What is a cable joint?
The permanent connection that joins two lengths of AGL cable — the conductors are connected, the insulation is rebuilt, and the whole joint is sealed against water.
A cable joint, or splice, joins two lengths of cable so they behave as one unbroken cable. The two conductors are connected, usually with a crimped or compression connector, the insulation is rebuilt over the connection, and an outer sleeve or moulding seals the joint against water. It is used to join lengths on a long run, to repair a damaged section, or to extend a circuit.
A joint is only as good as its workmanship, so it is made to the kit manufacturer’s instructions, clean and dry. Moisture or a void lowers its insulation resistance and can lead to an earth fault or an open circuit that puts every lamp on the series loop out. Keep joints to a minimum, record each location on the as-built drawings, and treat the cable as live until the circuit has been isolated, locked out and proved dead.
- Isolate. CCR off, locked out and tagged; prove the circuit dead and earth it at the work point (see Entry 13, Circuit Isolation).
- Prepare. Cut back the jacket and insulation, clean and dry the ends.
- Connect. Join the conductors with the specified connector.
- Insulate & seal. Rebuild the insulation and fit the sealed outer sleeve.
- Test. Continuity and insulation resistance on the circuit.
- Record. Mark the joint on the as-built drawings and log the readings.
Frequently Asked Questions
Q1What is a cable joint in airfield ground lighting?
A cable joint, or splice, joins two lengths of cable into one continuous conductor. The conductors are connected, the insulation is rebuilt over the connection, and the joint is sealed so water cannot get in, so the circuit carries current as if the cable were unbroken.
Q2When is a cable joint needed?
To join cable lengths on a long run, to repair a damaged section, or to extend or modify a circuit. Because every joint is a possible weak point, the design keeps the number of joints to a minimum.
Q3What are the parts of a cable joint?
A connection between the two conductors (commonly a crimped or compression connector), a rebuilt insulation layer over it, and an outer seal such as a heat-shrink or cold-shrink sleeve, or a moulded or taped enclosure, that keeps moisture out.
Q4Why do water and poor workmanship matter so much?
Moisture or a void in a joint lowers its insulation resistance. That can lead to leakage to earth, an earth fault, or an open circuit, and a fault in one joint affects the whole series circuit.
Q5How is a cable joint different from a connector or a termination?
A joint is a permanent connection between two cable lengths. A connector is a plug-in coupling that can be disconnected, such as at a transformer or fixture. A termination is the way a cable end is finished where it meets equipment, such as at the CCR.
Q6How is a cable joint checked and recorded?
With the circuit isolated, locked out and proved dead, the joint is inspected and the circuit is tested for continuity and insulation resistance, with the readings compared against the commissioning baseline. The joint's location is marked on the as-built drawings.
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