This part of IEC 60919 which is a technical report provides guidance on the transient
performance and fault protection requirements of high voltage direct current (HVDC) systems.
It concerns the transient performance related to faults and switching for two-terminal HVDC
systems utilizing 12-pulse converter units comprised of three-phase bridge (double way)
connections but it does not cover multi-terminal HVDC transmission systems. However,
certain aspects of parallel converters and parallel lines, if part of a two-terminal system, are
discussed. The converters are assumed to use thyristor valves as the bridge arms, with
gapless metal oxide arresters for insulation co-ordination and to have power flow capability in
both directions. Diode valves are not considered in this report. 
Only line-commutated converters are covered in this report, which includes capacitor
commutated converter circuit configurations. General requirements for semiconductor line-
commutated converters are given in IEC 60146-1-1, IEC 60146-1-2 and IEC 60146-1-3.
Voltage-sourced converters are not considered. 
The report is comprised of three parts. IEC 60919-2, which covers transient performance, will
be accompanied by companion documents, IEC 60919-1 for steady-state performance and
IEC 60919-3 for dynamic performance. An effort has been made to avoid duplication in the
three parts. Consequently users of this report are urged to consider all three parts when
preparing a specification for purchase of a two-terminal HVDC system. 
Readers are cautioned to be aware of the difference between system performance
specifications and equipment design specifications for individual components of a system.
While equipment specifications and testing requirements are not defined herein, attention is
drawn to those which could affect performance specifications for a system. Note that detailed
seismic performance requirements are excluded from this technical report. In addition,
because of the many possible variations between different HVDC systems, these are not
considered in detail. Consequently this report should not be used directly as a specification
for a specific project, but rather to provide the basis for an appropriate specification tailored to
fit actual system requirements for a particular electric power transmission scheme. This report
does not intend to discriminate the responsibility of users and manufacturers for the work
specified.
Terms and definitions for high-voltage direct current (HVDC) transmission used in this report
are given in IEC 60633.
 Since the equipment items are usually separately specified and purchased, the HVDC transmission line, earth electrode line and earth electrode are included only because of their influence on the HVDC system performance.
For the purpose of this report, an HVDC substation is assumed to consist of one or more converter units installed in a single location together with buildings, reactors, filters, reactive power supply, control, monitoring, protective, measuring and auxiliary equipment. While there is no discussion of a.c. switching substations in this report, a.c. filters and reactive power sources are included, although they may be connected to an a.c. bus separate from the HVDC substation.dition 2.2 2020-04 CONSOLIDATED VERSION colour inside Performance of high-voltage direct current (HVDC) systems with line- commutated converters – Part 2: Faults and switching IEC TR 60919-2:2008-11+AMD1:2015-06+AMD2:2020-04 CSV(en) THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright ？ 2020 IEC, Geneva, Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be