KEMA has developed a method to continuously monitor the condition of medium-voltage cables while they remain in service. The patented system, which was created in partnership with the Eindhoven University of Technology in the Netherlands, uses inductive sensors to detect, diagnose and locate partial discharge activity along a medium-voltage power cable while the cable remains on-line.

Partial discharges (PDs) are short pulses that originate from weak spots along a cable. Failures in medium-voltage power cables and their components cause a large proportion of annual power service interruptions, especially in high-density urban areas. Locating and repairing cable weak spots at an early stage can considerably improve the reliability of the energy supply. 

KEMA’s PD detection On-line with Localization (PD-OL) system provides  benefits over the current off-line test systems. While the off-line systems require disconnecting a cable from the grid and energizing it with a separate power supply to generate PDs and are performed on an occasional basis, KEMA’s PD-OL enables continuous on-line cable monitoring, allowing utilities to:

• Maintain continuous power supply during measurement.
• Test the cable system under exact operating conditions, including overvoltages and load variations.
• Cost-effective operation with minimal personnel effort required after installation.
• Continuously registering data that capture time-related information, such as variation of PD activity in time, the effects of sudden overvoltages, and cable temperature variations.
• Detecting PDs occurring shortly before failure.