6 Wiring and Shielding
Ensure maximum spatial separation between signal and power lines. If sufficient
spatial separation is not possible, then shielded lines must be routed in shielded,
earthed, metallic cable ducts.
6.1 Cable running
All lines within the control cabinet must basically be routed as close as possible
along metallic housing parts (e.g. control cabinet walls, assembly plates,
supporting bars, metal bars). Long routing through the free space can lead to
interference couplings (antenna effect).
Requirements for line routing
Signal and power lines may cross at right angles, but they may never run
parallel closely side by side.
Signal/data lines are to be routed spatially separated from power lines and
power supply lines (avoid coupling paths). Minimum distance in the control
cabinet: 20 cm. Use an earthed baffle, if necessary.
Twist unshielded lines of the same circuit (forward and return conductor) if
possible or minimize the distance between the forward and return conductor.
Route signal lines and the appropriate equipotential bonding line as close as
possible to one another.
Signal lines may never be routed through devices which generate strong
magnetic fields (e.g. motors, transformers).
Insert the signal/data lines possibly into the cabinet at only one level (e.g. only
Avoid unnecessary line lengths (also with spare lines).
Signal lines, particularly nominal and actual value lines should be routed
without breaks. Ensure continuous shielding at the dividing points.
Ensure a continuous shield connection at the line dividing points of shielded
Pulse-loaded high-current/high-voltage lines must basically be routed
completely separately from all other lines.
Route the lines on metallic cable bearers.
Interconnect abutting joints of the cable bearers galvanically.
Earth the cable bearer.
Provide lightning protection (internal and external lightning protection) and
earthing measures as far as they are applicable to the application case.
© Siemens AG, 2004. All rights reserved
EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition