The most basic difference lies in their physical location.

• An overhead distribution line consists of bare or insulated conductors suspended on structures like utility poles, typically visible and accessible above ground. This system is the traditional method of power distribution and is widely used due to its lower cost and easier maintenance access.

• An underground distribution line consists of insulated cables that are buried in trenches or pulled through conduits below the ground. This system is often preferred for its improved aesthetics, public safety, and enhanced reliability against weather and external damage.

While both systems serve the same purpose, their components are tailored to their specific environment.

• Overhead System Components: The system includes conductors, which carry the electricity; insulators, which prevent current from leaking to the ground; and support structures like poles and crossarms, which hold everything in place. The installation of these components requires a wide array of specialized tools.

• Underground System Components: The system is composed of insulated cables, often placed within conduits to protect them. The cables are connected and terminated in specialized vaults, manholes, or cabinets.

Our comprehensive product lines, including Overhead Transmission Line Equipment and Underground Cable Laying Equipment, provide the necessary tools for the installation and maintenance of all these components.

The tools needed for each type of line reflect the distinct nature of the work.

• Overhead Line Installation: This work focuses on tension and aerial construction. Essential tools include hydraulic pullers and tensioners for stringing conductors, gin poles and hoists for lifting, and a full suite of hand tools and accessories for assembly and termination.

• Underground Line Installation: This work focuses on safely pulling and protecting the heavy cables. Key tools include cable pulling winches and cable pushers, cable rollers and stands for guiding the cables, and specialized crimping and cutting tools for cable preparation.

As a one-stop supplier, Ningbo Changshi provides a complete and reliable solution for every stage of both overhead and underground power distribution projects.

Finding your local electricity distribution company is usually straightforward. The easiest way is to check your electricity bill. The bill should clearly list the name of your distribution network operator (DNO) or a similar title, distinct from your energy supplier. Many utility websites also offer a simple postcode or address checker to help you identify your DNO. You cannot choose your distribution company; it is determined by your geographical location.

This is a key distinction. The electricity supplier is the company you pay your bill to; they purchase electricity from generators and sell it to you. You can often choose your supplier to find the best rate.

The electricity distribution company, on the other hand, is the company that owns and operates the physical infrastructure that delivers the power to your home or business. They are responsible for the utility poles, overhead lines, underground cables, and transformers in your area. You do not get to choose your distribution company. When a power outage occurs or if you see a downed power line, you should always contact your distribution company's emergency number.

Our company provides a wide range of specialized tools and equipment that are essential for the operation and maintenance of these distribution networks. For the distribution company responsible for your area's infrastructure, our equipment is vital for:

• Overhead Line Projects: We supply hydraulic puller and tensioner machines for stringing new conductors, as well as gin poles, hoists, and accessories for pole erection and maintenance.

• Underground Cable Projects: We provide cable pulling winches, rollers, and pushers for laying and repairing underground cables in trenches and conduits.

Our equipment helps these companies to install new power lines, perform routine maintenance, and respond to emergencies, ensuring that electricity is delivered safely and reliably to your area.

The most common materials used for electrical transmission conductors are aluminum and, in some cases, copper. However, for overhead transmission lines, a hybrid conductor called ACSR (Aluminum Conductor Steel Reinforced) is the overwhelming industry standard.

• Aluminum: Aluminum is the most widely used material due to its low cost, light weight, and good electrical conductivity. Its light weight is a significant advantage, as it reduces the mechanical load on support structures, allowing for longer spans between towers and lower overall construction costs.

• Copper: Copper has superior electrical conductivity and higher tensile strength compared to aluminum. However, its higher cost and significantly greater weight make it less economical for the long spans of modern high-voltage transmission lines. Copper is still frequently used for underground cables and certain specialized applications.

• Steel: While steel has poor electrical conductivity, it has excellent tensile strength. It is often used as a reinforcing core in conductors to provide the necessary mechanical strength to support the aluminum conductors over long distances.

The most common materials used for electrical transmission conductors are aluminum and, in some cases, copper. However, for overhead transmission lines, a hybrid conductor called ACSR (Aluminum Conductor Steel Reinforced) is the overwhelming industry standard.

• Aluminum: Aluminum is the most widely used material due to its low cost, light weight, and good electrical conductivity. Its light weight is a significant advantage, as it reduces the mechanical load on support structures, allowing for longer spans between towers and lower overall construction costs.

• Copper: Copper has superior electrical conductivity and higher tensile strength compared to aluminum. However, its higher cost and significantly greater weight make it less economical for the long spans of modern high-voltage transmission lines. Copper is still frequently used for underground cables and certain specialized applications.

• Steel: While steel has poor electrical conductivity, it has excellent tensile strength. It is often used as a reinforcing core in conductors to provide the necessary mechanical strength to support the aluminum conductors over long distances.

ACSR conductors are a perfect example of engineering innovation, combining the best properties of two materials. An ACSR conductor consists of a central steel core for strength, surrounded by outer strands of aluminum for conductivity.

This composite design provides several key advantages:

• High Strength-to-Weight Ratio: The steel core provides exceptional mechanical strength, allowing for longer spans and reducing the number of support towers required.

• Cost-Effectiveness: Using aluminum for the conducting part of the cable is much cheaper than using copper.

• Excellent Conductivity: While not as conductive as copper, aluminum's conductivity is more than sufficient for high-voltage transmission, especially when a larger diameter is used, which helps reduce the corona effect.

Our hydraulic puller and tensioner machines are specifically designed to handle the heavy tensioning required for ACSR conductors, ensuring a safe and precise installation that meets all design specifications.

ACSR conductors are a perfect example of engineering innovation, combining the best properties of two materials. An ACSR conductor consists of a central steel core for strength, surrounded by outer strands of aluminum for conductivity.

This composite design provides several key advantages:

• High Strength-to-Weight Ratio: The steel core provides exceptional mechanical strength, allowing for longer spans and reducing the number of support towers required.

• Cost-Effectiveness: Using aluminum for the conducting part of the cable is much cheaper than using copper.

• Excellent Conductivity: While not as conductive as copper, aluminum's conductivity is more than sufficient for high-voltage transmission, especially when a larger diameter is used, which helps reduce the corona effect.

Our hydraulic puller and tensioner machines are specifically designed to handle the heavy tensioning required for ACSR conductors, ensuring a safe and precise installation that meets all design specifications.

Beyond ACSR, other conductor types are tailored for specific applications, and our equipment is designed to handle them all.

• AAC (All-Aluminum Conductor): Used in short-span urban distribution networks where a high strength-to-weight ratio is less critical than conductivity.

• AAAC (All-Aluminum Alloy Conductor): Used where a balance of good strength and conductivity is needed, often for rural distribution.

• HTLS (High-Temperature Low-Sag) Conductors: These advanced conductors are designed for high-capacity lines and use a composite or alloy core to minimize sag at high temperatures.

Our full range of Overhead Transmission Line Equipment and Overhead Tools and Accessories—including stringing blocks, conductor grips, and swivels—are engineered to handle the varying diameters and mechanical properties of all these conductor types, providing our clients with the versatility they need for any project.

The statement that it's true is: Proper tensioning is critical for the lifespan and safety of a power line.

Conductor tensioning is a precise and non-negotiable part of the stringing process. The correct tension must be applied to achieve the design-specified sag and clearance. If the tension is too low, the sag will be excessive, potentially causing the conductor to contact the ground, trees, or other objects. If the tension is too high, the conductor and support structures could be overstressed, leading to premature failure, especially under heavy wind or ice loads. Our hydraulic puller and tensioner machines are designed with advanced controls to maintain a consistent, precise tension throughout the entire stringing operation, directly preventing these issues.

The statement that it's true is: Proper tensioning is critical for the lifespan and safety of a power line.

Conductor tensioning is a precise and non-negotiable part of the stringing process. The correct tension must be applied to achieve the design-specified sag and clearance. If the tension is too low, the sag will be excessive, potentially causing the conductor to contact the ground, trees, or other objects. If the tension is too high, the conductor and support structures could be overstressed, leading to premature failure, especially under heavy wind or ice loads. Our hydraulic puller and tensioner machines are designed with advanced controls to maintain a consistent, precise tension throughout the entire stringing operation, directly preventing these issues.

The statement that it's true is: The conductor's surface must be protected from damage throughout the installation process.

Any nick, scratch, or abrasion on a conductor's surface can create a weak point, compromising its strength and electrical integrity. This is especially true for overhead lines where the conductor is exposed to the elements. During installation, the conductor must not be dragged on the ground, pulled over sharp edges, or improperly gripped. Our stringing blocks, with their wide grooves and non-damaging linings, and our specialized conductor grips are all designed to handle the conductor gently, ensuring its surface remains pristine from the reel to its final position on the pole.

The statement that it's true is: A safe work zone must be established with proper grounding at all times.

Safety is the paramount concern during any electrical construction project. For conductor installation, this means establishing an "equipotential zone" by grounding all equipment, conductors, and structures. This protects workers from dangerous step and touch voltages that could occur from induced currents or a fault. Proper grounding and the use of running grounds are essential steps. We manufacture a full range of portable grounding and earthing kits, as well as other insulated tools and accessories, to ensure that our customers can create a safe working environment and protect their crews.

For modern high-voltage and extra-high-voltage (EHV) transmission lines, the tension stringing method is the universally preferred and recommended practice. This method, often referred to as "controlled tension stringing," involves using specialized machines to pull the conductor into place while simultaneously applying a controlled back tension. This ensures the conductor is kept off the ground and away from obstructions throughout the entire stringing process.

Tension stringing is preferred for several key reasons:

• Prevents Conductor Damage: This is the most critical advantage. By keeping the conductor suspended and off the ground, tension stringing eliminates the risk of scratches, nicks, or other surface damage that can occur from dragging the conductor over rough terrain. Such damage can significantly reduce the conductor's lifespan and ampacity.

• Enhanced Safety: The method provides greater safety for both the conductor and the crew. A controlled process reduces the risk of the conductor breaking or snapping back unexpectedly. It also minimizes the risk of the conductor making contact with energized lines or other obstacles.

• Greater Efficiency: Tension stringing is highly efficient for long spans and mountainous or difficult terrain. It reduces the need for extensive ground-level clearing and minimizes the number of joints required.

The tension stringing method requires a synchronized system of specialized equipment to function effectively. Our company, Ningbo Changshi, provides all of these essential tools.

• Hydraulic Puller and Tensioner Machines: These are the core of the system. The puller is used to pull a pilot rope, which in turn pulls the conductor, while the tensioner applies a constant back tension to keep the conductor elevated and taut. Our hydraulic machines are designed for precise control and reliability.

• Conductor Stringing Blocks: These blocks (also called "sheaves" or "travelers") are mounted on the utility poles or towers. They guide the conductor smoothly along the line, ensuring it does not get damaged during the stringing process.

• Anti-Twisting Swivels and Conductor Grips: Swivels are crucial for preventing the conductor from twisting as it is being pulled. Conductor grips are used to securely attach the pulling rope to the conductor without causing damage.

This combination of state-of-the-art equipment ensures a safe, efficient, and damage-free installation, making tension stringing the only acceptable method for modern overhead line projects.

The true statement is: A proper pre-installation check of all equipment and the line route is mandatory for safety and efficiency.

Before a single reel of conductor is unspooled, a comprehensive inspection is necessary. This includes verifying that all our hydraulic pullers, tensioners, and other stringing equipment are in good working order and that all safety devices are functional. It also involves a detailed review of the line route to identify any potential hazards or obstacles. This proactive step prevents equipment failures, minimizes delays, and, most importantly, ensures the safety of the entire crew. Our products are designed to be reliable, and a pre-installation check guarantees they're operating at their best.

The true statement is: A pilot rope is always used to pull the heavier conductor into place, preventing damage to the conductor itself.

You never directly pull the heavy conductor with a pulling machine. Instead, a lighter, often synthetic, pilot rope is first threaded through the stringing blocks along the entire length of the line. This pilot rope is then attached to a heavier pulling rope, which in turn is connected to the actual conductor. This staged process ensures that the heavy conductor is lifted and pulled gently, preventing it from touching the ground or other obstructions and safeguarding its integrity. We provide high-quality anti-twisting pilot ropes and other ropes for this precise and damage-free process.