Jännitepalautumisen

Jännitepalautuminen, a Finnish term, translates to "voltage recovery" or "restrike" in English, particularly in the context of electrical circuits. It refers to the phenomenon where voltage reappears across the contacts of a circuit breaker or switch after it has been opened, especially during the interruption of an electrical current. This voltage reappearance can be transient or sustained and poses a significant challenge in achieving successful current interruption.

When a circuit breaker opens, an arc is formed as the contacts separate, carrying the electrical current. This arc is then extinguished by various means, such as lengthening the gap, introducing a quenching medium like oil or gas, or magnetic deflection. However, immediately after the arc is extinguished, a transient voltage can appear across the breaker contacts. This voltage is due to the rapid change in current and the inductance of the circuit.

If this transient voltage exceeds the dielectric strength of the gap between the contacts, a restrike occurs, meaning the arc reignites. This restrike can lead to a series of oscillations and further attempts to interrupt the current. In severe cases, multiple restrikes can prevent the successful isolation of the faulty section of the circuit, potentially causing damage to equipment or prolonging an outage. Understanding and mitigating jännitepalautuminen is crucial for the reliable operation of electrical power systems. Circuit breaker design incorporates features to limit this phenomenon, such as the rate of rise of transient recovery voltage (RRV) and the initial voltage recovery.