Primary Cable Joint/Splice Connector

The Primary Cable Joint/Splice Connector (also known as a primary splice connector or series cable joint) is a specialised termination device used to make permanent or semi‑permanent connections between two sections of L‑824 primary AGL cable. These connectors are essential for creating cable runs of the required length, repairing damaged cable sections, and making tap‑offs or branch connections in the series circuit.

Key characteristics include:

• Conductor Connection: Provides a low‑resistance mechanical or compression connection between the copper conductors, ensuring minimal voltage drop and heat generation.
• Insulation and Sealing: Restores the electrical insulation and provides a waterproof seal (IP68) to prevent moisture ingress, which is critical for buried and submerged installations.
• Screen Continuity: For shielded cables (L‑824), the connector includes provisions to reconnect the metallic screen (shield) to maintain EMI protection and earth continuity.
• Mechanical Strength: Provides mechanical strain relief to prevent the joint from pulling apart under tension or during backfilling.
• Types: Available in several configurations, including compression‑type (crimp), bolted mechanical connectors, heat‑shrink splice kits, and resin‑filled joints.

The connector is typically installed in a joint pit, handhole, or directly buried, and is covered with a protective housing or filled with encapsulating compound for additional mechanical and environmental protection.

The splice connector exists because a real airfield cable run almost never comes from a single continuous length of cable — damaged sections need repair, circuits need extending, and branch taps need to be added — and any of these situations requires a way to join two cable ends that performs as reliably as the continuous cable itself, at the full 5kV operating stress of the primary circuit. A poorly made joint is a likely point of future failure, whether from resistance heating, insulation breakdown, or moisture ingress at exactly the seam where protection is hardest to maintain.

Because these joints are typically buried or installed in handholes where they're difficult to inspect or access after installation, getting the connection, insulation, and screen continuity right the first time matters enormously — a fault discovered years later at a buried splice means locating and excavating a specific point along a long cable run, which is far more costly than a proper joint made correctly during installation.

The primary cable joint/splice connector is used throughout the airfield wherever primary cable splices are required, including:

• Runway and Taxiway Lighting Circuits: Splicing L‑824 cable to extend the series loop around the airfield, including connections at circuit transitions and turns.
• Repair of Damaged Cable: Cutting out damaged sections of cable and splicing in new cable, restoring circuit continuity with minimal disruption.
• Tap‑Offs and Branch Connections: Creating a tap‑off point to feed a separate series circuit or to connect to an isolating transformer (though L‑823 connectors are more common for transformer connections).
• Transition Points: Joining cable from different installation methods (e.g., underground to elevated) or connecting cable to equipment such as CCR output panels.
• Junction Boxes and Handholes: Installing splices within junction boxes or handholes to allow for future maintenance and testing.
• System Expansion: Adding new sections of primary cable during airport expansion or runway extension projects.

The connector is available for cable sizes from 6 AWG to 2 AWG (6mm² to 35mm²) and is rated for continuous operation at the full primary current (6.6A or 20A) and voltage (5kV).

Splices are made in an accessible splice pit or handhole set along the cable duct route, rather than buried directly in an unmarked trench, so the joint can be located and re-opened for future fault-finding without excavating blind. The pit is backfilled with sand or a marker tape laid above it once the splice is tested and potted/sealed, and its location is logged on the as-built cable route drawing since a splice is otherwise invisible once buried. Where the splice makes a tap-off or transition (underground to elevated, or into a CCR output panel), the pit or enclosure is sized to keep minimum bend radius on both the incoming and outgoing cable runs, and is sited clear of the pavement's frost/frangibility zone where the route runs near a runway or taxiway edge.

The primary cable splice connector provides a reliable electrical and mechanical joint between two cable ends. The specific method varies by connector type:

• Compression (Crimp) Connectors: The stripped conductor ends are inserted into a cylindrical connector (barrel) and crimped with a hydraulic or manual crimping tool. The crimp deforms the barrel, creating a gas‑tight, low‑resistance connection. The joint is then insulated with heat‑shrink tubing or covered with a resin‑filled sleeve.
• Bolted Mechanical Connectors: The conductor ends are clamped into the connector using set screws or bolts. These are easier to install but require careful torque control to ensure low resistance. They are often used in junction boxes where future disconnection may be needed.
• Heat‑Shrink Splice Kits: After the conductors are joined (often with a crimp connector), a dual‑wall heat‑shrink tubing with adhesive liner is slid over the joint and heated. The tubing shrinks and the adhesive melts, creating a watertight seal and restoring insulation.
• Resin‑Filled (Cold‑Shrink) Joints: The conductor connection is placed inside a mould, and a two‑part epoxy or polyurethane resin is poured in. The resin cures to form a solid, waterproof, and mechanically robust insulation block. This method provides the highest level of protection for buried splices.
• Screen Connection: For shielded cables, the screen (copper tape or braid) is reconnected using a screen connector or by twisting and soldering the braid, and then it is earthed at one end of the splice (or both ends, depending on design).

The splice must also restore the cable's overall diameter and mechanical strength to withstand handling and backfilling. Proper installation using the correct tooling and materials is essential for long‑term reliability.

The splice connector carries no control logic of its own — like the cable it joins, it is a passive link in the CCR's series loop, and its only "function" from the loop's point of view is to be electrically indistinguishable from an unbroken run of L-824 cable. Whatever the ALCMS commands and the CCR regulates, the splice simply has to pass the full loop current through with negligible added resistance and no leakage path through the screen or insulation. Because the loop is monitored only at its ends (loop voltage against commanded current), a degrading splice — rising contact resistance in a crimp, a compromised heat-shrink seal — shows up to the CCR as the same gradual voltage rise or eventual open circuit as any other loop fault, with no way to tell from the ALCMS console alone whether the fault is at a splice, a fixture, or a length of cable; locating it falls to insulation-resistance testing and sectionalised loop testing, then physically inspecting the suspect joint.

A primary splice connector kit typically comprises a crimp or compression connector body to join the two conductor ends, layers of self-amalgamating rubber and vinyl electrical tape (or heat-shrink insulating tubing) to rebuild the insulation and voltage-grading layers around the splice, and a copper braid or mesh sleeve to restore electrical continuity of the cable's shield across the joint. The completed splice is then encapsulated in a moulded, resin-filled splice kit body or a heat-shrink outer sleeve, forming a continuous, void-free seal rated for direct burial and continuous submersion. Some designs use a pre-moulded rubber or silicone splice sleeve that stretches over the prepared joint, relying on its own elastomeric memory to maintain a watertight, high-dielectric-strength seal without a resin pour. Stress cones or grading layers are built into the kit to control the electric field at the point where the shield is interrupted, preventing partial discharge and premature insulation failure at the splice.