The distance between copper busbars is an important part of electrical design. Two conductors may have enough space to operate normally at one voltage level, but the same spacing may not be appropriate for a different voltage, pollution environment, or insulation system.
This is why copper busbar clearance should not be selected only by looking at the busbar current rating or its physical size. Voltage, impulse withstand requirements, pollution, altitude, insulation materials, conductor arrangement, and the surrounding enclosure all need to be considered.
Another important distinction is the difference between clearance e creepage distance. These two terms describe different paths between conductive parts and should not be treated as interchangeable.
This guide explains how clearance and creepage apply to copper busbar systems and what engineers should consider when defining busbar spacing for electrical distribution systems.
Clearance is the shortest distance through air between two conductive parts.
For a copper busbar assembly, this may be the distance between:
The purpose of maintaining adequate clearance is to reduce the possibility of an electrical flashover or unintended discharge between conductive parts under the specified operating and transient conditions.
For low-voltage equipment, IEC 60664-1 provides principles and requirements for insulation coordination, including the determination of clearances and creepage distances. The current consolidated edition, IEC 60664-1:2020+AMD1:2025, includes requirements for equipment up to AC 1,000 V or DC 1,500 V connected to low-voltage supply systems. IEC 60664-1.
Clearance and creepage describe two different distances between conductive parts.
| Parâmetro | Liberação | Creepage Distance |
|---|---|---|
| Path | Shortest path through air | Shortest path along an insulating surface |
| Main concern | Electrical flashover through air | Surface leakage and tracking |
| Typical location | Between exposed conductive parts | Between conductors separated by solid insulation |
| Important factors | Voltage, impulse withstand, altitude, field geometry | Voltage, pollution degree, insulating material, CTI, surface path |
This distinction is particularly important when describing laminated or multi-layer copper products.
For a multi-layer copper connection in which the individual layers are all conductive copper and directly joined together, there is no insulating material between the copper layers. In that construction, the stacked copper layers form one conductive assembly rather than separate electrically isolated conductors.
Creepage becomes relevant when conductive parts are separated by a solid insulating material and the electrical path can travel along that surface.
There is no single clearance value that can safely be applied to every copper busbar system.
The required distance depends on the electrical insulation coordination of the complete equipment.
Important factors include:
IEC 60664-1 specifically provides methods and requirements for determining clearances and creepage distances rather than assigning one fixed spacing to every low-voltage application. Its current consolidated version also includes updated altitude guidance and dedicated flowcharts for clearance and creepage determination. IEC 60664-1:2020+AMD1:2025.
Therefore, statements such as “all copper busbars need at least X mm clearance” are not appropriate as a general engineering rule.
Higher voltage generally requires greater attention to the spacing between conductive parts.
The relevant voltage is not necessarily just the nominal system voltage. Insulation coordination also considers transient overvoltages and the required impulse withstand level.
For this reason, the busbar spacing should be selected as part of the electrical insulation design of the equipment.
Electrical equipment can experience transient overvoltages caused by switching events, lightning-related disturbances, or other system conditions.
The rated impulse withstand voltage, often expressed as Uimp, is therefore an important input when determining clearance.
The required clearance increases with the applicable insulation coordination requirements. The exact value should be taken from the relevant standard tables for the equipment and operating conditions.
The surrounding environment can affect insulation performance.
Dust, moisture, condensation, salt, industrial contamination, and other pollutants can create conductive paths on insulating surfaces.
This is particularly important for creepage distance because creepage follows the surface of an insulating material.
The pollution degree used in the insulation coordination process therefore affects the required creepage distance.
Air insulation performance changes with altitude because air density decreases as altitude increases.
For equipment installed above the altitude range covered directly by the basic dimensioning assumptions, appropriate altitude correction needs to be considered.
IEC 60664-1 includes specific guidance for altitude and updated altitude correction information in its current consolidated edition. IEC 60664-1:2020+AMD1:2025.
The physical shape of the copper busbar can affect the actual shortest distance between conductive parts.
A straight busbar is usually easier to evaluate than a complex three-dimensional conductor with several bends, holes, steps, or offset sections.
During design, engineers should check the closest point between:
The closest point may occur at a bend, corner, bolt head, or terminal rather than along the main flat section of the conductor.
A copper busbar can be bent into U-shaped, Z-shaped, offset, stepped, or other three-dimensional geometries.
Changing the shape can change the distance between conductive parts even when the original flat pattern remains unchanged.
For example, bringing two bent sections closer together may reduce the local clearance at the bend while leaving the rest of the busbar unchanged.
This means clearance should be checked on the finished three-dimensional assembly rather than only on the flat copper blank.
For complex custom busbars, a 3D model can be useful for checking the relationship between the conductor and surrounding components before manufacturing.
The busbar itself is not the only conductive part that needs to be considered.
Bolts, nuts, washers, terminals, mounting brackets, and other conductive hardware can become the closest conductive object to another phase or grounded structure.
For example, a copper busbar may have an adequate distance from the adjacent phase conductor, but a bolt head near the edge of the busbar may create a smaller local clearance.
Therefore, clearance checks should include the complete connection assembly rather than the copper bar alone.
This is especially important for customized busbars containing:
The required spacing can be affected by how conductors are arranged inside the equipment.
Phase-to-phase clearance must be evaluated between separate energized conductors according to the applicable insulation coordination requirements.
The closest point between the phases should be considered rather than using the average distance between the conductors.
The distance from an energized copper busbar to grounded metalwork is another important design dimension.
Enclosure walls, mounting structures, support brackets, and other grounded components may all affect this distance.
When several copper bars overlap or cross within an assembly, the spacing around the connection must be checked carefully.
This is particularly relevant when multiple phases are arranged within a compact electrical cabinet.
Insufficient spacing can reduce the insulation margin of an electrical assembly.
Depending on the application and environmental conditions, inadequate spacing can increase the risk of:
The actual risk depends on the electrical system, insulation coordination, environmental conditions, and the verified design of the complete assembly.
This is why busbar spacing should be established during the design stage rather than adjusted after the equipment has already been manufactured.
For a custom copper busbar assembly, the drawing should clearly identify critical spacing requirements.
Useful drawing information can include:
For complex assemblies, it is useful to identify the relevant datums and critical clearance dimensions rather than simply providing one overall cabinet dimension.
A 2D drawing can define the critical dimensions, while a 3D model can show the complete spatial relationship between the copper busbars and surrounding components.
The electrical clearance of a custom busbar is closely connected to its physical geometry.
A small manufacturing change can alter the final position of a conductor, especially when the component contains several bends or closely positioned holes.
For example, incorrect bend dimensions may bring one section of the conductor closer to another phase or to a grounded mounting structure.
This is why copper busbar fabrication and electrical design should be considered together.
A custom copper busbar manufacturer should be able to work from the specified dimensions, bend geometry, tolerances, connection locations, and applicable surface-treatment requirements.
Copper busbar clearance is not a fixed dimension that can be selected from the busbar current rating alone. The required spacing depends on the electrical insulation coordination of the complete equipment, including voltage, impulse withstand requirements, pollution, altitude, conductor arrangement, and surrounding conductive structures.
Clearance describes the shortest path through air between conductive parts, while creepage describes the shortest path along an insulating surface. For a multi-layer copper connection made from stacked pure copper layers with no insulation between them, the copper layers themselves form one conductive assembly; creepage should only be considered where an insulating surface separates different conductive parts.
For custom copper busbars, critical clearances should be defined on the engineering drawing and verified on the finished three-dimensional assembly. This helps ensure that the manufactured conductor remains compatible with the electrical and mechanical requirements of the equipment.
GRL Copper provides customized fabricação de barramento de cobre, including cutting, punching, drilling, bending, multi-layer copper joining, surface treatment, and dimensional inspection according to customer drawings and electrical connection requirements.
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