Testing High Voltage Cable Without Ageing the Cable

Cables & Accessories

These days it has become possible to determine the status of a cable circuit after laying using various diagnostic measurements. With these methods, emerging defects or assembly errors can be localized and repaired proactively, without unnecessarily overstressing the cable circuit.

Fig. 1: Hotspot detected with infrared measurement of AIS termination.

During maintenance, an after laying test is performed on one cable circuit. Most of the cable circuits will then be left to rest until either this one fails or until the end of its life cycle.

Risk of cable failure has been low over past decades because a parallel cable could handle the demand of energy transported by any failed cable circuit. These days, however, every circuit has become increasingly critical due to rapidly growing demand for electrical power. The result is that failure of even a single cable system becomes an unacceptably high risk for operation of the grid.

Fortunately, with present day diagnostic methodologies and the ability to store large data files, it has become possible to apply new maintenance strategies for cable systems. For example, diagnostic measurements can help determine the status of the cable as an asset and perform condition- or risk-based maintenance instead of either no or only period-based maintenance.

Traditional site acceptance testing using an AC resonance test without additional (temporary) partial discharge measurement techniques meant only a binary result – either ‘break-down’ or ‘no break-down’. As such, this technique offered no useful data that could assist in developing a SMART maintenance strategy for the cable circuit.

Fig. 2: Example of DAC test setup.

Attend the 2022 INMR WORLD CONGRESS to hear a lecture by cable diagnostics expert, Maarten van Riet of the Netherlands. His presentation will present case studies of After Laying Testing and outline the advantages of partial discharge measurement on short as well as long cable circuits up to 30 km. These practical cases will help demonstrate how knowledge of partial discharges will allow predicting that a cable circuit can operate safely for years or, alternatively, determining at which location of the circuit a weak point exists, whether in a joint or in a termination.