---
title: "Constructional features of belted cable"
subject: "High Voltage Engineering"
chapter: 1
key: "semester_8/high_voltage_engineering:belted-cable-construction"
source: https://www.bctengineer.com/q/semester_8/high_voltage_engineering/belted-cable-construction
site: BCT Engineering
---

# Constructional features of belted cable

High Voltage Engineering · Chapter 1: Evolution of Power System

- Asked in: 2073 Bhadra, 4 marks
- Video: [Construction of cable , and it's voltage level belted cable, screend cable, pressure cable](https://www.youtube.com/watch?v=XgkxfWyaWBg) — Engineer dose
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/high_voltage_engineering/belted-cable-construction
- Whole chapter: https://www.bctengineer.com/md/semester_8/high_voltage_engineering/chapter-1

## Question

Explain the constructional features of belted cable used in HVAC transmission.

## Short answer

A belted cable has three paper-insulated cores with fillers, a surrounding paper belt, lead sheath, bedding, armour and serving. It is used up to about 22 kV. Tangential electric field and void formation limit its use at higher voltages.

## Answer

A **belted cable** is a three-core, paper-insulated cable used for voltages up to about 11 kV (sometimes 22 kV). It gets its name from an extra layer of paper insulation, the **belt**, wound around the three insulated cores together.

#### Constructional features
```text
        lead sheath
     ____________________
    /  belt insulation   \
   |   ( C1 )    ( C2 )   |
   |     fillers (jute)   |
   |        ( C3 )        |
    \____________________/
     bedding, armour, serving
```
1. **Conductors:** three stranded copper or aluminium conductors, usually sector (D) shaped to reduce overall size.
2. **Core insulation:** each conductor is wrapped with impregnated paper.
3. **Fillers:** the gaps between the cores are filled with jute or paper fillers to give a round shape.
4. **Belt:** an impregnated paper belt is wound over the three cores and fillers together.
5. **Lead sheath:** keeps moisture out and protects insulation.
6. **Bedding, armouring and serving:** bedding of jute/paper, steel tape or wire armour for mechanical protection, and outer serving of jute.

#### Limitations (why not used above about 22 kV)
- The electric field is not purely radial; it has a **tangential component** along the paper layers. Paper is weak along its layers, so leakage current flows tangentially and heats the insulation.
- Heating and load cycles create **voids** in the insulation (between fillers and belt), leading to ionisation, partial discharge and breakdown.

For these reasons, screened (H-type, SL-type) and pressure cables are used for higher voltages.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the belt in a belted cable?
   A. A steel band
   B. A copper screen on each core
   C. An extra layer of impregnated paper wound over the three insulated cores together
   D. A lead layer on each core
   Answer: C. The belt gives it the name. (Key point: Belt)

2. Why are jute or paper fillers used?
   A. To carry current
   B. To raise voltage
   C. To cool the cable
   D. To fill gaps between cores and give a round shape
   Answer: D. Cores are sector-shaped. (Key point: Fillers)

3. Why is the belted cable not used above about 22 kV?
   A. The field has a tangential component along weak paper layers, causing leakage heating and voids
   B. The field is purely radial
   C. Paper is stronger along layers
   D. Lead sheath melts
   Answer: A. Voids cause partial discharge. (Key point: Limitation)

4. Belted cables are used up to about
   A. 400 kV
   B. 11 kV (sometimes 22 kV)
   C. 132 kV
   D. 765 kV
   Answer: B. Beyond that use screened or pressure cables. (Key point: Voltage)

## Related in High Voltage Engineering

- [HVDC vs HVAC and HVDC scope in Nepal](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Ahvdc-hvac-compare-nepal) — High Voltage Engineering, chapter 1
- [Criteria for choosing HVDC or HVAC](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Ahvdc-hvac-choice-criteria) — High Voltage Engineering, chapter 1
- [Voltage build-up at line–cable junction](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Aline-cable-junction-voltage) — High Voltage Engineering, chapter 3

## Related in other subjects

- [Transmission impairments; attenuation of cable](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aattenuation-cable-numeric) — Data Communication, chapter 1
- [HVDC two conductors vs HVAC three conductors](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Ahvdc-two-vs-three-conductors) — Power Electronics, chapter 7, asked 2×
- [Why HVDC over HVAC: mathematical comparison](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Ahvdc-vs-hvac-comparison) — Power Electronics, chapter 7, asked 4×
- [HVDC power loss is 2/3 of HVAC](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Ahvdc-two-thirds-loss) — Power Electronics, chapter 7, asked 2×