Guide
What a cable joint has to put back
A cut cable loses four things. The kit is the parts list that answers each one, packed in the order you meet them.
Four losses, one box
Cut a cable through and you have not made one problem. You have made four. The conductor stops. The insulation stops. The metallic screen and the earth path stop. The sheath and the armour stop.
Everything a jointer does after the cut is answering those four, in that order, with named parts out of one box. Nothing in the kit is decorative and nothing in it is spare.
Count the cable ends first, because that decides which product you are holding. Two cable ends is a joint. One cable end facing a bushing, a transformer or an overhead line is a termination. That is a separate range with its own kit codes.
The distinction earns its keep on site, not just on a requisition. When a joint is finished the field is still inside a cable. Nothing in the box has to survive sunlight or a wet insulator surface. Everything in it has to survive being buried, flooded and loaded.
The four losses, and the part that answers each
- Conductor continuity: the inline connector
- The ferrule sits at the top of every joint manifest. GPS/1112 ships a crimping-type ferrule in copper or aluminium. The GTJ transition kits ship a barrier type instead, because oil must not travel out of the paper side into the XLPE side. One per core, so three on a three-core kit and one on a GXSS single-core kit. Crimp it and the electrical join is made. Everything after that rebuilds what you cut away to reach it.
- Insulation: red tubing, counted by voltage class
- GXS/1236 carries 3 red heat-shrinkable insulation tubes on a 12 kV kit and 6 on the 24 kV and 36 kV kits. GXSS-1236 carries 1 insulating tube at 12 kV, 1 at 24 kV and 2 at 36 kV. Check the count against the packing list before anyone cuts back. The number is the voltage class, not a generous allowance, and a short kit stops the job.
- Screen and earth path: mastic, tubing, mesh and plumbing
- GXS/1236 rebuilds the screen with copper woven flexible mesh tape and dual-wall screened tubing. One tinned copper braid carries the earth out, listed as the main earthing. On paper cable GPS/1112 supplies the armour and lead-sheath earthing as one material item. Copper braid, plumbing metal, flux and copper binding wire, together. Continuity is a listed part with a quantity against it, not something you improvise at the end.
- Sheath and armour: joint case and outer sleeves
- GXS/1236 closes with a wraparound metallic protection case and 3 outer jacketing sleeves, one centre and two sides, held by 4 worm drive clips. GI mesh tape is offered as the alternative to the case. Paper cable adds parts the extruded kits never carry. GTJ/2436 lists 3 oil barrier sleeves, an EPDM insulating wedge and a set of plumbing metal. Item by item: every part in a cable joint kit.
The cut edge of the screen
On shielded MV cable the earthed insulation screen has to be cut back to reach the core. Field lines crowd at that cut edge. Left alone, the crowding finds the void between the screen edge and whatever you shrink over it. Removing that void is the job of the next two components.
They go on in a fixed order. Stress control mastic is worked into the step at the cut and around the ferrule region. It fills the void, so nothing is left for a discharge to sit in. Stress control tubing then shrinks over the graded area and spreads the field along its own length.
The counts are on the manifest and they move with the class. GXS/1236 lists stress control mastic twice: 6 or 9 pieces as item 2, and 6 grey or yellow strips as item 6. Three black stress control sleeves sit beside them. GXSS-1236 names its mastic specifically for the ferrule region and carries one stress control tubing. GTJ/2436 adds a high-permittivity void filler and a heat-shrink conducting breakout at the crutch, where three cores become one cable.
At 1.1 and 3.3 kV none of this applies. There is no insulation screen, so there is no cut-back to grade, and GXLT/GPLT carries no stress control item of any kind. Its numbered list runs ferrule, insulation sleeve, armour continuity connection, worm drive clamps, wraparound joint case and outer jacketing sleeves, then stops. If a quotation puts stress control tubing into an LV straight-through joint, the wrong kit has been priced.
One kit per construction, core count and voltage class
| Series | Cable it is built for | Voltage classes | Conductor range (sq mm) | Kit codes |
|---|---|---|---|---|
| GXLT / GPLT | 1, 2, 3, 3½ or 4-core extruded or paper, armoured or unarmoured | 1.1 kV, 3.3 kV | 4x1.5–6 up to 4x300–400 | GXLT-1 to GXLT-6, GXLT-11 to GXLT-16 |
| GXS/1236 | 3-core extruded dielectric, shielded, armoured or unarmoured | 12 kV, 15–24 kV, 36 kV | 16 to 500 | GXS-11 to GXS-15, GXS-21 to GXS-25, GXS-31 to GXS-34 |
| GXSS-1236 | Single-core extruded dielectric, shielded | 12 kV, 15–24 kV, 36 kV | 16 to 1000 | GXSS-11 to GXSS-15, GXSS-21 to GXSS-25, GXSS-31 to GXSS-35 |
| GPS/1112 | 3-core PILC at 11 kV | Umax 12 kV | 16 to 630 | GPS-11 to GPS-15 |
| GPS/2436 | 3-core screened PILC | 24 kV, 36 kV | 25 to 500 at 24 kV, 35 to 400 at 36 kV | GPS-21 to GPS-24, GPS-31 to GPS-34 |
| GTJ/1112 | PILC one side, XLPE the other | 12 kV | 3x16–35 up to 3x630 | GTJ-11 to GTJ-15, GTJ-17 |
| GTJ/2436 | PILC one side, XLPE the other | 24 kV, 36 kV | 25 to 500 at 24 kV, 35 to 400 at 36 kV | GTJ-21 to GTJ-25, GTJ-31 to GTJ-34 |
Kit codes and conductor ranges as printed in the manufacturer's Heat Shrinkable Cable Accessories catalogue. Ranges are shown as a span across the whole series; the class-by-class charts are on cable joint kit sizes.
Tested wet, because that is where joints live
A joint is the one metre of the circuit nobody built in a factory. The type-test sequence says so in its conditions, not in its voltages. Terminations are given 60 heating cycles in air. The straight-through joint is given 63 cycles in water. The impact test is written for the joint alone, judged on insulation resistance taken before and after, immersed.
At the low classes the GXLT/GPLT sheet is blunt about it. AC withstand is 3.5 kV at 1.1 kV and 6 kV at 3.3 kV, held 5 minutes, with the joint immersed in water. Then 63 heating cycles in water of 5 hours heating and 3 hours cooling, conductor temperature 95°C, and no breakdown or flashover permitted.
Compliance sets are not uniform across the range. GXLT/GPLT declares IEC 60502, 60060 and 60230. The MV sequence below is declared against IEC 60502-4 and CENELEC HD 629.1. The catalogue's design-standard list also names IEEE 48 and 404, BS 6480 and IS 13573. Of that pair, IEEE Std 404 is the joints document and IEEE Std 48 the terminations one. That split comes from the standards' own titles, not from the catalogue.
The MV type-test sequence, and the rows that belong to the joint
| Test | Parameter for evaluation | 12 kV | 24 kV | 36 kV |
|---|---|---|---|---|
| DC high voltage, dry | 15 minutes | 38 kV | 76 kV | 114 kV |
| AC high voltage, dry | 5 minutes | 29 kV | 57 kV | 86 kV |
| Partial discharge | At ambient and at 95 to 100°C | 11 kV | 22 kV | 33 kV |
| Impulse withstand at elevated temperature | 10 impulses each polarity, conductor held at 95 to 100°C | 95 kV | 125 kV | 170 kV |
| Heating cycle in air | 3 cycles, 5 hours heating then 3 hours cooling | 16 kV AC | 30 kV AC | 45 kV AC |
| Heating cycle in water, straight-through joint | 63 cycles of 8 hours, 5 hours heating then 3 hours cooling | 16 kV AC | 30 kV AC | 45 kV AC |
| Impact test, straight-through joint | Insulation resistance at 500 V DC before and after, immersed | – | – | – |
| Thermal short-circuit | Two short-circuits raising the conductors to the cable's θsc | – | – | – |
One sequence is printed covering both joints and terminations, as guaranteed technical particulars in compliance with IEC 60502-4 and CENELEC HD 629.1. The two rows flagged below are the joint's own. Every row's stated result is no breakdown and no flashover, except partial discharge at ≤ 5 pC and insulation resistance at >10³ Ω.
No source for that
Four things a specifier reasonably asks about a joint, and the published record answers none of them. The finished size. Termination sheets print a setting-out tail length of 450 mm to 900 mm. No joint sheet prints an overall length or a recovered outside diameter. Per-item quantities on GXLT/GPLT. GXS, GXSS, GPS/2436 and GTJ all carry a Qty column against every numbered item; the LV joint list carries none. The GXLTS submersible straight-through joint. It is named in the manufacturer's range index and appears in none of the published datasheets. No kit code, no conductor range, no test value. Price, lead time, stock and how long a joint takes to make off. Nothing here is sourced on any of those. Ask through contact with the cable make-up in the first message.
Where this goes next
- The four types of cable jointStraight-through, transition, branch and single-core, and the series that covers each.
- Every part in a cable joint kit, namedThe manifest item by item, with the published quantities against it.
- The order an MV joint goes togetherSetting-out through to plumbing, and where the earth path is picked up.
- Six ways a cable joint failsWhat each of the four losses looks like when it is not put back properly.
- Which joint kit series fits the cable in front of youGXLT, GXS, GXSS, GPS and GTJ against construction and class.
- The sleeves inside a joint kitStress control, insulating, screened and oil barrier, and which kit carries which.
Send the cable, not the kit code
Construction (XLPE, EPR, PVC or PILC), core count, conductor area in sq mm, Umax, and whether the run is buried, ducted or submerged. Those five settle the series and the size in one reply instead of five. The kits described here are manufactured by Gala Thermo Shrink Pvt. Ltd. of Mumbai, whose own cable joints index lists the series.