Coiled to prevent a spike

Lightning-fast trouble shooter

Designing a special superconducting cable and winding it into a coil creates a truly remarkable fault current limiting device – that acts just like a cable during normal operation, but “quenches” or limits short circuits within milliseconds on a high-voltage line. 

Hair trigger action

In this device, a short circuit current triggers events that reduce both the magnitude of the fault current as well as the sudden temperature increase. However, in normal operation, it acts like any other cable, thanks to the remarkable properties of superconductors.

Generational divide

Today’s commercial superconductors are either 1st or 2nd generation. While their behavior is identical up to their nominal current carrying capacity (critical current), their behavior for currents larger than critical current differs: 1st generation wires carry additional current with little resistance, while 2nd generation wires exhibit significant resistance for currents above critical current. Combining both types of superconductors gives the cable remarkable magnetic properties, where the cable is ‘magnetically invisible’ in normal operation and only exhibits an external magnetic field in case of a fault current.

Self-protection

If we now wind this remarkable cable into a coil around an iron core, we have an effective fault current limiter: Once a fault current hits the cable, it generates an external magnetic field that penetrates the iron core. The significantly increased impedance of the device reduces the size of the fault current, and the short-circuit energy is dissipated in the iron core. This means that it protects itself and other devices connected to it by immediately reducing the fault current it is exposed to! This allows network operators to reduce the magnitude of fault currents and protect their assets.