Grounding, bonding and safety
The two are not simply a metallic connection between pathways and/or ITS cabinets, but a system where impedance is a major factor.
September 1, 2008
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In light of an upcoming feature on grounding and bonding in the November/December issue of CNS, I would like to share with you some information about what resources BICSI has available to help readers with an interest in vendor-neutral information and training about this important subject.
At BICSI, grounding (earthing) and bonding is one of the topics our subject matter experts (SMEs) take very seriously.
This is a subject many people either oversimplify or, of more concern, ignore altogether. There are many misconceptions which contribute to the lack of interest or concern about this element of proper and safe ITS installations.
One simple example that reinforced what I have learned at BICSI happened about a year ago when reports of crosstalk at a customer location was being investigated by a fellow BICSI RCDD, OSP.
Initially, all fingers pointed to the campus outside plant (OSP) cabling. The problem was isolated in the equipment room (ER) on the voice switch.
The unit was properly connected to building power with the traditional hot, neutral and ground connections. Logic would suggest the equipment would operate safely, which it did.
However, from a performance perspective, a missing telecommunications bonding connection caused service issues resulting in crosstalk.
Imagine the issues this could have on your business if conversations could be heard by others? Grounding (earthing) and bonding is not simply a metallic connection between pathways and/or ITS cabinets, but a system where impedance is a major factor.
BICSI’s newly released 5th edition of the Information Transport Systems Installation Methods Manual (ITSIMM) offers this as background information: Distinct differences exist between the terms grounding (earthing) and bonding.
Generally speaking, grounding (earthing) is the establishment of a reference for the electrical (alternating current (AC) or direct current (DC) power source, the electrical equipment, or both. Bonding, however, is the connection intended to equalize, safely and effectively, the potential differences between two metallic items (e. g., a telecommunications grounding busbar [TGB] and a cable tray).
Lightning strikes, AC and DC faults, electromagnetic interference (EMI) and simple static discharge can cause unbalanced electrical potentials between metallic surfaces which essentially cause the charge to seek a path of least resistance to ground.
Properly designed systems are installed to control the flow of electrons on a desired path as opposed to them finding their own path through equipment, or worse, people.
BICSI SMEs produce reference manuals such as the Telecommunications Distribution Methods Manual (TDMM), Outside Plant Design Reference Manual (OSPDRM), and the new 5th edition of the ITSMM that have chapters dedicated to this important and complex topic.
BICSI’s other four manuals (Wireless Design Reference Manual [WDRM], Network Design Reference Manual [NDRM], Electronic Safety & Security Design Reference Manual [ESSDRM], and AV Design Reference Manual [AVDRM], a joint publication between BICSI and InfoComm International®) address this important topic within key chapters.
The BICSI ITS Dictionary also lists important definitions and symbols related to grounding (earthing) and bonding.
BICSI also offers a three-day course entitled Grounding and Protection Fundamentals for Telecommunications Systems (DD120). DD120 covers 20 topics related to the subject. The BICSI instructor offers pros and cons of various commonly suggested approaches to an effective system.
I have taken the course and I highly recommend it to anyone who works on ITS installations.
Based on my 34 years in the industry, some of which were as a technician, I believed that basic electrical theory was sufficient to understand the flow and control of electrons as far as telecommunications were concerned.
My initial reaction about the length of the course was what could possibly take three days to cover? After the first day I found my overconfidence replaced with uneasy concern about what I had never considered.
By the end of the third day I had heard enough to be afraid of what I had taken for granted. Your safety and your customer’s may depend on what you learn in DD120.