Vocabulary
"Cable shroud" and "wire insulation cover" name four different parts
A bare overhead conductor 38 mm across the strands and a crimped lug on a flat tab are both called a cable shroud job, and they take nothing in common.
Four objects, one search phrase
A bare overhead conductor 38 mm across the strands. An insulated wire already carrying its own jacket. A gland spigot on a terminal box. A crimped lug sitting on a flat tab. All four get described as needing a cable shroud or a wire insulation cover, and only two of them take a part that is fitted over metal already in place and lifted off again afterwards.
If you typed high tension wire cover or high voltage wire cover, you almost certainly mean the first object. You have a bare line, something keeps brushing it, and you want insulation added without restringing the span. The trade name for that part is a line cover, and it is bought by the diameter of the conductor rather than by the voltage of the line. Two constructions exist. Cross-linked polyolefin is wrapped on with a split insulation tube tool that stays in one location for the fit. Silicone self-locks by hand with no special tool, and its voltage class sets the wall: 2.0 mm for GSOC-M up to 12 kV, 2.7 mm for GSOC-H and 3.0 mm for GSOC-H3 up to 36 kV, 5.0 mm for GSOC-EH up to 765 kV.
The distinction that decides everything downstream is neither material nor voltage. It is whether the part sits over the conductor or becomes the conductor's surface. A cover is fitted over metal that is already installed, and it is held by its own fasteners, by a self-locking edge or by a moulded interference fit. Tubing is slid on or closed around, then heated until it recovers down onto whatever lies beneath. From that moment it is not a cover on the wire; it is the outside of the wire. The bill for confusing the two arrives about two years later, when somebody has to get back in for a thermographic survey or to re-torque a bolt.
The four readings, and what each one actually is
- A cover over a bare overhead conductor
- The line cover. Five polyolefin sizes run by conductor diameter, GOC 1 for conductors up to 10 mm through GOC 4 for conductors up to 800 sq.mm and 38 mm in diameter, packed 30 metres to the roll. The silicone equivalent runs GSOC-M 15 to GSOC-M 38 at 15 metres to the roll. The polyolefin holds 20 kV/mm (min., ASTM D149) and shows no tracking, erosion or flame failure up to 3.25 kV for 20 min (ASTM D2303), with no colour change after 5000 hours of UV (ASTM G154).
- Tubing recovered onto an insulated wire
- Not a cover, and not published on these pages. It is selected by supplied and recovered diameter and by recovered wall, measured against the largest object it has to pass over, which is a different exercise from reading any chart on this site. Once it has recovered it cannot be lifted off, only cut off.
- A cover at a gland or a termination interface
- A gland shroud follows the shape of the gland body, so it is fixed and sized by the gland rather than by the cable. A cover sitting at a cable termination is governed by creepage across the interface instead. Neither part is chosen from a conductor-diameter chart, and neither is listed here; the refusals below say where each one lives.
- A cap or cover over a crimped terminal or a flat tab
- The other genuine cover of the four. Termicap is a flexible PVC cap moulded over the crimped wire-end terminal, TCV 12 to TCV 3251, dielectric strength 16 kV/mm (min., ASTM D149), continuous operating temperature −20 °C to 115 °C (IEC 216), tested to ANSI C37.20.2 for switchgear application up to 36 kV. Termicover is the flat-tab version, GTIC-1 to GTIC-3, 12 kV/mm (min., ASTM D149), tensile 12 N/mm² (min.) at 350% elongation (ASTM D638), self-extinguishing (ASTM D876). Recesses on the tab shoulders keep the terminal seated and the sleeve keeps dust out of the cable end.
Cover or recovered tubing
Six questions separate them, and every one of the six changes what you buy.
| Question | A cover | Recovered tubing |
|---|---|---|
| What it goes over | Metal or insulation that is already installed and in position | A free end it can slide onto, or a wrap-around form closed around the cable |
| What holds it | Its own fasteners, a self-locking edge, or a moulded interference fit | Applied heat, until it grips the substrate all the way round |
| Comes off again | Designed to. GPFIC bus connection covers are field-trimmed at the entry and exit holes and can be re-entered and reused for later maintenance; the Insulshroud PVC boot ships complete with fasteners and installs, removes or replaces | No. Cut it away and fit a fresh length |
| Chosen by | Conductor diameter, bar section, or the geometry of the terminal | Supplied and recovered diameter, plus recovered wall |
| Tool at the pole | None for the self-locking silicone cover; a split insulation tube tool, held in one location, for the wrap-around polyolefin | A heat source and enough working access to reach every side of the joint |
| Codes you will see | GOC 1A, GOC 4, GSOC-M 38, GSOC-EH15, TCV 3251, GTIC-2 | None here — no tubing selection table is published on this site |
What is not supplied under these names
Four things people ask for using this vocabulary, and the shortest honest answer to each.
- Heat-shrink tubing. No wall, no shrink ratio, no selection chart. Tubing is a different specification exercise from a cover, and shrink-tube.com is where that exercise is written out.
- Cable jointing kits. A joint rebuilds the cable's insulation and screen; it is not something laid over the outside. cablejointkit.com carries straight-through, transition and branch joints across the manufacturer's published range of 1.1 kV to 36 kV.
- Cable glands, and shrouds that follow a gland body. Different geometry, different fixing, different datasheet. anodecap.com holds that end of the range.
- Covers at a cable termination. Ask for the wrong one and you get a part sized against a conductor when the governing dimension was creepage. 66kvcabletermination.com is the reference for terminations.
A cover on a line does not make the line safe to touch
Every part named on this page is insulation enhancement fitted over metal that stays energised. It lowers the chance that a branch, a bird or a slack jumper brushing the conductor starts a fault, which is exactly what it is sold to do. It is not a voltage rating, it is not an insulated conductor, and none of these parts is sold as touch-proof. Once the cover is on, the line is still a bare line as far as anyone working near it is concerned. Covered conductor is a different product entirely, and the difference is worth reading before anyone climbs.
Straight to the part
If one of the four readings above is yours, this is the page that answers it.
- Wrap-around polyolefin line coverGOC 1 to GOC 4, conductors up to 800 sq.mm, 30 metre rolls
- Silicone line covers, GSOC and GSIOCFour voltage classes, 12 kV to 765 kV, fitted without a tool
- Termicap and TermicoverTCV caps over crimped lugs, GTIC covers over flat tabs
- Insulating shrouds over an assembled connectionThe indoor reading: a bolted joint inside a panel, covered and re-openable
- Shroud, boot, cover-up, cap or guardThe other vocabulary page, for when the word in your enquiry is shroud
- How to read a cover datasheetWhich figure on the sheet decides the part, and which figure is decoration
One measurement routes the whole enquiry
For a line cover, the conductor diameter in millimetres, measured across the strands. For a terminal cap, the crimped lug it has to sit over. For a shroud, the bar section and the length to be covered. Send the measurement and the answer comes back as a code instead of a question.