Shielding; Introduction; Filtration - Siemens SIROTEC Planning Manual

6.2 Shielding

6.2.1

Introduction

Shielding of areas
Shielding is understood to mean the measures which decouple two areas in
respect of radiation-related sizes. With these measures, the shield effect of the
control cabinets, the metallic cable ducts, the plug housings and the line/shielding
braid should be considered. The shielding is also used, together with filtration, for
the interference-free operation of the system.
What is also required?
The prerequisite for an optimal shielding is a good conductive connection of the
shield ends to the cabinet earth or shield bus.
How does the most simple measurement look?
The fundamental recommendation is the use of product-specific original lines as
standard, since the adherence of the EMC law and the EMC Guideline has been
proven with it. Only the respectively indicated plug types are permitted.
Basically, the standard lines and the lines in combination with the product
components possess the necessary shield connection. The connection from shield
to housing is executed on both line ends via the plug, with few exceptions. The
double-sided shield connection to the earth offers the best shield effect. Special
additional measures can be obtained from Chapter 10 of the product-specific
documentation.
When is simple shielding sufficient?
In most industrial plants, simple-shielded lines are sufficient for the reliability of the
plant. The double-sided connection of the shield to the earth is thereby the most
effective shielding measure.
When is double shielding necessary?
Double shielding is advantageous for signal transmission in a particularly
interference-prone environment.
Shield bus
The earth bar or if additionally available the equipotential bonding bus, may be
used as shield bus. The earth bar is available for protective earthing and the
equipotential bonding bus for functional earthing. It is also possible to provide only
one earthing bar, which simultaneously serves as the equipotential bonding bus.
© Siemens AG, 2004. All rights reserved
EMC Installation Guideline – Planning Guide (EMV) – 03.2004 Edition
Wiring and Shielding
6-37