---
title: "Stranded vs bundled conductors"
subject: "Power System Analysis I"
chapter: 2
key: "semester_4/power_system_analysis_i:differentiate-stranded-bundled-conductors"
source: https://www.bctengineer.com/q/semester_4/power_system_analysis_i/differentiate-stranded-bundled-conductors
site: BCT Engineering
---

# Stranded vs bundled conductors

Power System Analysis I · Chapter 2: Overhead and Underground Transmission

- Asked in: 2081 Chaitra (new course), 4 marks
- Video: [Solid vs Stranded vs Bundled Conductors | Which is Best for Power Transmission?](https://www.youtube.com/watch?v=JmtKNjKOQ38) — Electrology
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/power_system_analysis_i/differentiate-stranded-bundled-conductors
- Whole chapter: https://www.bctengineer.com/md/semester_4/power_system_analysis_i/chapter-2

## Question

Differentiate between stranded and bundled conductors.

## Short answer

Stranded conductor consists of many wires twisted together into one conductor for flexibility. Bundled conductor uses two or more sub conductors per phase separated by spacers to increase effective radius, reducing corona and line inductance in EHV lines.

## Answer

A **stranded conductor** is one conductor made of many thin wires twisted together. A **bundled conductor** is one phase made of two or more separate (usually stranded) sub-conductors held apart by spacers.

| Basis | Stranded conductor | Bundled conductor |
|---|---|---|
| Construction | Many strands twisted in layers into one conductor | 2, 3, 4 or more sub-conductors per phase, 30–45 cm apart |
| Main purpose | Flexibility and mechanical strength | Reduce corona and reactance at EHV |
| Used in | All overhead lines (LT to EHV) | EHV/UHV lines (220 kV and above) |
| Effect on GMR | Slightly lower than solid ($0.7788r$ for solid; e.g. $0.726r$ for 7 strands) | Much larger equivalent GMR ($\sqrt{d\,D_s}$ for 2-bundle) |
| Inductance | Almost unchanged | Reduced |
| Capacitance | Almost unchanged | Increased |
| Corona | Little effect | Corona loss and radio noise greatly reduced |
| SIL / capacity | No significant change | Increased (lower $Z_c$) |
| Accessories | None special | Spacers / spacer-dampers |
| Example | ACSR Dog (6/1 strands) | Twin ACSR Moose per phase on 400 kV |

```text
 Stranded (one conductor)   Bundled (one phase)
        o o                   (o)------(o)
       o O o                      spacer
        o o
```

## Check yourself

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

1. What is the main purpose of a bundled conductor compared with a stranded conductor?
   A. Bundling gives flexibility; stranding reduces corona
   B. Bundling reduces corona and reactance at EHV; stranding gives flexibility and strength
   C. Both mainly reduce cost
   D. Bundling increases inductance to limit fault current
   Answer: B. Stranding is for mechanical flexibility and strength; bundling is an electrical measure for EHV. (Key point: Main purpose)

2. Compared with a single conductor, how does a bundle change inductance and capacitance?
   A. Inductance increases, capacitance decreases
   B. Both decrease
   C. Inductance decreases, capacitance increases
   D. Both remain almost unchanged
   Answer: C. A bundle has a larger equivalent GMR/radius, so L falls and C rises. (Key point: Effect on inductance and capacitance)

3. How is a bundled conductor built?
   A. Many wires twisted into one conductor
   B. A steel core wrapped with aluminium strands
   C. Two or more separate sub-conductors per phase held 30-45 cm apart by spacers
   D. Two phases laid together in one cable
   Answer: C. A bundle is one phase made of several sub-conductors separated by spacers. (Key point: Bundle construction)

4. What happens to the surge impedance loading (SIL) with bundling?
   A. Decreases, because Zc rises
   B. Unchanged
   C. Increases, because Zc rises
   D. Increases, because Zc falls
   Answer: D. Lower L and higher C reduce Zc = sqrt(L/C), so SIL rises. (Key point: SIL effect)

## Related in Power System Analysis I

- [Reasons for stranded and bundled conductors](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Areasons-stranded-bundled-conductors) — Power System Analysis I, chapter 2, asked 5×
- [Stranded and bundled conductors; bundling in EHV](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Astranded-bundled-ehv) — Power System Analysis I, chapter 2
- [Effect of bundled conductors on L and C](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Abundled-conductor-effect-l-c) — Power System Analysis I, chapter 4
- [GMR of stranded vs solid conductor](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Agmr-stranded-lower-than-solid) — Power System Analysis I, chapter 4
- [Inductance of 3-conductor bundled line, 6.1 m spacing](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Ainductance-three-subconductor-bundle-6-1m) — Power System Analysis I, chapter 4

## Related in other subjects

- [Capacitance matrix of 400 kV bundled line](https://www.bctengineer.com/question.md?key=semester_8%2Fhigh_voltage_engineering%3Acapacitance-matrix-400kv-15m) — High Voltage Engineering, chapter 5, asked 2×
- [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×