Superconducting Fault Current Limiters to increase grid reliability

In the context of city growth and network expansion, adding new links and connections to networks creates an increase in fault currents which can damage equipment.

To solve this issue, it is necessary to either upgrade or change the network equipment, which can be quite expensive, or to add a limiter in the system upstream from the equipment.

The solutions usually applied are based on pyrotechnic fuses or series reactors which create voltage instabilities.

Moreover, they have specific drawbacks:

• When using a series reactor, an inrush current will create an overvoltage in the network.
• Pyrotechnic fuses require a human intervention on-site and extra fuses must be kept in storage to restore service.

We have developed superconducting fault currents limiters which are transparent (negligible impedance) for the networks during normal operation (absence of a fault current).

In case of a fault current, the superconductor becomes resistive, adding a resistance to the network which limits the current in just a few milliseconds, protecting the network until the breaker is triggered.

Superconducting fault current limiters operate and return to service without the need for human intervention after the closing of the breaker.

Their benefits include:

• Improving grid reliability and sustainability without overvoltage and instabilities in the network
• Being a passive device with no trigger or compensation system, unlike existing systems
• Superconducting fault current limiter systems are by design highly recyclable