Power Steel Strand (GJ Series)

Zinc-10% Aluminum-Mischmetal Alloy Coating · High-Corrosion-Resistance Steel Strand for Power Cables

Figure: Zinc-10% aluminum alloy-coated steel strand for overhead power transmission lines (overhead ground wire / earth wire)

Product Overview

Power steel strand is mainly used as overhead ground wire (shield wire), tower guy wire, and grounding down conductor in overhead power transmission and distribution lines.

The product uses high-carbon steel as the base material and features a hot-dip zinc-10% aluminum-mischmetal alloy coating. It combines high mechanical strength with significantly improved corrosion resistance, making it particularly suitable for power projects in highly corrosive environments such as coastal areas, salt spray zones, and industrial regions.

The product designation is GJ. Unlike electrical conductors, GJ power steel strand is not primarily designed for electrical conductivity; its main functions are mechanical strength, structural support, grounding, and corrosion resistance.

It should be distinguished from LGJ/JL/G1A, which are aluminum stranded conductors with steel cores used for power transmission. GJ power steel strand and LGJ/JL/G1A conductors are different product categories.

Applicable Standards

National Standards (GB)

1. GB/T 20492-2019 — Zinc-5% Aluminum-Mischmetal Alloy Coated Steel Wire and Steel Strand
   Basic national standard for zinc-aluminum alloy coated steel strands, applicable to Zn-5%Al and Zn-10%Al coated products.

2. GB/T 32963-2026 — Zinc-Aluminum Alloy Coated Steel Wire Ropes
   Latest national standard for zinc-aluminum alloy coated steel wire ropes. It will take effect in October 2026 and covers Zn-10%Al and ZnAlMg coatings.

3. GB/T 17101-2026 — Hot-Dip Galvanized or Zinc-Based Alloy Steel Wire for Bridge Cables
   Standard for galvanized and zinc-based alloy steel wire used in bridge cables, including Zn-10%Al alloy coatings. It will take effect in October 2026.

4. GB/T 45970-2025 — Steel Wire and Steel Wire Products: Zinc or Zinc-Aluminum Alloy Coatings
   General standard for zinc and zinc-aluminum alloy coatings on steel wires and related products. It will take effect in February 2026.

Electric Power Industry Standards (DL)

5. DL/T 700-2020 — Steel Strand for Ground Wires of Overhead Transmission Lines
   Specialized industry standard for steel strands used as ground wires in power transmission projects.

6. DL/T 1092-2008 — Technical Specification for Security and Stability Control Systems of Power Systems
   Reference standard for relevant electrical power engineering testing and system applications.

Ferrous Metallurgy Industry Standards (YB)

7. YB/T 183-2017 — Rare Earth Zinc-Aluminum Alloy Coated Steel Strand
   Industry standard for rare earth zinc-aluminum alloy coated steel strands.

8. YB/T 6287-2024 — Low-Carbon Steel Wire with Hot-Dip Zinc-10% Aluminum Alloy Coating
   Specialized industry standard for steel wire with a zinc-10% aluminum alloy coating, effective from May 2025.

9. YB/T 5004-2012 — Galvanized Steel Strand
   General industry standard for conventional galvanized steel strand, used as a reference where applicable.

Cable-Related Standards

10. GB/T 1179-2017 — Round Wire Concentric-Lay Overhead Electrical Conductors
    Standard related to overhead conductors and steel components used in power transmission applications.

11. YB/T 124-2017 — Aluminum-Clad Steel Strand
    Standard for aluminum-clad steel strands used as load-bearing components in electrical cables.

12. GB/T 17937-2009 — Aluminum-Clad Steel Wire for Electrical Purposes
    Standard for aluminum-clad steel wire used in electrical applications.

13. IEC 61089:2014 — Round Wire Concentric Lay Overhead Electrical Conductors
    International standard issued by the International Electrotechnical Commission (IEC) for overhead electrical conductors.

Figure: Finished zinc-10% aluminum alloy-coated steel strand coil

Structure and Common Specifications

The most common construction is 1×7, consisting of seven helically stranded wires and widely used in power engineering. 1×3 and 1×19 constructions are also available for specific applications.

Product designations include GJ-35, GJ-50, GJ-70, GJ-80, GJ-100, and GJ-120, where the number indicates the nominal cross-sectional area in mm².

Available tensile strength grades include 1270, 1370, 1470, 1570, and 1770 MPa.

The strand is designed to maintain its integrity after cutting without excessive strand separation, and the outer layer is generally manufactured with a right-hand lay.

Two Main Coating Types

① Conventional Hot-Dip Galvanized Steel Strand GJ — For Standard Inland Projects

• Coating: Pure zinc hot-dip coating, with coating classes A/B/C; Class C provides the heaviest zinc coating.

• Applications: Conventional inland environments, including 10–220 kV ground wires and tower guy wires.

• Limitation: In coastal, salt spray, and industrial environments, conventional galvanized steel strand may have a shorter service life due to accelerated corrosion.

② Zinc-10% Aluminum-Mischmetal Alloy Coated Power Steel Strand — High-Corrosion-Resistance Grade

• Coating: Zn + 10% Al + mischmetal.

• Corrosion resistance: Depending on the environment and coating specification, the expected outdoor corrosion life can be significantly longer than conventional galvanized products.

• Applicable standards: YB/T 6287-2024 and GB/T 32963-2026 where applicable.

• Recommended applications: Coastal areas, saline environments, chemical and industrial pollution zones, hot and humid regions, ultra-high-voltage ground wires, long-span guy wires, and marine engineering applications.

• Procurement note: Clearly specify “zinc-10% aluminum-mischmetal alloy coating” in purchasing specifications to avoid substitution with Zn-5%Al or conventional galvanized coatings.

Figure: Cross-section of zinc-10% aluminum alloy-coated steel strand — 7-wire construction with a uniform coating

Performance Comparison of Three Coating Types

* Actual service life and coating performance depend on coating thickness, material quality, installation conditions, atmospheric exposure, environmental severity, and maintenance conditions. The values above should be treated as reference ranges rather than guaranteed service life.

Main Applications

1. Overhead Ground Wire (Shield Wire)

Installed at the top of transmission towers and lines to provide lightning protection and grounding. GJ steel strand is widely used on 110 kV, 220 kV, and 500 kV transmission lines.

2. Tower and Pole Guy Wires

Used for guying concrete poles and steel towers to improve structural stability and resistance to wind loads in distribution and transmission systems.

3. Grounding Steel Strand

Used for grounding down conductors, substations, transmission towers, and other power infrastructure grounding systems.

4. Communication Tower Guy Wires and OPGW Applications

Used as guy wires for communication towers and in supporting applications associated with OPGW (Optical Ground Wire) systems.

5. Long-Span Bridge and Marine Applications

High-corrosion-resistance Zn-10%Al alloy coated steel strand can be considered for long-span bridge cable-related applications and marine structures where enhanced corrosion resistance is required.

Important: If the grounding wire must also provide significant electrical conductivity, aluminum-clad steel strand (JLB) should be selected instead of conventional GJ power steel strand.

Purchasing Guidelines

1. Specify the Complete Product Configuration

The purchasing specification should clearly state:

• Model: GJ-XX

• Construction: 1×7 or other required construction

• Tensile strength grade: e.g., 1270–1770 MPa

• Coating type: Hot-dip galvanized / Zn-5%Al / Zn-10%Al

• Coating weight or coating class: As required by the applicable standard

2. Select the Appropriate Standard

For power transmission projects, DL/T 700-2020 should be considered according to the specific application.

For Zn-10%Al alloy coated products, the procurement specification should clearly identify the applicable requirements of YB/T 6287-2024 or GB/T 32963-2026, as applicable, to reduce the risk of receiving a lower-grade coating or a substituted product.

3. Inspect Product Quality

Key inspection points include:

• Tight and uniform stranding

• No excessive strand separation after cutting

• No bare spots, peeling, blistering, or other obvious coating defects

• Uniform coating thickness

• Consistent wire diameter and strand dimensions

• Tensile strength and mechanical properties meeting the specified requirements

• Test reports and quality certificates corresponding to the applicable standard

4. Choose the Coating According to the Environment

For coastal areas, salt-affected environments, chemical plants, industrial pollution zones, and other highly corrosive locations, Zn-10%Al alloy coated steel strand can provide enhanced corrosion resistance and may offer better lifecycle economics than conventional galvanized steel strand.

When selecting a product, the coating composition, coating mass, mechanical properties, environmental exposure, design life, and applicable project standards should all be evaluated together rather than relying on coating type alone.