Fault current limiter surge protection device for the power grid based upon zero power consumption ceramic ferrite permanent magnets

This paper describes the development of a new Fault Current Limiter (FCL) surge protection device for the power grid based upon zero power consumption permanent magnets. FCL components will be vital to prevent grid damage and to facilitate the safe connection between renewable energy generators and the power grid, particularly the emerging smart grid. The technology behind the new FCL has been achieved from a combination of magnetic engineering insights, including: using low cost ferrite magnets to saturate an iron inductor; a configuration providing efficient magnetic coupling; achieving a high level of protection against demagnetisation damage from the huge current surges during a fault. This technology results in a completely passive, autonomous system which requires no external power, back-up or control, and recovers automatically when the fault is cleared. The key challenge is magnetic scalability and manufacturability using cost efficient permanent magnets. The paper describes how a proof-of-concept project using high cost rare earth magnets was adapted and developed to provide an economically feasible solution using ceramic ferrite magnets, ultimately leading to the development of the FCL for the commercial power class of 20MVA, 11kV.