Converter Substation

an electric substation for the conversion of electric current—primarily with respect to frequency or the number of phases. It can be used to convert a three-phase current of a commercial frequency generated by an electric power plant into a direct current to feed, for example, high-power electrolytic equipment, variable-speed electric drives for machine tools and rolling mills, galvanic baths, and contact systems of electrified transport. Conversion to an alternating current of a frequency that is higher or lower than the commercial frequency is used for supplying power to such devices as variable-speed AC electric drives, induction heating equipment, and induction furnaces. Conversion to a single-phase alternating current is done to supply power to, for example, high-capacity arc furnaces and single-phase contact systems. In DC power transmission lines, converter substations are used to convert a three-phase current to a direct current (rectification) at the sending end of the line and to achieve a reverse conversion (inversion) at the receiving end of the line. In addition, inversion is used when a DC source, such as a magnetohydrodynamic generator or a storage battery, must be connected to an AC distribution system.

Both rotating and static converters are used in converter substations, but the rotating equipment—such as motor-generator units or single-armature converters—is being generally replaced by the more economical and more reliable static rectifier-type converters. A high-capacity converter substation includes AC distribution equipment, a machine room with converting equipment, distribution equipment for direct (rectified) current, cooling and ventilating systems, and auxiliary equipment.