The voltages that appears across the breaking contact at the instant of arc extinction is called_______ 

Restriking voltage is the transient voltage that appears across the contacts of a circuit breaker at the instant the arc is extinguished. This voltage can cause the arc to restrike if the insulation strength across the contacts is not sufficient. It plays a crucial role in the interruption process and is usually damped out after a few oscillations, giving way to the steady-state recovery voltage.

Concept

The following are the important terms used in the circuit breaker analysis:

1.) Arc Voltage

• Arc voltage is the voltage that is responsible for maintaining the arc between the contacts of the circuit breaker.
• At the time of the circuit breaker contacts opening, an arc is struck between the contacts due to the ionization of the medium surrounding the contacts.
• A small potential difference exists between the contacts and it is responsible for maintaining the arc. This voltage is called the Arc Voltage.
   

2.) Restriking Voltage

• Whenever arc interruption occurs at zero current instant, the voltage across the circuit breaker gap will suddenly rise from zero to a very high value. This high voltage will be transient in nature.
• It is the transient voltage that appears across the contacts at or near current zero during the arcing period.
   

3.) Recovery Voltage

• ​It is defined as the voltage appearing across the circuit breaker contacts after the final arc extinction and after all the transients die out (or disappear). 
   

4.) Active Recovery Voltage

• Active Recovery Voltage refers to the voltage that reappears across the contacts of a circuit breaker after the arc between the contacts is extinguished. It represents the system voltage that stabilizes across the open contacts once the transient effects subside.

• This voltage can influence the breaker’s ability to prevent re-ignition of the arc and ensures the system remains stable after interruption.

• It's distinct from restriking voltage, which is the transient voltage that appears immediately after arc extinction and may cause re-ignition.