In a research conducted lately by CEPRI – China Electric Power Research Institute that was presented at the SPIE 2014 conference, the use of Ofil’s DayCor® Superb was analyzed. The purpose of the study was to establish operating principles taking into account the influence of external factors such as inspection distance, inspection angle, camera gain settings and ambient conditions. The study concluded that when performing comparative corona inspection of electrical apparatuses conditions should be kept similar (if not identical) and always documented.
The DayCor® Superb as remote non-destructive testing equipment (NDT) has an outstanding corona detection performance that is due to:
- Noise recognition reduction
- Pinpointing high resolution
- UV-Visible superimposing accuracy
- Highest sensitivity to UVc radiation
DayCor® cameras are used to capture UV radiation emitted by corona and use the location of the emission to zoom into the fault. Corona is expected to develop in locations with irregular high electrical fields. These are usually indicative of defects, incorrect design, bad installations workmanship, contamination and other. The camera can also display, upon calling the function, a count of corona events per second that reached the camera, The displayed value can be helpful in laboratories where all parameters that affect the results are controlled.
When conducted outdoors UV imaging is influenced by environmental conditions. Some of the conditions relate to optical laws, such as inverse-square law, some relate to quantum chemistry of particles, such as temperature, barometric pressure, humidity and some to electrical and electromagnetic fields such as raindrops and icicles. Whatever the factors are, they should be documented and mentioned in inspection reports.