Pete "you-are-the-man" Spud! does not "permanence" also imply a permanent connection, as in a hard ground stud? (no Viagra jokes, please)
ever know a telecom guy named Henry Lederman? I think he's at NORTEL, formerly of Canadian Marconi... D Peter Tarver wrote: > > Ron, you are correct that 6.4.1 makes testing between a TNV-1 or -3 circuit > and an SELV circuit moot, if there is a common earthing connection between > them. With regard to determining the reliability of the earthing of the > TNV-1 or -3 circuit, the method of 2.5.11 would be used, with the test > current set to 2A. UL, CSA and TUV Rheinland NA have endorsed the 2A value. > > Regards, > > Peter L. Tarver, PE > Senior Regulatory Engineer > Homologation Engineering > Nortel, MPK > ESN 655 > V: 408-565-2453 > F: 408-565-2575 > > > -----Original Message----- > > From: [email protected] [SMTP:[email protected]] > > Sent: Thursday, July 09, 1998 4:57 PM > > > > Alan, > > > > You stated that: > > >Paragraph 5 of clause 6.4 of EN60950/A4 which follows items a) b) > > >and c) states the following: > > > > > >'These requirements do not apply where circuit analysis and > > >equipment investigation indicate that safety is provided by > > >other means, for example between two circuits each of which > > >has a permanent connection to earth.' > > > > Your reference to 6.4 above should actually be 6.4.1 which specifically > > refers > > to electrical separation (see also Table 19), not the impulse test of > > 6.4.2.1. > > However, if a TNV-1 or TNV-3 circuit and an SELV circuit are permanently > > connected to earth, then there may be no separation requirements between > > them, > > therefore, no testing should be required, if I'm reading the standard > > correctly. > > > > If an overvoltage fault occurred (such as an impulse of 6.4.2.1 that you > > mentioned) between unearthed TNV-1 or TNV-3 circuits or conductive parts > > and an > > SELV circuit (in this case), that fault current must be reliably routed > > to > > earth (see 2.3.3.3). In particular, the "permanence" of the SELV > > connection to > > earth is described in 2.5.11, particularly the 2nd to last paragraph. See > > also > > 6.3.2. > > > > I hope this answers your questions and that you will be soon out of your > > misery. :-) > > > > Comments anyone? > > > > Best regards, > > Ron Pickard > > [email protected] > > -- DWIGHT HUNNICUTT Sr. Compliance Engineer **************************** * <[email protected]> * * (510) 413-1349 direct * * (510) 492-0808 fax * * VINA Technologies,Inc. * * 42709 Lawrence Place * * Fremont, CA 94538 * ****************************
