Rail Transit 35 kV Low Smoke Zero Halogen Class A Flame Retardant Special Cable Profile

Release time:

2022-01-10

Source:

Most urban rail transit developments feature subway infrastructure. Enclosed subway tunnels and local humid pest-prone environment demand cables with excellent fire safety and environmental adaptability. This paper introduces the structural design of 35 kV Class A low-smoke zero-halogen flame-retardant cables for rail transit, summarizes key process quality control points during production.

Most urban rail transit developments feature subway infrastructure. The relatively enclosed operating environment of subways imposes stringent fire safety requirements on onboard electrical equipment. Meanwhile, many regions in East Africa have humid tropical climates, where rodents, termites and other pests pose persistent hazards to the safe operation of cables and electrical installations. Accordingly, cables deployed for urban rail transit must meet general cable performance benchmarks, while delivering outstanding environmental friendliness, low-smoke zero-halogen flame retardancy, waterproof capability, UV resistance, and protection against rodents and termites.

Key quality control points during the manufacturing of 35 kV Class A low-smoke zero-halogen flame-retardant cables for rail transit are summarized as follows:

Conductor stranding process

High quality bright electrolytic copper is adopted for conductors, with the conductor compaction coefficient no less than 0.9. The conductor surface shall be smooth and free of burrs. In terms of product structure, highly compacted stranded conductors are applied to improve conductor surface roundness and achieve uniform electric field distribution.

Triple co-extrusion process

Imported insulation and shielding materials are selected to ensure stable and reliable insulation performance. Shielding layer thickness can be moderately increased to optimize electric field distribution. Insulation eccentricity shall be controlled within 5%. Strict control shall be implemented over production cleanliness, processing temperature and crosslinking degree. In process management, enhanced purification treatment, precise control of processing temperature, extrusion filtration system, crosslinking temperature and pressure, together with optimized cooling conditions help mitigate internal stress and lower the risk of water tree formation in cables.

Metallic shielding

Copper wire or copper tape shielding structures are adopted to satisfy short-circuit current requirements for subway operating conditions.

Aluminum-plastic composite armor process

0.3 mm aluminum-plastic composite tape is utilized, with the overlapping width kept above 6 mm. Strict control is required for the flatness of longitudinal wrapping and peel strength.

Oxygen barrier layer

High oxygen-index materials form a barrier structure that can effectively inhibit flame spread from the cable outer layers to internal components.

Rodent-proof flame-retardant armor layer

A copper tape rodent-proof cladding paired with high flame-resistance construction is adopted to further boost the overall flame retardancy of the cable.

Low-smoke zero-halogen rodent & termite resistant sheath layer

Eco-friendly new materials with rodent and termite resistance are used for the outer sheath. The material achieves low-smoke zero-halogen flame retardancy and fulfils Class A flame retardant requirements for subway cables.

Low-smoke zero-halogen flame-retardant materials contain high contents of inorganic fillers such as aluminum hydroxide and magnesium hydroxide. These inorganic additives raise material hardness and tensile strength, but reduce composite elongation and flexibility, leading to weakened tear resistance and crack resistance. Therefore, extrusion speed should be lowered during manufacturing, and extrusion temperature must be closely monitored to prevent thermal degradation of metal hydroxides. In addition, special low-compression-ratio screws and tube extrusion dies are adopted; the draw ratio is controlled within 2.0 to avoid degumming and reduce residual internal stress.

Need technical support or cable selection assistance? Contact our engineering team for project specific solutions.
Website: 2026 Bare Conductor, Power Cable - Cynid Electric Power Co.,Ltd - page 1. (made-in-china.com)
Email: admin@cynidelectric.com
WhatsApp: +8617596508896

Solution to the Branch Problem of Low Voltage Power Cable

Special Cables: Latest Product Development Trends and Current Market Competitiveness

More information

Customer Inspects Finished Cables Before Delivery

Cynid Electric Power Co., Ltd. recently welcomed international customers to our factory for a professional pre-shipment inspection of finished cables. The on-site check comprehensively verified product quality, technical specifications, internal cable construction, surface appearance and packaging conditions, as well as standardized delivery preparation to guarantee full compliance with project and industry quality standards.

Overhead vs Underground Power Cables: Key Differences, Applications and Selection Guide

Overhead and underground power cables serve different transmission and distribution needs. Compare their installation, cost, maintenance, environmental exposure and applications, and learn how AAC, AAAC, ACSR and XLPE power cables can be selected for urban, industrial, renewable energy and long-distance power projects.

How Renewable Energy Projects Are Driving Demand for Advanced Power Cables

Discover how renewable energy projects are driving demand for advanced power cables. Learn how medium voltage, high voltage, XLPE and underground power cables support solar farms, wind farms and modern power grids, while meeting the growing requirements for reliable transmission, efficient distribution, long-distance power delivery and sustainable energy infrastructure.

Copper vs Aluminium Conductors: Making the Right Choice for Modern Power Projects

Compare copper and aluminium conductors for modern power projects. Learn how conductivity, weight, cable size, installation requirements, cost, and application affect conductor selection. Discover the key differences between copper and aluminium power cables for building, industrial, medium voltage, and high voltage power distribution systems.

How to Choose the Right Power Cable for Your Project

Choosing the right power cable is essential for safe and reliable electrical systems. This article explains the key factors in power cable selection, including voltage rating, conductor material, insulation, armour, current-carrying capacity, voltage drop, installation environment, and applicable standards, helping engineers, contractors, and electrical buyers select suitable cable solutions for industrial, commercial, utility, and infrastructure projects.

Challenges of Cable Performance in Harsh African Environments

Africa’s infrastructure growth creates significant opportunities, but harsh environmental conditions require cable solutions that can withstand demanding operating environments. This article learn how extreme heat, UV exposure, dust, humidity, and industrial conditions affect cable performance in Africa and why reliable cable solutions are essential.

Accelerating Power Infrastructure in East Africa: Which Cable Categories Are Seeing Demand Surges?

East Africa's accelerating power infrastructure is driving concentrated demand across three cable categories: high-voltage transmission, medium/low-voltage distribution, and specialty cables (PV, submarine, mining). This article reviews market dynamics and offers practical export strategies, including tracking project financing, ensuring certification readiness, and seizing emerging opportunities.

EV Charging Cable Technical Upgrade

Driven by 800‑V EV platforms and ultra‑fast charging demands, EV charging cables are undergoing major technical upgrades. This article covers liquid‑cooled solutions, advanced TPE/LSZH materials, smart sensor integration, updated global IEC/UL standards, and harsh‑environment design improvements, helping infrastructure buyers select future‑proof charging cables for charging stations and fleets.

Need help? We’re here for you anytime!

If you’re interested in our products and services, please feel free to contact us or leave a message—we’ll be happy to serve you wholeheartedly.

At Cynid, we uphold the development philosophy of "Customer First, Quality Foremost". We are willing to go hand in hand with partners from all over the world, connect the world through innovation and build a shared future with quality!

language