Streamer Velocity Applet

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## Equation

## Parameters

## Diagram

- When pulsed voltage is applied between two electrodes, streamers will form once one electrode breaks down. The streamers (narrow channels of plasma) grow towards the other electrode and will short out the gap once they bridge the gap. If one electrode is highly field enhanced, then streamers forms at the beginning of the pulse and the streamer velocity is the gap length divided by the time until the gap is shorted and voltage collapses.
- Sources: Private communication with Ian Smith (for water when V>1MV [although he writes it as Ft^0.5 = 0.09 where F is the electric field]) and a report by H.G.Herbert left for me by Ron Boller and labelled "SSWA/HGH/6610/104" that describes the emperical fit to data from breakdown experiments with a sewing needle and a 2" ball (for all others). Pulse generators were a 1.0 MV transformer with 500 ns rise time and 1.3 MV Blumlein with 45 ns pulse width. input parameter "d" is not required to calculate velocity for oil and polyethylene (just for water) although it is required to calculate closure time for all three cases. These equations can be used to estimate the closure time of a switch where one electrode is highly enhanced or to determine the minimum possible gap closure time.

Copyright © 2003-2021 Raymond J. Allen