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Corona Detection

Corona discharges, detected using UV cameras, can indicate potential equipment failure due to various factors such as insulation damage, inadequate clearances, or faulty installations. Ofil’s DayCor® technology is designed to detect and pinpoint electric corona partial discharge emissions from faults on high voltage apparatus, so maintenance teams can perform preventative maintenance before they escalate to system failures.

Identifying these issues early prevents unexpected power outages, ensures safety and increases service reliability. By using Ofil handheld or mounted solutions, the inspections can also be carried out without interrupting the power supply, keeping customer inconvenience to a minimum.

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How it works


SBUV Filters

Ofil’s imagers utilise the fact that ultraviolet between 240-280nm is being absorbed by the Ozone, so that signals detected in this spectral range would have to originate on earth. Ofil’s solar blind filters completely block the sun radiation on the ground, yet have high transmission in the solar blind spectrum (240-280nm). While the conventional UV sensors are saturated by daylight, Ofil’s solar blind filters enable absolute detection of extremely weak UV signals in full daylight with high signal-to-background ratio and only negligible background noise.


The optics in DayCor® technology collect and transmit both the regular visible spectral range and the invisible UV photons and therefore efficiency is of a major concern. Ofil’s systems offer, by default, narrower Field-of-View (FOV) as more appropriate for longer viewing distances experienced in the field. Wider FOVs are available for shorter distances inspection routines. Ofil’s optics are made for and designed with special objective lenses, automatic/manual focus and aperture of  F/2.75.


Ofil cameras simultaneously detect and display the same image, but at two different spectral ranges: UV spectrum for detection of UV phenomena, and visible spectrum for accurate orientation of the source. Accurate detection and display are maintained over all possible working distances and FOVs. This is provided by overlapping the optic properties of both channels. The optical system merges the two optical axes, so there is never any parallax between them.

Digital Processing

Once captured, photons are filtered, intensified and displayed as blobs of corona. The goal is to present a flawless representation of reality by minimizing extraneous noise and quantifying the magnitude of corona activity. Eventually, results:

  • Aid in the detection of weak or intermittent sources
  • Help pinpoint origins of corona activity
  • Improve quality of recorded images

Solar Blind Range



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