Oct 09, 2025
When to Choose STACIR/AW or Hi-STACIR/AW for Transmission Line Upgrades
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One option is to build new lines, but that usually means long approval processes and very high costs. A faster way is reconductoring. This method swaps the existing conductors with stronger, higher-capacity ones while leaving towers and most hardware in place.
Two conductors are especially important in this space: STACIR/AW and Hi-STACIR/AW. Both are part of the high-temperature, low-sag family, and both are designed to double the ampacity of traditional ACSR. Yet they’re not identical. Let’s look at how they work, where they fit, and how to decide between them.
What Is STACIR/AW?
Design and Structure
STACIR/AW stands for super thermal-resistant aluminum alloy conductor aluminum-clad Invar reinforced. There is a core made of aluminum-clad Invar, a metal chosen because it barely expands with heat. Around the core sit strands of super thermal-resistant aluminum alloy. This kind of outer layer can run at much higher temperatures than ordinary aluminum conductors.
Electrical and Thermal Behavior
Because of this design, STACIR/AW can run continuously at 210°C without losing strength or sagging too much. Compared to the same size ACSR, it can carry nearly twice the current. What’s more, it keeps sag-tension values close to those of ACSR, so engineers don’t need to worry about clearance or tower geometry.
Why It Matters
-No tower modifications: Utilities can leave their towers and hardware as they are.
-Familiar work practices: Crews can string it with the same equipment they use for ACSR.
-Lower cost and less time: The upgrade can be finished quickly, which avoids long construction schedules.
What Is Hi-STACIR/AW?
Building on the Same Concept
Hi-STACIR/AW uses the same recipe: High tensile strength aluminum-clad Invar at the core, thermal-resistant aluminum alloy around it. Electrically it performs the same, with low resistance and high conductivity. The big difference is its strength. Hi-STACIR/AW is engineered with a higher breaking load, which makes it tougher in the field.
Numbers in Practice
Here’s how the two compare in breaking strength:
| Conductor Size (mm²) |
STACIR/AW | Hi-STACIR/AW |
| Min.Breaking Load (kgf) | Min.Breaking Load (kgf) | |
| 160 | 6140 | 6500 |
| 240 | 9170 | 9700 |
| 330 | 10000 | 10500 |
| 410 | 12720 | 13300 |
| 480 (Rail) | 10500 | 11000 |
| 480 (Cardinal) | 13280 | 13800 |
The table makes it clear: Hi-STACIR/AW is stronger at every size, even though diameter, weight, and resistance stay almost the same.
Where It Fits Best
-Long spans where higher tension is unavoidable.
-Regions with heavy ice, strong winds, or galloping risk.
-Challenging terrain such as mountains or coastal zones, where reliability is critical.
Choosing Between Them
When STACIR/AW Is Enough
-The budget is limited, but capacity still needs to go up.
-The spans are moderate and don’t put too much tension on the structures.
Matching ACSR’s sag-tension behavior is acceptable for the project.
Matching ACSR’s sag-tension behavior is acceptable for the project.
When Hi-STACIR/AW Is the Better Pick0
-Extra tensile strength is needed to deal with long spans or harsh weather.
-The environment includes snow, ice, or high winds that test conductor limits.
-Reliability and safety are valued more than saving on upfront installation cost.
Standards and Compliance
Both conductor types are designed to meet IEC, ASTM, and JCS 1405 standards. These certifications cover performance, safety, and in some cases environmental requirements. For utilities, that means confidence in using either conductor on projects that demand proven quality.
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Selecting the right one is less about technology and more about project conditions: span length, local climate, and budget priorities. With that in mind, both options give utilities a way to meet today’s demand without waiting years for new infrastructure.
If you’re looking at a line upgrade, the choice between STACIR/AW and Hi-STACIR/AW comes down to your project’s conditions.
Contact TDDL today to discuss your spans, loads, and climate challenges. With expert guidance, you can choose the right conductor and move your grid toward higher capacity, lower costs, and long-term reliability.
FAQ
Q: What installation issues might appear with STACIR/AW and Hi-STACIR/AW conductors?
A: Both work with standard ACSR equipment, so the process feels familiar. The main risk is pulling them too tight, which can stress older towers.
Q: How do local environmental conditions affect the choice between STACIR/AW and Hi-STACIR/AW?
A: Weather plays a big role. Extreme heat, high humidity, or salty coastal air can shorten conductor life. Hi-STACIR/AW, with its added strength, is better in windy, icy, or seismic zones. In calmer climates, STACIR/AW is usually more than enough.
Q: Are these conductors suitable where environmental rules are strict?
A: Yes. Both comply with global standards like IEC and ASTM. Their aluminum-clad Invar core and thermal-resistant alloy mean fewer replacements over time, reducing waste. Still, always check local regulations before final approval.
