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A thyristor controlled ground fault current limiting system (TGCL) was proposed to prevent one-line ground fault current rises due to increased capacitance to ground. Basic components of the TGCL are a main ground fault current limiter, which rapidly adjusts a compensating reactor level for the capacitance to ground, and the TGCL's controller. Control is ensured by an in-phase control method for zero-phase sequence voltage and current. The method determines the direction of ground faults and the compensating reactor level. The fast control which can be realized shows the TGCL is a valuable protecting system for high ground fault current distribution systems. Keywords: Current Limiter, Ground Fault, Thyristor Control, Fault Protection, Distribution System.

A fault current limiter with series compensation, which is composed of a compensation capacitor and a limiting reactor in series, is proposed. A solid-state switch connected in parallel with the capacitor controls either the ordinal series compensation or fault current limitation. A feasibility study of the current limiter by simulation analysis is presented and the effectiveness of the current limiter is evaluated from the viewpoints of transient stability improvement and device capacity. The current limiter is a useful protection device for large, high power transmission systems. Keywords: Current Limiter, Series Compensation, Thyristor Control, Fault Protection, System Stability.

To prevent voltage decrease of distribution systems, the principle and fundamental characteristics of a solid-state current limiter using GTO thyristors were investigated. Basic components of the apparatus were a fast solid-state switch and a current limiting impedance of low resistance in parallel with the switch. Experimental results of the test current limiter showed the fault current was limited successfully, regardless of DC component size. The time from detection of fault occurrence to interruption of the fault current by the solid-state switch was 40 microseconds. This time was very short in comparison with that before the fault current reached a large value. Thermal rise of the solid-state switch for conduction was solved by a self-cooling apparatus using a non-combustible cooling liquid. The results indicated that the solid-state current limiter was a valuable protecting device for high fault current distribution systems.