A power cable that fails on first energisation is usually a cable that was damaged on site and never tested before the breaker was closed. A short sequence of checks, done in the same order every time, catches most of these faults while the cable is still accessible. This checklist covers the checks to complete before a low voltage or medium voltage power cable is energised. Test voltages, durations and acceptance values are not listed here because they depend on the cable standard, the voltage grade and the project specification, which must be followed.
Before testing
| Check | What to confirm |
|---|---|
| Drum and cable condition | No crushed, kinked or cut sections. Cable end seals intact when received. Drum label matches the order. |
| Cable marking | Printed voltage grade, size and standard match the design. See the datasheet reading guide. |
| Installation record | Pulling tension and bending radius respected. Reference: cable pulling guide. |
| Terminations and joints | Completed to the kit maker instructions, with lugs crimped using the correct tool and die. |
| Isolation and safety | Cable isolated at both ends, earthed before handling, and warning notices in place. |
Electrical checks, in order
| Step | Test | Purpose |
|---|---|---|
| 1 | Continuity of each conductor | Confirms that every core is unbroken from end to end and that no core is crossed with another. |
| 2 | Phase identification | Confirms that each core is connected to the intended phase at both ends, which prevents a phase reversal at the motor or switchboard. |
| 3 | Insulation resistance | Measured with an insulation resistance tester between each conductor and earth, and between conductors, to find damaged insulation or moisture entry. Use the test voltage the cable standard or project specification states, and record the temperature. |
| 4 | Outer sheath test (where specified) | Applied to the outer sheath of armoured and single-core medium voltage cables to confirm that the sheath was not punctured during laying. |
| 5 | Voltage withstand test (where specified) | Performed only when the project specification requires it, using the method and values it names. |
After testing
Discharge the cable and earth the conductors after any test that charges the insulation, and do not remove the earth until the cable is ready to be connected. Record the results for each core on a test sheet that names the cable reference, drum number, date, instrument and test voltage. A comparison with the factory test report is explained in the guide to routine, sample and type tests.
The cables themselves are described on the pages for LV XLPE power cables and MV/HV XLPE power cables.