Pulling ropes are primarily classified by their material, each offering distinct advantages for different applications.

• Anti-Twisting Braided Steel Wire Rope: This is the industry standard for overhead tension stringing. It's specially braided from multiple strands of high-strength, high-flexibility galvanized steel wire. The braided design prevents the rope from twisting under tension, ensuring a smooth pull and preventing damage to the conductor. It's the ideal choice for long-distance, high-tension pulls.

• High-Strength Synthetic Ropes: These are often used for underground cable laying and medium-voltage overhead projects. Made from materials like double-braided polyester or High Modulus Polyethylene (HMPE), they are lightweight, have very low stretch, and are resistant to moisture and chemicals. Their non-conductive properties make them a safer option for certain environments.

Choosing the correct pulling rope is crucial for safety and project efficiency. Here are the key factors to consider:

1. Tensile Strength: The rope's minimum breaking strength (MBS) must be significantly higher than the maximum anticipated pulling force. A safety factor of at least 4:1 is recommended, meaning the rope's MBS should be four times the maximum working load of the pulling machine.

2. Anti-Twisting Properties: For overhead tension stringing, an anti-twisting braided rope is non-negotiable. This prevents the transfer of torque from the pulling machine to the conductor, which can cause severe kinking and damage.

3. Application Environment: Consider the environment. For overhead work, a heavy-duty steel rope is best. For underground projects, a lightweight, flexible synthetic rope is often preferred as it's easier to handle and less prone to corrosion in wet environments.

As a prominent manufacturer and exporter, Ningbo Changshi offers a wide selection of pulling ropes, including galvanized anti-twisting steel ropes and high-strength synthetic ropes. Our products are designed to meet strict international standards, providing a complete and reliable one-stop solution for your projects.

A successful tension stringing operation requires a coordinated system of specialized equipment working in unison.

1. Preparation:

   • Pilot Line Installation: A lightweight, non-conductive rope (pilot line) is first pulled across the spans, often by a drone or manually. This rope is then used to pull the heavier, anti-twisting steel pulling rope.

   • Equipment Setup: A hydraulic tensioner is positioned at one end of the section with the conductor reel, and a hydraulic puller is set up at the other end.

2. The Pull:

   • The hydraulic puller starts to pull the steel wire rope, which is connected to the conductor by a specialized conductor pulling grip and a swivel to prevent twisting.

   • Simultaneously, the hydraulic tensioner applies a controlled back-tension to the conductor. This is the key to the entire process, as it keeps the conductor elevated and taut as it moves through the stringing blocks (sheaves) on the tower arms.

3. Sagging & Termination:

   • Once the conductor is fully installed in the section, the tension is adjusted to achieve the pre-calculated sag. This is a crucial step that ensures the conductor's safety clearances are met and the tension is within safe limits for the supporting structures. Our sagging scopes are used for this.

   • Finally, the conductor is secured to the dead-end towers with tension clamps, and the temporary stringing blocks are replaced with final suspension clamps.

As a premier manufacturer of power line tools, we offer the full suite of equipment required for tension stringing.

• Hydraulic Pullers and Tensioners: These are the core machines that apply and control the pulling and braking forces. Our models feature precise, real-time tension monitoring to prevent over-stressing the conductor.

• Conductor Stringing Blocks: These are durable, high-quality sheaves that allow the conductor to glide smoothly over towers, reducing friction and protecting its surface.

• Anti-Twisting Braided Steel Ropes: These ropes are specifically designed to prevent torque buildup from the pulling machine from transferring to the conductor.

• Conductor Pulling Grips and Swivels: These accessories provide a secure, non-damaging connection between the rope and the conductor, with swivels preventing twisting and kinking.

By using the right tools and following the tension stringing methodology, crews can ensure the integrity of the conductor and the long-term reliability of the electrical system.

An OHTL (Overhead Transmission Line) conductor is a specialized cable designed to transmit electrical energy through the air, supported by towers or poles. Unlike underground cables, OHTL conductors are typically uninsulated or "bare," and their design must balance several critical factors:

1. High Electrical Conductivity: To minimize energy loss during transmission.

2. High Tensile Strength: To withstand the conductor's own weight, wind, ice, and other environmental loads over long spans.

3. Light Weight: To reduce the structural load on the supporting towers and poles, which lowers construction costs.

The material of an OHTL conductor is a strategic compromise between these factors. While copper has higher conductivity, aluminum is the preferred material due to its much lower weight and cost.

Conductors are manufactured in various types to meet specific requirements for strength, conductivity, and corrosion resistance. The most common types for OHTL are:

• AAC (All-Aluminum Conductor): Made entirely of aluminum strands, AAC conductors are lightweight and cost-effective. They have excellent conductivity and are highly resistant to corrosion. Due to their lower tensile strength, they are typically used for low-voltage distribution lines with shorter spans.

• ACSR (Aluminum Conductor Steel Reinforced): This is the most prevalent type of overhead conductor. It consists of a central steel core for mechanical strength and outer layers of aluminum strands for electrical conductivity. This composite structure provides an excellent strength-to-weight ratio, allowing for long spans and high-tension applications. Our hydraulic tensioners and pullers are specifically designed to handle the high tensions required for installing ACSR conductors.

• AAAC (All-Aluminum Alloy Conductor): This conductor is made from a high-strength aluminum-magnesium-silicon alloy. It offers better mechanical strength and improved sag characteristics compared to AAC, along with excellent corrosion resistance. This makes it a great choice for coastal regions or where a stronger conductor than AAC is needed without the steel core.

The correct conductor choice is paramount for the safety, reliability, and economic viability of a power line project.

• Sag and Tension: The weight and strength of the conductor directly impact the sag and tension of the line. Using the wrong conductor can lead to insufficient ground clearance (too much sag) or excessive tension, which can damage the conductor and towers.

• Cost Efficiency: The choice of conductor influences the number of towers needed. A stronger conductor (like ACSR) can be strung over longer spans, reducing the number of towers and the overall project cost.

• Environmental Factors: For corrosive environments (e.g., coastal areas), a conductor like AAAC with high corrosion resistance is essential for longevity.

By understanding these distinctions, professionals can make informed decisions. Ningbo Changshi is a one-stop supplier of the specialized tools and equipment required to handle all types of OHTL conductors, from the lightweight AAC to the high-strength ACSR.

A distribution line conductor is the final stage of the power delivery network, responsible for carrying electricity from a substation directly to homes, businesses, and other end-users. Unlike high-voltage transmission conductors that span vast distances, distribution conductors operate at lower voltages and typically have shorter spans. Their design focuses on balancing cost, safety, and reliability for local, often densely populated, areas.

The choice of conductor for distribution lines is often based on the specific application, whether it's an urban, suburban, or rural environment.

• Bare Conductors: These are uninsulated conductors, and their safety relies on the air clearance between the conductor and surrounding objects. They are common in rural areas with fewer trees or buildings.

  • AAC (All-Aluminum Conductor): Made entirely of aluminum strands, AAC is lightweight and cost-effective. It is an excellent choice for short-span lines where weight and cost are the primary considerations.

  • AAAC (All-Aluminum Alloy Conductor): This conductor uses a high-strength aluminum alloy, offering better mechanical strength than AAC. It is widely used in distribution lines where strength and corrosion resistance are needed.

  • ACSR (Aluminum Conductor Steel Reinforced): While also used for transmission, the ACSR conductor is a popular choice for distribution as well, especially where longer spans or higher tensions are required. The steel core provides extra mechanical strength to withstand heavy loads from wind and ice.

• Covered Conductors: These are conductors with a protective polymeric covering. They are a popular choice in environments with a higher risk of accidental contact, such as urban areas with many trees.

  • Spacer Cable System: This system consists of multiple covered conductors held in a tight configuration by insulating spacers. This allows for closer spacing and a more compact line, reducing the risk of faults caused by trees or animals.

  • Aerial Bundled Cable (ABC): This is a bundle of covered conductors twisted together with a bare neutral. ABC is used to create a highly compact and safe line, minimizing the risk of a phase-to-phase short circuit.

The primary differences stem from their function and operating environment:

• Voltage and Current: Distribution conductors carry lower voltage and current than transmission conductors.

• Span Length: Distribution lines typically have much shorter spans between poles compared to the long-distance, high-tension spans of a transmission line.

• Safety and Environment: Distribution lines are closer to populated areas, making safety and resilience against environmental factors (e.g., trees, animals) a top priority. This is why covered conductors and ABC are popular for distribution.

Ningbo Changshi offers a full range of tools and equipment for the installation of all types of distribution conductors. From our hydraulic pullers and tensioners to our specialized stringing blocks for bundled cables, we provide the reliable solutions needed to ensure the safety and efficiency of your distribution line projects.

A transmission line conductor is the essential component used for the bulk transfer of electrical energy from a power plant to a substation. These conductors operate at high to extra-high voltages (e.g., 110 kV, 220 kV, 400 kV) and are designed to carry large amounts of power over long distances with minimal loss. Unlike distribution conductors, which prioritize safety and cost for local delivery, transmission conductors must excel in three key areas:

1. High Tensile Strength: To withstand the conductor's own weight, wind, and ice loads over very long spans.

2. High Electrical Conductivity: To minimize energy loss (I²R losses) and maximize power transfer.

3. Low Weight: To reduce the structural load on the expensive and large transmission towers.

The design of a transmission conductor is a strategic compromise between strength, conductivity, and weight. The most common types are:

• ACSR (Aluminum Conductor Steel Reinforced): This is the most widely used conductor for overhead transmission lines. Its genius lies in its composite structure:

  • Outer Strands: Made of high-purity aluminum for excellent electrical conductivity and light weight.

  • Central Core: Made of high-tensile galvanized steel, which provides the necessary mechanical strength to support the conductor over long spans and withstand heavy weather loads.

  • Application: ACSR conductors are a perfect balance of strength and conductivity, making them suitable for almost all long-distance transmission applications. Our hydraulic tensioners and pullers are specifically designed for the high-tension stringing of ACSR conductors.

• AAAC (All-Aluminum Alloy Conductor): This conductor is made from a single high-strength aluminum-magnesium-silicon alloy.

  • Advantage: It offers better mechanical strength and improved sag characteristics than pure aluminum (AAC) while providing better corrosion resistance than ACSR.

  • Application: AAAC conductors are commonly used in medium-to-long span transmission lines and are a popular choice in coastal or other corrosive environments.

• HTLS (High-Temperature Low-Sag) Conductors: These are advanced conductors designed to carry more current without the excessive sag that plagues traditional conductors at high operating temperatures.

  • Core: They use a high-strength, low-expansion core made from materials like a steel-aluminum alloy or a carbon-fiber composite.

  • Advantage: HTLS conductors can operate at temperatures up to 250°C, which increases their current-carrying capacity by 1.5 to 2 times that of a standard ACSR conductor of the same diameter.

  • Application: They are primarily used for upgrading existing transmission lines to increase capacity without the need for new towers.

A high-voltage electricity transmission network, also known as the power grid, is the system that delivers bulk electrical energy from generating stations to electrical substations. It is the backbone of modern power systems and is responsible for ensuring a reliable and efficient supply of electricity to our local communities.

The core principle behind using high voltage (typically 110 kV and above) is to minimize energy loss. According to the formula for power loss, Ploss=I2R, where I is the current and R is the resistance of the conductors. By raising the voltage (V), the current (I) can be significantly reduced for the same amount of power (P=VI), which dramatically decreases the energy lost as heat in the transmission lines. This makes long-distance power delivery economically viable.

Key Components of the Transmission Network

A transmission network is a complex system of interconnected components.

• Generating Stations: Where electricity is produced (e.g., power plants). Here, a step-up transformer increases the voltage from a low generating level to the high transmission level.

• Transmission Towers & Poles: The large lattice steel towers or tubular steel poles that support the conductors, keeping them elevated and safely insulated from the ground. Their design is a key consideration in a power line project, and our hydraulic drum stands are used to manage the massive reels required for these installations.

• Conductors: The "wires" that carry the electricity. In transmission, these are typically high-strength, aluminum-based cables like ACSR (Aluminum Conductor Steel Reinforced), designed to handle high tension and long spans.

• Substations: These are critical nodes in the network that contain transformers and switchgear. They "step down" the voltage from the high-voltage transmission level to a lower voltage for the local distribution network.

How We Fit In

For high-voltage lines (typically above 220 kV), conductors are often "bundled," meaning two or more sub-conductors are used per phase. This is done to mitigate a phenomenon called corona effect.

• What is Corona? At very high voltages, the electric field around a single, large conductor can become so intense that it ionizes the surrounding air, leading to a visible glow, a hissing noise, power loss, and radio interference.

• Why Bundle? By using multiple sub-conductors, the effective diameter of the phase is increased, which significantly lowers the electric field gradient at the conductor's surface. This effectively reduces corona losses and improves the overall efficiency of the line. Spacers are used to maintain the correct distance between the sub-conductors.

Ningbo Changshi is a one-stop supplier of the specialized tools and equipment required for the safe and efficient installation of all types of transmission conductors, including the complex setup of bundled conductor lines.

The highest operational electricity transmission voltages are in the Ultra-High Voltage (UHV) class, defined as 1,000 kV (1 million volts) and above for alternating current (AC) and ±800 kV and above for direct current (DC).

• UHVDC: The world's highest voltage and longest transmission line is the ±1,100 kV Zhundong–South Anhui UHVDC line in China. It spans over 3,000 km, carrying power from Xinjiang to Anhui. This line is a testament to China's leadership in UHV technology.

• UHVAC: The highest operational AC voltage is 1,150 kV on the Ekibastuz–Kokshetau line in Kazakhstan, which was built during the Soviet era. However, China is a world leader in developing and operating modern 1,000 kV UHVAC lines, which form the backbone of its "West-to-East" power transmission initiative.

The primary reason for using ultra-high voltages is to transmit a massive amount of power over an extremely long distance with minimal energy loss. The power loss in a transmission line is directly proportional to the square of the current (Ploss=I2R). By increasing the voltage, the current can be dramatically reduced for the same amount of power delivered, leading to a significant decrease in energy lost as heat.

Using UHV technology allows for:

• Higher Capacity: A single UHV line can transfer as much power as several lower-voltage lines, reducing the need for multiple corridors and minimizing land use.

• Greater Efficiency: UHV lines have significantly lower line losses, with reductions of up to 75% compared to EHV (Extra-High Voltage, 500-765 kV) lines.

• Long-Distance Transmission: UHVDC is particularly effective for transmitting power over thousands of kilometers, making it ideal for connecting remote renewable energy sources (like solar and wind farms in western China) to major load centers in the east.

Building UHV lines is considered the "Mount Everest" of the power industry due to several challenges:

• Insulation and Overvoltage: The extreme voltages require massive, highly engineered insulators and significant air clearances to prevent arcing and flashovers, especially in adverse weather conditions.

• Corona Discharge: At these high voltages, a phenomenon called corona occurs, causing energy loss, noise, and radio interference. This is mitigated by using bundled conductors, where multiple sub-conductors are used per phase.

• Specialized Equipment: The sheer size and weight of UHV components, from towers to conductors, demand specialized, high-capacity equipment.

Our Role in UHV Construction

Transmission infrastructure is made up of a few key components that work together to form the grid.

• Transmission Towers & Poles: These large steel structures support the conductors high above the ground. Their design varies based on the voltage and terrain, from lattice steel towers to tubular steel poles.

• Conductors: The bare wires that carry the electricity. They are typically made of high-strength, aluminum-based alloys (like ACSR) designed for long spans and high tensile strength to withstand wind and ice.

• Substations: Critical nodes in the network that contain transformers, switchgear, and other equipment to "step up" or "step down" voltage. They are vital for interconnecting different parts of the grid and transitioning from transmission to distribution.

• Insulators: Made of porcelain, glass, or polymer, insulators support the conductors on the towers and prevent electrical current from flowing to the support structures.