Why 11kV MV Cables Matter in South Africa

South Africa’s energy landscape has always relied heavily on robust medium-voltage (MV) distribution systems. Whether it is powering deep-level platinum shafts in Rustenburg, feeding coal operations in Mpumalanga, or running long overhead and underground feeders in the Northern Cape, the country’s industries run on reliable 11kV circuits.

This is where 6.35/11kV XLPE insulated, MDPE sheathed, armoured medium voltage power cables—commonly known by international type designations such as N2XSYB2Y (ATA armoured) and N2XSYR2Y (AWA armoured)—play a crucial role.

Why the demand is rising

South Africa’s mining and heavy industrial sectors are electrifying further, introducing:

✔ Longer MV feeders
✔ Higher motor loads
✔ More underground electrification
✔ Tougher requirements for moisture, abrasion and chemical resistance

As a result, 11kV MV cables have become the “sweet spot” for balancing voltage drop, safety and installation flexibility.

Quick definition

This cable type generally includes:

• XLPE insulation

• MDPE outer sheath (ST7)

• Armour (ATA or AWA)

• Copper conductor (Class 2)

These components create a cable capable of handling harsh African conditions—heat, UV, moisture, and aggressive ground chemicals.

Keywords introduced

11kV cable, XLPE insulated cable, MDPE sheathed cable, medium-voltage armoured cable, MV power cable

Purpose of this article

This guide breaks down:

• Construction

• Technical specifications

• Electrical performance

• South African installation practices

• Real case studies

• Selection guidance

• Troubleshooting and FAQs

Applicable Standards & Compliance Requirements

The design and construction of 11kV MV cables follow strict global and South African requirements.

IEC 60502-2 — Core Design Standard

Defines construction, dimensions, insulation levels, testing and performance for MV cables (1–30 kV).

Conductor Requirements — BS EN 60228 Class 2

• Stranded copper conductor

• Ensures conductivity stability

• Provides mechanical durability during installation

Fire, UV, Water & Hydrocarbon Resistance

These cables may include:

• UV-resistant MDPE

• Oil- and hydrocarbon-resistant sheath

• Anti-rodent materials

• Water blocking

Especially important in wet mining tunnels, fuel-rich industrial sites, and sun-exposed tray installations.

South African Context

Eskom Requirements

Eskom’s distribution networks require cables that:

• Withstand long MV runs

• Maintain low charging current

• Have robust metallic screens for fault clearing

Municipal Distribution Norms

Cities like Johannesburg, Tshwane and eThekwini commonly specify XLPE/MDPE construction.

Mining Sector Expectations

Mines require:

• Strong armour resistance

• Wet-location performance

• High screening capability

• Corrosion-resistant sheaths

Why MDPE Matters in South Africa

MDPE (Medium-Density Polyethylene):

✔ Superior moisture resistance
✔ High abrasion resistance
✔ Better impact toughness
✔ UV stability for tray/solar installations

Cable Construction Explained Step-by-Step

Below is a deep technical breakdown of every layer and its purpose.

Conductor — Plain Annealed Copper, Class 2

• Cross-sections: 70 to 630 mm²

• Excellent conductivity

• Mechanically stable for long pulls and bends

SA relevance: Useful for long runs in open-pit mines and cable routes with vertical drops.

Conductor Screen

A semi-conductive extruded layer that:

• Smooths electrical stress around the conductor

• Prevents partial discharge

• Ensures uniform electric field distribution

XLPE Insulation

• Thermal rating: 90°C continuous

• Short-circuit rating: 250°C

• Low dielectric losses

• High chemical and moisture resistance

Why XLPE suits Africa:
It handles hot climates (Northern Cape temperatures > 40°C) without performance loss.

Insulation Screen

A second semi-conductive layer that ensures:

• Full bonding between insulation and metallic screen

• Enhanced insulation integrity under MV stress

Metallic Screen (Copper Tapes and/or Wires)

Purpose:

• Provides earth fault return path

• Ensures reliable fault clearance

• Controls electromagnetic interference (EMI)

Wire vs tape combinations:

• Copper wires: Higher fault current capability

• Copper tapes: More uniform coverage

• Hybrid: Common in mining to maximise protection

Separation (Bedding) Layer — PVC

Separates the metallic screen from armour, providing:

• Cushioning

• Mechanical stability

• Thermal buffering

Armour Options

ATA — Aluminium Tape Armour

• Good mechanical protection

• Lower cost

• Suitable for fixed installations

AWA — Aluminium Wire Armour

• High tensile strength

• Ideal for long vertical drops

• Common in mining conveyors and pump areas

Rule of thumb in South Africa:

• ATA for industrial & municipal networks

• AWA for mining and high-mechanical-stress routes

Outer Sheath — MDPE (ST7)

Why MDPE is preferred over PVC:

• Better water resistance

• Higher abrasion resistance

• Outstanding UV protection

• Suitable for underground, wet, and exposed environments

Colour: Red — standard for MV power cables.

Optional enhancements:

• Anti-rodent

• Oil-resistant

• Hydrocarbon-resistant

Technical Specifications Deep Dive

Voltage Levels

Rated VoltageOperating VoltageTest Voltage6.35/11kV12kV25.5kV AC

Temperature Ratings

• Operating: 90°C

• Short-circuit: 250°C

• Minimum installation temp: -5°C

• Bending radius: 20 × overall diameter (OD)

Mechanical Properties

• High impact strength

• Suitable for underground and duct installations

• Resists crushing in mining haul roads

MDPE vs PE vs PVC

PropertyMDPEHDPEPVCWater resistanceExcellentExcellentGoodUV resistanceHighModeratePoorChemical resistanceHighVery highModerateMechanical toughnessHighModerateLow

MDPE is the best balance for SA conditions.

Dimensional Data & Interpretation

N2XSYB2Y (ATA Armoured)

Table provided in outline—typical values include:

• Insulation thickness: 3.4 mm

• Sheath thickness: 1.9–2.6 mm

• OD: 30.8–54.4 mm

• Weight: 1700–7590 kg/km

N2XSYR2Y (AWA Armoured)

Heavier due to wire armour, offering higher tensile strength.

Practical Meaning for SA Installers

Understanding OD and mass helps determine:

• Trench width

• Cable tray loading

• Pulling tension

• Minimum bending radius

Electrical Performance Analysis

AC vs DC Resistance

AC resistance increases due to skin effect—important for long 11kV runs.

Short-Circuit Ratings

Copper screen + conductor must withstand 250°C for 5 seconds.

Capacitance & Charging Current

Affects long-feeder performance—especially in mining and solar farms.

Impedance and Inductance

Trefoil reduces inductance, making it preferred for single-core routes.

SA Application

Long MV feeders in mines (500–1500 m) require careful charging current calculations.

Current Ratings in Various Installations

IEC 60287 Thermal Model

Used for current rating calculations.

Installation Methods

• Buried in ground

• In ducts

• In air/tray

• Trefoil vs flat vs spaced

Soil Thermal Resistivity in SA

• Limpopo clay soils: higher resistivity, derating needed

• Northern Cape sandy soils: lower resistivity, better heat dissipation

Temperature

Derate above 30°C ambient.

Applications Across South Africa

Mining Sector

Used for:

• Underground pumps

• Ventilation fans

• Conveyor motors

• Main 11kV feeders

Locations:

• Platinum mines — Rustenburg

• Coal mines — Mpumalanga

• Iron ore — Northern Cape

Power Utilities

Common in:

• Mini-substations

• RMUs

• MV switchgear

Industrial

Used in:

• Cement plants

• Smelters

• Steel mills

• Petrochemical facilities

Renewable Energy

Solar and wind farms use 11kV MV collector circuits.

South African Case Study (Real Example)

Platinum Mine MV Feeder Upgrade — Rustenburg

Problem

Frequent MV cable failures due to:

• Water ingress

• Armour corrosion

• High charging current

• Mechanical damage from haul trucks

Solution

Replaced old PVC-sheathed cable with:

• N2XSYR2Y 185 mm²

• AWA armour for mechanical strength

• MDPE sheath (ST7) for moisture and abrasion protection

• Trefoil installation over 1.2 km

Results After 3 Years

✔ Zero moisture-related failures
✔ Charging current reduced by 35%
✔ Improved fault clearing from enhanced copper screen
✔ Reduced downtime

This upgrade became a benchmark for other platinum operations.

Selection Guide for 11kV MV Cables

ATA vs AWA

• ATA: Low mechanical stress

• AWA: High mechanical stress (mining, long pulling)

Screen Size Selection

Based on fault current.

Conductor Size

Choose based on voltage drop + load.

When MDPE Sheath is Mandatory

• Wet areas

• Chemical exposure

• Sun-exposed trays

Optional Properties

UV-resistance for solar
Anti-rodent for mining tunnels

Cross-Section Selection

• 70–150 mm²: Short feeders

• 185–300 mm²: Mining circuits

• 400–630 mm²: Utility & industrial networks

Quick Checklist

• Voltage?

• Armour type?

• Soil conditions?

• Installation route?

• Fault level?

• Screen size?

Installation Best Practices in South Africa

Trenching Depth

Typically 700–900 mm, depending on municipal requirements.

Minimum Bending Radius

20 × OD.

Earthing

Single-core cables require careful screen bonding.

Trefoil Installation

Reduces electromagnetic forces.

Avoid Induced Voltage

Ensure proper spacing.

Testing Before Energisation

• VLF test

• Insulation resistance

• Sheath integrity test

Common Problems & Troubleshooting

Water Ingress

Use MDPE or water-blocked versions.

Armour Corrosion

AWA performs better in mines.

Incorrect Spacing

Causes overheating.

Pulling Damage

Use rollers and avoid sharp bends.

Screen Overheating

Due to undersized screen.

Poor Terminations

Common cause of partial discharge.

FAQ Section

Q1: What is the difference between N2XSYB2Y and N2XSYR2Y?

ATA vs AWA armour.

Q2: Can these cables be installed underwater or in wet soil?

Yes—MDPE sheath is ideal.

Q3: Why is MDPE better than PVC for South Africa?

Better water, UV and chemical resistance.

Q4: 185 mm² or 240 mm² for a mine feeder?

Depends on voltage drop and load.

Q5: Why use aluminium wire armour?

Higher tensile strength.

Q6: Required MV tests?

VLF, insulation resistance, sheath testing.

Q7: Cable lifespan in SA mines?

15–25 years with proper installation.

Q8: Can they be used in sunlight?

Yes—MDPE is UV-resistant.

Q9: Why trefoil?

Reduces magnetic field imbalance and heating.

Why 6.35/11kV XLPE/MDPE Armoured Cables Matter in South Africa

South Africa’s mining, industrial and utility sectors rely heavily on cables that can withstand extreme environments. 6.35/11kV XLPE insulated, MDPE sheathed, armoured MV cables offer:

• Long-term reliability

• Excellent electrical performance

• Superb resistance to moisture, UV and abrasion

• Suitability for harsh African conditions

• Proven track record across mines and utilities

Choosing the right construction (ATA vs AWA, MDPE, screen size) ensures safe, efficient and long-lasting MV networks.

Contact Anhui Feichun Special Cable Co., Ltd.

For comprehensive technical specifications and quotations, please contact our specialized mining cable engineering team:

Technical Engineering Support:

tech@feichuncables.com

Sales Engineering Department:

Li.wang@feichuncables.com

WhatsApp Contact:

Manufacturer: Anhui Feichun Special Cable Co., Ltd. (安徽飞纯特种电缆有限公司)

Manufacturing Headquarters: Building A, Private Science and Technology Park, Hefei Economic and Technological Development Zone, Anhui Province, People’s Republic of China

+86 17333223430