. It also measures capacitance, voltage and frequency delivering more information to help assess the health of the system.

The insulation monitoring device within RS4 enables fault location at Tier 3 electrical system network level for the signalling system.

It has proved very effective in meeting the ‘Red’ requirements within the standard, which must be complied with and achieved at all times.

Earth Fault Location is the effective solution for sub-network Tier 2 monitoring to assist in locating the fault on a circuit, a key element in the Amber requirements within the new standard.

The RS system continually monitors insulation values to show real time status of the power system. When the insulation value (IR) drops, the system records the fault and the Bender units put a test current signal or pulse into the system which is pulled to earth at the point where a fault exists.

The new RS4 unit is much smaller and more compact to make it easier to incorporate in the panels serving systems operating at a lower power rating.

Later this year, a variant will be available tested and ready for easy ‘plug and play’ installation and commissioning alongside existing power infrastructure systems up to AC650V.

Integration of RS4 devices with Network Rail’s Intelligent Infrastructure systems is achieved by incorporating GSM-enabled data loggers equipped for real time communication to deliver immediate notification of insulation faults which are identified by the system.

Once the fault has been identified on a specific circuit, the portable EDS 3090 case is used in the field to pinpoint the location trackside by monitoring the pulse on the cable.  In line with the new standard Bender has made significant improvements to the EDS 3090 unit which has more sensitive clamps and receiver technology.

The unit is self-powered through connection to the trackside signal electrical network.  It delivers live monitoring of the system status to immediately indicate if there is an earth fault and the status of the insulation.  The portable unit can also be used to provide independent verification of the RS system performance.

The new RS4 is just part of the huge Bender rail offering which includes power quality meters, insulation monitoring devices and monitoring software for rolling stock, signal power, points heating and trackside use.

Tony Edwards isIndustrial Sales Manager at Bender

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