Cable Testing

DC testing of modern XLPE cable can leave trapped space charge and, in aged insulation, contribute to the very degradation it is trying to detect. Very Low Frequency testing applies an AC waveform at around 0.1Hz, which stresses the insulation in a way that is representative of service conditions while keeping test set size and power demand practical for site work.

The result is a test that finds real defects — water trees, poor joints, incorrectly assembled terminations, mechanical damage from installation — without unnecessarily prejudicing the cable's remaining life.

A withstand test tells you the cable survived. Tan delta and leakage current trending tell you how much margin it has left. On critical circuits, or where a cable is being adopted into a DNO network, that distinction matters: it converts a binary result into an asset management decision.

HV cable testing is a high-energy activity carried out on assets that often run into occupied buildings. Every test is preceded by isolation, proving dead, earthing at remote ends, exclusion zones at both ends and a documented point of control. Discharge and re-earthing after each test step are part of the method, not an afterthought.