--- title: "T/F: ACSR preferred over AAAC" subject: "Transmission and Distribution System Design" chapter: 4 key: "semester_8/transmission_and_distribution_system_design:tf-acsr-vs-aaac" source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/tf-acsr-vs-aaac site: BCT Engineering --- # T/F: ACSR preferred over AAAC Transmission and Distribution System Design · Chapter 4: Conductor and Support Selection - Asked in: 2072 Asoj, 3 marks - Video: [Conductors used in transmission line](https://www.youtube.com/watch?v=EZszSVZ9G6s) — Sourabh Sharma Hindi Channel - 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-acsr-vs-aaac - 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: ACSR is preferred choice than AAAC (All Aluminum alloyed conductor) for transmission line because of its high tensile strength. ## Short answer TRUE. ACSR has a steel core that provides higher tensile strength than AAAC, enabling higher working tension, smaller sag, and longer spans. This makes it the standard choice for most transmission lines. ## Answer **TRUE (in general practice).** - **ACSR** (Aluminium Conductor Steel Reinforced) has a galvanized steel core inside aluminium layers. The steel, especially in high-steel strandings such as 30/7, gives a higher ultimate tensile strength than an AAAC of the same conductance. The steel core also does not creep, so the sag stays stable over the years. - Higher strength allows higher working tension, so the sag is smaller for a given span. This allows **longer spans, fewer or shorter towers**, and a lower line cost. ACSR also performs better at long river or valley crossings and under ice and wind loads. - This is why ACSR is the standard choice for most transmission lines, including NEA lines in Nepal. AAAC is still preferred in some cases: | Point | ACSR | AAAC | |---|---|---| | Tensile strength | High (steel core) | Moderate | | Corrosion | Galvanic risk at steel–Al interface | Very good (homogeneous) | | Weight | Heavier | Lighter | | Surface hardness | Softer outer Al | Harder alloy, less damage | | Best use | Long spans, normal sites | Coastal or polluted areas, short spans, distribution | So ACSR is preferred mainly because of its high tensile strength. AAAC is chosen where corrosion resistance and lower weight matter more. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is ACSR generally preferred to AAAC? A. Because of its high tensile strength from the steel core B. Because it is lighter C. Because it has no corrosion risk D. Because it is cheaper per kg of aluminium only Answer: A. The steel core gives high strength, allowing higher tension and longer spans. (Key point: Verdict) 2. What does the higher strength of ACSR allow? A. Larger sag B. Higher working tension, smaller sag, longer spans, fewer towers C. Lower current rating D. Shorter spans Answer: B. Smaller sag and longer spans reduce the number or height of towers and lower line cost. (Key point: Consequence of strength) 3. Where is AAAC preferred? A. Long river crossings B. Coastal or polluted areas where corrosion resistance and low weight matter C. Heavy ice areas D. Very long spans Answer: B. AAAC is homogeneous so avoids galvanic corrosion at the steel-aluminium interface. 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