Resistive-type superconducting fault current limiters (R-SFCLs) can limit short-circuit fault current and help DC circuit breakers (DCCBs) to isolate short-circuit faults in medium voltage and high voltage DC (HVDC) systems. SFCLs are always used with circuit breakers to break short-circuit current in power systems. The interruption characteristics of the DCCBs influence the current-limiting characteristics of the SFCLs. However, there has been a lack of investigation into the current-limiting and interruption characteristics when R-SFCLs are combined with mechanical-type DCCBs (M-DCCBs) based on the self-excited oscillation interruption principle in medium voltage and HVDC systems. The objective of this paper is to obtain the short-circuit fault current-limiting characteristics of a designed R-SFCL combined with an M-DCCB in DC grids. This paper describes the design of a 10 kV DC R-SFCL which was tested in combination with an M-DCCB in a DC circuit in order to obtain the quenched resistance and the required current interruption characteristics. Besides, a modular multilevel converter-based multi-terminal direct current (MMC-MTDC) grid was used to investigate the current-limiting and interrupting characteristics of the R-SFCL and the M-DCCB in a realistic HVDC grid. The experimental results show that in the 10 kV DC circuit the R-SFCL combined with the M-DCCB limited a 10 kA DC to the peak value of 1416 A and then interrupted this limited current successfully. And unlike other methods of DC interruption, this did not create overvoltage after interruption. The highest voltage on the R-SFCL is the system voltage during interruption. This means that the R-SFCL can effectively delay the voltage drop in MMC-MTDC grids, and provide enough time for the M-DCCB to interrupt the limited current. Thus, a combination of R-SFCLs and M-DCCBs might be an effective and reliable method to interrupt short-circuit fault currents in medium voltage and HVDC grids.

The coordination of resistive-type superconducting fault current limiters (R-SFCLs) and DC circuit breakers (DCCBs) have been investigated. However, the use of R-SFCLs with mechanical DCCBs (M-DCCBs) in hybrid transmission systems has not been studied. The objective of this paper is to investigate the parameter requirements of R-SFCLs and M-DCCBs for a detailed system protection strategy in a hybrid AC/DC system considering the influence of AC faults and three types of DC faults. When the AC fault is far from all MMCs, its impact on the DC system is weak. If the AC fault is close to one MMC, it will produce a strong transient response in the DC part. Therefore, a bypass switch in parallel with an R-SFCL is used to remove the R-SFCL from the system if it quenches during the AC fault. Then, the parameters of the protection devices are designed based on pole-to-pole DC fault. System restoration can be achieved within 200 ms after the fault. For pole-to-neutral and pole-to-ground faults, except for the R-SFCLs at the faulty pole, the R-SFCLs at the healthy pole will also quench, but the resistances are very low. The system may be restored within 250 ms after the DC fault.

Researchers have investigated the interruption properties of CO2 gas, including CO2 and O2 mixed gas. However, there has been no research on the passive resonance DC interrupting characteristics of CO2/O2 mixed gas. The objective of this paper is to learn the passive resonance DC interrupting properties of CO2/O2 mixed gas with superconducting fault current-limiting technology. A proposed passive resonance DCCB that includes a superconducting current-limiting module (SCLM) and a DC interrupting module (DCIM) connected in series was tested for DC voltages of 1.3, 3 and 10 kV and DC currents from 50 A to 10 kA. The experimental results show that the DCCB could successfully interrupt a 10 kA current in a 10 kV DC system. The response time of the DCCB was only 0.3 ms. After interruption, there was no overvoltage. The arcing time and the arc voltage of the SF6 gas and the CO2/O2 mixed gas were also compared experimentally. Experimental results show that CO2/O2 mixed gas may be a good substitute for the SF6 gas in passive resonance interruption. The CO2/O2 mixed gas passive resonance DCCB combined with the SCLM is an effective way to interrupt high short-circuit fault currents in medium-voltage and high-voltage DC systems.

Resistive type fault current limiters (SFCLs) have attracted lots of attention from research interests and engineering applications, due to their self-triggering, fast and effective fault current limitation ability. Fast recovery of SFCL after quench is highly attractive, yet still remains challenge when recover with load compared to recovering without load. We investigated the dependence of recovery time of a helical SFCL coil on the ratio of prospective current over critical current I _pros /I _c . A multilayer simulation model was built in MATLAB/Simulink to investigate the electro-thermal behavior of SFCL coil during a fault and recovery period, and the model was validated by experimental results. Quench simulations were carried out under different I _pros /I _c , ranging from 15 to 119 and in different recovery conditions including recovery with load condition and recovery without load condition, while keeping the fault duration of 100 ms. We observed that the SFCL coil reached 85 K and 195 K at the time when the fault was cleared, in the quench tests with I _pros /I _c = 15 and 119, respectively. SFCL coil recovered without load in 0.5 s to 10 s, depending on the ratio of I _pros /I _c .

A dc circuit breaker (DCCB), which combines a superconducting current-limiting technology and a self-excited oscillation interrupting technology, was proposed. The proposed DCCB includes a superconducting current-limiting module and an interrupter module. The objective of this paper is to investigate the effects of a transverse magnetic field (TMF) on dc interruption based on the self-excited oscillation principle. The dc interruption characteristics of CO2 and SF6 were investigated by applying a TMF of 0 and 200 mT with a puffer-type structure as a benchmark. The experimental results show that applying a TMF of 200 mT can significantly reduce the arcing time compared with a TMF of 0 mT and puffer-type structure. The dc interruption capacity for the SF6 insulation is higher than that for the CO2 insulation in the interrupter module under the same experimental condition. The simulation results of rated voltage of 10 kV show that the superconducting current-limit module limited the short current of 20 kA to less than 1 kA, and the arcing time was 4.5 ms. The results of rated voltage of 200 kV, short current of 30 kA, show that the DCCB only needed to interrupt the limited current of 3.5 kA and the overvoltage was less than 200 kV.

AbstractWith regard to the state-of-the-art technologies in the fields of applied superconductivity and electromagnetic devices, research and development highlights are presented. The recent progress and achievement described with principle and technical details include mainly i) applied superconducting materials; ii) superconducting magnets and their applications such as in ITER and Tokamaks; iii) high Tc superconducting (HTS) magnetic levitation and applications; iv) HTS smart grids; v) superconducting and electromagnetic material modelling and characteristics; vi) advanced electromagnetic devices. The applied superconductivity technology and availability are especially focused and verified with the trend of its development prospection.