HV Cable Link Boxes: Inspection Questions for Bonding-System Reliability
Engineering guide: The link box is a visible point in an otherwise buried bonding system. Its condition and connections can reveal problems, but inspection must preserve the approved configuration and electrical safety boundaries.
On this page: Start with identity and drawing match · Look for environmental evidence · Trend electrical indicators · Protect configuration control · Close the record loop
Start with identity and drawing match
Confirm the asset and major-section identifier from outside the equipment. The approved bonding diagram should show whether the box contains straight links, cross-bonding connections, earth links or sheath voltage limiters.
Look for environmental evidence
From an authorized safe position, note enclosure damage, water ingress indicators, corrosion, seal condition, cable-entry stress, overheating marks and unauthorized modifications. Moisture can degrade insulation and connections.
Trend electrical indicators
Where the owner’s program provides fixed sensors or approved measurements, compare sheath current, temperature or alarms among phases and against historical data. A single unexplained value should trigger engineering review, not improvised reconnection.
Protect configuration control
Link positions define the bonding system. Opening, moving or testing them can expose hazardous voltage and alter protection. Only qualified personnel following the owner’s isolation, test and restoration procedure should intervene.
Close the record loop
Record date, load condition, findings, photographs where permitted, instrument identity, drawing revision and corrective action. CIGRE includes maintenance and monitoring because bonding reliability is a lifecycle responsibility.
Related engineering guides
Continue with the main topic guide. The design concepts here require project-specific studies, applicable standards and qualified personnel.
Next in this series: Single-Point Cable Sheath Bonding: Purpose, Limits and Design Inputs · Both-End Bonding of Cable Sheaths: Circulating Current and Rating Impact · Cross-Bonding of HV Cable Sheaths: Major Sections and Transposition Logic
Sources and image credit
Technical reference: primary engineering source. Photo by American Public Power Association under the Unsplash License. Original educational content by ST College.