IEC61914 Short Circuit Testing Of Cable Cleats

By on 11th June, 2013

Follow @ThorneanDerrick

Short Circuit Testing Of Cable Cleats.

 

 

 

Conducting a short-circuit test is the only reliable way of proving that a cable cleat is capable of withstanding a specific set of fault conditions. 

Ellis Patents always recommend that any claims of cable cleat strength should be supported by a short-circuit test carried out in an independent and accredited laboratory and appropriately certified. 

Specifiers, consultants and engineers should also request, as standard, a complete test report that includes before and after photographs, and a table of results and conclusions.

This practice is becoming commonplace, but prior to the publication of the international standard IEC 61914 many cable cleats were not tested and those that were had no standardised testing method by which to gauge success or failure, as a result, test results were open to a wide range of different interpretations.

IEC 61914 has provided a standardised method for conducting a short-circuit test and a definition of the criteria for a pass. It does though allow for a significant degree of latitude and so caution must be employed when interpreting results.

Note should also be taken of the full report as opposed to just its headline page.

Example: Comparing Test Results

Two manufacturers have tested cable cleats to the international standard IEC 61914 and both claim their cleat is capable of withstanding a peak short-circuit current of 140kA.

• Manufacturer 'A' conducted a test using a 35mm cable cleated at  600mm centres.
• Manufacturer 'B' conducted a test using a 45mm cable cleated at 300mm centres.

Your system peak fault level is 60kA, you are using a 30mm diameter cable and you wish to cleat at 1200mm centres.

 

Q) Are Both Cable Cleats Suitable? A) No

Using the formula from The international standard IEC 61914 (provided and explained in the following section) the force each cleat was subjected to was:

Manufacturer B's product does not meet the requirement.

This example reinforces the importance of protecting a specification throughout the procurement process. An engineer can diligently calculate the forces and optimise the whole job cost through careful choice of cleat and spacing.

Yet when the project reaches the buyers they may see a requirement for 20,000 cleats, which they view as commodity products and so specify and install a cheaper option.

The risks of under specification, given the dangers involved, are obvious.

Category:  HV Cable Jointing & Terminating

Go back to blog index