Line cover size chart: conductor size to cover code
A 300 sq.mm stranded conductor is accepted up to 22 mm across the strands on the polyolefin chart and up to 20 mm on the silicone one, which is why the cross-section figure on its own will not pick your code.
The diameter column is the one that decides
A line cover passes over the outside of the strands, so the figure that picks the code is the measured overall diameter, not the nominal cross-section printed on the conductor schedule. Two conductors of the same nominal sq.mm can sit several millimetres apart across the strands, because strand count and a steel core change the overall diameter without changing the area of aluminium. Both charts below carry both columns for exactly that reason, and where the two columns point at different rows, the diameter column is the one to follow.
The two published charts also disagree with each other at the same cross-section, which is worth knowing before anyone converts one to the other. At 300 sq.mm the polyolefin chart runs to 22 mm and the silicone chart stops at 20 mm. At 400 sq.mm the polyolefin chart stops at 28 mm while the silicone chart runs to 32 mm. Silicone additionally publishes a 350 sq.mm band that polyolefin does not, and polyolefin publishes a small size — up to 99 sq.mm and 10 mm — that the silicone range does not reach at all.
Both tables here are the manufacturer's own selection charts retyped without change, with the source sheet named above each one so any row can be checked against it. Nothing is interpolated. Where a size does not appear, it is because the manufacturer does not publish it, and that gap is a written question to the supplier rather than a licence to take the nearest row.
GOC is the polyolefin wrap-around Insulcover: five sizes, 30 metre rolls, fitted with the Split Insulation Tube Tool from one stationary position. GSOC is the self-locking silicone cover: 15 metre rolls, field-installed with no special tool, in four voltage classes — GSOC-M to 12 kV, GSOC-H and GSOC-H3 to 36 kV, GSOC-EH to 765 kV. The polyolefin range is published with two different insulation-enhancement ceilings, 66 kV on the Insulation Enhancement Products sheet and 400 kV on the Polyolefin Overhead Line Cover sheet, and both appear here because the manufacturer publishes both. Neither product makes the conductor safe to touch; both are insulation enhancement over metal that stays live.
Polyolefin wrap-around cover — GOC selection chart
| Gala code | Conductor size (sq.mm) | Conductor size in dia. (mm) | Packaging (m/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 |
Reproduced from the selection chart on the manufacturer's polyolefin overhead line cover page. Packaging does not change with the code — every GOC size is supplied on a 30 metre roll.
Self-locking silicone cover — GSOC-M selection chart, to 12 kV
| Gala code | Conductor size (sq.mm) | Conductor size in dia. (mm) | Thickness (mm) | Packaging (m/roll) |
|---|---|---|---|---|
| GSOC-M 15 | upto 185 | upto 15 | 2.0 | 15 |
| GSOC-M 20 | upto 300 | upto 20 | 2.0 | 15 |
| GSOC-M 24 | upto 350 | upto 24 | 2.0 | 15 |
| GSOC-M 32 | upto 400 | upto 32 | 2.0 | 15 |
| GSOC-M 38 | upto 800 | upto 38 | 2.0 | 15 |
Reproduced from the GSOC-M chart on the manufacturer's self-locking silicone line cover page. The three higher classes repeat these same five conductor bands and change only the wall: GSOC-H at 2.7 mm and GSOC-H3 at 3.0 mm, both to 36 kV, and GSOC-EH at 5.0 mm to 765 kV. All four classes are packed 15 metres to a roll.
When the conductor sits on a boundary
Every figure in both charts is an upper limit — upto, in the manufacturer's own wording — so a code takes your conductor when the measured diameter falls at or below that row's figure and above the row beneath it. Measure the metal rather than reading the schedule, and step up only when the measurement genuinely passes the band below; a cover taken two bands large gapes at the seam and stops being a barrier at the point where it was fitted to be one. The 400 sq.mm case shows what a converted figure costs. A conductor of that cross-section measuring 30 mm across the strands has already left GOC 3, which stops at 28 mm, and moves to GOC 4 — while on the silicone chart the same conductor is still comfortably inside GSOC-M 32. Same copper, two charts, two different answers, and only the measurement tells you which one you are on.
Roll length, and how much line one roll actually covers
Packaging is the only length either chart publishes, so the metres per roll are what the order is written in.
- One 30 metre polyolefin roll covers a 10 metre length on each of three phases, or a single 30 metre run on one phase. Three phases through a 30 metre tree section is three rolls, not one.
- One 15 metre silicone roll covers five metres per phase across three phases — half the reach of the polyolefin roll, from a chart that is otherwise the same shape.
- Cover length comes from the contact risk, not from the span. The metres either side of the tree, the jumper at the pole top, the section crossing the access road: that is what gets covered, and the rest of the span stays bare on purpose.
- The polyolefin cover is installed with the Split Insulation Tube Tool, which stays in one location while the cover goes on. Work the roll out from that fixed point rather than from the middle of the run.
- The silicone cover needs no special tool and locks to itself, so a crew can move along the conductor and stop where the risk stops.
- Any cut length other than the published roll is a question to put to the supplier before the order rather than an assumption made at the pole.
- On derating, the silicone sheet states that the cover does not require further derating of the conductor. The polyolefin sheet carries no equivalent line, so treat it as open on a fully loaded feeder and ask.
Before the code goes on the order
- The polyolefin GOC cover in fullTensile, dielectric and tracking figures with the test method beside each, and a plain statement of what the cover is not for.
- The silicone GSOC cover in fullFour voltage classes, the self-locking fit, and the optional self-fusing tape at 63.5 mm x 0.76 mm.
- Polyolefin or siliconeWhether the crew can carry the Split Insulation Tube Tool to the location decides more of these jobs than the polymer does.
- Covering the line you have, or restringing itA retrofit cover and a factory-covered conductor answer the same outage with different outage plans.
- What a cover datasheet is promisingTypical against minimum, and what a kV figure printed on a cover does and does not commit to.
- Why covers failTracking, ultraviolet ageing, and the band chosen one size too large.
- Fitting covers and shroudsTools, trimming, and what has to be de-energised before anyone climbs.
Send the measurement, not the schedule figure
Measured diameter across the strands in mm, nominal cross-section in sq.mm, system voltage, metres needed per phase, and whether the cover has to come off again for inspection. Those five lines are enough to return a GOC or GSOC code without a second round of questions. If the enquiry is going to more than one supplier, attach the manufacturer's Insulcover datasheet so every quote is priced against the same chart.