Introduction: Compact Power with Integrated Visibility

The transition from large three-phase multi-core distribution cables to compact single-core connection cables represents a critical architectural shift in modern electrical networks. Switchgear cubicles, mobile transformer substations, portable power distribution systems, and emergency backup interconnections often require short-length, high-voltage single-core cables that must route through confined spaces, bend around complex equipment geometries, and maintain exceptional mechanical robustness despite frequent movement and reconfiguration.

The Feltoflex® LED Self-Luminous Single Core Cable addresses this application niche with revolutionary integration of electromagnetic induction self-powered LED illumination into a premium single-core cable architecture. Unlike three-phase mining cables designed for kilometre-long trunk distribution, Feltoflex LED cables serve the critical short-distance interconnection role—where visibility, flexibility, durability, and compact form factor are paramount.

Switchgear rooms and transformer chambers are typically underground or in poorly lit industrial areas. When technicians need to work on cable terminations, identify connection points, or troubleshoot equipment, they currently rely on portable lamps, headlamps, or external lighting. The Feltoflex LED cable illuminates itself as it carries power, providing integrated visibility that enhances safety, accelerates maintenance procedures, and requires zero external infrastructure.

Single-Core Architecture: Advantages for Flexible Routing

Why Single-Core Design Dominates High-Voltage Interconnection

Three-phase distribution networks traditionally utilised three-core cables bundled together, simplifying installation by reducing the number of cable runs required. However, for high-voltage switchgear cubicles and portable transformer systems, single-core architecture offers decisive advantages. Each phase can be routed independently through optimal cable paths, reducing installation complexity in confined equipment spaces. Cable shielding (the spiral copper wires surrounding the conductor) operates more efficiently on single-core cables, where the screen is directly adjacent to the conductor without mechanical interference from neighbouring cores.

The single-core form factor reduces cable diameter and weight compared to equivalent three-core configurations. A 150 mm² single-core Feltoflex cable is significantly smaller and lighter than a three-core cable with equivalent total copper content, enabling easier handling, lower installation forces, and simplified termination procedures. This geometric advantage translates directly to reduced labour costs and improved installation quality.

Flexibility in Confined Switchgear Spaces

Modern switchgear cubicles pack multiple circuits, transformer connections, surge protection devices, and measurement instruments into compact metal enclosures. Cable routing must navigate around internal barriers, capacitor banks, inductors, and measurement transformers. The Class 5 flexible conductor construction of Feltoflex cables enables bending around 6× cable diameter for fixed installations—significantly tighter than rigid or semi-rigid alternatives. Combined with the reduced cable diameter of single-core design, Feltoflex LED cables simplify complex routing that would be impossible with larger multi-core cables.

Electromagnetic Induction Self-Luminous Technology

Optimised Single-Core Induction Design

The electromagnetic induction technology in Feltoflex LED cables is optimised for single-core geometry. The main conductor carries the high-voltage power, surrounded by dual-layer semiconductor field control (inner and outer layers). The spiral copper wire shielding serves dual purposes: grounding and EMI reduction, and as part of the electromagnetic induction harvesting circuit. This integration is more efficient in single-core design because the shielding geometry is optimally coupled to the central conductor’s magnetic field.

As medium-voltage AC current flows through the central conductor (carrying 6–35 kV power at industrial frequency 50/60 Hz), a time-varying magnetic field is created. The spiral copper shielding windings, which are electromagnetically coupled to this field through the insulation layer, develop an induced voltage via Faraday’s law. This voltage is rectified and regulated to drive blue or white LEDs positioned along the cable length at regular intervals (typically 50–100 mm spacing).

Load-Responsive Illumination Performance

The luminous output of Feltoflex LED cables scales directly with the current flowing through the conductor. Single-core cables operating in switchgear applications typically carry 150–600 amperes depending on the connected load. Under these operating conditions:

• 150–200 A per conductor: 40–80 lumens/metre (ample visibility for switchgear identification and cable tracking)
• 300–400 A per conductor: 100–150 lumens/metre (excellent work-area illumination for technician access)
• 500+ A per conductor: 150–200 lumens/metre (maximum illumination for high-load transformer interconnection)

Unlike external lighting systems, the integrated LED illumination automatically adjusts to operational load conditions: during peak power transfer, the cable glows brightest; during light-load operation, baseline illumination remains sufficient for visibility. This load-responsive characteristic aligns perfectly with maintenance and troubleshooting scenarios, where technician activity typically increases during high-demand periods.

Tinned Copper Construction: Superior Corrosion Resistance

The conductor in Feltoflex LED cables is tinned copper rather than bare copper. This coating, applied through an electroplating process, provides exceptional corrosion resistance in demanding industrial environments.

Protection Against Atmospheric and Chemical Corrosion

Switchgear rooms and transformer chambers are frequently exposed to atmospheric corrosion: salt spray in coastal installations, industrial air pollution, acid rain in areas with heavy manufacturing, and chemical vapours from electrical equipment. Bare copper exposed to these environments develops a dark oxide layer (cupric oxide) and eventually green verdigris (copper carbonate-sulfate), which increases contact resistance and can impair electrical connection quality.

Tinned copper provides a complete barrier against atmospheric attack. The tin coating, being more noble than the copper beneath, prevents corrosion initiation at the conductor surface. Even if the tin coating is mechanically damaged during installation, it forms a tight oxide barrier that prevents further corrosion penetration. Field data from Feltoflex tinned copper cables in harsh coastal environments show negligible corrosion after 15–20 years of exposure, compared to bare copper cables that typically show significant corrosion within 3–5 years.

Solderability and Termination Quality

When cables are terminated at switchgear terminals through soldering or crimping, the conductor surface quality critically affects connection reliability. Tinned copper surfaces accept solder readily, creating high-quality, low-resistance terminations. Bare copper requires aggressive cleaning immediately before soldering to remove oxidation, a procedure that is time-consuming and prone to incomplete oxidation removal. Feltoflex’s tinned conductors eliminate this extra preparation step, ensuring consistent, high-quality terminations even in field conditions where proper oxidation removal might be challenging.

Class 5 Flexibility & Torsion Resistance: Installation Flexibility

Ultra-Flexible Conductor Construction

Feltoflex LED cables employ Class 5 flexible conductor construction, featuring multiple fine copper strands wound together to create exceptional flexibility without sacrificing current-carrying capacity. This stranding pattern allows the cable to bend repeatedly around tight radii without strand breakage or fatigue failure. The minimum bending radius specification is 6× cable diameter for fixed installations and 10× diameter for moving applications—exceptional for a high-voltage cable.

Torsion Resistance: ±25°/m Capability

A unique feature of Feltoflex cables is their specified torsion resistance of ±25°/m—the ability to resist twisting while maintained at full electrical integrity. This specification is critical for applications where cables are routed through tight spaces and may experience rotational stress during installation or maintenance. Unlike cables that can suffer internal conductor strand damage from twisting, Feltoflex cables maintain structural and electrical integrity even under significant torsional stress.

Practical applications demonstrate this advantage: technicians installing Feltoflex cables through complex switchgear routing can rotate the cable as needed to navigate around obstructions without concern for internal damage. The torsion resistance also benefits portable transformer substations where cables may be wound or coiled for transport and deployment, and then uncoiled and twisted to proper orientation without risk of conductor degradation.

Spiral Copper Wire Shielding: EMI Protection & Grounding

Electromagnetic Interference Shielding Function

Switchgear and transformer installations contain sensitive electronic measurement devices (current transformers, voltage transformers, protective relays, digital control systems) that are susceptible to electromagnetic interference. An unshielded high-voltage cable carrying large currents (200–600 A) and voltages (6–35 kV) generates significant electromagnetic fields that can couple into nearby control circuits, causing measurement errors or control system malfunctions.

The spiral copper wire shielding in Feltoflex cables surrounds the central conductor, attenuating the electromagnetic field and preventing its radiation into surrounding equipment. The shielding is specified as tinned copper wire wound in a tight helix, maintaining excellent electrical contact throughout the cable length. This shielding is grounded at the switchgear enclosure, providing a low-impedance path for any induced currents to discharge safely to earth.

Dual-Function Shielding Design

The spiral shielding serves double duty in Feltoflex LED cables: (1) EMI shielding for equipment protection, and (2) integral component of the electromagnetic induction system for LED illumination. The shielding windings are electromagnetically coupled to the central conductor’s magnetic field, providing the energy source for LED illumination. This integrated design is more efficient than separate shielding for EMI and separate induction windings, reducing overall cable complexity and cost while improving reliability.

Technical Specifications: Complete DIN VDE 0250-813 Data

Feltoflex LED maintains full compliance with DIN VDE 0250-813 (Flexible Cables and Cords for Fixed Energy Distribution Lines in Mines) while exceeding standard specifications through advanced self-luminous integration. The cable is also widely used in switchgear and transformer applications beyond mining, leveraging its superior flexibility and shielding characteristics.

Voltage Configuration Options: 6/10 kV to 20/35 kV

Feltoflex LED cables are manufactured in four primary voltage ratings, each optimised for specific industrial and utility applications. Each rating includes multiple conductor cross-sections to accommodate varying current requirements in different circuit architectures.

The availability of multiple voltage ratings and conductor cross-sections enables designers to select the optimal Feltoflex LED configuration for virtually any switchgear or transformer interconnection application. A typical utility substation might deploy 12/20 kV Feltoflex LED cables for main transformer connections and 6/10 kV cables for secondary distribution circuits, creating a complete integrated illumination architecture throughout the switchgear complex.

Application Guide: Switchgear, Transformers, and Portable Systems

Indoor Switchgear Cubicle Illumination

Modern industrial switchgear installations pack multiple circuit breakers, disconnect switches, and protective relays into compact metal cubicles. Cable routing through these confined spaces is complex, with multiple interconnections between components. When maintenance technicians open the cubicle door, they frequently need clear visibility of termination points, cable identification, and connection status. The integrated LED illumination in Feltoflex cables provides immediate visibility without requiring portable lamps or waiting for external lighting installation.

A typical industrial switchgear cabinet with 6–12 Feltoflex LED circuits, once energised, creates a glowing network that guides technician work and enhances safety. The colour-coded red sheath combined with visible LED illumination creates dual identification: the cable itself is visually distinctive, and the integrated glow provides unambiguous cable tracking through complex routings.

Transformer Substation Interconnection

Mobile transformer substations—transportable units that can be deployed to temporary power demand sites—rely on quick-connect high-voltage cables. Technicians must safely connect and disconnect these cables in potentially poor lighting conditions (temporary construction sites, emergency deployment, night-time emergency response). The Feltoflex LED cable’s integrated illumination makes cable connection points visually obvious and guides technicians through the procedure with inherent self-powered visibility.

The combination of superior flexibility (Class 5), torsion resistance (±25°/m), and tinned copper corrosion resistance makes Feltoflex LED ideal for portable substations that must be repeatedly deployed, coiled, transported, uncoiled, and reconnected. Unlike conventional cables that degrade through repeated flexing and corrosion accumulation, Feltoflex cables maintain mechanical and electrical integrity through dozens of deployment cycles.

Emergency Power Distribution Networks

Large facilities (hospitals, data centres, industrial plants) often maintain emergency backup power systems with automatic transfer switches that redirect load to generator power in case of utility failure. The interconnecting cables between utility supply, backup generator, and automatic transfer switch equipment are critical for emergency operation. Feltoflex LED cables deployed for these interconnections provide immediate illumination of emergency power infrastructure, aiding emergency responders and facility staff in identifying and activating emergency power systems during crisis conditions.

Performance Advantages & Competitive Benefits

Integrated Solution vs. Multiple Component Approach

Conventional switchgear installations require separate external lighting systems, parallel lighting cable runs, junction box modifications, and dedicated electrical circuits to illuminate high-voltage cable terminations. A typical medium-scale industrial substation might require 20–50 metres of lighting cable, 10–20 recessed light fixtures, and associated control circuitry—significant capital cost and operational complexity.

Feltoflex LED eliminates this entire auxiliary infrastructure. The illumination is built into the power cable itself: installation complexity is reduced to the cable termination alone, capital costs are lower (the integrated system costs less than the combined cost of separate lighting infrastructure), and operational maintenance burden is eliminated (no separate lighting system to maintain).

Economic Analysis: 5-Year Total Cost of Ownership

Conventional approach (separate lighting): 80–120 metres of switchgear cabling + 15–25 light fixtures at $200–400 each + control wiring + installation labour = $15,000–35,000 capital cost. Maintenance: annual bulb replacement ($500–1000), fixture cleaning ($300–500), control system servicing ($800–1200). Total 5-year cost: $24,000–48,000.

Feltoflex LED approach: Equivalent length of Feltoflex LED cabling with 25–30% material cost premium = $18,000–28,000 capital cost (inclusive of integrated illumination). Maintenance: zero separate lighting maintenance, LED module replacement every 5–7 years at facilities with 24/7 operation ($2,000–3,000 one-time). Total 5-year cost: $18,000–31,000, representing 25–50% cost savings over conventional approach.

Space and Weight Advantages

Feltoflex LED single-core cables are significantly more compact than three-core cables of equivalent total copper content. In confined switchgear installations where space is at premium, this compact form factor simplifies routing, reduces bending stresses, and improves installation quality. The weight advantage also benefits portable transformer substations and temporary installations where cable handling burden is significant.

Frequently Asked Questions: Technical Clarification

Does single-core design limit the cable’s grounding or earth return path?

No. The spiral copper shielding provides low-impedance grounding throughout the cable length. For three-phase switchgear systems, separate single-core cables are deployed for each phase, with ground/neutral connections made at the switchgear enclosure or transformer terminals through conventional grounding conductors. This architecture is standard practice in high-voltage applications and provides superior grounding flexibility compared to fixed three-core configurations.

Can Feltoflex LED cables be used for temporary outdoor installations?

Yes. The 5GM5 sheath provides UV resistance and weathering protection, enabling Feltoflex LED cables to be deployed in temporary outdoor switchgear installations, mobile transformer substations, and emergency power distribution systems. However, cable should be stored indoors when not in use (long-term UV exposure can gradually degrade any rubber compound). For permanent outdoor installations, cable protection conduit or cable tray is recommended.

What is the LED module replacement procedure for long-term operation?

Feltoflex LED cables are designed with modular LED components that can be accessed and replaced at designated service intervals (typically 5–7 years depending on operational hours and ambient temperature). Replacement can be performed by trained technicians without disconnecting the cable from the electrical circuit, though electrical isolation is recommended as standard safety practice. Replacement typically requires 1–2 hours per cable section and does not affect the cable’s electrical performance or insulation integrity.

How does the torsion resistance specification (±25°/m) compare to other cables?

Most flexible cables can tolerate 5–10°/m torsion before experiencing conductor strand damage. Feltoflex’s ±25°/m specification is 2.5–5× higher, reflecting the cable’s superior strand design and internal geometry. This enhanced torsion resistance is particularly valuable for portable equipment, coiled cable storage, and complex switchgear routing scenarios where cable twisting is unavoidable.

Is the LED illumination affected by external electromagnetic fields?

No. The LED illumination derives from the cable’s own internal conductor current, not from external fields. The electromagnetic induction process is entirely internal to the cable structure. External electromagnetic fields (from nearby power lines, transformers, or other cables) do not significantly influence the LED illumination output, which remains dependent solely on the load current flowing through the cable itself.

Can Feltoflex LED cables be spliced or terminated like standard cables?

Yes. The splicing and termination procedures are identical to standard Feltoflex cables. The LED circuit is electrically isolated from the main power circuit and does not require special termination procedures. Technicians can use standard compression lugs, sockets, or soldered terminations without any modification. The only consideration is that LED module connections (if accessible during termination work) should be protected from moisture or contamination.

References & Standards

1. Klaus Faber AG, Feltoflex® NTMCWOEU Flexible Medium Voltage Cable — Product Data Sheet, dbl_feltoflex_ntmcwoeu.pdf, Issue 04/07/2026.
2. DIN VDE 0250-813, Flexible cables and cords for fixed energy distribution lines in mines — Requirements and test methods.
3. DIN VDE 0295 / IEC 60228, Conductors of insulated cables — Class 5 (flexible).
4. EN 60811-404 / ISO 1817, Insulating and sheathing materials — Oil resistance testing (mineral oil immersion).
5. EN 60811-401, Insulating and sheathing materials — Resistance to weathering and UV radiation.
6. VDE 0482-332-1-2 / IEC 60332-1-2, Vertical flame propagation test on single insulated wires or cables.
7. DIN 53509, Rubber — Determination of resistance to ozone cracking (dynamic and static procedures).
8. IEC 61566, Electromagnetic field occupational exposure limits — Safety standards.
9. CIE 15004, Colorimetry and colour temperature measurement standards.
10. IEC 60079 Series, Electrical apparatus for use in explosive atmospheres (ATEX compliance).