GRL Copper Busbar: Splice Plate vs Fishplate vs Flexible Connector

When connecting copper busbars inside an electrical assembly, engineers may encounter three different terms: splice plate, fishplate, and flexible connector. Although all three are used in electrical connection systems, they do not necessarily serve the same purpose.

A splice plate or fishplate typically joins adjacent busbar sections to create a fixed electrical connection. A flexible copper connector, by contrast, is designed to accommodate a specified amount of movement while maintaining electrical continuity.

Choosing the wrong connection structure can create installation difficulties, transfer unnecessary mechanical stress to terminals, or make future maintenance more complicated. This guide explains the differences between busbar splice plates, fishplates, and flexible copper connectors, including when each is appropriate and what information to provide for custom fabrication.

What Is a Busbar Splice Plate?

A busbar splice plate is a conductive plate used to join two busbar sections. It normally overlaps the adjoining conductors and is secured using a specified bolted connection or another designed joining method.

Splice plates are commonly used when an electrical distribution assembly is manufactured or transported in separate sections and the busbars must be connected during installation.

Depending on the equipment design, a splice plate may be used to connect:

• Two straight copper busbar sections
• Adjacent switchboard sections
• Busbar sections inside a distribution cabinet
• Busbar extensions within a fixed electrical assembly

The exact shape and installation method depend on the equipment. Some arrangements use a separate plate on one or both sides of the joint, while other designs use overlapping conductors or dedicated connection hardware.

When Should You Use a Splice Plate?

A splice plate is generally suitable when the adjoining busbar sections need to form a mechanically fixed joint and their relative positions are defined by the assembly design.

The joint must be designed for the required current, contact area, mechanical loading, and short-circuit conditions where applicable.

Important design details include:

• Busbar width and thickness
• Splice plate dimensions
• Overlap length
• Hole diameter and position
• Fastener type and arrangement
• Contact surface condition
• Required tightening torque

A splice plate should not be treated as a universal component. Its dimensions and fastening arrangement must match the equipment manufacturer’s design or the approved engineering drawing.

What Is a Busbar Fishplate?

In some electrical switchboard and busbar systems, a fishplate is a connecting piece that bridges adjoining busbar sections. It can perform a function very similar to that of a splice plate.

For example, the Vertiv UL891 switchboard installation guide describes fish plates as busbar pieces that join the main horizontal or vertical bus between different switchboard sections.

You can refer to the equipment-specific terminology in the Vertiv UL891 Switchboard Installer/User Guide.

It is important to recognize that fishplate and splice plate are not universally separate categories with one fixed distinction. Their meanings can overlap, and the terminology may differ between manufacturers and equipment designs.

How Does a Fishplate Work?

A typical electrical fishplate bridges the ends or adjoining sections of a busbar arrangement. Fasteners hold the connection together and establish the required contact between the conductive surfaces.

Depending on the configuration, fishplates may have different outlines, hole patterns, thicknesses, or numbers of conductive layers.

The correct arrangement should follow the applicable equipment drawing and installation instructions rather than being selected from the name alone.

When Should You Use a Fishplate?

A fishplate is appropriate when the switchboard or busbar system specifically calls for that type of connection piece.

Before ordering a replacement or custom fishplate, confirm the following:

• The busbar configuration and equipment section
• The conductive material and dimensions
• The number, spacing, and diameter of mounting holes
• The number of conductor layers in the joint
• The specified fasteners and tightening requirements
• The required current and short-circuit performance

A fishplate designed for one switchboard configuration should not automatically be assumed suitable for another, even when the nominal busbar width appears identical.

What Is a Flexible Copper Connector?

A flexible copper connector is a conductive component designed to accommodate defined mechanical movement between two electrical connection points.

Unlike a conventional splice plate, which normally creates a fixed joint between busbar sections, a flexible connector contains a section designed to bend or deform within its intended operating limits.

Common constructions include:

• Stacked copper foil connections: Multiple thin copper sheets are stacked together, with the terminal areas consolidated or joined as specified by the design.
• Braided copper connectors: Fine copper strands are woven together to form a flexible conductive connection.
• Other engineered flexible links: Specialized conductor structures designed for a particular movement or installation requirement.

For the stacked copper foil construction, the copper layers form a conductive stack; there is no insulating layer between the individual copper sheets. External insulation, if needed, is a separate design requirement.

When Should You Use a Flexible Copper Connector?

A flexible connector is worth considering when the connection must accommodate movement that a fixed joint cannot safely absorb.

Typical reasons include:

• Thermal expansion and contraction
• Equipment vibration
• Limited terminal alignment tolerance
• Movement between separately mounted components
• Mechanical stress reduction at terminals
• Installation layouts that require a flexible connection path

Applications can include transformer connections, battery systems, power electronics, industrial equipment, and other electrical assemblies where the connected parts may move relative to each other.

However, flexibility does not mean unlimited movement. The required displacement, bend direction, connection geometry, current, and service conditions must all be considered when designing the flexible section.

Splice Plate vs Fishplate vs Flexible Connector

The distinction between splice plate and fishplate is often terminology-dependent. The more important engineering distinction is between a fixed connection designed to join adjacent sections and a flexible conductor designed to accommodate movement.

Can a Flexible Connector Replace a Busbar Splice Plate?

Sometimes, but not automatically.

A flexible connector may be appropriate when two connection points need electrical continuity and also experience vibration, thermal movement, or installation variation.

A splice plate may be more suitable when two rigid busbar sections are designed to form a fixed joint within a defined assembly.

Before replacing a splice plate with a flexible connector, engineers should verify:

• Continuous current-carrying requirements
• Short-circuit requirements where applicable
• Terminal compatibility and mounting dimensions
• Clearance and installation space
• Required movement and flexibility
• Contact resistance and temperature-rise requirements
• Mechanical support and applicable assembly approvals

The replacement should be evaluated as part of the complete electrical assembly. Matching the hole spacing or nominal conductor area alone is not enough to confirm interchangeability.

How Do You Choose the Right Busbar Connection?

Start with the mechanical function of the joint, then verify its electrical requirements.

Choose a Splice Plate When:

• Two busbar sections must be joined into a fixed connection.
• The equipment design specifies a conductive joining plate.
• The busbar alignment and mounting positions are already defined.
• The connection must meet the specified electrical and mechanical requirements of the assembly.

Choose a Fishplate When:

• The equipment drawing or manufacturer documentation specifies a fishplate.
• A designated connecting piece is required between adjoining busbar sections.
• The required plate geometry and fastening arrangement are defined for the relevant assembly.

Choose a Flexible Copper Connector When:

• The connection needs to accommodate specified movement.
• Vibration or thermal expansion must be considered.
• Small positional variations between terminals need to be accommodated by the connection design.
• A fixed rigid joint would transfer excessive mechanical stress to connected components.

If the equipment experiences no meaningful movement, adding a flexible connector may not provide a benefit that justifies its cost or installation complexity. Conversely, a rigid joining plate should not be forced into a position that creates mechanical stress simply to avoid using a flexible connection.

What Information Should You Provide for a Custom Connection?

If the required component is not an off-the-shelf part, a clear engineering drawing helps the manufacturer evaluate the correct construction and manufacturing route.

For an existing component, provide a dimensioned drawing or a sample together with the relevant electrical and mechanical requirements. A photograph can help explain the application, but it normally cannot establish all critical dimensions or performance requirements.

Common Busbar Connection Mistakes to Avoid

• Confusing terminology with function: Confirm what the equipment manufacturer means by splice plate or fishplate.
• Using a fixed plate where movement must be accommodated: Assess thermal expansion, vibration, and terminal loading before selecting the connection.
• Substituting a flexible connector based only on current rating: Verify geometry, temperature rise, fault requirements, and mechanical limits.
• Ignoring the contact interface: Plate overlap, contact condition, fasteners, and tightening requirements all affect joint performance.
• Ordering from incomplete dimensions: Confirm hole locations, thicknesses, terminal geometry, and critical tolerances against the approved drawing.

Busbar splice plates and fishplates are generally used to connect adjoining sections of a rigid busbar system. Their terminology can overlap, so the correct meaning should be confirmed from the relevant equipment drawing and manufacturer documentation.

Flexible copper connectors serve a different mechanical purpose. They provide an electrical connection while accommodating a defined amount of movement, vibration, thermal expansion, or installation variation.

The appropriate choice depends on whether the joint must remain fixed or accommodate movement, together with the required current, contact geometry, mounting arrangement, temperature rise, and mechanical conditions.

GRL Copper provides customized copper electrical connection components according to customer drawings and application requirements. Providing the connection type, electrical data, mounting dimensions, mechanical conditions, material specification, and surface treatment helps the manufacturer evaluate a suitable fabrication solution.