Outdoors · bare conductor
Overhead line covers for bare distribution and transmission conductors
A bare 800 sq.mm conductor measures 38 mm across the strands, and every one of those millimetres is live metal.
Three constructions, and one question that picks between them
All three put a wall of non-tracking polymer between a bare conductor and whatever is about to touch it. They differ in how they get onto the conductor, and that is a crew question rather than a design-office one. Insulcover, the wrap-around polyolefin cover in the GOC series, goes on with the Split Insulation Tube Tool, which stays in one location while the cover is drawn onto the line. The silicone covers need no such tool: GSOC self-locks along its own seam, and GSIOC interlocks. If the tool is not going up the pole, the specification has already narrowed to silicone before anyone opens a size chart.
The voltage ceilings are four separate numbers, not one, and they must be read as the manufacturer publishes them. GSOC splits into classes on the same five conductor sizes, separated only by wall thickness: GSOC-M to 12 kV at 2.0 mm, GSOC-H to 36 kV at 2.7 mm, GSOC-H3 to 36 kV at 3.0 mm, and GSOC-EH to 765 kV at 5.0 mm. GSIOC, the interlocking silicone cover, is published to 33 kV. Insulcover carries two different ceilings on two of the manufacturer's own pages: the Insulation Enhancement Products page states 66 kV, while the older Polyolefin Overhead Line Cover page states 400 kV for the same material. Design to 66 kV. Both figures are printed here rather than the convenient one, and anything above 66 kV belongs in a written confirmation, not in a number lifted off a web page.
Non-tracking is the claim that matters outdoors, and it is the one with a graded test behind it. Polyolefin Insulcover shows no tracking, erosion or flame failure up to 3.25 kV for 20 min (ASTM D2303), holds 20 kV/mm (ASTM D149), runs continuously at −45 to +105 °C (IEC 216) and came through 5000 hours of UV exposure with no colour change (ASTM G154). GSOC reaches the same 3.25 kV step after an hour each at 2.5, 2.75 and 3.0 kV, and is quoted at more than 210 kV/cm (ASTM D149). GSIOC is a softer compound at 65 ±5 Shore A (ASTM D2240) and quoted lower, at 10 kV/mm (ASTM D149). A figure printed without a method in brackets is a claim, not a result.
A cover is bought by the metre. Nothing about it touches the conductor itself — no replacement, no re-stringing, no added line hardware — so the work stops at the spans where something is genuinely close: the branch grown into a phase, the crossarm a jumper swings toward, the structure birds and animals use to cross the clearance. Insulcover is supplied 30 metres to the roll, GSOC 15. Counting the metres at risk sizes the order; the system voltage only picks the series, and the engineer who has walked the feeder already holds the harder number.
The overhead range, and the pages that decide between them
Two products, two decisions and one chart. Everything else on this site is indoor metal.
Wrap-around polyolefin (GOC)
Insulcover: five sizes covering conductors to 800 sq.mm, halogen-free and flame retardant, fitted with the split insulation tube tool.
Silicone: GSOC and GSIOC
Self-locking and interlocking silicone covers that field-install with no special tool, across four voltage classes from 12 kV to 765 kV.
Size chart, both units
Every published cover code against conductor area in sq.mm and conductor diameter in mm, with wall thickness and roll length.
Polyolefin or silicone?
Where the two materials genuinely differ — tool access, wall thickness, tracking performance and what each is quoted at.
Covered conductor is a different product
A factory-covered conductor and a retrofit cover answer the same outage in opposite ways. Confusing the two is the expensive mistake here.
Wildlife protection covers
Which asset the animal actually bridges — conductor, jumper, insulator or bus connection — and what goes over each one.
The three overhead constructions side by side
Every figure is the manufacturer's published value for that specific product. "Not stated" means the source page is silent, not that the value is zero.
| Insulcover (GOC) | GSOC self-locking silicone | GSIOC interlocking silicone | |
|---|---|---|---|
| Material | Non-tracking cross-linked polyolefin | Non-tracking silicone rubber | Non-tracking silicone rubber |
| Voltage published | 66 kV (400 kV on one older page) | 12 kV (M), 36 kV (H and H3), 765 kV (EH) | 33 kV |
| Conductor area covered | ≤ 99 to 800 sq.mm | 185 to 800 sq.mm | Not stated on the source page |
| Conductor diameter covered | 10 to 38 mm | 15 to 38 mm | Not stated on the source page |
| Wall thickness | Not stated on the selection chart | 2.0, 2.7, 3.0 or 5.0 mm by class | Not stated on the source page |
| Tool needed at the pole | Split Insulation Tube Tool, worked from one stationary position | None | None |
| Supplied roll length | 30 metres | 15 metres | Not stated on the source page |
| Dielectric strength (ASTM D149) | 20 kV/mm min | > 210 kV/cm | 10 kV/mm min |
| Tracking and erosion (ASTM D2303) | No failure to 3.25 kV for 20 min | No failure to 3.25 kV for 20 min, after graded steps at 2.5, 2.75 and 3.0 kV | No failure to 3.25 kV for 20 min, after graded steps at 2.5, 2.75 and 3.0 kV |
| Derating of the conductor | Not addressed on the source page | Stated as not requiring further derating | Not addressed on the source page |
Insulcover selection chart (GOC series)
| Gala Code | Conductor size (sq.mm.) | Conductor size in Dia. (mm) | Packaging (Mtr./Roll) |
|---|---|---|---|
| GOC 1 | ≤ 99 | upto 10 | 30 |
| GOC 1A | upto 185 | upto 15 | 30 |
| GOC 2 | upto 300 | upto 22 | 30 |
| GOC 3 | upto 400 | upto 28 | 30 |
| GOC 4 | upto 800 | upto 38 | 30 |
Both units are printed because a line crew measures 38 mm across the strands and a design office writes 800 sq.mm for the same conductor. The four GSOC charts and the wall thickness per voltage class are reproduced in full on the line cover size chart; the source document is the manufacturer's Polyolefin Overhead Line Cover datasheet.
What a retrofit line cover does not do
A retrofit cover is insulation enhancement against momentary contact. It stops a branch, a bird or a swinging jumper turning a brush against bare metal into a flashover. It does not convert the conductor into an insulated conductor, it is not offered for sustained contact, and it does not make an energised line safe to touch. Approach distances, live-line procedure, isolation and earthing are all exactly what they were before the cover went on. A covered span is bare metal wearing a coat, and the crew must keep treating it that way.
"Pole top cover" names three different parts, and only one of them belongs here
A pole top holds three separable things: the electrical hardware, the sawn crown of the pole, and the band at ground line. All three get called a pole top cover. Only the first is a cover in the sense used here — insulator, jumper and bus connection, where the pre-formed GPFIC cover is field-trimmed at its entry and exit holes and can be re-entered later. The other two are a cap and a sleeve, published by named sibling properties rather than restated on this site.
- Insulator and bus connection covers (GPFIC)Circuit breaker bushings, standoff insulators, capacitors, transformer bushings, voltage regulators and potential transformers.
- Pole caps — anodecap.comThe sawn crown of the pole itself. A moulded cap over end grain, and not an electrical part at all.
- Pole protection sleeves — heatshrink-sleeve.comThe ground-line band on steel, concrete and wooden poles, where corrosion and rot start.
- Fitting, trimming and taking a cover off againFour procedures and one removal, including what re-entry costs on each construction.
Send the conductor size and the metres at risk
A cover code falls out of two numbers: conductor diameter in mm, or the area in sq.mm if that is what the drawing carries, and the length of line actually exposed. Add the system voltage and whether the crew has the split insulation tube tool, and the reply carries a series, a code and a roll count instead of a question.