Siemens SIMATIC NET PROFIBUS, Руководство пользователя

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Installing LAN Cables
C-8
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
C.4.2 Installation and Grounding of Inactive Metal Parts
Grounding
Connect all inactive metal parts in the immediate vicinity of your automation
components and LAN cables to ground (PE system). This includes all metal parts
of cabinets, machine parts etc. that have no electrical function in the automation
system. Connecting these parts to a uniform system chassis produces a uniform
reference potential for your system and reduces the effects of coupled-in
interference. For detailed information about grounding techniques, refer to the
system manuals of the SIMATIC S7–300 /11/ and S7–400 /12/ programmable
controllers.
C.4.3 Using the Shields of Electrical LAN Cables
Definition
Shielding is a technique used to counteract the effects of magnetic, electrical or
electromagnetic interference fields.
Interference currents on cable shields must be discharged to ground by short,
conductive, large-area connections. To prevent these interference currents
reaching a device or wiring closet, this discharge must take place immediately
before or at the point at which the cable enters the device casing/wiring closet.
Cable Shields
Note the following points about cable shields:
S
Use SIMATIC NET PROFIBUS cables throughout your system. The shields of
these cables have an adequate shield density to meet the legal requirements
regarding noise emission and immunity.
S
Always contact the shields of LAN cables at both ends. The legal requirements
for noise emission and noise immunity in your system (CE marking) can only be
achieved when the shields make contact at both ends.
S
Secure the shield of the LAN cable to the connector casing.
S
If cables are installed permanently, it is advisable to remove the insulation of the
shielded cable and to establish contact on the shield/PE conductor bar.