What’s the Problem?
UK Power Networks’ London underground network contains approximately 41,000 cable pits. Cable pits are underground chambers, usually located beneath the pavement, that provide access to electricity cables for inspection, maintenance and repair.
These pits are an important part of the underground network because they allow engineers to reach cable assets without exposing long sections of cable. This supports routine work and helps teams respond when faults occur.
Cable pits can contain a mixture of low voltage and high voltage cables. If a cable fault occurs inside a pit, it can produce a blast and flames. This means a single cable fault can affect nearby cables and equipment, increasing the scale of the incident.
Cable pits vary significantly in size from between 17m3 to 1m3. In smaller cable pits, sand is used to fill the void and help prevent/suppress damage. However, in larger pits, the use of sand is not practical in view of the volume required. If the issue is not addressed, cable faults in larger pits may continue to cause avoidable damage to nearby cables and equipment, making repairs more complex and increasing disruption to network operations.
There are currently no fire suppression systems that can provide the guarantee necessary to suppress any fire in a cable pit.
Preferred Output
UK Power Networks is seeking a fire suppression system that can protect cables and equipment inside larger cable pits where sand filling is not practical.
The solution should detect fire inside a cable pit if a cable fault occurs and extinguish the flames before other cable circuits are affected.
The solution must be suitable for use around electrical assets and capable of operating inside a brick-built cable pit.
The preferred solution should be sufficiently adaptable to accommodate cable pits of varying dimensions.
The solution should:
- Detect fire inside a cable pit following a cable fault
- Extinguish flames before other cable circuits are affected
- Use a suppression method that is compatible with electricity
- Be self-powered
- Be capable of being disabled or removed when access is required
- Be robust enough to withstand a moderate blast
- Have a low environmental impact and avoid greenhouse gases.