Proper bonding and grounding of communication systems provide reliable operation for voice/data equipment, while enhancing safety for the operator in the event of lightning and AC ground fault conditions. Using ANSI/EIA/TIA-607 grounding topologies, you can achieve these objectives.
Consistently engineering effective grounding systems allows for safe and reliable operation, regardless of the manufacturer and type of telecommunication equipment. ANSI-607 provides the design and installation requirements for various components of the telecommunication system including busbars, conductors, and conductor terminations.
The purpose of ANSI-607 states, in part: The telecommunications grounding and bonding infrastructure supports a multivendor, multiproduct environment, as well as the grounding practices for various systems you may install on customer premises.
Installation example. You can see an example of the ANSI-607 in the Figure (original article). This is a grounding system for a high-rise facility. At lower left, the telecommunication entrance facility (TEF) utilizes a single-point grounding system via the telecommunication main grounding busbar (TMGB). From there, the installer made three bonding connections at various grounding planes to establish a zero-volt reference for the telco infrastructure. First, they ran a conductor between the TMGB and the equipment grounding plane of the AC main service panelboard.
This connection leads to two events:
It establishes the zero-volt reference for the TEF, and
It makes sure the telco equipment is at the same potential as the electrical service during an AC system fault.
The installer makes another bonding connection from the TMGB to the structural steel of the facility. The structural steel will further supplement the grounding plane of the TMGB by providing a lower impedance path to an earth reference. To further equalize the voltage between the AC ground and telco ground, the installer makes a bonding connection to the AC electrical panelboard in the TEF.
ANSI-607 requires that all bonding conductors be minimum No. 6 AWG stranded, insulated conductors. The standard also states that you may need to increase the conductor size to No. 3/0 AWG: presumably in circumstances where the combination of conductor length and high-frequency currents are concerned.
Extending throughout the facility. From the TMGB, a telecommunication bonding backbone (TBB) conductor runs to the telco equipment room (at lower right) and continues to the third floor telecommunication closet (TC). Likewise, a TBB runs to the TC's along the left side of the building. Tap conductors run between the TBB and the telecommunication grounding busbar (TGB). ANSI-607 requires both bonding conductors to be unspliced to its last entrance point. If you splice a conductor, you must splice it with an irreversible high-compression fitting or exothermic weld. The installer should consider specifying a larger conductor (possibly a #3/0 conductor) since the length of the conductor may vary, thus affecting the impedance of the TBB.
If the TBB runs in a metallic conduit between floors or equipment rooms, you should bond it at both ends, if the conduit is longer than 3 ft. Bonding the TBB to conduit longer than 3 ft. reduces the chance that it will be a high inductance during surge conditions.
Within the telco closet, the TGB is required to have a supplementary bonding connection to structural steel and another to the closet's AC electrical panelboard, if applicable. Bonding to the structural steel is critical. With high frequency events, the TBB's impedance may be very high, as its length increases. The bonding connection to the building steel at each floor should keep equipment at the desired zero-volt potential.
Finally, a TBB interconnecting-bonding conductor is required to run between telecommunication closets and equipment rooms on the first floor, top floor, and every third floor in between. This conductor equalizes the potential between grounding planes within the telecommunication closets and equipment room.
The National Electrical Code grounding requirements of telecommunication systems must be supplemented with those of ANSI/EIA/TIA-607 and other industry-related standards. Failure to do so may result in unexplained equipment malfunctions, component damage/degradation, and personnel safety hazards.