Summary - MEASUREMENT AND ANALYSIS OF ELECTROMAGNETIC FIELDS RADIATED BY CORONA DISCHATGE

Purpose

The main objective of this report is analysis about the Electromagnetic Radiation that emit by Corona discharge and it behaviors. Corona discharge is a usual type of electrostatic discharge. It occurs due when ionizing fluid such as air surrounding a high voltage region. Specially, the objects which flying in the air with high speed, they get high electrostatic potential may be from 10 kV to 100 kV, even each 500 kV! Therefore, these objects always use discharge brushes to discharge the accumulating charge. This done as a corona discharge. The corona discharge, radiate strong electromagnetic radiation and this radiation can do serious damage to aviation, aerospace, and the microelectronics systems of weapons. Therefore, the analysis of electromagnetic radiation by corona discharge is essential to prevent these types of harmful effects.

Analysis of Corona Discharge

The corona discharge can be divided in to two types according to the polarity of the body as positive corona discharge and negative corona discharge. The characteristics of positive and negative corona discharge are different. Current is major produced by the movement of electrons. It future increase due to large number of anions, Photon emission. Fast ascending current pulse at electron stage. Then exponentially decayed at iron stage.

Positive Corona Discharge Negative Corona Discharge
Pulse voltage is positive Pulse voltage is nagetive
Rising time is greater than 2 ns Rising time can reach 0.8 ns
Current maximum pulse frequency can be upto  pulse/s Current pulse frequency can reach  pulse/s
Duration of pulse is longer Duration of pulse is shorter than positive discharge
Largest amplitude of current pulse is longer than negative corona discharge Largest amplitude of current pulse is shorter than positive corona discharge

In the positive corona discharge, the flow columns becomes more frequent until it becomes delf restraint with the voltage increase. And a steady, thin ray layers occurs in positive electrode.
The current pulse of the corona discharge conductor can be calculated by,
Pasted image 20240527114820.png

a and b get different values because of different characteristics of positive and negative corona currents.

Also, the corona current waveform can be express as the double exponential form as below,
Pasted image 20240527114844.png

When considering electrode to ground to discharge, -50kV voltage, testing distance 8m with 20 GHz sampling, 40000 sampling point digital oscilloscope, these results can be observed.

  • The characteristics of time domain waveform of the corona discharge radiation field are attenuation oscillation with a very fast rising edge.
  • The frequency distribution of the corona discharge radiation field is from 50 MHz to 650 MHz with main energy distribution is from 500 MHz to 600 MHz.
  • The amplitude can get to -50 dbm.