It is the rate of increase of restriking voltage and is abbreviated by R.R.R.V. its unit is kV/m sec.Consider the fig2 below showing the opening of circuit breaker under fault conditions.

**Rate of rise of recovery
voltage**

It is the rate of increase of restriking
voltage and is abbreviated by R.R.R.V. its unit is kV/m sec.Consider the fig2
below showing the opening of circuit breaker under fault conditions. Before
current interruption, the capacitance C is short circuited by the fault and the
short circuit current through the breaker is limited by inductance L of the
system

The short circuit current will lag the voltage
by 90° where i represents the short circuit current and *ea* represents the arc voltage. Under short circuit condition the
entire generator voltage appears across inductance L. when the contacts are
opened and the arc finally extinguishes at some current zero, the generator
voltage *e* is suddenly applied to the
inductance and capacitance in series. This L-C combination forms an oscillatory
circuit produces a transient of
frequency;*fn*= 1/ [ 2π(LC)1/2] , which
appears across the capacitor and hence across the contacts of the circuit
breaker. This transient voltage is known as restriking voltage and may reach an
instantaneous peak value twice the peak phase neutral voltage i.e. 2 *Em*.

It is R.R.R.V, which decides whether the arc
will re-strike. If R.R.R.V is greater than the rate of rise of dielectric
strength between the contacts, the arc will re-strike. The arc will fail to
re-strike if R.R.R.V is less than the rate of increase of dielectric strength
between the contacts of the breaker.

The value of R.R.R.V depends on:

·
Recovery
voltage

·
Natural
frequency of oscillations

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Protection and Switchgear : Theory of Circuit Interruption : Rate of rise of recovery voltage |

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