DC superconducting fault current limiter

Abstract

There is a lack of satisfying solutions for fault currents using conventional technologies, especially in DC networks, where a superconducting fault current limiter could play a very important part. DC networks bring a lot of advantages when compared to traditional AC ones, in particular within the context of the liberalization of the electric market. Under normal operation in a DC network, the losses in the superconducting element are nearly zero and only a small, i.e. a low cost, refrigeration system is then required. The absence of zero crossing of a DC fault current favourably accelerates the normal zone propagation. The very high current slope at the time of the short circuit in a DC grid is another favourable parameter. The material used for the experiments is YBCO deposited on Al 2 O 3 as well as YBCO coated conductors. The DC limitation experiments are compared to AC ones at different frequencies (50-2000 Hz). Careful attention is paid to the quench homogenization, which is one of the key issues for an SC FCL. The University of Geneva has proposed constrictions. We have investigated an operating temperature higher than 77 K. As for YBCO bulk, an operation closer to the critical temperature brings a highly improved homogeneity in the electric field development. The material can then absorb large energies without degradation. We present tests at various temperatures. These promising results are to be confirmed over long lengths.

Electrothermal Phenomena About Current Limitation With Coated Conductors

“…3 shows such an experiment with the Theva conductor during the limitation phase. The operating temperature is 86 K using pressurized liquid nitrogen [10]. Three different (see Fig.…”

“…The quench is homogenous over the length if and are close, otherwise the maximum temperature is higher than the mean one [10].…”

YBaCuO and REBaCuO HTS for Applications

“…The actual testing led to peak currents of 2.7 kA within 1 ms and a limitation to approximately the nominal current within 5 ms. The voltage decline at the source was seen for only 0.25 ms, which demonstrates that in power grids with bus‐bar coupling through FCLs, the faultless parts remain practically unaffected; see also Tixador et al 46 . Compared with conventional equipment, which uses a Cu bar and a circuit breaker rated to 50–100 times the nominal current, the superconducting FCL offers a much safer and versatile clearing of faults in DC power systems.…”

Hybrid superconducting fault current limiting CORC® wires with millisecond response time

“…Isolation devices such as circuit breakers are needed to provide active protection of crucial systems within power distribution networks when faults occur. The interruption capabilities of traditional protection devices are not necessarily scalable to the large fault currents in some existing networks and future power distribution networks, particularly for direct current (DC) systems [1][2][3][4]. This presents a need for superconducting cables that can effectively respond to fault currents by introducing an instantaneous impedance into circuits to limit the fault currents to levels that will not damage crucial components [5][6][7].…”