Article: Investigating and diagnosing cable failure mechanisms

By Luca Garagnani, Principal Technical Authority - Cables & Switchgears, Machinemonitor


Never has the reliability of cables and their associated terminations been more critical in our plants and infrastructure. Like the network of blood vessels in our bodies, cables are the lifeblood of connected assets. However, cables are by and large a hidden asset and often overlooked.

Pressures arising from complex interconnected cabling requirements

The electrical world is becoming more distributed and thus more interconnected. The electrification of everything demands cabling, often copper. Copper is valuable and energy losses are the anathema of climate change. Hence the drive to increase interconnected voltage, both in DC and AC systems. This allows a reduction in materials usage and associated losses.

But as voltage increases, so does the need to ensure that the correct standards are followed for cable selection. It is critical that the appropriate in-service condition monitoring techniques are employed to ensure the safe and reliable operation of the interconnected system.

Avoiding costly failures and unscheduled downtime

Specialised cable condition monitoring techniques should be used to diagnose cable and termination developing failure modes. Enabling prognosis and corrective action ensure costly failures and unscheduled downtime is avoided.

The monitoring method should be selected based on the type of cable, the environment, and the criticality of the system and operational requirements. For example, a high voltage cable in a critical application may require more frequent and advanced monitoring methods than a cable in a less critical application. It is important for electrical engineers to choose the appropriate monitoring method for each cable installation.

Critical condition monitoring techniques

Condition monitoring techniques include:

  • Insulation testing: The insulation of high voltage cables is critical to their safe and reliable operation. Insulation testing is performed to detect any defects or weaknesses that could lead to failures. This testing can be performed using a variety of techniques, including AC and DC hipot testing, partial discharge testing, and tan delta testing.
  • Visual inspections: Regular visual inspections of high voltage cables can help identify any physical damage or degradation of the cable's insulation or sheath. This can include checking for cracks, bulges, or discolouration of the cable.
  • Online monitoring: Some high voltage cable systems can be equipped with online monitoring systems that continuously monitor cable parameters, such as temperature and partial discharge. These systems can provide real-time alerts to operators if any abnormalities are detected.

New online techniques enable 24/7 remote monitoring to be deployed, utilising existing and established telecommunication infrastructure. Suitably qualified electrical engineering experts can then be made available for interpretation and diagnosis if anomalies are flagged.

Cable condition monitoring helps ensure the safe, reliable, and cost-effective operation of power systems, which is critical for businesses, communities, and society as a whole.

Hear from Luca Garagnani sharing his insights on the 'Investigating and diagnosing causes of failure and how to monitor cables'

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