Electronic Tap Changer for Very High-Power Medium-Voltage Lines With No Series–Parallel Thyristors

Abstract

Tap changers are commonly used to maintain the limits in medium-voltage lines. Initially based on electromechanical switches, efforts have been made since the 1990’s to reduce maintenance expenses with thyristorbased versions. Among the methods to limit the shortcircuiting current in commutating taps, the multiwinding coil has demonstrated, during decades of use in the lowvoltage field, to be reliable and cheap. Two previous papers showed that multiwinding changers can be applied to medium-voltage lines up to 34.5 kV, 15 MVA with no parallel or series thyristor association. This paper proposes a new topology, based on a double array of tap switches per phase, allowing for step-up the power from 15 to 36 MVA and insertion in any point of the line with no connection to the head transformer. A comparative cost analysis gives technical and economical results for a typical 10 MVA, 34.5 kV stabilizer demonstrating the advantages of the proposed circuit over the electronic single array topology and the classic mechanical solutions.