Bostjan, I would suggest you begin by reviewing this article at the IEC.
http://www.iec.ch/etech/2013/etech_0313/tech-2.htm Thanks, - doug Douglas Powell http://www.linkedin.com/in/dougp01 Original Message From: Boštjan Glavič Sent: Friday, August 8, 2014 8:51 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Reply To: Boštjan Glavič Subject: Re: [PSES] question with regard of inverter Dear Rich, dear Doug Thank you very much for your professional answer. I really appreciate it. It helps me a lot and also to my client. One more question, is there any expert in this group who has real experience with new Hazard Based Standard IEC 62368-1? We are currently working on few projects and i think that some requirements are not really clear. Best regards, Bostjan Boštjan Glavič Vodja laboratorija, Laboratorij za elektroniko Head of Laboratory, Laboratory of Electronic Engineering [SIQlogo60px] www.siq.si<http://www.siq.si/> SIQ Ljubljana, Trzaska c. 2, SI-1000 Ljubljana, Slovenia, VAT ID: SI23509678 t +386 (0)1 4778 265<tel:+386%20(0)1%204778%20265>, m +386 (0)41 391 283<tel:+386%20(0)41%20391%20283>, f +386 (0)1 4778 444<tel:+386%20(0)1%204778%20444> On 6. avg. 2014, at 22:04, "Richard Nute" <ri...@ieee.org<mailto:ri...@ieee.org>> wrote: Dear Boštjan: If the solar cells are hit by lightning, then the DC and inverter system will likely be destroyed, and the transient will propagate into the AC system. There is no way to protect against a direct lightning strike except to use a system of lightning rods, and they may not provide protection against propagation. Except for a direct lightning strike, no transients appear on the DC side, so OVC does not apply. The 120/240 V AC probably is OVC III, and maybe OVC IV. Since there is no isolation between the AC and the DC, both will see the same AC transients. Your DC side should use the same OVC as the AC side. In my opinion, UL has not fully studied IEC 60664 which is the definitive standard for OVC. UL has extended the OVC requirements to DC without researching the origin and value of transients on DC mains and instead has simply applied the AC OVC to DC mains. According to IEC 60664 and other authorities such as Francois Martzloff, transients on AC systems come from two sources, lightning and load switching. Your solar cell DC source is not subject to load switching, but is subject to a direct lightning strike. Your DC OVC due to load switching is zero, and your OVC due to lightning is beyond OVC IV. Some references: http://www.metrel.si/dl?d=PDF_dokumentacija/White_papers/Ang/White_paper_Overvoltages_and_high_current_breakdowns.pdf http://www.denverpels.org/Downloads/Denver_PELS_20090915_Aldous_Insulation_Coordination.pdf Best regards, Rich On 8/6/2014 11:25 AM, Boštjan Glavič wrote: Dear Rich, Thank you. DC input comes from solar cells therefore from outside. UL 1741 states that OVC IV needs to be used and for 120/240V it means 4000V. So what transient should I use from DC side? Why table 8.1 in UL840 also mentions dc input? Best regards, Bostjan Boštjan Glavič Vodja laboratorija, Laboratorij za elektroniko Head of Laboratory, Laboratory of Electronic Engineering - ---------------------------------------------------------------- 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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.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 <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
