Step 1 – Cable Isolation and Safety Procedures: Identifying and addressing cable faults begins with isolating and grounding the cable to ensure safety. This initial step is crucial, as it allows testing personnel to approach the cable securely. The cable is isolated but remains ungrounded after protection devices at the cable ends have tripped.

Step 2 – Cable Identification: In scenarios with multiple cables, accurate cable identification is essential to avoid fatal mistakes during maintenance work. Clear identification before cutting any cables is critical for safe and efficient operations.

Step 3 – Cable Tracing: Tracing underground cables is necessary due to their often meandering paths. Determining the expected route of the cable ensures accurate fault location and proper maintenance.

Step 4 – Fault Identification: Identifying the phase and resistance of the fault is pivotal for selecting the correct diagnostic technique and equipment. Low resistance faults are addressed with a low voltage pulse from a Time Domain Reflectometer (TDR), while high resistance faults may require an impulse generator or bridge.

Step 5 – Fault Prelocation: Efficient pre-location methods are employed to quickly locate cable faults. Depending on fault resistance, techniques such as ARM (Arc Reflection Method), ICE (Impulse Current), or HV DC testing are utilized.

Step 6 – Pinpointing: After pre-location, acoustic pinpointing techniques are employed to narrow down the fault location with precision. Shock discharge generators, in conjunction with acoustic methods, create a loud noise that aids in pinpointing the exact fault location.

Step 7 – Re-energisation of the Cable: Following testing and repairs, the cable is re-energized, and safety/testing documentation is canceled. The cable is then returned to the appropriate operators for reinstatement and re-energization of the loads on the newly repaired cable.

Important advice when using the ARM/ICE Equipment:
It is important to find the lowest voltage that will cause the fault to appear during the above-applied testing procedure. The idea of ‘thumping the cable with the maximum available voltage (Joules)’ should not be condoned. For example, if a cable fault has left damage in the faulted phase that, when applying a gradually increasing ARM voltage, appears at 6 kV, then once this is established, only 10% more voltage, say 7 kV, need be applied for the fault location position show up clearly. What is fundamentally important is that the energy used is proportional to a square of the voltage (V2). If the cable is repeatedly ‘thumped with very high over-working voltages’, other lesser points of damage could be initiated into insulation failure, thus creating more jointing/repairs needed on the cable.