Branch coupling or feedthrough? Comparison of connection types 2026 

Branch coupling or feed-through: Selection criteria for high-voltage splicing in 2026

The choice between a branch coupling and a feed-through coupling determines not only the reliability of the node, but also the architecture of the entire distribution network. In the context of growing loads on the energy systems of the CIS countries and changes in climate standards in 2025–2026, an error in the type of connection leads to emergency outages, the cost of eliminating which exceeds the price of the equipment tens of times.High voltage splicingrequires a precise understanding of the physics of the processes: where the electric field breaks, how the mechanical loads on the cable are distributed, and what the role of potential control is.

We are seeing a trend where designers are choosing feed-through couplings “by default”, ignoring the possibility of using compact branch solutions where it is technologically justified. This leads to excessive consumption of materials and complication of installation in cramped conditions of urban sewers. In this article, we'll break down the technical differences based on real-world experience in challenging soils and industrial environments so you can make an informed engineering decision.

Fundamental Differences: Design and Operation

The main difference lies in the cable connection topology. A pass-through (through) coupling connects the two ends of one cable, restoring its integrity along the entire route. The branch coupling creates a T-shaped connection, allowing you to connect an additional line to the main line without breaking it or using special elements.

In a feed-through coupling, the electric field is symmetrical relative to the axis of the connection. The engineer's task is to ensure uniform stress distribution along the insulation and the tightness of the joint. There are no field concentration points caused by the branch, which simplifies the shielding task. However, the length of such a coupling is always longer, since it must accommodate two end sections of the cable with a margin for heat shrinking or cold shrinking.

The branch coupling is structurally more complex. It must simultaneously ensure reliable contact between the main core and the branch core, often of different cross-sections. The tee area is a critical point for the occurrence of partial discharges. If in a feed-through connection the force vectors are directed linearly, then in a branch connection radial loads arise on the insulation at the outlet. This is where breakdowns most often occur due to improper installation or the use of low-quality materials.

Experience shows that many accidents occur not because of the quality of the coupling itself, but because the type of coupling does not match the load dynamics in the network. For example, when using a pass-through coupling as a temporary solution for organizing a branch (with subsequent rework), the integrity of the screen is compromised, which over time leads to corrosion and failure.

Mechanical load and tightness

Pass-through couplings experience predominantly longitudinal tensile forces. When the ground moves or thermal expansion of the cable, the force acts along the axis. Quality feedthrough coupling, such as products manufactured in factories with level laboratoriesShijiazhuang Hist Electric Co.,Ltd, is designed to compensate for these movements due to the elasticity of polymer materials.

In branch couplings, the load vector changes. The spur cable may be pulled down or to the side, creating a bending moment at the point of entry into the coupling body. This requires increased reinforcement and more rigid fixation of cables inside the housing. Sealing in such conditions is more difficult: it is necessary to seal three inputs instead of two, and the cable diameters can differ significantly.

Comparative analysis: Technical parameters table

For clarity, we have summarized the key parameters in a comparative table. This data is based on testing of samples meeting GOST and IEC standards carried out in our partner laboratories.

Please note: the cost of an error when installing a branch coupling is higher. If a feed-through coupling can be relatively easily replaced in case of an installation defect (by cutting out a section), then replacing a branch coupling often requires dismantling a significant part of the network or using expensive repair kits.

Application scenarios: When to choose which coupling in 2026

Operating standards are changing. In 2026, requirements for network reliability in conditions of extreme weather events became more stringent. The choice of coupling type should be dictated not only by the convenience of the installer, but also by the long-term strategy for maintaining the network.

Scenario 1: Main power transmission lines (VL and CL)

For main lines with a voltage of 6–35 kV, where minimizing losses and maximum reliability are important, priority is given to feed-through couplings. Any branch on such a line must be carefully justified. We recommend using through connections to repair damaged areas or extend the length of the route.

In our practice, there was a case when a series of branch couplings were used at a substation in Siberia instead of installing a distribution point. This led to moisture accumulation in the tee areas due to condensation due to temperature changes. Replacing it with a circuit with feed-through couplings and a dedicated distribution unit solved the problem, but required capital costs.Conclusion:Avoid unnecessary branches on highways. Use feed-through couplings to ensure line continuity.

Scenario 2: Urban distribution networks and connection of subscribers

In dense urban areas, space in cable ducts is limited. This is where branch couplings become indispensable. They allow you to connect a new residential complex or shopping center to an existing line without breaking it and de-energizing other consumers (using special energized technologies, although this requires special equipment).

CompanyShijiazhuang Hist Electric Co.,Ltdoffers solutions adapted specifically for such conditions. Their cold-shrinkable branch couplings have a compact profile, which is critical for older manifolds where the pipe diameter does not allow for the placement of bulky units. It is important to remember: in cities there is a high level of stray currents. The branch coupling must have high-quality shielding and grounding of all three inputs to avoid electrochemical corrosion.

Scenario 3: Industrial facilities with variable loads

In factories where powerful motors and frequency converters operate, harmonic distortion is present in the network. This increases the risk of insulation overheating. In such conditions, we recommend the use of both types of heat-shrinkable sleeves, but with special attention to the quality of the semi-conductive tapes. For branches at industrial facilities, it is better to choose couplings with a cast body that provides mechanical protection from vibrations.

If you are planning to modernize a workshop in 2026, include reserve space for future branches in the project. The use of feed-through couplings with a power reserve on the main cable will make it possible in the future to install a branch coupling without replacing the entire line.

Installation technologies: Cold shrink vs. Heat shrink

The choice of coupling type (branch or feed-through) is closely related to its installation technology. Two approaches dominate the market: heat-shrinkable and cold-shrinkable products. Each has its own advantages for different types of connections.

Heat-shrinkable sleeves

A traditional solution proven over decades. The operating principle is based on the shape memory of the polymer: when heated with a burner, the tube decreases in diameter and fits tightly around the cable.

• Pros:High mechanical strength after shrinkage, good protection against moisture, relatively low cost.
• Cons:Risk of overheating or underheating. Installation depends on the skill of the worker and weather conditions (wind, rain). For branch couplings, heat shrinking is more difficult, so you need to evenly heat the complex profile of the tee.

We have seen cases where inexperienced installers have left air bubbles under the heat shrink in the branch area. After six months, these bubbles became sources of partial discharges. Therefore, heat shrink should only be used for branch connections by qualified personnel.

Cold shrink couplings

More modern technology, gaining popularity in 2025–2026. The coupling is supplied with the spiral support installed. When the support is removed, the elastic material automatically compresses the cable.

• Pros:The human factor of heating is excluded. Installation is faster and safer (no open flames). Ideal for branch couplings with complex geometries, as the material evenly fits all irregularities.
• Cons:Higher cost. Requires caution during transportation (the support may come off).

For high-voltage splices in hard-to-reach locations or in high wind conditions, cold-shrinkable branch joints are the clear choice. They provide stable contact quality regardless of external conditions.

Common mistakes during selection and installation

An analysis of complaints over the past two years has revealed three systemic errors made by purchasers and installers. Avoiding these mistakes will save you money and reputation.

Mistake #1: Ignoring the difference in cable cross-sections.
Often they try to connect a cable of a smaller cross-section to a main line of a larger cross-section through a universal coupling without adapter sleeves. This leads to uneven distribution of the electric field and local overheating. Always use couplings certified for the specific cross-section range or use adapter connectors.

Mistake #2: Saving on branch shielding.
In a pass-through coupling, the screen is restored automatically when the braids are connected. In the branch coupling, it is necessary to correctly connect the shields of the three cables. A common mistake is simply twisting the screens without using contact springs or soldering. This creates a high contact resistance. In the event of a short circuit, such a screen may burn out, which will lead to insulation breakdown. Use ready-made kits with integrated grounding systems, such as those offered byShijiazhuang Hist Electric Co.,Ltd, where the process is standardized.

Mistake #3: Wrong choice of insulation material for the climate.
For northern regions (temperatures below -40°C) conventional PVC components are not suitable. Silicone rubber or special frost-resistant polymers are required. Installing standard heat shrink in winter without preheating the cable leads to the formation of microcracks during shrinkage. These cracks are not visible to the eye, but after a year of operation, moisture will penetrate inside.

Business Case: TCO (Total Cost of Ownership)

When estimating the cost of a project in 2026, it is important to look not at the list price of the coupling, but at the total cost of ownership (TCO). A branch coupling costs more than a feedthrough coupling. But if it allows you to avoid excavation work to lay a separate line from the distribution board, savings on construction can amount to hundreds of thousands of rubles.

On the other hand, the use of cheap, uncertified products leads to increased operating costs. The cost of a mobile team to repair a high-voltage cable line starts at significant amounts, not counting fines for undersupply of energy to consumers. Investment in quality couplings from a manufacturer with its own laboratory, such asShijiazhuang Hist Electric Co.,Ltd, pays off by reducing the frequency of accidents.

Laboratory tests up to 1000 kV carried out in production ensure that each batch of products meets the declared characteristics. This reduces the risk of receiving a defective batch, which often happens when purchasing from traders without technical control.

Frequently Asked Questions

Can a bushing be used to create a branch?

No, this is technically incorrect and dangerous. The pass-through coupling is not structurally intended for the insertion of a third cable. Attempts to make a hole in the body of the feed-through coupling violate its tightness and electrical strength. For branches, there are specialized branch couplings or distribution boxes.

What is the service life of a high-quality high-voltage coupling?

With proper installation and compliance with operating conditions, the service life of modern polymer couplings is at least 30 years. However, the first 5–7 years are a period of running-in, when hidden installation defects may appear. Regular monitoring of partial discharges in the first year of operation is mandatory.

What is the difference between single-core and three-core couplings?

Single-core couplings are used for cables with individual phases (often at voltages above 35 kV or in specific industrial applications). Three-core couplings combine all three phases in one housing. For urban networks of 6–10 kV, three-core couplings are more often used due to their compactness. The choice depends on the type of cable used.

Is it necessary to ground the shields in the branch coupling?

Yes, definitely. An ungrounded screen becomes a source of high potential, which is dangerous for personnel and leads to rapid destruction of the insulation. In branch couplings, it is necessary to ground the screens of all three connected cables, ensuring their electrical connection with each other.

Conclusion and recommendations

Choosing between a branch coupling and a feed-through coupling is not simply a matter of connection geometry, but a matter of your grid reliability strategy. In 2026, when requirements for uninterruptible power supply increase, you cannot skimp on the quality of components. Feed-through couplings remain the gold standard for highway applications, providing simplicity and reliability. Branch couplings are a necessary tool for network flexibility and connecting new facilities, but they require higher qualifications during installation.

We recommend:

• For main lines, use only certified feed-through couplings with shrinkage quality control.
• For branches in difficult conditions (city, industry), give preference to cold-shrinkable technologies.
• Choose suppliers with their own testing facilities, such asShijiazhuang Hist Electric Co.,Ltdto ensure product compliance with international standards and operating conditions in the Russian Federation and CIS countries.

Correcthigh voltage splicingis the key to stable operation of the enterprise for decades to come. Don't compromise on insulation and sealing quality.

Contact us today to receive technical advice and select the best solutions for your project.