Setup and preliminary results of a pilot on-line cable PD monitoring system on an 11 kV switchboard using capacitive couplers

In today´s competitive power transmission and distribution (T&D) industry the need for predictive and scheduled maintenance of the infrastructure has become a vital necessity. On-line condition monitoring of underground cables and switchboards for the dominant failure mechanism of Partial Discharge (PD) has been in use for some time now. It has been shown that on-line measurements for monitoring the activity and the degradation severity of the PD can not be calibrated in terms of their charge (pC). Although the direct interpretation of the measured voltage gives some indication, for more profound results specific locations have to be monitored over time to record the evolution of the amplitude and/or phase shift (trending). For these reasons a pilot on-line cable monitoring system is currently being implemented in a substation of the Electricity Authority of Cyprus (EAC) on selected breakers of the 11 kV switchboard. This system will alleviate the need for the physical presence of expert personnel on site, as measurements from sensors that will be non-invasively installed will automatically be recorded and processed on a continuous basis thus allowing potential dangerous PD events to be captured. Furthermore, the proposed system will implement permanent capacitive couplers that offer better sensitivity compared to other sensors. In this paper the setup and calibration of these sensors, together with some preliminary results will be presented.