Termination kits for PILC cable (GPO/E series)
Five inputs fix the code before anything else is discussed: lead sheath or armour, core count, Umax, conductor size in mm², and indoor or outdoor.
GPO/E series — heat-shrink terminations for paper-insulated lead-covered cable
GPO/E terminates three-core paper-insulated lead-covered cable at 12 kV, 24 kV and 33/36 kV, indoors or outdoors. Each kit is an itemised set of parts rather than a single moulded component, and the paper-specific items in that set — oil barrier sleeves, belting oil barrier, glass cushion tape and a conducting breakout — are what separate it from the extruded-cable GXO/E kit of the same voltage class. The outdoor kit code begins GPO, the indoor code begins GPE, and the two are not interchangeable once a requisition is raised.
- Terminal lug, lug sealing mastic and a heat-shrinkable terminal sleeve
- Oil barrier sleeve per core and a belting oil barrier sleeve over the belt
- Stress control sleeve under a non-tracking weather-resistant sleeve
- Glass cushion tape and a heat-shrinkable cable breakout at the crutch
- Tinned copper braid earthing, with an earthing plumb from lead sheath to armour at 24 and 33/36 kV
- Rain sheds on outdoor kits; the indoor shed count differs by voltage class
| Cable construction | 3-core PILC, screened or armoured, lead sheathed |
|---|---|
| Voltage classes | 12 kV, 24 kV and 33/36 kV (Umax) |
| Conductor range | 16–500 mm² at 12 kV; 25–500 mm² at 24 kV; 35–400 mm² at 33/36 kV |
| Classification | Class I heat-shrinkable termination kit |
| Kit codes | GPO-11..15 / GPO-21..24 / GPO-31..34 outdoor; GPE equivalents indoor |
| Series ceiling | 36 kV — GPO/E-3336 is the last kit in the range |
| Rain sheds | 6 per kit at 12 kV, 9 at 24 kV and 9 at 33/36 kV, outdoor |
Kit codes by conductor size, as ordered
| Umax | Cable size (sq mm) | Outdoor code | Indoor code |
|---|---|---|---|
| 12 kV | 16–35 | GPO-11 | GPE-11 |
| 12 kV | 50–95 | GPO-12 | GPE-12 |
| 12 kV | 120–185 | GPO-13 | GPE-13 |
| 12 kV | 240–400 | GPO-14 | GPE-14 |
| 12 kV | 500 | GPO-15 | GPE-15 |
| 24 kV | 25–50 | GPO-21 | GPE-21 |
| 24 kV | 70–120 | GPO-22 | GPE-22 |
| 24 kV | 150–240 | GPO-23 | GPE-23 |
| 24 kV | 300–500 | GPO-24 | GPE-24 |
| 33/36 kV | 35–70 | GPO-31 | GPE-31 |
| 33/36 kV | 95–150 | GPO-32 | GPE-32 |
| 33/36 kV | 185–300 | GPO-33 | GPE-33 |
| 33/36 kV | 400 | GPO-34 | GPE-34 |
From the catalogue's ordering charts. Outdoor and indoor kits are separate part numbers drawn from the same series. Nothing on site converts one into the other.
Published withstand figures, tail lengths and shed count
| Kit series | AC dry withstand | DC withstand | Lightning impulse | Tail outdoor / indoor | Sheds outdoor / indoor |
|---|---|---|---|---|---|
| GPO/E-1112 | 35 kV / 1 minute | 48 kV / 30 minutes | Above 75 kV | 600 mm / 450 mm | 6 per kit / none |
| GPO/E-1524 | 50 kV / 1 minute | 96 kV / 15 minutes | Above 125 kV | 800 mm / 550 mm | 9 per kit / 1 per core |
| GPO/E-3336 | 75 kV / 1 minute | 144 kV / 30 minutes | Above 170 kV | 900 mm / 700 mm | 9 per kit / 2 per core |
Reproduced from the catalogue's electrical-performance and accessories pages, per kit. Impulse figures are published as minima, not as measured results. Outdoor shed counts are the kit totals from the component list; divide by three for the per-core figure.
The series stops at 36 kV
GPO/E-3336 is the highest paper-cable termination the manufacturer publishes, and no 66 kV cable termination kit exists in the range. Read nothing on this page as an offer above 36 kV: the only 66 kV item in the catalogue is a busbar sleeve, which is not a cable accessory. What a 66 kV termination would actually require.
What paper insulation adds that extruded cable does not
Set the GPO/E component list beside the GXO/E list at the same voltage class. Six items appear on one and not the other, and every one of them exists because the dielectric is impregnated paper inside a lead sheath.
- Oil barrier sleeve on each core and a belting oil barrier sleeve over the belt — listed on all three GPO/E kits, on none of the extruded-cable kits.
- Glass cushion tape, published at 12 kV, 24 kV and 33/36 kV alike.
- An earthing plumb bonding lead sheath to armour, published on GPO/E-1524 and GPO/E-3336; the 12 kV kit lists an earthing lead in its place.
- A heat-shrinkable conducting breakout at 24 and 33/36 kV, where the equivalent extruded-cable kit lists a non-tracking breakout instead.
- Lug sealing mastic beneath the terminal sleeve on all three kits; that sleeve is published as adhesive-lined at 24 and 33/36 kV.
- Optional worm drive clips at 24 and 33/36 kV. At 12 kV the published installation aids are mastic sealing tape and cleaning solvent.
Why the breakout on belted paper cable conducts
Belted PILC carries one belt of paper over all three laid-up cores and no screen on any core individually. Cut the belt back at the crutch and each core is left with paper insulation and no defined earth reference along its length, which is a different starting condition from screened extruded cable.
Insulcore, the semi-conductive breakout, is built for exactly that. It seals the crutch and reconstructs the missing per-core screen at the same time, in cross-linked semi-conductive polyolefin lined with red water-resistant mastic, and the manufacturer publishes it as meeting IP68. Volume resistivity is 1 × 10⁷ ohm.cm minimum [ASTM D257] — seven decades below the non-tracking version, and the whole point of the part.
Insulcore-NT is the other breakout published for a paper crutch, in non-tracking rather than semi-conductive material, rated to 36 kV and selected GAB-0820 to GAB-3060. It insulates where the semi-conductive part screens. Both sit under the same stress control and non-tracking sleeves that every kit in the range carries: see stress control tube and the four sleeves inside an HT kit.
Semi-conductive against non-tracking breakout, property by property
| Property | Insulcore semi-conductive (GCB) | Insulcore-NT non-tracking (GAB) | Test method |
|---|---|---|---|
| Volume resistivity | 1 × 10⁷ ohm.cm max. | 1 × 10¹⁴ ohm.cm min. | ASTM D257 |
| Tensile strength | 12 N/mm² min. | 12 N/mm² min. | ASTM D638 |
| Ultimate elongation | 350% min. | 350% min. | ASTM D638 |
| Density | 1.10 ± 0.2 g/cm³ | 1.15 ± 0.2 g/cm³ | ASTM D792 |
| Dielectric strength | Not published | 15 kV/mm min. on the datasheet; 12 kV/mm min. on the product page | ASTM D149 |
| Tracking and erosion | Not published | No failure to 3.25 kV for 20 minutes | ASTM D2303 |
| Shrink temperature | 125 °C | 125 °C | — |
| Continuous temperature limit | −40 °C to +100 °C on the datasheet; +110 °C on the product page | −40 °C to +100 °C on the datasheet; +110 °C on the product page | IEC 216 |
| Ingress protection | IP68 | Not published | — |
Both are published for a PILC crutch. The resistivity row is the one that decides which of the two a belted cable needs.
Insulcore semi-conductive breakout selection chart
| Code | Cores | D s min. | D f max. | d s min. | d f max. | L s min. | L f min. | l s min. | l f min. | Tb ±10% | Tc ±10% |
|---|---|---|---|---|---|---|---|---|---|---|---|
| GCB-0820 | 3 | 55 | 20 | 25 | 8 | 160 | 188 | 52 | 62 | 3.3 | 2.7 |
| GCB-1330 | 3 | 80 | 30 | 36 | 13 | 185 | 215 | 60 | 75 | 3.6 | 3.3 / 3.7 |
| GCB-2145 N | 3 | 113 | 45 | 57 | 21 | 247 | 215 | 70 | 85 | 2.1 | 3.1 |
| GCB-2755 | 3 | 140 | 56 | 68 / 70 | 29 / 28 | 200 | 250 | 75 | 90 | 3.5 / 4.6 | 3.9 / 3.4 |
D, d: internal diameter. L: body length. l: leg length. s: as supplied. f: after free recovery. Tb, Tc: thickness of body and core. All dimensions in mm. Where the datasheet and the manufacturer's product page differ, both are given.
Not published — ask the manufacturer
Two things a specifier needs are absent from the published GPO/E material. First, which breakout code ships inside which kit: the component lists say “cable breakout” and “heat-shrinkable conducting breakout” without naming a GCB or GAB code against a conductor size, so the breakout charts above cannot be walked back to a kit code. Second, no dielectric strength and no tracking figure is published for the semi-conductive breakout at all — only its resistivity, which is the property that matters for screening but says nothing about what it will withstand. One oddity is published rather than missing: the DC withstand duration on GPO/E-1524 is 15 minutes where the kits either side of it are 30. That is stated in the catalogue, not inferred, and it is worth confirming before a site test is written around it.
Sources disagree — the breakout figures
The Insulcore datasheets and the manufacturer's product pages for the same two breakouts do not match on four points. Continuous temperature limit is −40 to +100 °C on both datasheets and +110 °C on both pages. Insulcore-NT dielectric strength is 15 kV/mm min on the datasheet and 12 kV/mm min on the page. And two cells of the GCB chart differ: GCB-2755 reads d 68/29 with Tb 3.5 and Tc 3.9 on the datasheet, and d 70/28 with Tb 4.6 and Tc 3.4 on the page; GCB-1330's Tc reads 3.3 against 3.7. Both sets are printed above and neither is averaged. On a crutch that has to close, take the smaller recovered figure and confirm it.
A paper run extended in XLPE is a joint, not two terminations
Where an old paper feeder is extended with extruded cable, the correct part is a GTJ transition joint that matches paper-side components to XLPE-side components in one splice — GTJ-11 to GTJ-17 at 12 kV, GTJ-21 to GTJ-25 at 15–24 kV, and GTJ-31 to GTJ-34 at 36 kV. Terminating both ends and bolting them together is not the same product and is not what the range offers: the manufacturer's GTJ page lists the component set, and the boundary between the two operations is drawn on cable joint or cable termination.
What third parties have actually tested, and what they have not
CPRI certified the manufacturer's 33 kV heat-shrink joints and terminations in August 2012. MSEDCL approval ran to 11 kV in 2015 and was extended to cover 11–33 kV in 2016. Both are company accreditations, not product standards, and they do not belong in a kit's specification block — the standards the kits themselves are qualified against are IEC 60502-4 and CENELEC HD 629.1, printed on the catalogue's guaranteed technical particulars. Partial-discharge and high-voltage testing is done in the manufacturer's own labs.
Neither third-party record is published against an individual GPO/E kit code, and neither covers the 36 kV class on its own — 33 kV is the certified figure, even though GPO/E-3336 is published for both classes. A tender clause that names a specific kit should therefore call for the report number and its scope rather than citing the certification in general. The withstand figures by class are collected on the termination type test chart.
One further limit worth writing into a specification: an indoor GPE kit in a coastal or cement-dust switchroom is not the same duty as an indoor kit in a clean substation, and the code letter does not know the difference. That judgement is compared page by page on indoor or outdoor termination.
Questions that come up at requisition
Can a GXO/E kit be used on PILC cable if the voltage class matches?
What does Class I mean on these kits?
Do 33 kV and 36 kV take different kits?
How many rain sheds does an outdoor GPO/E kit carry per core?
Which conductor size does GPO-23 cover?
Working out which GPO/E code your cable schedule needs
Send the cable make-up, the core count, the conductor size, the system Umax and whether the tail lands inside a panel or on an outdoor structure. Those five lines are the difference between one exchange and six.