Apparatus for protecting the thyristors of a high-voltage controlled converter from overvoltage

Abstract

An apparatus for protecting the thyristors of a high-voltage controlled converter against overvoltage, said thyristors being connected to form a chain of successively connected thyristor modules, each of which comprises at least one thyristor. The protecting apparatus consists of an additional circuit comprising at least one link formed by two avalanche diodes connected in series opposition, said circuit being connected parallel to the chain of thyristor modules. The additional circuit serves to limit the magnitude of the voltage applied to the thyristor modules. The protecting apparatus further includes a surge arrester controlled by signals from a current sensor whose input is connected in said additional circuit. In accordance with signals from the current sensor, the controlled surge arrester limits the voltage across the additional circuit in case of overvoltage. The apparatus is intended for protecting a chain of thyristor modules of high-voltage controlled converters used, for instance, in rectifier and inverter substations of direct current transmission lines, against overvoltage.

Dependencies are inferred from the claim text.