Circuit Breaker With Improved Re-Closing Functionality

A circuit breaker for protecting a power line comprising:

• a circuit breaking element for disconnecting the power line from a power source, and
• a control unit arranged to
• detect a fault on the power line,
• open the circuit breaking element based on said detected fault, which opening starts a pre-determined disconnection time interval,
• inject a test signal at a main frequency into said power line,
• measure a response voltage and a response current in the power line, where the response voltage and the response current result from the test signal (t(f))
• determine an impedance to ground of the power line from the response voltage and the response current,
• analyse the impedance to ground of the power line over time during said disconnection time interval, said analysing including comparing the impedance to ground with a reference threshold,
• determine a permanent or a temporary fault of the power line based on the change of the impedance to ground during the disconnection time interval,
• re-close the circuit breaking element after the expiry of the disconnection time interval if the fault is determined to be a temporary fault, and
• keep the circuit breaking element open after the expiry of the disconnection time interval if the fault is determined to be a permanent fault.