Hello safety experts,
A question regarding overvoltage categories and "reliable" earthing and some differences between standards. I would be interested to hear your thoughts. Background: When determining the required withstand voltage for insulation, EN 62368-1 states that: 5.4.2.3.3 Determining required withstand voltage . If a circuit isolated from the mains is connected to a main protective earthing terminal that complies with 5.6.7, the required withstand voltage may be one overvoltage category lower in Table 13 (JP: Table 13 in this case replicates table F.1 from IEC 60664-1 of OVC vs impulse voltage) 5.6.7 Reliable earthing . For permanently connected equipment earthing is considered to be reliable . Summary: A permanently connected piece of equipment with isolated (secondary) circuit connected to PE is classed as being one OVC lower than it's installation eg. OVC III becomes OVC II with all of the reductions in creepage/clearance/insulation that this results in. Problem: * I cannot find an equivalent clause regarding overvoltage categories and reliable earthing in EN 61010-1. * Also, I cannot see anything in EN 62368-2 that explains this decision. * It looks like EN 62368-1 is a bit of an outlier in this respect. Questions: * Have I missed the clause in EN 61010-1 that covers this? (I've looked carefully through Clause 6 and Annex K) * Do any other safety standards share this reduction in OVC for PE connected circuits? * Have I understood the clauses in EN 62368-1 properly? * I've seen (and subsequently unable to find again) a reference that resistance to transient overvoltages is partly a reliability of equipment issue. Are the writers of EN 62368-1 less concerned about reliability? ;-) As always, thanks in advance James James Pawson The EMC Problem Solver Unit 3 Compliance Ltd EMC : Environmental : Safety : CE + UKCA : Consultancy <http://www.unit3compliance.co.uk/> www.unit3compliance.co.uk | +44(0)1274 911747 | +44(0)7811 139957 2 Wellington Business Park, New Lane, Bradford, BD4 8AL Registered in England and Wales # 10574298 -- This email has been checked for viruses by AVG. https://www.avg.com - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
