The four types of cable joint

Q: Does the type change what is in the box?

Yes, and voltage class changes it again inside one type. A GTJ/2436 transition kit carries 6 heat-shrink screened tubings at 15–24 kV and 9 at 36 kV, off the same manifest. Count the parts against the list before assuming two kits are interchangeable — every part in a kit sets out the full list.

Q: Can a straight-through kit be used to make a branch joint?

Not from anything published. A GXS kit is built around two cable ends: one centre outer jacketing sleeve and two side sleeves. A tee needs a third leg insulated, screened and sealed, and no ordering table indexed here covers that. Sizes and codes are on the kit size charts.

Sorted by what the joint has to reconnect, not by what the kit is made of.

Match a kit series to your cable

Why the count keeps changing

Ask ten sources how many types there are and you get four, five or seven. The count moves because they are sorting by different things: what the joint reconnects, how the insulation is rebuilt on site, or how the cable itself is built. All three sorts are useful. Only the first is what a jointer means by type.

This page uses the functional sort: straight-through, transition, branch or tee, and sheath repair. The fourth is not electrically a joint at all. It earns its place because getting it wrong means cutting a cable that did not need cutting.

The four-type framing is a training-course convention, not a published classification. The standards these kits declare against — IEC 60502-4 and CENELEC HD 629.1 on the MV joints, IEC 60502, IEC 60060 and IEC 60230 at 1.1 and 3.3 kV — appear on the datasheets as test regimes. They set what a joint must survive, not what it is called. Do not quote the four types at a tender panel as though a standard said it.

Four ways to sort a joint, and what each one buys you

These rows are not alternatives. You walk down all four to get from a cable to a kit code.

Sorted by	The names you meet	What it actually tells you	In this manufacturer's range
What the joint reconnects	Straight-through · transition · branch or tee · sheath repair	Which kit family you are even looking at	GXS/1236 is straight-through, GTJ/2436 is transition
How the insulation is rebuilt	Heat-shrink · cold shrink · cast resin · gel-filled · taped	How the work is done on site, not what the joint does	Every kit indexed here is heat-shrink
Cable construction	Three-core · single-core · XLPE/EPR · PVC · PILC	Which family sits inside a function	GXS/1236 for three-core, GXSS-1236 for single-core
Voltage class	1.1 kV · 3.3 kV · 12 kV · 24 kV · 36 kV	Which kit code sits inside a family	GTJ-21 to GTJ-25 at 15–24 kV, GTJ-31 to GTJ-34 at 36 kV

The four, one at a time

The default job on a distribution run

1 · Straight-through

Same construction at both ends, rejoined in line. Conductor made off in an inline ferrule, insulation rebuilt, screen and armour carried across, outer sheath sealed. Four families cover it. GXLT/GPLT takes 1, 2, 3, 3½ and 4-core PVC, XLPE and paper cable at 1.1 and 3.3 kV, codes GXLT-1 to GXLT-6 and GXLT-11 to GXLT-16. GXS/1236 takes three-core XLPE/PVC, 12 to 36 kV. GXSS-1236 takes single-core extruded dielectric, GXSS-11 to GXSS-35, 16 to 1000 sq mm. GPS/1112 and GPS/2436 take three-core PILC. A GXLTS variant is listed for submersible cable.

Paper to XLPE, 12 kV to 36 kV

2 · Transition

Two constructions meeting in one splice, almost always an old paper-insulated lead-covered run extended in XLPE. The kit closes out one cable's world and opens the other inside a single body: XLPE insulation, semi-conducting screen and copper screen on one side; paper insulation, paper belting, lead sheath, steel armour and jute outer sheath on the other. What makes it a transition rather than two half joints is the heat-shrink oil barrier sleeve — three of them in a GTJ/2436. Codes GTJ-11 to GTJ-17 run 3x16–35 up to 3x630 sq mm at 12 kV.

Scope says yes, ordering table says ask

3 · Branch or tee

One cable in, two or more out, so a new feeder is picked up without breaking the run. The manufacturer's GTJ page names branch joints on MV distribution cable inside its scope, beside transition joints and PILC accessories. The catalogue prints ordering tables for straight-through and transition kits only. On telecom cable the branch is one moulded part rather than a kit: the GBOC clip in three sizes, adhesive-lined, ≥12 kV/mm dielectric strength to ASTM D149. It carries no cable voltage class.

Not a joint, and that is the point

4 · Sheath repair

The jacket is torn, the cores were never reached, nothing electrical is broken. So nothing gets cut. A wrap-around sleeve closes over the damage with the cable lying where it is. Insulsleeve zips shut on a stainless steel channel and then shrinks: GWS-55/8 up to GWS-240/50, 2.7 mm recovered wall, cable ranges 10 to 200 mm. The tubular GMRS range, GMRS-19 to GMRS-250 for 5 to 192 mm OD, does the same job but threads on from a free end.

The second axis: how the insulation is rebuilt

Heat-shrink, cold shrink, cast resin, gel-filled and taped are not types of joint. They are methods, and any of them can make a straight-through joint. The choice is a site question — hot work permit, cure time, what the crew is certified on. Mixing the two axes is why one page counts four and the next counts seven.

Every kit indexed here is heat-shrink: crosslinked polymer, expanded in the factory, recovered onto prepared cable with a torch. It fits a dimensional band rather than one diameter, which is why a single GXS-12 covers 70 to 120 sq mm at 12 kV. The bands tighten as the class rises — GXS-22 holds 70 to 95 sq mm at 24 kV, GXS-32 holds 95 to 150 sq mm at 36 kV. Read the band, not the sq mm chalked on the drum.

Cold shrink is the third method in regular use — a rubber body held expanded on a removable core, released by pulling the core out, no flame anywhere. The manufacturer's component index carries cold shrink tubing and a cold shrink breakout in EPDM, and no cold shrink joint kit. Nothing is argued about the two recovery mechanisms here.

Cast resin and gel-filled joints are the other two you meet, mostly on LV. A resin joint is a shell filled with a two-part compound that cures around the connection; a gel joint is a shell packed with self-healing gel and closed by hand. The reason given for both is usually the same: no torch, so no hot work permit. Neither is made by the manufacturer indexed here.

Repair, or cut and joint

Work inward from the outside of the cable and stop at the first layer that is damaged.

Outer sheath split, inner sheath and armour sound, cores never reached. Repair it where it lies. The wrap-around sleeve is built to go on without disconnecting the cable or de-energising the system, so there is no shutdown, no ferrule and no kit to order.

Armour cut through or corroded away, or the inner sheath breached with water tracking along the cores. Take it out. The cable may still hold volts on test. The earth path does not care what it holds.

Insulation nicked, semi-conducting screen scored, a strand broken. There is nothing to repair. Cut back to sound cable both sides and make a straight-through joint.

The middle case is where money gets lost. A wrap-around sleeve will physically close over armour damage and look like finished work. It seals the jacket. It does not put armour continuity back, and armour continuity is half the earth path through a joint. Sizing and the faults that kill a wrap-around repair sit on heatshrink-sleeve.com, a sister reference published by the same team as this site.

I don't have a source for that

Resin and gel. No cure time, pot life, temperature range or voltage rating for either appears here. Nothing in the published range is one, and quoting somebody else's datasheet as though it were theirs would be worse than the gap. Cold shrink joints. The component list holds tubing and a breakout, not a joint kit, so there is no OD window and no class to give you. Branch kits. The GTJ scope names branch joints; no branch ordering table appears in the catalogue held here. Ask before one goes into a schedule.

Questions this page gets

What are the four types of cable joint?

Straight-through, transition, branch or tee, and sheath repair. The first rejoins one cable to itself. The second links two constructions, usually paper to XLPE. The third takes a spur off a run. The fourth closes a damaged jacket and is not electrically a joint. Counts of five or seven fold in cold shrink and resin, which are methods.

Is a transition joint just a straight-through joint with another label?

No. Both join end to end, but a transition kit has to finish one construction and start another inside one body. On a GTJ/2436 that shows up in the manifest as 3 oil barrier sleeves, 6 stress relief mastics, a high permittivity void filler and an EPDM insulating wedge. A GPS paper kit has no XLPE side to match, so it carries none of that.

Does the type change what is in the box?

Yes, and voltage class changes it again inside one type. A GTJ/2436 transition kit carries 6 heat-shrink screened tubings at 15–24 kV and 9 at 36 kV, off the same manifest. Count the parts against the list before assuming two kits are interchangeable — every part in a kit sets out the full list.

Can a straight-through kit be used to make a branch joint?

Not from anything published. A GXS kit is built around two cable ends: one centre outer jacketing sleeve and two side sleeves. A tee needs a third leg insulated, screened and sealed, and no ordering table indexed here covers that. Sizes and codes are on the kit size charts.

Which type applies to a cable already in the ground and energised?

Only sheath repair, and only where the damage stops at the jacket. Everything else needs the run dead and the cable parted. Whether the finished joint then sits in standing water is a separate specification question — see joints that live in water.