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In the world of electrical utilities, the growing demand for power, aging infrastructure, and overloading of grids lead to an increasing number of failures. These issues disrupt the continuity of electricity supply, cause unexpected outages, and lead to significant financial losses.

One of the significant yet largely invisible threats to power systems is corona partial discharge (Corona PD). Corona PD is both an indicator of malfunction and an active destructive factor that should be eliminated. Over time, the discharges cause damage to the electrical components, eventually leading to system failures.

Detecting corona PD early is crucial to ensure the health of the power system. Accurate and timely detection allows for proactive identification and rectification of potential equipment failures, thus preventing costly, disruptive power outages. 

The Precision of Pinpointing: In detecting corona discharges, precisely locating the origin of PD is essential. Accurate localization aids in assessing a fault’s severity and distinguishing between multiple co-existing faults. This differentiation is vital for targeted maintenance efforts.

Comparing Ultraviolet (UV) and Ultrasonic (US) Technologies for Corona PD Detection

When it comes to detecting and visualizing corona discharges, the main contenders are UV and US technologies. Each offers distinct features:

Damages to components caused by Corona PD

Ultraviolet Technology Ultrasonic Technology
How it Works Detects corona PD by capturing the ultraviolet photons emitted during the ionization process. The UV camera visualizes these emissions, overlaying them on a visible light image to pinpoint the exact location of the discharge source. Identifies corona PD by capturing the acoustic waves they produce. Using an array of ultrasonic microphones, the technology estimates the source location of the PD by interpolating the sound waves' origins.
Sensitivity Laboratory-tested and certified sensitivity to PD. Sensitive to acoustic waves caused by PD.
Imaging Displays an overlay of the UV image atop a visible image, pinpointing corona on components. Offers wide fields of view but lacks detailed pinpointing of the PD source.
Reliability Minimal false results, reliable and repeatable outcomes. Prone to false positives due to environmental noises and noise reflections.
Multiple Sources Detection Can easily detect and distinguish multiple sources, without limitation on the number of sources in the field of view. Faces challenges in detecting and distinguishing several sources. Two nearby PD sources often get combined, making precise localization difficult. When in multi-source mode, the probability for false results is high.
Ease of Use Intuitive "point and shoot" operation, with zooming capabilities on both channels. Requires adjustments and frequent re-positioning during inspection.
Applications Versatile in use, from handheld devices, vehicle mounted to airborne applications. Handheld use primarily, with requirements to stand still during inspection.

Pinpointing the Source of Corona PD:

UV Camera: Corona on end fitting- pinpointed location

Ultrasonic imager: spot covering multiple components

UV Camera: Corona on insulator- pinpointed location

Ultrasonic imager: spot covering both insulators

Pinpointing Multiple Sources of Corona PD:

UV camera: pinpoints 2 separate spots of PD on the insulators

Ultrasonic imager: displays a large spot covering two insulators and the conductor

False Results – Ultrasonic imager:

Reflections on ground

Background noise due to car engine

Background noises due to machine

Validity of Results:

UV Camera: pinpoints discharge on arcing horn.

Ultrasonic Imager - False Alarm: Based on the location of the discharge it is impossible to decide whether there is a problem. Discharge on a horn is not an issue, while corona on the end fitting is a major problem.


For electrical utilities and MV/HV components manufacturers, UV technology emerges as the preferred choice for its superior sensitivity and precision in detecting corona PD. By visualizing the PD source using UV emission, UV cameras accurately pinpoint the source’s origin. 

While US technology may be more budget-friendly, it often faces challenges like proneness to false positives and difficulties in distinguishing multiple PD sources. In contrast, the unmatched accuracy of UV technology makes it essential for ensuring early detection and mitigation of corona discharges, ultimately safeguarding a reliable power system.

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