Important terms regarding Circuit breaker.

    A crucial part of the power system is the circuit breaker. It is used to safeguard every electrical component from faults. Therefore, the circuit breaker utilized must be capable of protecting the system from faults without causing damage to itself. When a circuit is interrupted, a circuit breaker should put out the arc that forms between its contacts caused to fault current.

Table of Contents.

1. What is Arc voltage?

2. What is Re-striking voltage?

3. What is Recovery voltage?

 Arc voltage: 

"It is the magnitude of the voltage that is present across the circuit breaker contacts while an arc is occurring."

    An arc forms as soon as the contacts of a circuit breaker separate. The voltage that appears across the contacts during this arcing period is called the arc voltage. Its value is low, except during the period when the fault current is at or close to the zero current point.

    At current zero, The peak voltage of the arc rises quickly, tending to keep the current flow in the form of an arc. The voltage necessary to maintain the arc between the circuit breaker's contacts is known as arc voltage.

Related post: Important terms regarding fuses.

Re-striking voltage: 

"It is the transient voltage that appears across the contacts at or near current zero point during arcing period"  

    The voltage across the circuit breaker gap will rapidly increase from zero to a very high value whenever an arc interruption occurs at a zero current moment. This high voltage will only exist momentarily.

    Restriking Voltage is the transient voltage that appears across the contacts of the circuit breaker immediately following the arc's extinction or at zero current during the arcing period.

    The reason why this voltage is called a transient voltage is because an arc can only restart during the time that it is present. The arc won't restart afterwards if it doesn't restart during this temporary period. Transient Recovery Voltage is another name for this restriking voltage.

    This voltage determines the circuit's current interruption. The arc will continue for another half-cycle if the re-striking voltage increases faster than the dielectric strength of the medium between the contacts. On the other hand, the arc won't restrike and the current will be cut off if the medium's dielectric strength increases more quickly than the re-striking voltage.

Re-striking, Recovery and Arc voltage(Ref.- switchgearcontent.com)

Recovery voltage: 

"It is the normal frequency RMS voltage that appears across the contacts of the circuit breaker after final arc extinction"

 It is approximately equal to the system voltage. 

    Think about a circuit breaker whose contacts are opened, and the fault current immediately vanishes. There are no ions in the space between the contacts at zero current instant.

    The medium (air or oil) between the contacts will have a high dielectric strength under these circumstances, which is sufficient to prevent breakdown from the re-striking voltage. 

    The last arc extinction occurs as a result, and the circuit current is cut off. Following the last arc extinction, the moment the current is cut off, a transient part of the voltage that occurs across the circuit breaker contacts.

    Therefore, recovery voltage is the voltage that appears across the contacts of the circuit breaker after all transient oscillations have stopped or vanished.

Read more:  

What are the different ratings of a circuit breaker?