Siemens SIMATIC NET PROFIBUS manual Routing Electrical LAN Cables, Cable Categories and Clearances

Installing LAN Cables

C.5 Routing Electrical LAN Cables

Voltages and Currents

Wiring and cables in a system conduct voltages and currents. Depending on the application, the amplitudes can be of an order much higher than the signal voltage on the cable. Switching supply voltages can, for example, produce sharply rising surge voltage peaks in the kV range. If other cables are laid parallel to the LAN cable, data exchange on the LAN cables can be disturbed by crosstalk. To achieve problem-free operation of the bus system, certain rules must be adhered to when installing cables. One extremely effective method of suppressing interference is to keep as large a distance as possible between the cable causing the interference (the culprit) and the cable affected by the interference (the victim).

Fiber-Optic Cables

Fiber-optic cables are not affected by electrical interference and, while mechanical protection is necessary, the EMC rules do not apply.

Telecom Cables

Cables for Telecom have special rules generally specified for a particular country (in Germany, Telecom cables must not be laid along with other cables).

C.5.1 Cable Categories and Clearances

Cable Groups

It is useful to group wires and cables into various categories according to the signals they carry, possible interference signals, and their sensitivity to interference. Minimum clearances can be specified for these categories so that interference-free operation can be expected under normal operating conditions if the clearance is adhered to.

PROFIBUS Networks SIMATIC NET	C-13
6GK1970-5CA20-0AA1 Release 2 05/2000