Eliminating burrs is not merely a matter of installation detail; it determines the reliability of medium-voltage cable joints for the next decade or more.
Many failures in medium-voltage cable joints are caused neither by overloading nor by the materials themselves.
The true hidden danger often stems from a tiny, almost invisible detail: a metal burr just a few millimeters high.
When traditional shear bolts break, a small remnant—a burr—often remains on the connector surface. Installers typically file this down manually before applying cold-shrink or heat-shrink insulation sleeves.
If the cleanup is thorough, everything appears fine.
However, if the burr is not completely removed, the seeds of failure are sown the very day of installation.
Once the insulation sleeve is installed, this burr becomes a geometric defect hidden within the insulation system. During the long-term operation of 11kV–33kV medium-voltage systems, the sharp metal edge causes local electric field concentration, subjecting that specific area to heightened electrical stress.
Over time, this electric field distortion can trigger partial discharge, which continuously erodes the insulation material, progresses into electrical tracking, and ultimately leads to dielectric breakdown.
Such failures rarely occur immediately.
They may happen months or even years after the equipment is put into service, making it nearly impossible to trace the issue back to the original installation defect.
For this reason, an increasing number of grid companies, EPC contractors, and QA/QC teams are focusing on a fundamental issue:
What truly needs to be eliminated is not the burr itself, but the design that creates it.
By adopting “Stepless Flush-Break” technology, SUNJ enables shear bolts to break flush below the terminal surface—eliminating protrusions and burrs entirely, and removing the need for manual filing.
The significance of this goes far beyond mere installation convenience. More importantly, by eliminating a potential source of long-term failure before the insulation sleeve is even installed, the electric field distribution is made more uniform, thereby enhancing the long-term reliability of the medium-voltage cable joint at the source.
Engineering Takeaway
A truly reliable design does not rely on installers executing every single detail to perfection.
Instead, it proactively eliminates risks that could evolve into future failures during the product design phase.
Finally, I would like to pose a question to my fellow engineering professionals:
In your QA/QC acceptance criteria, has a “burr-free” condition following bolt shear become a mandatory inspection requirement? Or do you still rely on field installers to handle this manually?
Note: This article and its accompanying images were generated with the assistance of AI tools; they are intended solely to aid understanding and strictly adhere to platform community guidelines. Thank you for reading!
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#DielectricBreakdown #MediumVoltageCable #QualityControl #UtilityEngineering #EPCProjects #Substation #ShearBoltConnector
