New methods for fault protection and high voltage regulation

During load fault conditions, high voltage power systems and loads can suffer from extreme peak currents. Conventional circuit breakers require several cycles and many milli-seconds to open potentially allowing a large amount of energy to be deposited into the load which can be destructive to the load as well as disruptive to the power system. A new method of combining a high temperature fault current limiter in conjunction with a solid-state circuit breaker has been developed to greatly reduce the potential damage in the event of a load fault. This fault current limiter, consisting of a number of YBCO HTc filaments submerged in a liquid nitrogen bath, is designed to be lossless during normal operation and resistive (current limiting) during a fault. A solid-state switch is placed in series with the fault current limiter allowing the system to open during fault events. In addition to the fault protection capabilities of this system, it can also be configured as an isolated, linear regulator for direct regulation of high voltages. A major advantage of this system is that a solid-state switch can be designed for the limited fault current, not the worst case fault current. This leads to systems that can be smaller, simpler and more cost effective. Application of this fault control/regulation system to a tube-based radar load may prevent permanent radar tube damage from arcing during faults and may also increase the radar system reliability and lifetime. Data from a laboratory demonstration system is presented and results from operation of this system during are reported.