Bare conductors

Bare conductors play a critical role in electrical power transmission systems. This article will provide you with a comprehensive understanding of bare conductor composition, classification, and applications, along with detailed guidance for selecting the most appropriate wire type for specific purposes.

1. Overview of bare conductors

1.1. What are bare conductors?

Bare conductors are electrical wires without an external insulating cover, commonly used for overhead distribution lines and grounding systems. These conductors are typically made from primary materials such as copper, aluminum, or steel. The most critical characteristic of bare conductors is their excellent heat dissipation capability due to the absence of an insulating cover. This allows the wire to carry larger electrical currents compared to similarly sized insulated wires. However, the lack of insulation also requires strict safety distance requirements and protective measures during installation and operation.

1.2. Structural composition

Bare conductors are typically designed with two main structural components:
Electrical conducting component
The electrical conducting component is usually made from copper or aluminum. Hard copper or aluminum strands are twisted into 1-3 layers around a load-bearing core. The number of strands is commonly 7, 19, or 37, depending on flexibility requirements. This structure increases the wire's flexibility, making installation and operation more convenient.
Load-Bearing component
The load-bearing part of bare cables is typically made from steel material. The steel core can be designed with 1 or 7 twisted steel strands. The primary task of the steel core is to ensure the necessary rigidity and tensile strength throughout installation and operation. This allows the cable to maintain appropriate sag when stretched across long electrical pole spans.  

1.3. Technical standards

Strict standards in cable production are essential for creating high-quality products. Some standards applied to bare conductors include:

• • Vietnamese Standards: TCVN 5064; TCVN 6483 (Currently applied by Ngoc Lan Cable for bare copper conductor, bare aluminum conductor, and aluminum conductor steel reinforced)
  • International Standards: IEC 61089; ASTM B232; ΓOCT 3062 & 3063 & ASTM B 498; BS 183:1972; JIS G 3537:1994; ASTM A 475:2003... (Currently applied by Ngoc Lan Cable for galvanized steel wires and aluminum steel core wires)

2. Bare conductor classification

Bare conductors are classified into three main groups based on material, structure, and cross-section. Each type has unique characteristics and practical applications.

2.1 Material

The material of bare conductors directly determines electrical conductivity and mechanical strength. There are two main types:
Bare Copper Conductors:
Conductors made from copper, with excellent electrical conductivity, suitable for high-performance electrical installations.
Bare Aluminum Conductors:
Conductors made from aluminum material, with lower electrical conductivity and cost compared to copper conductors, suitable for long-distance power transmission projects.

2.2 Classification by structure

The conductor structure affects flexibility and load-bearing capacity. There are several forms:
Braided conductors:
Constructed from 7, 19, or 37 hard strands twisted together, providing strength and stability in electrical transmission, suitable for applications requiring high stability.
Bare conductors with steel core:
Featuring a load-bearing core made of 1, 7, 19, or 37 galvanized steel strands twisted concentrically into one or multiple layers. Aluminum strands are twisted to cover the steel core. Especially in marine or corrosive environments, the conductor may be coated with a heat-resistant neutral grease, which can cover part or all of the wire depending on usage requirements.

2.3 Classification by cross-section

Bare conductors have diverse cross-sections ranging from 10 mm² to 400 mm².

• • Small cross-section: Below 50 mm²
  • Medium cross-section: 50 mm² to 240 mm²
  • Large cross-section: Above 240 mm

3. Comparison of bare conductors

Have you ever wondered how to choose the most suitable bare conductor for your project? Selecting a conductor is not just about comparing technical specifications, but also depends on multiple important factors. The following comparison table of common bare conductors can help you make an appropriate choice Based on the detailed analysis in the table above, we recommend:

• • Aluminum Wire (A): Suitable for areas with mild weather conditions and without high mechanical strength requirements.
  • Copper Wire (C): Ideal for systems requiring high electrical conductivity, such as substations, industrial zones, or critical connection points.
  • Aluminum Steel Core (ACSR): Preferred for long-distance power transmission lines, especially for river crossings or areas with harsh weather conditions.
  • Galvanized Steel Wire (TK): Typically used as a lightning protection wire for high-voltage lines or applications requiring high mechanical strength.

4. Applications of bare conductors

Bare conductors have numerous critical applications in electrical power distribution and transmission systems, such as the following:

4.1. Applications in overhead power transmission lines

Overhead power transmission lines are one of the most important applications of bare conductors, playing a crucial role in transmitting electrical energy from power plants to substations and ultimately to end-users.

4.2. Applications in grounding systems

With excellent electrical conductivity and high corrosion resistance, bare conductors help quickly and effectively channel leakage currents to the ground. This system acts as a "protective shield," preventing electrical shock accidents and protecting electrical equipment from overvoltage-related losses.

4.3. Other applications

In industry, bare conductors are used to connect large-capacity electrical equipment, ensuring stable system operation. In construction, bare conductors play a critical role in lightning protection and grounding systems for high-rise buildings, helping to ensure safety for structures and people.  

5. Guidelines for selecting bare conductors

Several important technical factors need to be considered when selecting bare conductors to ensure optimal efficiency and safety.

5.1 Permissible current

During design, electrical engineers calculate the permissible current based on the wire's cross-sectional area. For example, an aluminum wire with a 95mm² cross-section can have a rated current load of up to 330A at an ambient temperature of 30°C. However, this number will decrease as the ambient temperature rises, therefore requiring appropriate correction factors.

5.2 Environmental conditions

Installation environment significantly impacts the lifespan and performance of conductors. In temperatures above 40°C, the wire's current-carrying capacity decreases by approximately 10-15% compared to standard conditions. In coastal areas with high humidity and salty environments, using conductors with corrosion-resistant protection is mandatory to ensure project longevity.

5.3 Mechanical strength requirements

Mechanical strength is a critical factor when selecting conductors, especially in projects with wire spans longer than 80m. ACSR wires with steel cores have tensile strengths ranging from 10 kN to 280 kN, making them suitable for power lines crossing rivers, mountain passes, or areas experiencing wind loads over 30m/s.

5.4 Suppliers

Choose suppliers with reputable market brands, offering warranty conditions and technical support services. Most importantly, products must meet national and international standards such as TCVN, IEC, ASTM, BS, and quality certifications like ISO or QUACERT.

6. Safety regulations for use and maintenance of bare conductors

Since bare conductors lack external insulation, strictly following electrical safety regulations during construction and usage is mandatory. Adhere to the following guidelines:

6.1 Electrical safety procedures

Compliance with electrical safety procedures is essential when working with conductor systems. Key regulations include:

• • Inspect the electrical system before construction
  • Completely disconnect power before starting work
  • Use specialized testing equipment

6.2 Personal protective equipment

Preparing protective gear before construction is crucial for electrical safety. Essential equipment includes:

• • Specialized electrical insulation gloves
  • Insulated safety helmets
  • Electrical safety shoes
  • Non-conductive protective clothing

6.3 Periodic inspections

Frequent checks help detect potential electrical risk factors early:

• • Conduct regular monthly or quarterly inspections for critical electrical systems. Especially perform immediate checks after extreme weather conditions.
  • For the insulation system, assess the mechanical strength of support insulators, anchor insulators, and safe distances between conductors and surrounding structures. For physical wire conditions, focus on evaluating sag, twisting, fraying, strand breakage, and oxidation levels.
  • At connection and wire attachment points, check bolt tightness, contact point oxidation, and the strength of connection accessories. After inspection, prepare a report documenting parameters and propose remedial measures if necessary..

7. Frequently asked questions (FAQ) about bare conductors

7.1 What are the advantages and disadvantages of bare conductors compared to insulated wires?

Comparison table: Advantages and disadvantages of bare conductors versus insulated conductors:

7.2 What is the average lifespan of bare conductors under normal operating conditions, and what factors affect their lifespan?

The average lifespan of bare conductors under normal operating conditions can be quite long, typically 20-30 years or more, depending on several factors:

• • Conductor material: Copper wires typically have a longer lifespan than aluminum wires due to better corrosion resistance. ACSR wires with steel cores may rust over time.
  • Environment: Harsh environments (marine, chemical industrial zones, heavy pollution...) reduce lifespan due to corrosion and oxidation. Mild, dry climates offer longer lifespans.
  • Operating conditions: Frequent overloading, overheating, repeated short circuits can reduce lifespan.
  • Manufacturing quality: Conductors produced according to high-quality standards, using good materials, and with strict quality control processes will have longer lifespans.
  • Maintenance: Regular maintenance (inspection, cleaning, retightening connections, replacing damaged accessories...) helps detect and address issues early, extending lifespan.
  • System design: Designing power lines suitable for environmental conditions, load requirements, and with protective measures (lightning protection, overload prevention...) can also extend the lifespan of bare conductors.

8. Conclusion

For students and engineers new to the electrical field, this article provides a comprehensive overview of bare conductors - a common wire type in practical electrical installations. Through this content, you will grasp fundamental knowledge from structure and classification to selecting appropriate wire types based on factors such as working environment, operating conditions, and cost. Especially, the safety and maintenance guidelines in the article will be a valuable resource, helping you feel more confident when working with bare conductors in real-world scenarios.