The question then becomes how to assign maintenance priority? Many users immediately look at the “count” attained by the camera, but this is not correct as the counts are not easily comparable (due to the many factors influencing it). The count is at best useful as rate of damage indicator at the time of inspection, if it is back calculated to a standard condition. The count changes based on the ambient weather, this also means that the count cannot be used as part of a trending exercise – unless inspections can be done under exactly the same conditions – very unlikely.
The most reliable way of assigning a maintenance priority is by using the Maintenance Priority Rating system developed by the US Electrical Power Research Institute (EPRI). The system assigns a rating based on the discharge’s ability to damage the hardware it is on or near, the presence of physical damage and the expected timeframe until failure of the hardware.
The Maintenance Priority Rating levels and their associated questions are re-interpreted as a decision tree below.