IEC 60071-5:2014 provides guidance on the procedures for insulation co-ordination of high-voltage direct current (HVDC) converter stations, without prescribing standardized insulation levels. This standard applies only for HVDC applications in high-voltage a.c. power systems and not for industrial conversion equipment. Principles and guidance given are for insulation co-ordination purposes only. The requirements for human safety are not covered by this standard. This International Standard cancels and replaces IEC TS 60071-5 published in 2002. On the basis of technical experience gained since the Technical Specification was published, sufficient consensus has emerged for transformation of the Technical Specification into an International Standard. The technical content is essentially the same as that contained in the Technical Specification with amendments mainly for user convenience. The structure of the document has been changed to allow division and subdivision into complete integral parts to facilitate comprehension and ease of referencing. In addition to the high level revisions above, the following main technical changes have been made with respect to the previous edition:
- arresters have been added to several locations to reflect some recent 800 kV HVDC scheme practice, along with their justifications, expected voltages, overvoltages and arrester stresses in service;
- significant changes have been made in Clause 8 - all subclauses on the characteristics, schemes, stresses and specification of arresters have been consolidated into a single entity, Clause 8;
- the implications of a smoothing reactor and of a neutral blocking filter located on the neutral bus (as on some recent 800 kV schemes), on coordination of arresters connected to the neutral end have been added;
- possible use of sacrificial arresters on the neutral bus is introduced to cater for excessive arrester energy in the rather unlikely event of a particular rare fault;
- all subclauses dealing with study tools and modelling details have been consolidated into Clause 10;
- creepage distances and clearances have been consolidated into Clauses 11 and 12, respectively, with more details added.