Joe, The reason we (GR-1089 TTF) added the caveat regarding secondary protection to ground had to do with the possibility of longitudinal to metallic conversions as a result of asymmetric firing that would be synonymous with the firing of a primary protector. Protectors on the chip side of an isolation transformer will not do this conversion, thus performing a metallic surge on an Ethernet port would result in current flow paths that would not exist in the real world.
In the real world if a transient is induced into the cable, the voltage would be the same on all conductors and there would be no current flow through the windings of the Ethernet isolation transformer regardless of what paths to ground exist on the chip side. So basically the exemption was a practical way to eliminate a test that added no value. It also reduces cost to the industry by eliminating the need for an expensive and un-necessary component to protect an 10/100 baseT Ethernet port. There were also concerns with GigE interfaces and the ability to protect them >from metallic surges with commercially available devices and still meet performance criteria. So we felt the exemption was a positive and reasonable way of addressing the issue. As far as 4.6.9.1.1, I received the exact same question from a test lab yesterday. Here is essentially the same text I sent the lab. Dear XYZ LAB, The two conditions you mention below only apply to Ethernet interfaces with regard to metallic surges. Longitudinal surges on Ethernet ports always apply, unless exempted by one of the 3 bullets at the beginning of 4.6.9. As far as protection to ground, components on the IC side of the transformer that connect to ground do not cause the metallic exemption to be lost as the transformer provides isolation from a longitudinal to metallic conversion. If the TVS components that are grounded are on the surged side of the transformer, the metallic surges are not exempt. 4.6.9.1.1 applies to all products with any kind of secondary voltage protection. However, as with the rest of section 4, the intent of secondary protection relates to those components on the exposed side of an isolation transformer, not the chip side. For example interfaces with 65, 140, 200 or 270V sidactors/thyristors or Semtech LC-03 devices that are grounded that are on the surged side of the transformer need to be tested per 4.6.9.1.1. Generally protection on the IC side is about 5V and even with ADSLx is usually less than 20V and they are clamping devices. As a result there isn't really much if any value in trying to remove these and doing a surge on the exposed side at 5-20V, the energy is simply too low and is a waste of time. The IC's get as much or more energy from the full surge. Hopefully this answers your question. Jim Jim Wiese NEBS Project Manager/Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com From: Finlayson Joe-G3162C [mailto:joefinlay...@motorola.com] Sent: Thursday, November 30, 2006 2:16 PM To: JIM WIESE; Gelfand, David; emc-p...@ieee.org Subject: RE: GR-1089 Issue 4 and Surge on Ethernet Jim, I am not sure I understand your explanation of the location of the surge protection device with respect to the primary or secondary side of the transformer. The way I look at this requirement, the key is to *not* provide a path, direct or through a protection device, back to Ground (C.O. Ground, Shelf Ground, Frame Ground, Earth Ground, etc.). If there is surge protection on either side of the transformer and it is either not referenced to Ground at all or referenced to Logic Ground only, the exemption can be taken. While referencing Logic Ground on the line (surge) side of the transformer or Shelf Ground on the PHY side of the transformer makes no practical sense, it can still be done. Therefore, physical location of the surge protection device may not necessarily dictate the ability to take this exemption. Would you agree with that? Also, can you please clarify on the intent of Section 4.6.9.1.1? Referencing Section 4.6.9.1.1, Equipment Ports With Secondary Protection, was the intent to label this section, "Equipment Ports With Secondary Protection Not Referenced to Ground" and only apply that to the longitudinal surges if the following conditions are met? 1.) The port does not have any secondary voltage-limiting protection to ground 2.) The unused pins of the port are not grounded solidly. ...or does this section apply to the metallic surges as well? Thx, Joe ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Joe Finlayson Tel: (508) 357-8273 Fax: (508) 357-8289 Email: joefinlay...@motorola.com Motorola, Inc. Embedded Communications Computing 46 Lizotte Drive Marlborough, MA 01752 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ From: JIM WIESE [mailto:jim.wi...@adtran.com] Sent: Wednesday, November 29, 2006 3:16 PM To: Finlayson Joe-G3162C; Gelfand, David; emc-p...@ieee.org Subject: RE: GR-1089 Issue 4 and Surge on Ethernet David is correct, it is secondary protection. However, it does not cause you to loose the exemption from the metallic test in your case. To loose the exemption, the secondary protection component to ground would have to be on the opposite side of the transformer than the IC (surged side). That is the only way the longitudinal surge could be converted into a metallic surge. In your case, the isolation transformer prevents the conversion from a longitudinal to metallic surge, and you maintain the test exemption. Also as a clarification, C.O. ground is only partially correct. It depends upon where the equipment is deployed. Many locations such as EEC's (OSP cabinets), OSP equipment, and customer premises do not have C.O. grounds. GR-1089 covers the entire network. What is really meant by "ground" is "earth ground". In a C.O. this is the same as frame ground, or C.O. ground. In the OSP or the customer premises, it is the protective earthing connection on the equipment which is supposed to be connected to earth ground. One thing to remember is that virtually all network equipment has the return side of the battery voltage connected to ground, and thus secondary protection components tied to -48VR for instance are considered grounded. Jim Jim Wiese NEBS Project Manager/Senior Compliance Engineer ADTRAN, Inc. 901 Explorer Blvd. Huntsville, AL 35806 256-963-8431 256-714-5882 (cell) 256-963-6218 (fax) jim.wi...@adtran.com From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Finlayson Joe-G3162C Sent: Wednesday, November 29, 2006 12:00 PM To: Gelfand, David; emc-p...@ieee.org Subject: RE: GR-1089 Issue 4 and Surge on Ethernet David, As that represents a path to Ground, then I would say that the answer is *Yes*. Keep in mind that the term "Ground" means "C.O. Ground" when referencing this topic. Thx, Joe ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Joe Finlayson Tel: (508) 357-8273 Fax: (508) 357-8289 Email: joefinlay...@motorola.com Motorola, Inc. Embedded Communications Computing 46 Lizotte Drive Marlborough, MA 01752 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Gelfand, David Sent: Wednesday, November 29, 2006 12:38 PM To: emc-p...@ieee.org Subject: RE: GR-1089 Issue 4 and Surge on Ethernet Is a diode to ground on lines between the IC and the transformer considered secondary protection? Thanks, David David Gelfand Conformity Specialist / Specialiste de conformité 616 Curé-Boivin Boisbriand, Qc, Canada J7G 2A7 tel: (450)437-4661x2449 Fax: (450)437-8053 david.gelf...@ca.kontron.com From: emc-p...@ieee.org [mailto:emc-p...@ieee.org]On Behalf Of Nagel Michael-amn029 Sent: Wednesday, November 29, 2006 3:55 AM To: emc-p...@ieee.org Subject: GR-1089 Issue 4 and Surge on Ethernet Dear All, The Issue 4 of GR-1089 contains now (from my understanding) an exemption for Ethernet from the surge test 1 in Table 4-5 or 4-6 (metallic surge). Am I right with this interpretation? Is there any more information available on the history of the metallic surge test than the bit I contained in the Nebs Digest July 2006? Thanks for your comments. Best regards, Michael - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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