Engineers in a tunnel performing maintenance

Cable assessment during planned railway maintenance

Implementing planned maintenance for railway infrastructures is a significant aspect of ensuring components continue to meet operating requirements, in line with high levels of safety set by the industry.

However, the rigorous assessment and surveillance of the cable products within the rail network is often missed. It is essential that all parties involve learn about the cable assessment considerations which should be incorporated within planned maintenance schedules for the railway to safeguard whole systems performance.

Cable conditions

The UK railway networks are undergoing major developments across the infrastructure, with several upgrades underway and planned for implementation. Examples include the HS2 high speed rail project, as well as significant upgrades to the West Coast mainline and key stations along the Northern Powerhouse Rail network. Plans also exist to reopen previously closed stations, such as some within the Midlands area, to facilitate more environmentally friendly modes of transport for passengers.

Undertaking assessment to examine the age and condition of existing cabling that supports the wider rail networks is crucial. This helps to understand the current performance of the cable products and aids planning decisions regarding replacement sections or enhancement needs to improve the infrastructure. Planning in time to identify and assess cable condition is key and should be included into maintenance schedules to ensure cabling is operating efficiently, to provide power to railway networks.

Cable performance analysis can be evidenced through enhanced testing capabilities including thermogravimetric analysis (TGA), which explores different polymeric compositions of cables in your existing infrastructure. Additionally, Fourier Transform Infrared (FTIR) analysis works by scanning the samples with an infrared light to map, fingerprint and quantify the chemical properties of the cable sample. Information gathered from these assessments can be translated into insights around what materials the cable is comprised of and how that can impact on overall performance. These tools and expertise can be invaluable to planned maintenance work on the railways.

Train operating in snowy conditions in the UK

Impacts of climate change

The changing climate is resulting in more extreme weather events which is a significant factor requiring infrastructure to be more resilient and adaptable to the changing conditions. Increasingly this is impacting the railway’s planned maintenance schedules.

  • Winter conditions: Severe storms are being experienced, often resulting in more flooding or wind damage, which has challenging effects on the railway, such as delays to services due to tracks blocked by fallen trees, snow, water, or landslides. In relation to weather conditions such as flooding on a railway track, water penetration tests check that the cable can continue to operate when submerged in water with close inspection of the cable sheathing material to ensure the conductor is protected.

Summer conditions: The summer months provide a complete contrast, experiencing progressively hotter temperatures, meaning that components are exposed to the high temperatures for longer periods of time which can affect performance. To assess cable performance in high temperature weather conditions from exposure to the sun within the railway track infrastructure, a hot pressure test checks that the cable sheathing and insulation materials are resistant to indentation when exposed to elevated temperatures.

Cable products must continue to perform under these extreme conditions and withstand weather impacts to continuously transport power and transmit data, to maintain efficient operations. Resilient components that can withstand extreme environmental conditions must be considered across all railway projects to ensure the future network is equipped to perform. To mitigate risk of cable failure there are a variety of stringent tests to assess performance characteristics and measure their suitability for use in applications, whether that be rolling stock, signalling equipment or railway station and track infrastructures.

Cables that are independently tested and approved by notified bodies, such as BASEC, undergo several rigorous tests including areas such as:

  • Electrical: Conductor tests are undertaken to measure resistance across cable joints to measure efficiency of power supply
  • Mechanical and material: To ensure cable sheathing material can withstand impacts such as movement of components during travel within carriage systems
  • Chemical: Assessing the cables ability to withstand substances such as fuel oils that the products can come into contact with through railway vehicles
  • Fire: Cables where maintained power supply is required in the event of a fire, such as emergency alarm and smoke systems in railway stations must demonstrate resistance properties when exposed to flames
  • Data transmission: Monitoring levels of electrical interference to minimise risk of failure such as data communications cables used to provide data to update digital rail departure schedule boards.
Maintenance vehicle operating on the tracks

Tunnel cable standards

Due to the railway industry being heavily regulated, there is a need to routinely review old standards, which can require updates and introductions of new standards to improve the safety of the networks. In this case, exposed cable characteristics are outlined in the updated regulation below:

Application Guide GUI/SRT TSI/2019 'Guide for the application of the SRT TSI', in accordance with Article 19(3) of Regulation (EU) 2016/796 of the European Parliament and of the Council of 11 May 2016, clause 2.3.6 states that:

‘Exposed cables shall have the characteristics of low flammability, low fire spread, low toxicity and low smoke density. These requirements are fulfilled when the cables fulfil at least the requirements of classification B2ca,s1a,a1’

New tunnel cable requirements and enforcements outline that the length of a classified tunnel and regulations that must comply has changed from 1000m to 100m. So, what impact does this have for cable considerations in tunnels? Fire safety is of the upmost importance, therefore cables must be classed a ‘fire rated’ meaning they can continue to provide power when exposed to fire conditions. To help protect workers and passengers in the event of a fire, fire alarms systems must be in place, as well as emergency lighting applications. The new requirements mean that planned upgrades will need to be undertaken to install fire rated cables into the newly classed tunnels within the network.

Electrical faults are a common cause of railway tunnel and station cabling failures, as cables can overheat, short circuit and ultimately lead to a fire. Therefore, incorporating maintenance checks as part of ongoing surveillance can help to reduce risk of failure. BASEC’s third party testing and surveillance services provides an important safety assessment for the cable’s fire performance for both resistance to fire, maintaining circuit integrity of critical systems, and reaction to fire to minimise the risk of fire spread and toxic smoke.

Key takeaways

Planned maintenance of cabling within railway networks should be incorporated into schedules as it is central to the efficiency and safety of operations, particularly as electrification of infrastructures continues to develop. Prior to installation, understanding the condition and construction of particular cable products through service assessments helps to gain a better understanding of the cable’s performance. Ongoing surveillance of cables after installation is vital to evidence that the cable has not been damaged and continues to meet industry regulations. This is particularly key to measure the characteristics in relation to extreme weather conditions that are increasingly impacting railway operations.

New and updated regulations can often require components to evidence improved characteristics. It is highly important to ensure cable products perform in line with industry developments to keep workers and passengers safe. Protect your railway operations by incorporating third party cable characteristic testing and material assessments by notified bodies such as BASEC into your existing planned maintenance schedules and be confident of cable performance.

Download your free guide to understand more about cable testing and certification for the railway industry.

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