Covered conductor lines need far less attention than bare lines on the same route, because transient contact with branches, birds and clashing phases no longer causes outages. They are not maintenance free in the sense of never being looked at. The covering, the fittings and the protection devices each have failure modes that a planned patrol can catch before they become a fault. This checklist sets out what to inspect on a covered conductor line and why.
Routine patrol checklist
| Item | What to look for | Why it matters |
|---|---|---|
| Covering surface | Cuts, abrasion, crushed sections, bird or animal damage, signs of burning | Damage removes protection at that point and can admit water |
| Tracking marks | Dark, branching traces on the surface, especially near clamps and insulators | Shows surface leakage; common in polluted or coastal zones |
| Vegetation contact | Branches resting on or rubbing against the conductor | Short contact is tolerated; continuous rubbing wears the covering |
| Suspension and dead-end clamps | Slippage, cracked bodies, missing parts, covering squeezed out of the clamp | The clamp carries the line load through the covering |
| Insulation piercing connectors | Loose bolts, discolouration, heat marks, missing covers | A poor connection overheats under load |
| Junction sleeves | Insulation intact over the joint, no cracking at the ends | Exposed joints lose the benefit of the covering |
| Arc protection devices and surge arresters | Present where designed, undamaged, arc marks after storms | They keep lightning arcs away from the conductor |
| Sag and clearance | Abnormal sag, clearance to ground, roads and structures | Covering does not change statutory clearances |
| Earthing points | Present, accessible and covered when not in use | Crews need them for safe isolation |
When to patrol
Most utilities fold covered conductor lines into their normal patrol cycle. Extra patrols are worthwhile after severe storms and lightning activity, after the monsoon, and after any work by other agencies near the line, such as road widening or tree felling. A line that runs through forest or a coastal belt may justify a shorter cycle than a roadside feeder.
Vegetation management
The covering is designed to withstand temporary contact with a branch, not to support a tree. Clearance cutting is still needed, but the cycle can usually be planned around the season rather than driven by emergency tripping. Branches found lying on the line can be removed on a planned visit instead of as an outage. Where forest rules restrict cutting, the inspection record becomes the evidence of how the line is being managed.
Reading the findings
Isolated surface scuffs are normal on any overhead line. Tracking near a clamp, heat marks at a connector or damage that reaches the inner layer are not, and should be repaired with the line dead and earthed. Repeated tracking along one section points to a pollution source or an unsuitable fitting. Repeated damage at the same spans after storms usually means arc protection or surge arresters are missing or need repositioning.
The fittings themselves are described in the MVCC accessories and installation guide. APAR’s covered conductors, with an anti-tracking, UV-resistant outer layer over a longitudinally water-tight conductor for 11 kV to 132 kV, are detailed on the covered conductor product page.