T&D World Magazine

KEMA Collaboration Working to Enhance Partial Discharge Technology

Enexis, Alliander, automation company Locamation and energy consultancy company KEMA plan to collaborate for the next five years on the further development of Smart Cable Guard. Their goal is not only to track down weak spots in the medium-voltage network, and thus prevent short circuits (the present function of Smart Cable Guard), but also to detect and localize, within one minute, short circuits if any, caused for example by excavation activities. This technology fits into developments toward a smart grid. With this development, the parties envision further reducing the number of minutes that consumers and companies have to do without power.

The new technology builds from Smart Cable Guard (formally called PD-OL, or Partial Discharge Online). Smart Cable Guard is a successful measurement method to track down weak spots in the underground medium-voltage network while it is in operation, and to localize them accurately. Smart Guard Cable makes use of the principle that at weak spots small sparks occur, called partial discharges. A weak spot is, for example, caused by water penetration or a minor damage. The electrical pulses generated from this weak spot are measured, and based on the time difference in arrival at the sensors, the position is determined. A network operator can then remove the weak spot before a short circuit happens. In this way, short circuits can be prevented.

By now, some hundreds of measurement units have been installed in the Netherlands, and in countries such as Belgium, Germany, France, Macau and Dubai. The Smart Cable Guard measurement units have already demonstrated their worth because, thanks to them, weak spots could be tracked down early, thus preventing faults.

The success of the Smart Cable Guard has spurred the four companies to jointly accept the following challenge: to develop a system to establish immediately where a short circuit has occurred in a cable. Around half of all short circuits are caused by excavation damage. It must be possible with the new system to determine the location of the short circuit within one minute. This will save the network operators time in hunting for the short circuit, and outage minutes may thus be avoided. For this, the system must be modified, including the possibility of continuously searching for the signs of defects and short circuits.

The technology will be developed in the coming years. In this, KEMA’s knowledge of cable systems and measurement techniques will be built on, while network operators Alliander and Enexis will fill an important role in the system's development and testing. With its knowledge in the field of the automation of smart grids, Locamation will provide the actual hardware needed.

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