Concept of a combined short circuit limiter and series compensator

The modulation of the transmission line impedance improves system operation and power quality. The major advantages are the dynamic reduction of voltage drop, improvement of transient stability, and loop flow reduction. This paper presents a new concept for a combined short circuit circuit limiter and dynamic series compensator. The device consists of a fixed capacitor, thyristor switched capacitors, and a thyristor switched inductance. The circuit is designed to regulate the impedance in steps. The series compensation is controlled by the capacitors switching on and off, while the current limitation is achieved by the insertion of a resonant LC circuit in the transmission line. The thyristor switches are operated at zero current crossing, which eliminates the harmonics generation. The system operation has been analyzed and realistic components have been selected. The results have demonstrated that the device can regulate the line impedance effectively and significantly reduce the short circuit current. It can be built with commercially available components. The significant operation improvement is expected to justify the cost of the new device.