IEC 60700-2-2021 THYRISTOR VALVES FOR HIGH VOLTAGE DIRECT CURRENT (HVDC) POWER TRANSMISSION – Part 2: Terminology. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60027(all parts), Letter symbols to be used in electrical technology IEC 60633, Terminology for high-voltage direct current (HVDC) transmission 3 Symbols and abbreviations 3.1 General The lists in 3.2 and 3.3 cover only the most frequently used symbols. The lists of symbols of the IEC 60027 series and IEC 60633 apply. 3.2 List of letter symbols α(trigger/firing) delay angle β(trigger/firing) advance angle µcommutation overlap angle γextinction angle 3.3 List of abbreviations The following abbreviations are always in capital letters and without dots: ETT electrically triggered thyristor LTT light triggered thyristor TCU thyristor control unit HVDC high-voltage direct current VBE valve base electronics MVU multiple valve (unit) BOD breakover diode 4 General terms related to converter circuits 4.1 converter arm part of a bridge connecting two points of different potentials within a bridge, for example between an AC terminal and a DC terminal Note 1 to entry: The main function of a converter arm is conversion. 4.2 converter bridge equipment used to implement the bridge converter connection, if used SEE: Figure 1 Note 1 to entry: The term “bridge” may be used to describe either the circuit connection or the equipment implementing that circuit. [SOURCE: IEC 60633: 201 5, 6.2, modified – The expression “and the by-pass arm” has been deleted from the definition.] 4.3 converter unit indivisible operative unit comprising all equipment between the point of common coupling on the AC side and the point of common coupling on the DC side, essentially one or more converter bridges, together with one or more converter transformers, converter unit control equipment, essential protective and switching devices and auxiliaries, if any, used for conversion SEE: Figure 1 Note 1 to entry: If a converter unit comprises two converter bridges with a phase displacement of 30 degrees, then the converter unit forms a 1 2-pulse unit. 5 Converter performance 5.1 forward direction conducting direction direction of current through a valve, when current flows from the anode terminal to the cathode terminal 5.2 reverse direction non-conducting direction direction of current through a valve,...
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