Eaton XN-GWBR Series User Manual

8 Guidelines for electrical installation8.4 Shielding of cables190 XI/ON: XNE-GWBR-2ETH-IP 09/2011 MN05002007Z-EN www.eaton.com8.4 Shielding of cablesShielding is used to prevent interference from voltages and the radiation of interference fieldsby cables. Therefore, use only shielded cables with shielding braids made from goodconducting materials (copper or aluminum) with a minimum degree of coverage of 80 %.The cable shield should always be connected to both sides of the respective reference poten-tial (if no exception is made, for example, such as high-resistant, symmetrical, analog signalcables). Only then can the cable shield attain the best results possible against electrical andmagnetic fields.A one-sided shield connection merely achieves an isolation against electrical fields.The insulation of the shielded data-cable should be stripped and connected to the shield railwhen the system is not in operation. The connection and securing of the shield should bemade using metal shield clamps. The shield clamps must enclose the shielding braid and inso doing create a large surface contact area. The shield rail must have a low impedance (forexample, fixing points of 10 to 20 cm apart) and be connected to a reference potential area.The cable shield should not be severed, but routed further within the system (for example, tothe switchgear cabinet), right up to the interface connection.WarningWhen installing, please pay attention to the following...- the shield should be connected immediately when entering the system,- the shield connection to the shield rail should be of low impedance,- the stripped cable-ends are to be kept as short as possible,- the cable shield is not to be used as a bonding conductor.NoteShould it not be possible to ground the shield on both sides due to switching ar-rangements or device specific reasons, then it is possible to route the second cableshield side to the local reference potential via a capacitor (short connection distanc-es). If necessary, a varistor or resistor can be connected parallel to the capacitor, toprevent disruptive discharges when interference pulses occur.A further possibility is a double-shielded cable (galvanically separated), whereby theinnermost shield is connected on one side and the outermost shield is connected onboth sides.