Cable accessories are used to connect, seal, terminate, and insulate power cables from their surrounding environment at the transmission and distribution level. Cable accessories are installed on transmission and distribution power lines connected to distribution networks, substations, renewable energy ties, and industrial plants. They are typically used to either join two separate cables together or to join a cable with an electrical device such as a transformer.
Importance of Cable Accessories in Power Systems
High-quality cable accessories help maintain system safety and performance by:
- Ensuring electrical continuity and mechanical stability at joints and terminations.
- Protecting against moisture, corrosion, and environmental stresses.
- Withstanding system faults, surges, and harsh conditions.
To guarantee reliability, accessories should comply with IEC and IEEE standards, providing assurance that products are tested and validated for long-term performance.
Types of Cable Accessories
As an established cable accessories manufacturer since 1905, G&W offers a wide variety of different cable accessories to meet the needs of many different distribution applications:
Cable Joints
Used to join two sections of cable, joints are critical in both overhead and underground systems.
- Transmission examples:
- Python® pre-molded rubber joints (PMJ) – for XLPE/EPR cables from 72.5kV to 550kV IEC.
- TJNT140 transition joints – connect LPFF cables at 138kV with XLPE or EPR cables.
- LPP joints – designed for HPFF cables up to 345kV IEEE.
- Distribution examples:
- TJNT3-33 transition joints – for joining HPFF cables to XLPE/EPR on 33kV systems.
- Cable Transition Modules (CTM) – connect PILC, LPGF, or MPGF to XLPE/EPR up to 35kV.
Cable Terminations
Terminations provide mechanical support and insulation where cables connect to transformers, switchgear, or other devices.
- Transmission examples:
- Python® PAT style terminations – 72.5kV to 550kV IEC.
- Python® PAT130C dry type – for XLPE/EPR at 110–145kV IEC.
- Python® SSC terminations – GIS applications up to 550kV.
- ATA/ATL fluid-filled terminations – 69–345kV transmission systems.
- Distribution examples:
- PAT Style Slip-On terminations – factory-assembled for cables through 46kV.
- Capnut terminations – flexible field-assembled units up to 46kV.
- Sodertite terminations – sealed designs for oil/gas-filled or paper insulated cables.
Cold Shrink Cable Accessories
Pre-Molded Cold Shrink Accessories
The Pre-Molded (PM) series of cold shrink accessories are for extruded dielectric power cables from 8.7kV through 35kV and up to 630mm2. Through the use of cold shrink technology, these accessories allow for simple, reliable installation and excellent product performance. The PM series of cold shrink accessories encompasses the following: terminations, joints, shielded separable connectors, t body connectors, shielded load break elbow connectors, and inner cone plug-in separable connectors.
Choosing the Right Cable Accessories
There are three important aspects to consider when analyzing cable systems: the cables themselves, the right cable accessories for the application, and the installation process of these cable accessories. The following criteria are necessary for determining exactly what cable accessories are needed for a given cable system:
Voltage Rating
The voltage rating for the cable accessory depends on the voltage rating of the system or equipment it is connected to. It is critical that the cable accessory has been tested to the appropriate rating.
- Distribution systems: typically, 15.5kV to 46kV.
- Transmission systems: 72.5kV IEC and above.
Environmental Conditions
All cable accessories must be waterproof to combat moisture ingress since the joint, termination, or connector will be installed on cables that are above or below ground. To guarantee longevity, it is important to select cable accessories that are designed to withstand their intended environment, such as using an outdoor-rated accessory in an outdoor application.
Cable Types
The types of cables used in a power system can impact the ease of making upgrades. The evolution of cable technology has introduced various insulation materials and designs to improve performance. Most distribution and transmission cable systems in service today use one of four types of cables:
- Transmission:
- Medium-Pressure Gas-Filled (MPGF) and High-Pressure Gas-Filled (HPGF): MPGF and HPGF cables are pipe-type cables typically used in gas insulated substation applications. While effective, they require constant monitoring to ensure the gas pressure remains stable, making them difficult to integrate with modern switchgear.
- Medium-Pressure Fluid Filled (MPFF) and High-Pressure Fluid-Filled (HPFF): MPFF and HPFF are similar to MPGF and HPGF in that they are pipe-type cables but instead use a dielectric fluid for insulation.
- Cross-Linked Polyethylene (XLPE): Introduced in the 1960s, XLPE cables provide excellent thermal resistance and electrical properties. They are now a standard in modern electrical systems.
- Ethylene Propylene Rubber (EPR): Like XLPE, EPR cables are highly durable and flexible, offering similar benefits and reliability.
- Distribution:
- Paper Insulated Lead Covered (PILC): PILC cables were widely used in the 20th century, but they have largely been replaced due to their susceptibility to moisture and degradation.
- Low-Pressure Gas-Filled (LPGF) and Medium-Pressure Gas-Filled (MPGF): These cables were developed to address moisture ingress problems with PILC by maintaining pressurized nitrogen or other gases. While effective, they require constant monitoring to ensure the gas pressure remains stable, making them difficult to integrate with modern switchgear.
- Ethylene Propylene Rubber (EPR): Like XLPE, EPR cables are highly durable and flexible, offering similar benefits and reliability.
- Cross-Linked Polyethylene (XLPE): Introduced in the 1960s, XLPE cables provide excellent thermal resistance and electrical properties. They are now a standard in modern electrical systems.
Installation Method
Field-installed terminations (Capnut)
Given the nature of requiring adjustments at specific locations on a given cable system, the installation of cable accessories must be done on-site. Every site faces different challenges, such as a lack of complete cable data. G&W’s field-installed terminations have the adaptability of handling these scenarios, ensuring flexible installations.
- Capnut terminations are designed with many interchangeable components to provide maximum system flexibility, including aerial lugs, hood nut connector assemblies, porcelains, bodies, and cable entrance fittings. This adaptability allows for these terminations to accept any construction of extruded dielectric, paper insulated, or armored cable on distribution systems up to 46kV.
Preassembled and Premolded Components
The installation of cable accessories is typically a very lengthy process that requires special expertise from an installer. G&W provides preassembled and premolded components for certain cable accessories, simplifying the process. As such, installations will take less time to complete and can remove the need for special installation tools.
- Transmission:
- All Python® terminations feature a pre-molded rubber stress cone. This stress cone can be shipped unexpanded for long term storage and be returned to G&W Electric at a later time for expansion prior to installation.
- The Python® SSC terminations feature a pre-molded rubber stress cone that can be sold separately from the plug, or together as a full termination kit. It has the added benefits of allowing equipment manufacturers to install the cone at the factory for testing purposes and can be assembled with the rest of the termination in the field.
- The PMJ uses a factory premolded joint body with self-contained stress control relief. The mechanical shrink capabilities allow for a reduction in equipment usage and installation space, removing the need for special installation tools.
- Distribution:
- PAT Style Slip-On terminations are factory assembled terminations designed for ease of installation and adaptability to a wide range of cable types and sizes. After cable preparation, simply insert the cable into the terminator and attach the ground and aerial connections. Cable centering plugs are used to guide small size cables into the terminator. Additionally, the factory installed, internal stress relief devices provide effective electrical stress relief without having to build a taped stress cone on the cable.
- The PM series of cold shrink accessories simplify installation with the single piece, pre-molded design. This eliminates errors that could occur with multiple piece accessories and does not require special skills for installing. Cold shrink also eliminates the issue of uneven heating that may occur when installing heat shrink accessories.
Mechanical Shrink
Mechanical shrink is a method that, unlike heat shrink, forgoes the need for special tools and uses prefabricated components to ensure a quicker and simpler installation. It allows for installation in tight spaces and eliminates the issue of uneven heating that may occur when installing heat shrink accessories. All Python terminations (with the exception of the SSC) come with the option of mechanical shrink installation.
Applications of Cable Accessories
Cable accessories play a vital role across industries:
- Utility infrastructure: MV/HV distribution networks.
- Substations: reliable terminations and joints.
- Renewable energy: connecting cables in solar and wind farms.
- Industrial facilities: automation, oil & gas, mining.
- Commercial/data centers: ensuring uptime for critical operations.
Why High-Quality Cable Accessories Matter
Cable accessories must be durable and reliable to maintain the safety and function of a given system. They must be able to withstand the environment of installation, any faults, or power surges. By validating that the cable accessories conform to IEC and/or IEEE standards, these considerations are all accounted for, ensuring high quality performance.
Failure of a single joint or termination can cause outages, equipment damage, and costly downtime. That’s why selecting durable, standard-compliant accessories is essential.
With a team of experienced engineers in cable accessories that are also involved in developing the standards, G&W Electric is able to help you select the right accessory for the cables in your system. We offer system audits to help identify requirements, spare audits based on existing stock of spares, and replacement programs that will suit your needs. Explore our Cable Accessories Solutions built for performance and reliability.
