New approach for online detection of partial discharges in cable systems via VDS ports

Medium voltage cables systems should be checked at regular intervals for their insulation quality and reliability. Partial discharge (PD) testing is one of the most suitable technologies available for regular cable-by-cable testing. Various PD technologies are available, which are basically divided into offline PD test and online applications. During offline PD testing, the cable system is disconnected from the power grid for a short period of time. Also for online measurement, the cable is disconnected from the grid for a short time for installing the required PD sensors on the cable. The power shutdowns for today's heavily loaded medium-voltage cables are undesirable and require a long planning phase as well as a time window, often in the off-peak night time, which also represents an undesirable burden for the staff involved. Alternative methods are required for avoiding a shutdown of the cable. The paper describes a new technology for PD testing using easy connection via the VDS ports, which are installed on every self-contained compact switchgear or ring main unit. The new technology also allows for a more efficient use of offline PD test systems by quickly pre-selecting cables with PD during operation.