Why Correct Specification of Cable Cleats According to Short-Circuit Levels is Critical for System Safety

In electrical installations, safety is paramount. One often overlooked component that plays a vital role in ensuring system integrity during fault conditions is the cable cleat. These seemingly simple devices are responsible for securing cables in place, preventing dangerous movement during short-circuit events. However, specifying cable cleats incorrectly or neglecting to consider short-circuit forces can lead to catastrophic failures, posing risks to equipment, property, and human life. This article explores why cable cleats must be correctly specified according to short-circuit levels, the relevant standards governing their use, and the responsibility of the person signing off on the system to demonstrate compliance and safety.

Understanding the Role of Cable Cleats

Cable cleats are mechanical devices designed to restrain cables under electrical fault conditions. When a short circuit occurs, the resulting electromagnetic forces between conductors can be immense. These forces can cause cables to whip violently, damaging insulation, breaking supports, and even injuring personnel nearby.

Without properly rated cable cleats, the installation becomes vulnerable to:

Cable displacement leading to insulation damage and fire hazards.
Structural damage to trays, ladders, and enclosures.
Extended downtime due to equipment failure and costly repairs.

In short, cable cleats are not optional accessories; they are essential safety components.

Why Short-Circuit Level Matters

The magnitude of force exerted on cables during a short circuit depends on:

Fault current (kA): Higher currents generate stronger electromagnetic forces.
Cable core separation: The closer the cores, the higher the forces.
System configuration: Single-core cables in trefoil or flat formation behave differently under fault conditions.

If cleats are not specified to withstand these forces, they can fail at the very moment they are needed most. This is why international standards require that cable cleats be tested and rated for short-circuit conditions.

Relevant Standards and Compliance

Two key standards govern cable cleat performance:

IEC 61914 – Cable Cleats for Electrical Installations: This international standard specifies requirements for the mechanical retention of cables, including short-circuit testing.
BS EN 61914 – The European adoption of IEC 61914.

These standards mandate that manufacturers test cleats under fault conditions to verify their ability to restrain cables safely. When specifying cleats, engineers must ensure:

The cleat’s short-circuit withstand rating matches or exceeds the calculated fault level.
Installation spacing complies with manufacturer recommendations.
Cleats are installed on a secure support system capable of handling the forces.

Failure to adhere to these standards can result in non-compliance, exposing the organisation to legal and financial liabilities.

The Responsibility of the Sign-Off Authority

The person who signs off on the electrical system, whether an engineer, project manager, or compliance officer, carries significant responsibility. Their signature is not just a formality; it is a declaration that the system is safe, compliant, and fit for purpose.

To demonstrate this, they must:

Verify calculations for short-circuit forces and cleat selection.
Ensure documentation includes manufacturer test certificates and compliance with IEC 61914.
Confirm installation practices align with design specifications.

In the event of an incident, investigators will scrutinise these records. If the sign-off authority cannot prove due diligence, they may face professional and legal consequences.

Consequences of Incorrect Specification

The risks of under-specifying cable cleats are severe:

Safety hazards: Unrestrained cables can cause arc flashes, fires, and injuries.
Equipment damage: Cable movement can destroy switchgear, transformers, and control panels.
Financial loss: Repairs, downtime, and liability claims can far exceed the cost of proper cleats.
Reputational damage: Non-compliance undermines trust and credibility.

Conversely, correct specification ensures peace of mind, regulatory compliance, and long-term reliability.

Best Practices for Specifying Cable Cleats

Start with accurate fault level data: Obtain short-circuit calculations from the system designer.
Use certified products: Only select cleats tested to IEC 61914.
Follow manufacturer guidelines: Pay attention to spacing and installation instructions.
Document everything: Keep records of calculations, product certifications, and installation checks.
Train personnel: Ensure installers understand the importance of cleat specification and placement.

Conclusion

Cable cleats may seem like minor components, but their role in system safety during short-circuit events is critical. Correct specification according to short-circuit levels is not optional—it is a legal and ethical obligation. Standards like IEC 61914 exist to guide this process, but compliance ultimately depends on the diligence of engineers and sign-off authorities.

When you sign off on an electrical system, you are certifying its safety. Make sure you can demonstrate that every component, including cable cleats, meets the required standards. The cost of getting it wrong is far greater than the effort to get it right.