Difference between transient recovery voltage and restriking voltage

Transient recovery voltage generally occurs because of current chopping phenomena before natural current zero. In case of low current there may be a chance of current Chopping i.e. ARC INTERRUPTION before natural current zero, so whatever the stored magnetic energy i.e. 1/2 Li^2 present in the circuit is converted in to electrostatic energy i.e. 1/2 CV^2. So generated transient recovery voltage = (L/C)^1/2 X i

Now because of transient recovery voltage dielectric strength of dielectric medium may get deteriorate and there is a chance of reignition or restriking of ARC. At which Voltage level restrike of ARC occurs is called as restriking Voltage.

When the contacts of a circuit breaker start separating due to a fault current, an arc will be established between the contacts. After few cycles, this arc is interrupted as the dielectric strength of the arc space between the contacts builds sufficiently due to the removal of ionized particles and this will avoid continuation of the arc and the arc will be extinguished. When the contacts start separating the voltage across them starts increasing and will represent the voltage drop across the arc. Immediately when the arc is extinguished, a transient high frequency voltage appears across the contacts that also is superimposed on the power frequency voltage. The high frequency voltage tries to restrike the arc hence it is called restriking or transient recovery voltage and if succeeding will result in failure of current interruption.

In clear terms, this is the voltage that appears across the circuit breaker contacts that is responsible for restriking the arc immediately after its extension. The normal frequency (60 Hz) r.m.s. voltage that appears across the contacts of the circuit breaker after final arc extinction in the steady state is the recovery voltage and is equal to the system voltage.

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