LSZH Cable for Metro and Tunnel Projects

Metro systems, tunnels, airports, and large public buildings need safe electrical networks. These sites often have enclosed spaces, long evacuation routes, and high passenger numbers. Therefore, smoke and corrosive gas from burning cables can create a major risk.

An LSZH cable uses low smoke zero halogen materials. When exposed to fire, the cable produces less smoke and fewer corrosive gases than a standard PVC cable.

Shenghua Cable Group manufactures LSZH power cables, fire-resistant cables, control cables, and other special cables for infrastructure and industrial projects. The company supports EPC contractors, distributors, system integrators, and project owners with custom cable structures and bulk project supply.

Why Public Infrastructure Uses LSZH Cable

In an open area, smoke can disperse more easily. However, smoke may collect quickly inside a tunnel, station, control room, or underground facility.

Dense smoke can reduce visibility. It can hide exit signs and make evacuation more difficult. Corrosive gases can also damage control panels, communication devices, servers, and other electrical equipment.

For this reason, project designers often select low smoke zero halogen cable for:

• Metro stations
• Railway tunnels
• Road tunnels
• Airports
• Hospitals
• Data centers
• High-rise buildings
• Shopping centers
• Theaters
• Power stations
• Control rooms
• Emergency systems

The final cable specification should match the building type, cable route, electrical load, and local fire safety requirements.

What Is a Low Smoke Zero Halogen Cable?

A low smoke zero halogen cable uses insulation or sheath compounds that contain no halogen-based materials within the limits of the required test.

During fire exposure, these materials release less dense smoke than common PVC compounds. They also limit corrosive halogen acid gas.

However, LSZH describes smoke and gas performance. It does not automatically mean that the cable can maintain circuit operation during a fire.

A project may require an LSZH cable with one or more added properties, such as:

• Flame retardancy
• Fire resistance
• Circuit integrity
• Mechanical protection
• Water resistance
• Oil resistance
• Electromagnetic shielding

Therefore, buyers should list each required property in the cable specification.

LSZH, Flame-Retardant, and Fire-Resistant Cables

These terms describe different cable functions.

An LSZH cable limits smoke and halogen gas emissions. A flame-retardant cable limits flame spread along the cable. A fire resistant cable helps keep the circuit operating for a stated period during fire exposure.

The phrase “flame resistant and retardant” often appears in general sourcing requests. However, buyers should replace broad wording with exact test requirements before placing an order.

A fire rated electrical cable may combine LSZH, flame-retardant, and circuit integrity properties. Still, the test report should confirm each claimed performance.

This distinction matters because a cable may pass a smoke test but not a circuit integrity test. It may also resist flame spread without continuing to carry power during a fire.

Cable Construction for Metro and Tunnel Systems

A typical LSZH power cable may use a copper conductor, XLPE or halogen-free insulation, inner covering, armor, and an LSZH outer sheath.

For critical emergency circuits, the design may also include mica tape around the conductor. Mica tape forms a heat-resistant barrier and helps protect electrical insulation during fire exposure.

Common construction options include:

• Class 1, Class 2, or flexible copper conductor
• XLPE or LSZH insulation
• Mica tape fire barrier
• Single-core or multicore design
• Steel tape armor
• Steel wire armor
• Copper wire shielding
• LSZH inner covering
• Black or custom-color LSZH sheath

Armor can protect cables installed in utility tunnels, underground ducts, and areas with a high risk of mechanical damage. Meanwhile, shielding can help control electrical interference in signal and monitoring circuits.

Shenghua can adjust these elements according to the approved cable schedule.

Standards Buyers Should Review

A professional cable inquiry should list the required standards. Different tests measure different parts of cable fire performance.

Common standards may include:

• IEC 60332 for flame propagation
• IEC 60754 for halogen acid gas
• IEC 61034 for smoke density
• IEC 60331 for circuit integrity
• IEC 60502 for power cable construction
• Project-specific BS or national standards

IEC 61034 measures the density of smoke produced by burning cables under defined conditions. Meanwhile, IEC 60754 evaluates gases released during cable combustion.

IEC 60331 applies when a cable must maintain circuit integrity during fire exposure. Therefore, it may be required for emergency pumps, lighting, alarms, and smoke control systems.

Buyers should confirm the exact standard, test method, and cable model before approving production.

LSZH Cable Applications in Metro Projects

A metro project may use several cable types. Power cables distribute electricity, while control and instrument cables connect operating and monitoring systems.

LSZH cable may support:

• Station power distribution
• Platform lighting
• Emergency lighting
• Ventilation systems
• Smoke extraction fans
• Fire alarm circuits
• Passenger information systems
• Communication equipment
• Escalator controls
• Signaling equipment
• Equipment rooms
• Backup power systems

Not every circuit needs the same cable construction. For example, an emergency fan circuit may require fire survival performance. A communication circuit may need shielding and low smoke materials.

Therefore, EPC teams should separate cable requirements by circuit function.

Selecting Tunnel Cable Specifications

Tunnel cable selection begins with the operating environment.

Engineers should review:

• Rated voltage
• Electrical load
• Conductor size
• Number of cores
• Cable route
• Installation method
• Ambient temperature
• Moisture exposure
• Mechanical stress
• Required bending radius
• Smoke density limits
• Halogen gas limits
• Flame-retardant class
• Circuit survival time
• Armor and shielding needs

Cable weight and drum length also matter. Large drums may reduce the number of joints, but they can be difficult to move through narrow access areas.

As a result, cable length planning should consider the route, joint positions, transport limits, and installation equipment.

Custom Manufacturing for Project Orders

Standard cables do not meet every infrastructure specification. A project may require a special core configuration, sheath color, armor type, printing format, or drum length.

Shenghua supports custom cable manufacturing based on technical documents and project drawings. Available options may include:

• Copper conductor sizes
• Customized core numbers
• XLPE or LSZH materials
• Mica tape barriers
• Armored cable structures
• Shielded control cable
• Custom sheath colors
• Meter marking
• Project identification
• OEM branding
• Specified drum lengths
• Export packaging

Clear technical approval before production helps reduce specification changes and delivery delays.

Quality Control and Documentation

LSZH performance depends on both material selection and stable production. Therefore, cable manufacturers must control the conductor, insulation, fire barrier, sheath, and finished dimensions.

The inspection plan may include:

• Conductor resistance testing
• Insulation thickness checks
• Voltage testing
• Insulation resistance testing
• Cable diameter inspection
• Sheath surface inspection
• Flame propagation testing
• Smoke density testing
• Halogen gas testing
• Cable marking and length checks

For B2B projects, Shenghua can prepare technical data sheets, construction drawings, inspection records, packing lists, and related product documents.

Buyers should request reports for the exact cable structure offered. A report for a different model may not prove that the proposed cable meets the project specification.

Information to Include in Your Inquiry

To receive a clear proposal, buyers should provide:

• Project name and application
• Cable type
• Rated voltage
• Conductor size
• Core quantity
• LSZH requirements
• Flame-retardant requirements
• Fire resistance requirements
• Armor or shielding type
• Applicable standards
• Total cable length
• Drum length
• Destination country
• Required delivery schedule

If the final model is not confirmed, buyers can send the cable schedule, tender document, or engineering drawing for review.

Partner With Shenghua Cable Group

Founded in 1997, Shenghua Cable Group produces cables for power transmission, buildings, transportation, mining, marine, renewable energy, and industrial systems.

Its product range includes LSZH cables, fire-resistant cables, XLPE power cables, armored cables, control cables, instrument cables, railway cables, and other custom products.

For a metro, tunnel, airport, hospital, or public building project, contact Shenghua Cable Group with your cable schedule and technical requirements.