A methodology to coordinate solid-state fault current limiters with conventional protective devices

A silicon carbide fault current limiter for distribution systems

“…4. Unlike the electromechanical CB and recloser, which can only open the fault current after the voltage goes across zero (usually the operating time is longer than half the fundamental-cycle), all SSFCLs are expected to open the fault current under a quarter cycle [2]. In the case of the proposed SiC SGTO, the turn-off time is negligible compared with the period of the line frequency (tens of microseconds versus 16.67 milliseconds).…”

“…The SSFCL microcontroller generates a fault current signal when detecting a value greater than a defined current threshold. The SSFCL not only limit the fault current by turning off the SGTOs but also determine whether the fault is permanent or temporary by a "soft" method: after a few cycles of temporarily blocking the current flow by not firing, the SGTO turn-on signals, the SSFCL goes into a phase-control mode [2]. The phase control decreases the firing angle of the SGTO turn-on signals by a defined step (e.g., 5° per cycle in the simulation example) every subsequent line-frequency cycle from 180° to 0° for letting the current slowly increase from zero back to normal conditions.…”

“…The basic advantages of the SSFCL's phase-control are illustrated clearly in the example: the line current of the power distribution system is limited to around 2 pu; the fault is able to be classified as a temporary or permanent fault. In order to configure the SSFCL to cooperate with various power system protective devices, such as fuses, CBs, recloser, the number n bk and degreed deg dct can be adjusted for achieving different coordination methods [2]. Also, additional iterations of the phase control can be applied before it goes into the permanent blocking mode.…”

“…Standard protective devices with multiple vendors in the space like 15-kV circuit breakers are mostly limited to 63 kA of symmetrical interrupting current. With the advances of new semiconductor materials in recent years, fault current limiters (FCL) based on semiconductor devices have become a promising solution for the above issues [2]- [5]. There are two main FCL technologies: superconducting [3] (which is beyond the scope of this paper) and solid-state [4].…”