Hello Chris In an ideal world. The Ethernet cables would all be enclosed in metal conduit or cable trays. Routed only with similar communications and signal level circuits. The Cabinets would all have provisions to either ground or capacitively couple any cable shields. And the final connections would all be made via patch cables, which in the LV Comm Cabinate wouldn't require shielding. Nor would the 90meter cables in conduit.
But how will your customer actually expect to use it? Cable nicely coiled and Tie-Wrapped almost a meter away from the Medium Voltage Disconnect? Cable run bundled with the 480VAC and/or Spot Welder cables? Will there be any transient protection on the Contactors/starters? What is the expected operation of the system during spurious events such as lightning storms? Can your Ethernet ports handle Surge for Unshielded Cables? I believe the ODVA had concidered a Ethernet/IP Standard where a Single Point grounding system was created by Grounding the Switch and leaving the Nodes to Capacatively Couple the Shield. Although when implementing RSTP this defeats the principal. FWIW my own philosophy is to treat small machines (10meters?) as a Mesh and ground everything, everywhere to create a single ground node. And when it becomes a transmission line to break the ground loops, preferably by Fibre. Regards, John ______________________________________ ______________________________________________ John Merrill | Schneider Electric | Process & Machine Business | Principal Product Safety Engineer Phone: 978-975-9710 ext. 9710 | Email: john.merr...@us.schneider-electric.com | Site: www.schneider-electric.com | Address: M.S. 7-1B, 1 High Street, North Andover, MA 01845 USA *** Please consider the environment before printing this e-mail "Chris Wells" <radioactive55man@c To: <EMC-PSTC@LISTSERV.IEEE.ORG> omcast.net> cc: <christopherdwe...@eaton.com> Sent by: Subject: Shield bonding on STP Cat5 Ethernet cables emc-p...@ieee.org 11/24/2010 02:22 PM I am looking for some feedback on the proper/practical treatment of Ethernet STP Cat5 cable shields. The interfaces are running 100 Base Tx. The STP cables typically are DC grounded at each end to the RJ45 jack and then often metal shield fingers contact a metal housing that is grounded. From a High Frequency point of view this works well but what about differences in local grounds at each end? Is Ethernet affected by shield noise due to ground loops? I put Ethernet into Commercial and Industrial power distribution applications for monitoring purposes. At a site we typically have islands of localized well bonded distribution gear that is actually bolted together with ground bus bars. There may be several of these in one location but then some separation between building wings. What we have been recommending is that one can use STP within a local assembly gear line ups but when leaving use Fiber Optic instead. This has worked well but there is always an economic pressure to cut out the FO up link. We also use multipoint RS485 serial communication links in our power gear that can go thousands of feet between separate gear line ups. In this application we reference shield at each tap AC to ground through a surge rated cap or 4.7 to perhaps 10 nF to ground. Also the RS485 nodes are electrically isolated. This approach blocks power ground loops but helps us deal with Electrical Fast transient or RF conducted EMI type exposures. It appears to be most meaningful from around 100KHz up to perhaps 10MHz. Does this AC shield approach translate into Ethernet? How do others deal with the treatment of shields for Cat5 Ethernet in noisy wide spread applications like this? Are there IEEE Standards on Cat5 STP shield treatment that I should be looking at? Thanks Chris Wells Eaton Corp. - ---------------------------------------------------------------- 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://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. 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