---
title: "T/F: maximum sag in stringing condition"
subject: "Transmission and Distribution System Design"
chapter: 4
key: "semester_8/transmission_and_distribution_system_design:tf-max-sag-stringing-condition"
source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-max-sag-stringing-condition
site: BCT Engineering
---

# T/F: maximum sag in stringing condition

Transmission and Distribution System Design · Chapter 4: Conductor and Support Selection

- Asked in: 2073 Magh, 1+3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-max-sag-stringing-condition
- Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-4

## Question

State whether the following statement is TRUE or FALSE. Justify your answer with a brief explanation: Maximum sag in stringing condition is greater than in toughest and easiest conditions.

## Short answer

FALSE. Stringing sag is smaller than the sag in the easiest condition because the conductor is at a lower temperature (around 25°C) than the highest ambient, so tension is higher and sag is lower. It lies between the toughest and easiest extremes.

## Answer

**FALSE.**

The sag at stringing lies between the sags of the two extreme design conditions. It is never larger than both of them.

- **Toughest condition** (lowest temperature, maximum wind, ice if any): tension is at its maximum, $T = \text{UTS}/\text{FS}$. The effective weight $W_1=\sqrt{(w_c+w_i)^2+w_w^2}$ is also at its maximum. The resulting sag is inclined and is used for checking strength.
- **Easiest condition** (highest temperature, still air, no ice): the conductor is at its longest and tension is lowest. This gives the **maximum vertical sag**, which fixes the ground clearance and the tower height.
- **Stringing condition** (normal erection temperature, about 20–30°C, no wind, no ice): the temperature is below the easiest-condition temperature. The conductor is therefore shorter and tighter, so

$$
D_{\text{stringing}} = \frac{w_c L^2}{8T_{\text{str}}} < D_{\text{easiest}} = \frac{w_c L^2}{8T_{\text{easiest}}}
$$

because $T_{\text{str}} > T_{\text{easiest}}$ for the same weight $w_c$.

Example: for a 300 m span of a 462.6 mm² ACSR conductor, the toughest-condition sag is about 9.9 m and the stringing sag at 25°C is about 8.8 m. So the stringing sag is the smaller one.

The stringing sag is found from the change-of-state (stringing) equation, starting from the toughest condition. The conductor is pulled to this sag during erection so that the line meets its limits at the two extremes.

## Check yourself

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

1. Is the stringing sag greater than the sags of both toughest and easiest conditions?
   A. True
   B. False, it lies between the two extremes
   C. True only for long spans
   D. False, it is always the maximum
   Answer: B. Stringing at normal temperature gives a sag below the easiest-condition (hot) sag. (Key point: Verdict)

2. Which condition gives the maximum vertical sag that fixes ground clearance?
   A. Toughest
   B. Stringing
   C. Easiest (highest temperature, no wind)
   D. Lowest temperature
   Answer: C. At high temperature the conductor is longest and tension lowest, so vertical sag is largest. (Key point: Maximum vertical sag)

3. Why is D_stringing < D_easiest?
   A. Tension at stringing is greater than at the easiest condition for the same weight, D = wL^2/(8T)
   B. Weight is less at stringing
   C. Span is shorter
   D. Wind helps
   Answer: A. Cooler conductor is shorter and tighter, so higher T gives smaller sag. (Key point: Sag-tension relation)

4. What defines the toughest condition?
   A. Highest temperature, still air
   B. Lowest temperature, maximum wind (and ice), tension at UTS/FS
   C. Normal erection temperature
   D. No loading
   Answer: B. It gives maximum tension and effective weight, used to check strength. (Key point: Toughest condition)

## Related in Transmission and Distribution System Design

- [Sag and tension in easiest condition](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Asag-tension-easiest-condition) — Transmission and Distribution System Design, chapter 4
- [T/F: sag absent with supports at different heights](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-sag-absent-different-heights) — Transmission and Distribution System Design, chapter 4
- [T/F: radial more reliable than network](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-radial-more-reliable-network) — Transmission and Distribution System Design, chapter 5, asked 2×
- [Conductor tension in stringing condition](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Astringing-tension-300m-span) — Transmission and Distribution System Design, chapter 4
- [Position of maximum sag, unequal supports](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Amax-sag-position-unequal-levels) — Transmission and Distribution System Design, chapter 4, asked 4×
- [Location of maximum sag, supports at different levels](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Amax-sag-location-derivation) — Transmission and Distribution System Design, chapter 4, asked 2×

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