Dielectric breakdown voltage of air vs. Electric field in thunderstorm

In summary, the dielectric strength of air is 3,000 kV, meaning that it can withstand an electric field of that magnitude without becoming electrically conductive. However, in real conditions, the threshold for lightning occurrence is set much lower, between 1kV and 3kV, due to factors such as humidity and sharpness of points on structures. This lower threshold allows for more warning for lightning strikes, which can be unpredictable.
  • #1
The dielectric strength of air (ie the maximum electric field that the material can withstand under ideal conditions without undergoing electrical breakdown and becoming electrically conductive) is 3 000 kV ( https://en.wikipedia.org/wiki/Dielectric_strength#Break_down_field_strength ).

In many articles I have read, some facilities that need lightning protection like NASA's Kennedy Space Center, electric field mills are used to measure the electric field's magnitude. When it reaches a certain threshold, there is a risk of lightning occurrence and so, all operations are suspended.

This threshold is usually situated between 1kV and 3kV ( https://www.vaisala.com/sites/defau...ric_field_mill_and_lightning_observations.pdf p : 4 ), and I find this really curious since air can't conduct electricity unless the electric field is 3000kV in normal conditions, which is not even close to the threshold chosen.

Is there any explanation for this apparent contradiction?
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  • #2
Electric field strength has units of V/m (or kV/m or MV/m), not Volts.

The 3MV/m number from Wikipedia is for dry air, so I'm guessing that you would set the threshold much lower under real conditions (high humidity, rain, etc.).
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  • #3
It also depends on the sharpness of the points on the structure. Sharp points create a stronger field. Lightning is unpredictable, and will sometimes strike low down on a tall structure, for instance. Conditions are likely to vary from minute to minute, so a lower threshold will give more warning.
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  • #4
@ilovepudding -- this thead is locked temporarily until you respond to my PM
  • #5
berkeman said:
@ilovepudding -- this thead is locked temporarily until you respond to my PM
There has been no reply to my PM, but the issue was handled another way. Thread is re-opened.

What is dielectric breakdown voltage of air?

Dielectric breakdown voltage of air is the minimum amount of electric field strength required to cause a sudden increase in the flow of electric current through air, resulting in a breakdown of its insulating properties.

How is electric field related to thunderstorms?

Thunderstorms are characterized by strong electric fields, which are generated by the separation of positive and negative charges within the storm clouds. This separation creates a large potential difference, leading to the formation of lightning.

What factors affect the dielectric breakdown voltage of air in thunderstorms?

The dielectric breakdown voltage of air in thunderstorms is affected by several factors, including the strength of the electric field, temperature, humidity, and the presence of impurities in the air. These factors can vary greatly within a thunderstorm, leading to fluctuations in the breakdown voltage.

Why is understanding the dielectric breakdown voltage of air important in thunderstorms?

Understanding the dielectric breakdown voltage of air is important in thunderstorms because it helps us predict and prevent potential hazards, such as lightning strikes. It also plays a crucial role in the design and maintenance of electrical systems and equipment.

How is the dielectric breakdown voltage of air measured?

The dielectric breakdown voltage of air is typically measured using a high-voltage source and a gap between two electrodes. The voltage is gradually increased until the air between the electrodes breaks down and allows current to flow. This breakdown voltage is then recorded as the dielectric breakdown voltage of air for that particular set of conditions.