installed using Class II and, over the next two years, a significant
amount of signalling power system renewals will replace Class I with
Class II. This includes the West Coast power signal boxes north of
Crewe.
Location case and equipment buildings will be provided with
Class II switchgear housings and Class II signalling transformers,
with approved conduit and fittings, will be used to provide
supplementary insulation and protection to wiring between
the items of Class II equipment. Distribution equipment can be
connected by either two-core enhanced unarmoured cable or
two-core armoured solid-bonded cable, provided that the armour
is not allowed to traverse the Class II-fitted functional supply
points. However, extensive testing identified that an enhanced
unarmoured cable option presents the highest overall level of
safety.
The overall Class II strategy will result in improvements to
personnel safety, compliance with standards, greater tolerability
to DC corrosion, simplified earthing and bonding in AC electrified
areas, along with reduced capital costs, better reliability, less
maintenance and the ability to integrate into legacy systems.
To support the strategy, Network Rail has issued a range of new
standards. The key standards are issued as both signalling and
electrification/plant (SIGELP) standards, are designed to be user
friendly and to inform the right person what they need to do to
control the risk.
The strategy was accepted by the ORR and the Improvement
Notice was closed down on 22 August 2017, with the ORR
monitoring the situation.Thanks to Graeme Christmas, Martin O’Connor and especially
Graeme Beale, of Network Rail, for their help with this article.The challenge of implementation...
In history, there are often moments or circumstances that turn necessary actions
into unforeseen opportunities. As a result of the improvement notice, the
introduction and roll out of retrofittable Class II as a compliance strategy now
provides Network Rail with the tools and the methodology to deliver widespread
enhancements to all signalling power supplies, with minimal disruption.
As with most new systems and technology, one key challenge is its
implementation within the existing infrastructure. This challenge is one of
understanding and joined-up process driven by survey, integrated design,
option selection and efficient deployment. It has been discovered that, over the
past four to five years, this package of works is ideally suited to support Network
Rail’s existing route delivery teams. An example of this efficient process can be seen above.New technology born out of change!
Maintenance of the existing signalling power network places a high demand on existing human resources. Routine testing and the
assessment of the existing 650V signalling power cable presents existing maintenance teams with both safety and logistical challenges.
Cable and system monitoring technology offers a significant improvement in the management of these assets. Insulation monitoring
and fault location devices enable rapid response and proactive maintenance regimes to be implemented. The key success of the roll out
of this technology is the ability to deploy alongside the Class II retrofitting process, thereby leaving the asset in both a fully compliant
and digital-ready state.
There have already been several examples of significant infrastructure reliability improvements as a result of Class II deployment. One
is the elimination of low insulation monitoring values as a result of prescribed Class II retrofits, a second is confirmation of potential cost
savings in unnecessary cable replacement across a large section of the Thameslink Route.
Lewis Westbury - Ilecsys RailInstallation at Stenson before (left) and after rework.62 FE ATURE