This document applies to all high-voltage direct current (HVDC) converter stations with line-commutated converters (LCC) as well with voltage-sourced converters (VSC) used for power exchange (power transmission or back-to-back installation) in utility systems. For line-commutated converters (LCC) this document presumes the use of 12-pulse thyristor converters, but can with due care, also be used for 6-pulse thyristor converters. Where VSC is referred to in this document, it is assumed to be of the MMC-type or similar, with very low harmonic generation. Other types of VSC HVDC should be treated as appropriate. In some applications, synchronous compensators, static var compensators (SVC), or static synchronous compensator (STATCOM) may be connected to the AC bus of the HVDC converter station. The loss determination procedures for such equipment are not included in this document. This document presents a set of standard procedures for determining the total losses of an HVDC converter station, except for VSC valves which are covered by IEC 62751. The procedures cover all parts, except as noted above, and address no-load operation and operating losses together with their methods of calculation which use, wherever possible, measured parameters. Converter station designs employing novel components or circuit configurations compared to the typical design assumed in this document, or designs equipped with unusual auxiliary circuits that could affect the losses, are assessed on their own merits.