On-site, on-line power cable diagnostics.

Instead of de-electrifying power cables for off-line PD testing, since 2007 on-line monitoring is a sound alternative. Many grid owners indicated the need for the on-line monitoring of partial discharges in high and medium voltage power cables.

On-line PD testing for MV cable circuits
Over the past years, KEMA developed an on-line monitoring system for partial discharges with location (PD-OL). A pulse-injection system is used for the time synchronization of the data intake at both cable ends and for the on-line calibration. Partial discharge data is send via internet to KEMA’s data acquisition and control center for interpretation and visualization of the data. Network owners have direct, 24/7 on-line access to their data via a secured extranet. The PD-OL system comprises two separate measurement units, to be installed at both ends of the cable circuit to be monitored. Each measuring unit consists of a sensor/injector unit to measure and generate the time synchronization pulses and a controller unit to control the measurement sequence, the data collection and signal processing. The controller unit transmits the data to KEMA’s data acquisition and control center and can remotely be accessed for diagnostics and updates. Based on extensive field testing and long-term monitoring during 2007 and 2008, the system has proven its reliability. As on-line access is facilitated, one can monitor in time the existence, magnitude and location in a 3D graph.