Cables selection Methodology in electrical systems

By -

Cable Selection Guide: Voltage, Current Capacity, Insulation, and Installation Methods

 Learn how to select the right electrical cables based on voltage level, current carrying capacity, insulation type, installation method, number of cores, and environmental conditions.

Introduction

Selecting the right power cable is crucial in electrical systems to ensure safety, efficiency, and long-term reliability. Cable selection depends on various factors such as voltage level, current carrying capacity (ampacity), insulation type, number of cores, installation method, and environmental conditions. Using the wrong cable can lead to overheating, excessive voltage drop, or even failure of the electrical system.



1. Cable Selection According to Voltage Level

Cables are categorized based on their nominal voltage ratings. The classification is as follows:

  • Low Tension (LT) Cables: Up to 1000 V

  • High Tension (HT) Cables: Up to 11 kV

  • Super Tension Cables: From 22 kV to 33 kV

  • Extra High Tension (EHT) Cables: From 33 kV to 66 kV

  • Extra Super Voltage Cables: Beyond 132 kV

Key Insight: Higher voltage levels require specialized insulation and armoring to withstand stress and prevent breakdown.

2. Cable Selection According to Current Carrying Capacity (Ampacity)

The ampacity of a cable determines how much current it can safely carry.

  • Cables are usually selected 20% higher than the maximum expected load current.

  • Short circuit current ratings must be checked since a short circuit leads to a rapid rise in cable temperature.

  • Voltage drop also influences cable sizing. The resistance of a cable depends on its length and cross-sectional area. Longer runs require larger sizes to minimize power losses.

3. Cable Selection Based on Number of Cores

Different applications require different core configurations:

  • Single-phase supply → 2-core cables

  • Three-phase supply → 3-core, 3.5-core, or 4-core cables

    • 3.5-core is most common, as the neutral conductor is half-sized compared to phase conductors.

    • 4-core cables have a full-size neutral, used in systems with high unbalanced loads.

  • Multicore cables (14, 26, 48 cores, etc.) → Used in control and instrumentation applications.

    • Shielded multicore cables prevent electromagnetic interference in sensitive circuits.

4. Cable Selection According to Insulation Type

The insulation material defines the cable’s durability, cost, and performance:

  • PVC (Polyvinyl Chloride): Chemically resistant, cost-effective, widely used.

  • XLPE (Cross-Linked Polyethylene): Higher current carrying capacity, thermal resistance, more economical than PVC.

  • Rubber/Elastomeric: Flexible, used in mines, wind turbines, panel wiring, and battery applications.

Standards: IS:7098 / IEC:60502 / BS:6622 / BS:7835

5. Cable Selection According to Method of Installation

The laying method significantly impacts performance and protection:

  1. Underground Installation → Requires armored cables for mechanical protection.

  2. Cable Tray Installation → Generally uses unarmored cables, cost-effective and easy to maintain.

  3. Overhead / In Air Installation → Allows cables to carry higher currents due to better cooling.

Armoring is done as per: IS:7098 / IS:3975 / IEC:60502 / BS:6622 / BS:7835.

6. Cable Selection Based on Environmental Conditions

Cables must withstand the surrounding industrial and environmental stresses:

  • XLPE insulated cables → Suitable for moist and wet environments.

  • PVC jacketed cables → Resist a wide range of chemicals.

  • HDPE jacketed cables → Best for wet and underground locations.

  • Elastomeric cables → Used in mining, coal cutters, wind turbines, and heavy-duty applications.

Conclusion

Proper cable selection ensures safety, efficiency, and reliability in electrical systems. Factors such as voltage level, ampacity, insulation, number of cores, laying method, and environmental conditions must be carefully evaluated before choosing a cable. Following IS and IEC standards ensures compliance, durability, and optimal performance.


Comments

Post a Comment

Popular posts from this blog

A2XWY; A2XFY Cables meaning; XLPE cables advantages over PVC cables

By -
Image
🏗 ️ Technical Specification of Aluminium Cables (IS 7098: Part 1 – 1988) When specifying aluminium cables, you will often come across codes like A2XWY . This code represents the construction, insulation, armouring, and sheath of the cable. 🔑 Cable Nomenclature Codes Code Meaning A Aluminium Conductor 2X XLPE (Cross-linked Polyethylene) Insulation Y PVC Outer Sheath W Steel Round Wire Armour F Steel Strip Armour WW Double Steel Round Wire Armour FF Double Steel Strip Armour Wa Non-Magnetic Round Wire Armour Fa Non-Magnetic Strip Armour AW Aluminium Wire Armour 👉 Example: A2XWY = Aluminium conductor + XLPE insulation + Steel round wire armour + PVC outer sheath. 📌 Note: For Copper Cables , no pref...
Read more

YWY, AYFY, AYY, AYCY, A2XCY Cables Meanings

By -
Image
📘 Cable Nomenclature Explained (PVC & XLPE Cables) Cable designations like YWY, AYFY, A2XCY might look confusing at first glance. But once you understand the logic behind each letter , reading technical specs becomes straightforward. 1. Basic Conductor Material ·          A → Aluminium conductor ·          (If “A” is absent, it means Copper conductor) 2. Insulation Material ·          Y → TROPODUR = PVC insulation ·          2X → TROPOTHEN-X = XLPE insulation 3. Armouring Types ·          W → Round Steel Wire Armouring ·          WW → Double Round Steel Wire Armouring ·          F → Flat (formed) Steel Strip Armouring ·       ...
Read more

Cable size and current carrying capacity

By -
Image
Cable size and current carrying capacity for XLPE insulated cable, non-armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. Cable size and current carrying capacity for XLPE insulated, Armored, Twin or multicore cable is as below:- Conductor operating temperature is 90 degree Celsius Ambient temperature: 30 degree Celsius. For air and 20 degree Celsius for ground for installations require to comply with BS: 7671 Correction factors:- For Ambient temperature: Ambient temperature in degree Celsius Correction Factor 25 1.02 30 1.00 35 0.96 40 0.91 45 0.87 50 0.82 55 0.76 60 0.65 65 0.58 70 0.50 75 0.41 80 Ground Temperature Ambient temperature in degree Celsius Correction F...
Read more