Use of multi-turn railguns as high-speed limiters of short-circuit current for large power plants

Abstract

The concept of using multi-turn railguns as high-speed limiters of short-circuit current has been considered. The principle of similar devices is based on quickly bringing a large ballast impedance in the power supply circuit at a synchronic movement of several electric arcs along the insulated channels of the multi-turn launcher with its electrodes made of material with high specific resistance. Due to good magnetic coupling between the contours of the moving electric arc one can maintain a high velocity of the motion along the electrodes even at relatively weak currents. Limitation of the outside circuit current is basically achieved at the cost of electric energy dissipation in the rails. The advantages of the proposed device in comparison with existing analogs are as follows: high-speed limitation of short-circuit current with its subsequent reduction to a level which is lower by several fold than nominal (at time less than 0.01 s) with low overvoltages in the interrupted circuit; low cost-price of manufacturing and its high reliability; high energy absorption (several MJ). The experimental data on the tests of the pilot model of the current limiter with five turns, 80 mm inter-electrode distance and 1.3 m rail length is given. The setup resistance gradient is 1.2 Ohm/m and inductance gradient is 15 /spl mu/H/m. This model device efficiently limited and interrupted the direct current at voltage of 3 kV. The paper also considers a design of a current limiter for 200 MVA power systems.