Why NSGAFOEU / NSHXAFOE Cables Matter in South Africa

South Africa’s transport, mining, and heavy-industry sectors are undergoing some of the most aggressive modernisation efforts in decades. PRASA’s ongoing commuter rail upgrades, Transnet’s freight-rail recovery strategy, and the enormous electrical loads in mining all demand medium-voltage (MV) cables that are simultaneously flexible, heat-resistant, mechanically robust, and fire-safe.

Among the wide variety of MV cable technologies available worldwide, NSGAFOEU and NSHXAFOE single-core cables have emerged as a preferred choice for systems that require reliability under vibration, moisture, oil exposure, mechanical bending, and thermal stress — conditions that are unavoidable in South Africa’s real-world environments.

Unlike traditional PVC or XLPE-insulated MV cables, these rubber-insulated, EPR-based rolling-stock cables are engineered specifically for mobile and high-vibration installations:

• Moving parts inside diesel locomotives

• Auxiliary and traction circuits

• Mining pump stations and conveyors

• Underground tunnel ducts

• Bus and rail vehicle wiring

• Switchboards requiring short-circuit-proof behaviour

South Africa’s climate magnifies these stresses:

• High heat (Northern Cape 40+°C summers)

• Dust and vibration (Transnet heavy-haul corridors)

• Oil-rich equipment (mining workshops, locomotive pits)

• Humidity (coastal rail, deep-level mines)

In these settings, NSGAFOEU and NSHXAFOE medium-voltage rubber cables offer a blend of flexibility, fire performance, and electrical integrity that PVC and XLPE cables simply cannot match.

Cable Standards and Compliance Framework

DIN VDE 0250 Part 602 — The Core Standard Behind NSGAFOEU

DIN VDE 0250-602 governs flexible rubber-insulated MV cables for rolling-stock and industrial applications. It defines:

• Stranded, highly flexible Class 5 copper conductors

• EPR insulation thickness requirements

• Chlorinated rubber outer sheath (5GM3)

• Optional copper screening for EMC-sensitive installations

• Testing for vibration, bending fatigue, and thermal shock

These parameters ensure that NSGAFOEU cables maintain insulation integrity even under continuous bending — critical in rail bogies and mobile mining machinery.

DIN VDE 0250 Part 606 — Halogen-Free NSHXAFOE

Part 606 extends the same MV cable principles but replaces the outer sheath with a halogen-free, low-smoke HM3 compound, creating the NSHXAFOE family.

Key benefits:

• Produces non-corrosive smoke

• Dramatically reduces visibility loss in fires

• Complies with tunnel and enclosed-space safety codes

• Suitable for buses, passenger coaches, and underground mines

Alignment with South African Regulations

Although these cables originate from European VDE standards, they integrate well within South Africa’s regulatory framework:

• SANS 1507 – general cable requirements

• SANS 95 – rail-specific electrical systems

• Fire-safety requirements – especially for tunnels, depots, and passenger rail

• NRCS approvals – mandatory for imported cables above certain voltages

Many South African engineers already specify VDE-compliant rolling-stock cables because Transnet, PRASA, Eskom, and large mining houses accept VDE standards as equivalent or superior in mobile MV applications.

Deep Dive into Cable Construction

This section provides engineering-grade detail for professionals who need material science insight for design, maintenance, and procurement.

Conductor — Stranded Tinned Copper (Class 5)

The conductor is made from flexible, fine-stranded tinned copper, according to:

• VDE 0295

• IEC 60228 Class 5

Why tinned copper?

• Resists corrosion in humid tunnels and mining shafts

• Performs better in areas with chemical pollution

• Superior solderability for locomotive control cabinets

• Slows down surface oxidation in warm coastal environments

This is a crucial advantage in South African regions like KwaZulu-Natal, where salty, humid air rapidly corrodes bare copper.

Semi-Conductive Inner Layer (6 kV variants)

For 3.6/6 kV designs, a semi-conductive layer ensures:

• Even distribution of electrical field stress

• Prevention of partial discharge, especially under bending

• Improved lifespan compared to XLPE MV cables

In XLPE MV cables, micro-cracks under vibration can cause discharge. EPR + semi-conductive layers prevent that.

EPR Insulation (3GI3/3GJ3)

EPR (Ethylene-Propylene Rubber) is the heart of these cables.

Key benefits:

• High thermal resistance (90°C continuous / 120°C overload)

• Superior elasticity

• Resistant to oil, fuels, and lubricants

• Outstanding mechanical strength

• Maintains dielectric integrity under constant bending

In South Africa, EPR’s heat and vibration tolerance are particularly valuable:

• Diesel locomotives operate in hot engine compartments

• Mining machines vibrate continuously

• Rail bogies experience dynamic bending every kilometre

PVC or XLPE cannot survive these conditions long-term.

Optional Copper Screen (NSGAFCMOEU / NSHXAFCMOE)

A screen made of tinned copper wires is added when:

• EMC protection is required

• Sensitive electronics are nearby

• Earth-fault detection needs enhancement

• MV switchboards demand short-circuit-proof construction

Screened versions are frequently chosen for mining MV pump stations and rail traction auxiliary power systems.

Outer Sheath Options

A. Chlorinated Rubber (5GM3) – NSGAFOEU

Strengths:

• Flame retardant

• Oil resistant

• Superb fatigue resistance

• Performs reliably in heat-exposed environments

This is the preferred option for:

• Diesel locomotive engine rooms

• Mining conveyor drives

• Outdoor installations exposed to oil and UV

B. Halogen-Free HM3 – NSHXAFOE

Advantages:

• Low smoke output

• Produces no corrosive gases

• Fire safe for confined spaces

• Mandatory for tunnels and passenger systems

South Africa’s increasing focus on safe evacuation and reduced smoke inhalation risks makes HM3 highly relevant.

Technical Specifications & Electrical Parameters

Voltage Ratings

Two common MV ratings:

• 1.8/3 kV – auxiliary systems, control circuits, lighting, power distribution

• 3.6/6 kV – traction drives, pump motors, MV switchboard connections

These match South African rail and mining voltage levels.

Conductor Sizes

Available sizes range from 1.5 mm² to 400 mm².

• Smaller sizes: coach wiring, lighting, control systems

• Larger sizes: traction power, MV motors, mining pumps

Engineers must balance flexibility, current carrying capacity, and bending radius.

Dimensions & Weight

MV rolling-stock cables are heavier and thicker due to:

• Robust insulation

• Thick outer sheaths

• Optional copper screens

The increased diameter affects bending radius — critical inside crowded locomotive equipment bays.

Electrical Characteristics

• EPR dielectric strength: extremely stable under heat and bending

• Short-circuit withstand: excellent due to temperature tolerance

• EMC performance: superior with screened versions

• Thermal endurance: long service life even in 80–100°C ambient zones

Fire Performance

5GM3 (chlorinated rubber):

• Flame retardant

• Produces some smoke and acid gases

HM3 (halogen-free):

• Low smoke

• Zero halogens

• Ideal for passenger-safety environments

South African tunnel guidelines increasingly require low-smoke halogen-free (LSHF) solutions.

Real-World Applications in South Africa

Rail Sector

Used by:

• PRASA – refurbishing substations and rolling stock

• Transnet Freight Rail – heavy-haul locomotive upgrades

• Gibela/Alstom – passenger train manufacturing

• Rail depots and workshops

Chosen because:

• They handle vibration better than XLPE

• They resist heat in engine rooms

• They survive long-term bending stress

Mining Industry

Applications include:

• MV pump stations (6 kV)

• Conveyor drives

• Mobile drilling rigs

• Underground substations

Mines prefer these cables because they:

• Resist oil contamination

• Perform in humid, corrosive environments

• Offer strong mechanical flexibility

Enclosed Environments

NSHXAFOE is used in:

• Tunnels

• Bus depots

• Mining refuge bays

• Cable ducts

Any environment with human occupancy or fire-risk restrictions benefits from LSHF performance.

South African Case Studies

Case Study 1: Gauteng Rail Corridor — Heat & Vibration

Challenge:
PVC-insulated MV cables in older locomotives suffered:

• Thermal cracking

• Hardening

• Insulation failure during summer peaks

Solution:
Replaced with NSGAFOEU 3.6/6 kV EPR-insulated cables.

Results:

• 45% reduction in unplanned cable-related failures

• Significant uptime improvements

• Better mechanical stability during vibration

• Lower fire risk in engine compartments

Case Study 2: Limpopo Platinum Mine — Oil-Rich Environments

Challenge:
Underground pump stations experienced frequent MV auxiliary cable failures due to:

• Oil contamination

• High humidity

• Tight bending during installation

Solution:
Installed NSHXAFOE halogen-free oil-resistant 6 kV cables.

Outcome:

• Improved insulation life

• Better resistance to hydrocarbon exposure

• Enhanced worker safety due to low-smoke properties

Advantages of NSGAFOEU / NSHXAFOE Cables

• Exceptional flexibility for moving equipment

• High oil and heat resistance

• Outstanding arc-tracking resistance

• Available in screened versions for EMC control

• Halogen-free options for safe evacuation

• Engineered for vibration and bending

• Proven durability in South Africa’s heat and dust

These strengths directly align with the needs of rail and mining operators.

Selection Guide for South African Engineers

Key considerations:

1. Sheath Type

• NSGAFOEU = durable, oil-resistant

• NSHXAFOE = low-smoke, halogen-free

2. Voltage Class

• 3 kV: auxiliary and control

• 6 kV: traction and MV pumps

3. Mechanical Loads

• Tight bends → choose smaller sizes or flexible routing

• Mobile installations → ensure correct bending radius

4. EMC Requirements

• Screened versions recommended for locomotives and mines

5. Fire Zones

• Tunnels → must use halogen-free

Installation Guidance

• Follow minimum bending radius recommendations

• Avoid excessive cable-tie pressure

• Ensure proper torque for Class 5 conductor terminations

• Use correct stripping tools for EPR insulation

• Prevent stress points in vibrating parts

• Maintain proper clearance in MV switchboards to avoid partial discharge

These factors significantly influence long-term reliability.

Common Installer Mistakes in South Africa

• Using XLPE cables in vibrating applications

• Over-tightening lugs on fine-stranded conductors

• Mixing LSHF and non-LSHF in fire-rated rooms

• Installing cables too close to heat sources

• Failing to allow expansion and contraction in mobile systems

Avoiding these pitfalls can extend service life by years.

FAQ — Frequently Asked Questions

Q1: What is the difference between NSGAFOEU and NSHXAFOE?

NSGAFOEU uses chlorinated rubber; NSHXAFOE uses halogen-free low-smoke HM3. The latter is safer in tunnels and passenger spaces.

Q2: Are these cables suitable for underground mines?

Yes — especially NSHXAFOE, which reduces smoke toxicity during fires.

Q3: Why EPR instead of XLPE for rolling stock?

EPR is more flexible, bend-tolerant, heat-resistant, and better for vibration.

Q4: Can these cables be directly buried?

Not recommended — designed for ducts, trays, rolling stock, and mobile systems.

Q5: Are they compatible with South African MV switchgear?

Yes — both 3 kV and 6 kV variants match common utility and mining systems.

Q6: What is the typical service life?

15–30 years depending on temperature, vibration, and oil exposure.

Conclusion

NSGAFOEU and NSHXAFOE medium-voltage single-core cables provide a unique combination of flexibility, mechanical strength, thermal stability, and fire safety. In South Africa’s harsh environments — characterised by dust, heat, vibration, and demanding electrical loads — these EPR-insulated cables repeatedly prove their superiority over traditional PVC and XLPE alternatives.

They support:

• PRASA’s rail modernisation

• Transnet’s heavy freight operations

• Deep-level mining pump stations

• Tunnels, depots, and enclosed infrastructure

For engineers, installers, and procurement teams, choosing the correct variant (oil-resistant vs halogen-free, screened vs unscreened, 3 kV vs 6 kV) is essential for ensuring safe, reliable, and long-lasting installations.