R&M Data Center Handbook
R&M Data Center Handbook
R&M Data Center Handbook
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
www.datacenter.rdm.com<br />
In buildings in which no continuous meshed structure can be set up for the earthing system, the situation can be<br />
improved by setting up cells. A locally meshed grounding system of this type is achieved by using cable ducts<br />
made of metal, conductive raised floors or parallel copper conductors.<br />
Building Structural Steel<br />
Metallic conduit<br />
TO<br />
Building Structural Steel<br />
Note: power connections shown are logical, not physical.<br />
MET<br />
Grounding Options for Patch Panels<br />
All patch panels should be suitable for both tree as well as meshed grounding systems, so that customer options<br />
remain completely flexible. In addition to the grounding system in use (mesh or tree), selection of the method to be<br />
used is also based on whether or not the 19” cabinet or mounting rail is conductive.<br />
The earthing connection for patch panels may not be daisy chained from one patch panel to another, since this<br />
increases impedance. Every patch panel in the cabinet must be grounded individually as a tree structure to the<br />
cabinet or to ground busbars.<br />
Grounding and Ground Connection in the Cabinet<br />
Once the patch panel has been bonded to the cabinet, the cabinet itself must be bonded to ground. In a tree<br />
configuration it would connect to the telecommunication main ground busbars (TMGB), or telecommunication<br />
ground busbar (TGB).<br />
In a mesh configuration it would be connected to the nearest grounding point of the building structure. It is crucial<br />
in this ground connection that the impedance from the current path to the ground is as low as possible. The<br />
impedance (Z) is dependent on ohmic resistance (R) and line inductance (L):<br />
Ζ = ωL<br />
+ R<br />
ω = 2πf<br />
with<br />
This relationship should be considered when choosing the earthing strap to bond the cabinet to ground. Flat<br />
cables, woven bands or copper sheet metal strips exhibit low impedance characteristics. At a minimum, a stranded<br />
conductor with a diameter of 4-6 mm 2 should be considered (16 mm 2 is better).<br />
With regard to EMC, an HF-shielded housing with improved shielding effectiveness may be required in applications<br />
with high-frequency field-related influences. A definite statement regarding what housing version is required to<br />
satisfy specific standard limits can be made only after measurements have been taken.<br />
Page 68 of 156 © 08/2011 Reichle & De-Massari AG R&M <strong>Data</strong> <strong>Center</strong> <strong>Handbook</strong> V2.0
Change language