Siemens SIMATIC NET PROFIBUS Installation and Grounding of Inactive Metal Parts, Cable Shields

Installing LAN Cables

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:

SUse 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.

SAlways 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.

SSecure the shield of the LAN cable to the connector casing.

SIf 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.

C-8	PROFIBUS Networks SIMATIC NET
	6GK1970-5CA20-0AA1 Release 2 05/2000