04/08/2026
NYY Cable — Detailed Engineering Explanation
NYY cable is a low-voltage power cable designed mainly for fixed electrical installations, especially underground, outdoor, industrial, and building power distribution systems.
The designation NYY follows the German/VDE cable naming system:
N = Standardized cable according to German standards (Normenleitung)
Y = PVC insulation (Polyvinyl Chloride)
Y = PVC outer sheath (Polyvinyl Chloride)
So, NYY = Copper/Aluminium conductor + PVC insulation + PVC outer sheath power cable.
1. Basic Construction of NYY Cable
A typical NYY cable consists of:
1. Conductor
Material:
Copper (Cu) — most common
Aluminium (Al) — available for larger sizes
Conductor type:
Class 1: Solid conductor
Class 2: Stranded conductor (more flexible)
Example:
NYY 4×25 mm² Cu
NYY 4×95 mm² Al
2. Insulation Layer
Material: PVC (Polyvinyl Chloride)
Functions:
Electrical isolation between conductors
Withstands operating voltage
Protects against moisture and chemical effects
Typical insulation colour:
Phase: Brown / Black / Grey
Neutral: Blue
Earth: Green-yellow
3. Inner Filler / Bedding
Used in multi-core cables to:
Maintain circular shape
Provide mechanical support
Fill gaps between cores
4. Outer Sheath
Material: PVC
Functions:
Mechanical protection
Moisture resistance
Protection from soil contact
Chemical resistance
Colour:
Usually black
Black colour provides:
UV resistance
Better outdoor durability
2. Electrical Characteristics
Voltage Rating
Common rating:
0.6/1 kV
Meaning:
0.6 kV = permissible voltage between conductor and earth
1 kV = permissible voltage between phase conductors
Suitable for:
400/230 V systems
Low voltage distribution networks
3. Temperature Rating
Typical values:
Condition Temperature
Maximum continuous conductor temperature 70°C
Short circuit temperature (5 sec) 160°C
Minimum installation temperature Around -5°C
(Values depend on manufacturer standard.)
4. Common NYY Cable Types
Single Core
Example:
NYY 1×240 mm²
Application:
Transformer LV output
Main feeder
High current distribution
Multi Core
Examples:
NYY 4×16 mm²
Application:
Three phase + neutral supply
NYY 5×6 mm²
Application:
Three phase + neutral + earth
5. Current Carrying Capacity (Approx.)
Example values (Cu conductor, buried):
Cable Size Approx. Current
4 mm² 35–45 A
10 mm² 65–75 A
25 mm² 110–130 A
50 mm² 180–200 A
95 mm² 280–320 A
240 mm² 500–550 A
Actual ampacity depends on:
Installation method
Soil thermal resistance
Ambient temperature
Cable grouping
Depth of burial
6. Installation Methods
NYY cable can be installed:
✅ Direct buried underground
✅ Cable trench
✅ Cable duct
✅ Cable tray (indoor)
✅ Outdoor exposed installation
✅ Concrete encased ducts
Recommended underground installation:
Depth: approximately 600–1000 mm (depending on regulation)
Sand bedding
Warning tape above cable
Mechanical protection where required
7. Advantages of NYY Cable
1. Good Moisture Resistance
PVC sheath prevents water pe*******on.
2. Suitable for Underground Use
No additional armouring required for normal installations.
3. Economical
Cheaper than XLPE armoured cables.
4. Chemical Resistance
Suitable for industrial environments.
5. Long Service Life
Typically 25–40 years depending on installation conditions.
8. Limitations
NYY cable has some disadvantages:
❌ Lower temperature capability than XLPE cables
(NYY: 70°C, XLPE: 90°C)
❌ PVC has higher dielectric losses
❌ Not suitable for very high short-circuit current applications without proper calculation
❌ Limited mechanical protection compared with armoured cables (SWA/STA)
