Partial discharge in insulators is one of the leading causes of asset failure in medium voltage (MV) generation, transmission, and distribution assets. One estimate attributes nearly 46% of failures in MV electrical equipment to partial discharge (PD). A significant number of these failures are ultimately humidity driven and the next highest proportion of failures is thermal in nature. The assets with the highest average downtime hours per year are distribution switchgear. Because of the quantity of switchgear in the distribution system and their downtime they are ideal candidates for continuous asset monitoring.

The PD Early Warning System uses wide band UHF antennae located inside each bay cabinet to detect both surface (corona) and internal discharge activity. Since no electrical connection is required it is much easier to install and safer to use than other systems.

The antennae are connected to reader modules which analyse the signals and report any PD activity in pC. The reader modules are connected together and linked to sub.net that stores the measurements and analyses them for long term trends. Emailed reports are sent if the status of any bay changes state. In addition regular reports can be sent showing the trend of PD activity in each bay. The present state of each device may also be seen using a web browser.

The averaged data are available for the previous 6 months and a trend analysis looks for increasing levels of PD activity. Warning and alarm levels are set to report any significant change in condition that may warrant further action. The ambient temperature and relative humidity levels may also be recorded and monitored to assist with the analysis process.