Low Smoke Zero Halogen Power Cable

Introduction to LSZH Power Cables

Low Smoke Zero Halogen (LSZH) power cables are specialized Electrical Cables designed with safety and environmental considerations in mind. These cables are constructed using materials that emit minimal smoke and no halogen gases when exposed to fire or high temperatures. This makes them particularly valuable in environments where human safety and equipment protection are paramount.

Key characteristics of LSZH power cables include:

Smoke emission: Produces ≤ 20% optical density when tested according to IEC 61034, significantly lower than standard PVC cables (which typically produce 60-80% optical density)

Halogen content: Contains ≤ 0.2% chlorine, bromine, fluorine, and iodine by weight (compared to 30-40% in conventional cables)

Acidity: pH value ≥ 4.3 and conductivity ≤ 10 μS/mm when tested per EN 50267-2-3

Temperature rating: Typically rated for -40°C to +90°C continuous operation, with short-term overload capability up to 120°C

Flame retardancy: Meets IEC 60332-1 vertical flame test standards with self-extinguishing times under 60 seconds

Technical Specifications and Performance Data

The superior performance of LSZH cables is achieved through advanced material science. The insulation and sheathing typically use specially formulated polyolefin compounds with metal hydroxide flame retardants (usually aluminum or magnesium hydroxide at 50-65% loading by weight). These materials provide:

Dielectric strength: ≥ 20 kV/mm for insulation materials

Volume resistivity: > 1×10¹⁴ Ω·cm at 20°C

Tensile strength: 10-15 MPa for insulation, 12-18 MPa for sheathing

Elongation at break: 150-300% depending on specific compound formulation

Oxygen index: Typically 28-32 (compared to 18-22 for standard PVC)

Primary Applications of LSZH Power Cables

The unique properties of LSZH cables make them essential in several critical environments:

1. Public Transportation Systems

LSZH cables are mandated in most modern subway systems, trains, and aircraft due to their ability to maintain circuit integrity while minimizing toxic emissions in confined spaces. For example, the London Underground requires all new installations to use LSZH cables with flame spread ≤ 1.5m when tested to BS 6853.

2. Data Centers and Telecommunications

Modern Tier IV data centers extensively use LSZH cables in both power distribution and network infrastructure. The reduced smoke emission (< 20% optical density) prevents obscuration of emergency lighting and signage, while the absence of corrosive halogens protects sensitive server equipment worth millions of dollars.

3. Healthcare Facilities

Hospitals and medical centers utilize LSZH cables in critical care areas where evacuation might be challenging. The cables meet NFPA 99 requirements for healthcare facilities, ensuring that in case of fire, the emission of hydrogen chloride (HCl) remains below 0.5% by mass.

4. Offshore and Marine Applications

LSZH cables with additional oil resistance (tested to IEC 60811-404) are used in offshore platforms and naval vessels. These cables maintain flexibility at -40°C and resist degradation from saltwater exposure while meeting IMO FTP Code requirements for low flame spread.

5. High-Rise Buildings

Modern building codes in many jurisdictions (including NFPA 72 and EN 13501-6) require LSZH cables for vertical risers and emergency systems. The cables' performance in the BS 8434-2 30-minute fire test makes them suitable for evacuation routes and firefighter access areas.

Installation and Maintenance Best Practices

Proper handling and maintenance are crucial to maintain LSZH cable performance throughout its typical 25-30 year service life.

Installation Guidelines

Bending radius: Maintain minimum 8× cable diameter for fixed installations, 10× for flexible applications

Pulling tension: Limit to 50N/mm² of conductor cross-section during installation

Temperature conditions: Install only when ambient temperature is above -5°C to prevent material brittleness

Support intervals: Maximum 1.5m for horizontal runs, 1.0m for vertical runs in cable trays

Maintenance Procedures

Visual inspections: Quarterly checks for abrasion, cracking, or deformation (particularly at bend points)

Insulation resistance testing: Annual megger tests at 500V DC for LV systems (minimum 1MΩ/km)

Infrared thermography: Annual scans to identify hotspots exceeding 10°C above ambient

Cleaning: Use only pH-neutral cleaners (6.5-7.5) to prevent material degradation

Storage conditions: When not in use, store in controlled environments (15-25°C, 40-60% RH) away from UV exposure

Special Considerations

Unlike conventional cables, LSZH materials require specific attention to:

Avoid exposure to hydrocarbon-based lubricants during installation (use only silicone-based pulling compounds)

Prevent contact with PVC cables to avoid plasticizer migration that could affect material properties

Use only LSZH-compatible cable ties and markers (standard nylon ties may cause stress cracking over time)

Environmental and Regulatory Compliance

LSZH cables meet numerous international standards including:

IEC 60754-1/2 (halogen acid gas emission testing)

EN 50575 (CPR classification for construction products)

UL 1685 (vertical tray flame test)

RoHS 3 Directive 2015/863/EU compliance

REACH SVHC compliance (no substances > 0.1% w/w)