Development of high voltage, self-healing current limiting element and verification of its operating parameters as a CLD for distribution substations

The use of a current-limiting device (CLD) for the operation of transformers connected in parallel at distribution substations is considered as a way to cope with the increase in load capacity and enhance the efficiency of station equipment use. A high voltage, self-healing current-limiting element (CLE) using sodium has been developed as a functional part of the CLD. The CLE has a rating of 3.6 kV and 500 A and can limit a fault current of 20 kA, RMS (50 kA, p) to less than 23 kA, p. Computer simulations for evaluating the feasibility of the CLE have been carried out for a CLD with a CLE installed in the bus-tie section of a 66/6.6 kV distribution substation. It has been shown that parallel connection of transformers becomes feasible without replacing the existing equipment, since the short circuit capacity of any fault point on the secondary side of the transformer can be reduced below the stress capability of the equipment (150 MVA, or 32 kA, p at 6.6 kV)