Cable Fault Location & Repair

R&D Cable Jointing provides cable fault investigation and location for LV and HV cables, helping establish where a fault has occurred so excavation can be targeted. Depending on the cable and fault type, our work can include electrical testing, confirming or tracing the cable route, TDR pre-location and specialist pinpointing where required.

We mark the identified fault position ready for excavation. R&D does not undertake excavation or groundworks, but we can provide details of a groundworks contractor. Once the affected cable has been exposed, we can return to carry out the required cable repair or jointing and appropriate testing.

Common Fault Types

The nature of the fault helps determine which investigation and location techniques are appropriate:

• Third-party damage — damage caused by excavation or other works, affecting the cable sheath, insulation or conductors. The damage may be visible or require further investigation.
• Joint failure — a fault at a cable joint, which may affect insulation or conductor continuity. Existing joint records can help guide the investigation.
• Termination failure — a fault at a cable termination into switchgear, a transformer or other equipment. Inspection and testing help establish the affected component.
• Insulation breakdown — deterioration or damage to cable insulation, which may result in an earth or phase-to-phase fault and can require specialist location techniques.
• Sheath fault — damage to the outer cable sheath that may allow moisture ingress. This may require investigation even where the circuit has not lost supply.

Fault Location Techniques

We select the approach to suit the reported fault, cable construction, access and site conditions. The process can include route tracing, pre-location to estimate the distance along the cable, and specialist pinpointing where required to narrow down the position on site. Not every fault requires every technique.

• Electrical testing and fault investigation — testing helps establish the nature of the reported fault and guides the next stage of the location work.
• Cable route tracing — a signal is applied to the cable and detected above ground using a cable locator. This helps confirm and mark the buried route so fault-distance measurements can be related to a physical position on site.
• TDR pre-location (Time Domain Reflectometry) — reflected pulses are analysed to estimate the distance to a fault or significant impedance change along the cable, providing a starting point for further location work.
• Specialist surge pre-location — where conventional TDR does not adequately identify the fault, specialist surge methods may be used, where appropriate, to help establish the fault distance.
• Acoustic/electromagnetic pinpointing — specialist equipment can be used where required to narrow the pre-located fault to an identified position for targeted excavation.

The aim is to identify and mark the fault position ready for excavation. The accuracy achievable depends on fault characteristics, cable condition, access and site conditions; exact pinpointing cannot always be guaranteed.

Planning the Repair Once the Fault Is Located

Once the fault area has been identified, excavation and the subsequent repair can be planned. R&D does not undertake excavation, groundworks or reinstatement. These works must be arranged with the client's own contractor; we can provide details of a groundworks contractor if required.

• Cable details and repair scope — cable type, size and condition help determine the joint or replacement section required. The final repair scope may depend on what is found once the cable is exposed.
• Excavation and access — the groundworks contractor must provide a safe, stable excavation with suitable access and enough working space for the repair.
• Environmental protection — suitable protection from moisture and contamination is needed throughout the jointing work.
• Safety arrangements — the isolation, access and any SAP requirements must be agreed for the circuit and site before work begins.
• Testing and return to service — appropriate post-repair testing and the arrangements for returning the circuit to service should be agreed as part of the repair scope.

From Fault Location to Repair

R&D Cable Jointing can provide both fault investigation and location and the subsequent cable repair, giving you a single point of contact for those stages. We can confirm or trace the cable route as required, pre-locate and pinpoint the fault where required, and mark the identified position ready for excavation by others.

Once the affected section has been exposed, our cable jointers can carry out the necessary repair, joint replacement or cable section replacement, followed by appropriate testing. Repair, jointing and testing are quoted separately from fault location once the scope is established. Fault location can also be provided as a standalone service if you have your own repair contractor.

CableFaultLocation.co.uk is R&D Cable Jointing's dedicated cable fault location service and enquiry website. You can submit an LV or HV fault-location enquiry there or contact R&D directly.