Wireless Aggression from Corona Discharge - aeonSolutions/AeonLabs-Safety-Health GitHub Wiki

Corona discharges are partial discharges that occur in a gaseous medium. They are produced in highly inhomogeneous electric fields and are formed at lower voltages needed for a complete breakdown.

Corona discharges ionize the gaseous insulation surrounding an energized electrode when the electric field intensity surpasses a critical inception value.

Similar to partial discharges, corona discharge also produces other chemical elements such as ozone or NOx compounds, as well as ultraviolet and visible light, electromagnetic radiation, audible noise (AN), and other types of radiation.

Corona discharge is challenging to detect in daylight because of the low level of visible radiation. High-voltage laboratories often use high-performance digital cameras to find corona discharges at night.

Air is a conductor if enough energy is available to ionize the air molecules. This creates both negative and positive charges, which drift, creating a current flow.

The breakdown field strength for dry air is, IIRC 3MV/m. In practice sharp points allow even a few hundred volts to create field-strengths exceeding that, and certainly by 1kV you have to avoid sharp points or you just get strong corona discharge around them.

Corona discharge is the principal mechanism for low current flow into the air, the high electric field strength causes a local breakdown in the air and the ions move towards the point or away depending on the sign. It's commonly seen when removing nylon clothing in the dark when static build-up discharges.

Higher powers available lead to sparks with a well-defined channel of ionized air that carries a far higher current density (heating the air enough to make it a blue-white hot plasma (10 to 20kK or thereabouts I think). By comparison corona discharge is a much colder phenomenon, giving off very faint light (recombination of ion pairs?).

The behavior of DC and high-frequency AC discharges is rather different, but it's still ionized air molecules and free electrons as charge carriers.[2]

“.. the audible corona ( the hissing sound) is the result of the movement of electrons in sufficient numbers to momentarily displace the air molecules. This displacement results in a mini-vacuum the collapse of which creates a miniature thunderclap. The movement of the electrons in sufficient numbers constitutes a micro-arc which creates Hertzian waves that can be detected as radio interference [1]”.

Depending on the type of electrical discharge in the surrounding environment, different visual, auditory and vibration phenomenons can be identified.

mid-air dark spot
By producing a silent electrical discharge in the surrounding air, it produces UV rays which in turn, converts O₂ to O₃ in the atmosphere. In the conversation process, photons are absorbed, creating a dark spot effect.

Partial discharges emit UV and visible light, as well as chemicals, a local temperature rise, and current pulses. As a result, partial discharges are frequently detected using electromagnetic techniques, such as X-ray detectors, UHF and VHF antennas, acoustic and ultrasonic sensors, optical and infrared detectors, and radio interference voltage and partial discharge detectors. Only particular detection techniques enable the precise determination of partial discharge sites.

Open hardware electronics capable of doing corona discharge active monitoring

• ⌛ Smart Corona Discharge Detector

[1] is an excellent, in-depth treatment of the phenomenon of corona discharge. T. Gregory Lewis, George Karady and Murray D. Sirkis, “An Analysis of the Frequency Characteristics of Corona Discharge at Low Pressure “ July 1991, available on National Technical Reports Library, USA

[2] https://forum.arduino.cc/t/can-anyone-explain-how-current-discharging-into-the-air-works/194160/2

[3] https://www.azooptics.com/News.aspx?newsID=27955

[4] Riba, J.-R., & Bas-Calopa, P. (2022) Use of DSLR and Sonic Cameras to Detect and Locate High-Voltage Corona Discharges. Sensors, 22(19), 7250. https://www.mdpi.com/1424-8220/22/19/7250/htm