This part of IEC 62672 applies to all line-commutated high-voltage direct current (HVDC) transmission systems used for power exchange in utility systems. HVDC stations with voltage sourced converters (VSC) are not covered.

In order to assess the operational performance of HVDC transmission systems, reliability and availability need to be evaluated. For this purpose the HVDC users/owners are encouraged to compile reports on an annual basis based on the recommendations given in this Technical Specification. The purpose of this part of IEC 62672 is to define a standardized reporting protocol so that data collected from different HVDC transmission systems can be compared on an equitable basis. It is recommended that such reports are sent to Cigré SC B4, “HVDC and Power Electronics” (http://b4.cigre.org) who collects such data and publishes a survey of HVDC systems throughout the world on a bi-annual basis.

This part of IEC 62672 covers point-to-point transmission systems, back-to-back interconnections and multi-terminal transmission systems. For point-to-point systems and back-to-back interconnections, i.e. two-terminal systems, statistics are to be reported based on the total transmission capability from the sending end to the receiving end measured at a given point. If, however, the two terminals are operated by different users/owners, or are composed of equipment of different vintage or of equipment from different suppliers, statistics can be reported on an individual station basis if so desired by those responsible for reporting. In such a case, the outage should only be reported under the originating converter station taking care not to report the same event twice. For distributed multi-terminal systems, i.e. systems with more than two terminals, statistics are to be reported separately for each converter station based on its own individual capability.

Multi-terminal systems, incorporating parallel converters but having only two converter stations on the d.c. line, can be considered as either point-to-point systems or as multi-terminal systems for purpose of reporting. Therefore, statistics for this special type of multi-terminal system can be reported based on either total transmission capability or on individual station capability. If the converters at one station use different technology, converter station statistics can be reported separately for each different type of capacity if desired. Multiple bipoles are also to be reported individually. Special mention should be given in the text and in the tabulations to any common events resulting in bipolar outages.