HPFF Pipe Cable System
These underground transmission lines system consists of a steel pipe that contains three high-voltage conductors. Each conductor is made of copper or aluminum; insulated with high-quality, oil-impregnated kraft paper insulation; and covered with metal shielding (usually lead) and skid wires (for protection during construction). Inside steel pipes, three conductors are surrounded by a dielectric oil which is maintained at 200 pounds per square inch (psi). This fluid acts as an insulator and does not conduct electricity.
High-Pressure, Fluid-Filled Systems
The external steel pipe in HPFF feeders must maintain greater than 250 psi internal pressure to ensure there is no damage to the internal conductors. In many cases, the pipes are aged and the external coating systems in place are well past their service lives. A plan to address this corrosion and remediate any structural deficiencies is essential to the continued operation of these critical power supply systems. Advanced FRP Systems provides specifically engineered solutions to prevent further corrosion while building a fully structural composite pipe around the existing steel pipe. The system provides high thermal conductivity to allow for heat release and is applied while the HPFF feeders are still online and active.
High-Pressure, Gas-Filled Systems
Many pipe-type cable systems must cross rivers, lakes, or other environmentally sensitive areas. Instead of using an HPFF system that has hazardous liquid inside, some utilities chose to use a gas-filled system. Those leaks do not have the same level of environmental impact but are costly to repair due to the need for clean, dry nitrogen inside the pipes. Advanced FRP Systems provides a fully structural, composite repair solution that prevents further corrosion of the external steel pipe and stops leaks. This system can be installed while the feeders are online on vertical, horizontal, or curved piping systems. Using high strength carbon fiber-based composites, the added weight is much less than would be required with similar strength in a metallic repair, alleviating the need to redesign pipe supports.
More recently, there is another type of underground transmission lines called solid dielectric cable which requires no fluids or gas. These XLPE insulated cables, unlike HPFF cables, pose no environmental threat and have less insulation losses. Additionally, these XLPE (cross linked polyethylene) also lasts longer and is a more affordable option.
Pipe-Type Cables within Manholes
External corrosion of pipe-type cables can be significantly accelerated inside of manholes. Manholes fill with water occasionally and often have high levels of salinity creating a more difficult environment for corrosion protection systems. Further, splice joints, bypass valves, and other complex geometries make the installation of these systems more difficult. Advanced FRP Systems can install a fully structural repair that prevents corrosion for more than 50 years, even in constant immersion conditions. Further, the composite repair can be designed for easy removal and later repair if access to the pipe-type cables is required.
Horizontal Directional Drilled Pipes
Areas where traditional excavation is expensive or impossible often have cables applied via a horizontal directionally drilled technique. This technique often saves money on the installation but it exposes the pipe to an increased risk of coating damage during the installation process. This means that corrosion can set in immediately upon the installation of these systems. Girth welds on these pipes are extremely problematic and typical girth weld protection systems do not provide 100% reliability. Our composite repair solutions are excellent solutions for spot repairs of girth welds and corrosion spots on these pipes or for system repairs designed to extend the life of these valuable assets.
Lead Sheathed Feeder Pipes
Lower pressure, older electrical transmission lines may have a lead sheathed design. While lead is less prone to corrosion than a steel pipe, the reduced strength of the lead alloys allows for leaks to form over time, especially at splice joints. Our composite solutions can be used to completely rebuild the external shell of lead sheathed feeders. Systems can be designed for easy removal and repair at splice joints if required. Ensure the long term reliability of these aging assets by protecting them from structural damage and corrosion with an external composite pipe system.
FREE ON-DEMAND WEBINAR:
Composite Repair of Underground Power Transmission Lines
In need of a spot repair on your pipes?
Check out our Carbon Fiber Pipe Repair Kits
Our versatile Carbon Fiber Pipe Repair Kits are ideal for external repairs of metallic, fiberglass, PVC, concrete or copper cables pipe ranging from 1 inch up to 60 inches in diameter. After proper surface preparation, these kits contain everything you need for a full composite repair and thus proper power cable insulation.
Advanced FRP Systems will train your internal maintenance staff so they are qualified to perform a long term repair!
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