5 Copper Busbar Jointing Methods
5 Copper Busbar Jointing Methods (photo credit:

Efficient joints in copper busbar conductors

Efficient joints in copper busbar conductors can be made very simply by:

  1. Bolting
  2. Clamping
  3. Riveting
  4. Soldering
  5. Welding

Bolting and clamping are used extensively on-site. Shaped busbars may be prefabricated by using friction stir welding.

1. Bolted joints (most common)

Bolted joints are formed by overlapping the bars and bolting through the overlap area. They are compact, reliable and versatile but have the disadvantage that holes must be drilled or punched through the conductors, causing some distortion of the current flow in the bar.

Bolted joints also tend to have a less uniform contact pressure than those made by clamping but, despite these issues, bolted joints are very commonly used and have proven to be reliable.

They can be assembled on-site without difficulty.

A typical bolted joint
Figure 1 – A typical bolted joint

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2. Clamped joints (most common)

Clamped joints are formed by overlapping the bars and applying an external clamp around the overlap. Since there are no bolt holes, the current flow is not disturbed resulting in lower joint resistance. The extra mass at the joint helps to reduce temperature excursions under cyclic loads.

Well-designed clamps give an even contact pressure and are easy to assemble, but take up more space than a bolted joint and are more expensive to manufacture.

A simple clamped joint
Figure 2 – A simple clamped joint

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3. Riveted joints (difficult, but…)

Riveted joints are similar to bolted joints. They can be efficient if well made. It is difficult to control the contact pressure. They cannot easily be dismantled or tightened in service and they are difficult to install.

A riveted joint
Figure 3 – A riveted joint

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4. Soldered or brazed joints (rare)

Soldered or brazed joints are rarely used for busbars unless they are reinforced with bolts or clamps since heating under short-circuit conditions can make them both mechanically and electrically unsound.

A soldered joint
Figure 4 – A soldered joint

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5. Welded joints (not very safe…)

Welded joints are made by butting the ends of the bars and welding. They are compact and have the advantage that the current-carrying capacity is unimpaired, as the joint is effectively a continuous copper conductor. However, it may not be safe or desirable to make welded joints in situ.

Welding of copper is discussed in Copper Development Association Publication 98, Cost-Effective Manufacturing: Joining of Copper and Copper Alloys (Download here).

A welded joint
Figure 5 – A welded joint

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Joint Resistance Calculation

In principle, a clamped or bolted joint is made by bringing together two flat surfaces under controlled (and maintained) pressure, as shown in Figure 6.

An overlapped joint
Figure 6 – An overlapped joint

The resistance of a joint is mainly dependent on two factors:

  1. The streamline effect or spreading resistance, Rs, due to the diversion of the current flow through the joint
  2. The contact resistance or interface resistance of the joint, Ri.

The total joint resistance, Rj, is given by:

Rj = Rs+ Ri

This applies specifically to direct current applications. Where alternating currents are flowing, the changes in resistance due to skin and proximity effects in the joint zone must also be taken into account.

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Reference // Copper for Busbars – Guidance for Design and Installation – Copper Development Association (Download guidance)

About Author //


Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on


  1. David Braudo
    Jun 19, 2015

    Dear Edvard ,
    What about contact between tin plated copper bus bars with silver plated part of CB bur or CB ” out “and “incom” connector ( this applies both to the networks medium and low voltage) .
    This problem exist for systems operating in H2S atmosfere

  2. Kevin
    Jun 18, 2015

    Should add to bolted connections that selection of bolt material is important as well as the addition of compression washers.

  3. Dear Edvard Congratulations for this article and others that you have been writing. I am interested in more details about soldering and welding of busbars for high permanent currents like 10.000A . Can you indicate some literature ?

  4. bertrand COHARD
    Jun 18, 2015

    Hi Edvard,
    The article is very good and simple. Can you go deeper in the overlap area calculation ?
    For copper to copper : mm²/A and daN
    Same for Alu to Alu
    And a special notice for the use of different material : alu/copper AND the use of magnetic steel for the clamp due to induced current.
    (I can give you some figures if needed up to 6300A)

    Bertrand COHARD

    • Tomas Gavenda
      Jun 18, 2015

      Hello, I agree with Bertrand. Also add how many screws per overlap

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