Communications Grounding

[slushin]

Can anyone help me figure out what the purpose of a telecommunications grounding system is? Since the TMGB is ultimately bonded to the service grounding system, I’m not understanding why communications equipment cannot just be bonded directly to the ground at the service entrance as opposed to the TMGB. Also, it seems to me that all that the telecommunications grounding system is only bonded to is the panelboards which feed the communications equipment … is this correct or does it actually have to bond to the communications equipment itself?

 

[peebee]

The ground conductor run from the equiopment to the main service entrance may be a long high-impedance run -- it might be fine for safety's sake, but you might get enough voltage developed on the long ground & neutral wires to cause problems with the operation of the communications equipment. This may be less of a problem than it used to be as most modern comm equipment no longer uses earth ground as a signal reference. Regardless, it is still common practice (and recommended by EIA/TIA) to provide a low-impedance ground system independant of the power system safety ground system, and to bond the comm ground system to the equipment racks and cable trays in addition to any grounding provided via the equipment plugs.