BICSI Forum.

Status
Not open for further replies.
dereckbc

dereckbc

Moderator
Staff member
Location
Plano, TX
I was surfing over on the BICSI forum today to see about a post I was watching and seen a very funny comment I thought I would share. It has to do with what is called a Coupled Bonding Conductor (CBC) someone had asked about. The last response I found quite interesting and very uninformed. Seems to be the conception that by running a single grounding conductor with signal cables you can get rid of transient noises and power frequency grounding has not much to do with telecom grounding.

All of which was news to me. Read and laugh along with me. I would reply back, but it wouldn't do any good over there. Seems PE's in the telcom sector don't get much respect over there or anyone associated with electrical.


Bicsi Telecom Dictionary Posted on: 12/22/2005 10:06:00 AM by edited out address.

Coupled Bonding Conductor (CBC)
A bonding conductor placed (e.g. Strapped) on the outside surface of telcommunications cable; used to reduce transient noise.
Make sure that responses apply to our industry not the power industry.And yes they are very effective if properly installed with good bonding pratices.

CBC Posted on: 12/22/2005 8:49:00 AM by

In response to the post below, we had a problem in a hospital where the cables were laid in bonded metal cable basket, then were extended to a plastic back box through plastic conduit, which was then fitted with a metal face plate. We were required to extend the bond from the cable tray to the metal face plate in order to comply with the electrical regulations.
If any form of metal containment is used, and there is a break in the continuity of the containment, then there must be a bonding conductor which joins the two pieces of metal containment together to maintain the CBN ( Common Bonding Network ).

CBC Posted on: 12/21/2005 9:48:00 PM by
Yours truly DERECKBC

A CBC (Coupled Bonding Conductor) is a secondary conductor bonded to the DC power plant frame in a isolated ground plane configuration to supplement the plant frame ground in the event of a battery fault. Most generally used when the DC plant is used on a lower floor while serving equipment on above floors. Other than that it has no other purpose and I doubt applies to what you are doing.

Dereck Campbell, PE

Coupled Bonding Conductor Posted on: 12/21/2005 3:48:00 PM by

Has anyone ever run a CBC along with there 4-pair station cables? Page 17-27 of the TDMM 9th edition explains what a CBC is. Is this the correct application?

[ December 22, 2005, 11:15 PM: Message edited by: dereckbc ]
 
Re: BICSI Forum.

Its more sad than funny. Maybe telecoom electrons are different than electrical electrons.
It could be that sneaky ground loop.
 
Re: BICSI Forum.

I should add start reading from the bottom up.

Tom you are right it is more sad than funny. I would really like to go back and ask how running a single ground cable could possible attenuate transient or impulse noise on signal cables.

I doubt they would understand that the impedance of a single ground cable of any appreciable length is more or less a open ciruit to impulses and high frequencies and more likely to amplify the problem they are trying to solve.

[ December 22, 2005, 11:25 PM: Message edited by: dereckbc ]
 
Re: BICSI Forum.

Well, the BICSI Telecom Dictionary says so so it MUST be true!

I have not heard of this either. Wonder if there is a "white paper" on it.

-Hal
 
Re: BICSI Forum.

Originally posted by hbiss:
I have not heard of this either. Wonder if there is a "white paper" on it.
Click to expand...
No, there is no foundation for it. I have written the grounding standards for MCI, WorldCom, Alltel, and contributing author of IEEE Emerald book, Bellcore TRW-000-295, and ANSI T1.333-2001. Is all those publications where a CBC is defined as supplementary conductor to the DC power plant to aid in a frame ground fault. Most often used where an isolated ground plane DC plant is located on lower floors serving equipment on the higher floors.

A SRG (signal reference grid) has the ability to reduce transient noise on signal cables providing the cables a laid on top of it and the grid spacing is close enough to attenuate the frequencies of interest like on 2-foot centers or less. A single free-air ground conductor impedance is for all practical purposes an open circuit to impulse or transient noise. There is no mechanism for any magnetic cancellation to take place since any induced signal would be in phase with both signal and ground cables. For cancellation to occur the signals must be out of phase, like 180 degrees for maximum effect.

It is pure rubbish to think a single ground cable can reduce noise on adjacent cables. I just cannot believe BICSI would recommend such a practice. OK enough ranting for now.
 
Re: BICSI Forum.

I have always felt that BICSI was more of a cult than anything else. I think that last remark about "responses must apply to our industry" pretty much confirms it. Apparently a CBC must be accepted as their "bible" says and nobody can explain it or is allowed to dispute it.

-Hal
 
Re: BICSI Forum.

Hal and others, I am not really trying to kick BICSI around. I have read a lot of their publications, and most are sound documents, although most are taken straight from Belcore, ANSI/IEEE, or ATIS.

I have also worked with a few of their certified installers on occasion. Telco's have their own standards/certifications, and when ours does not reflect what they have been taught, I have noticed some strongly object and I have to remind them I am the customer and it is my way or the highway :)

[ December 28, 2005, 11:34 PM: Message edited by: dereckbc ]
 
Re: BICSI Forum.

Dereck
There are many publications out there that have many errors in them. Look at NFPA 780 There are several inconsistency's in it that have been pointed out by scientist, as well with the NEC (some of the grounding electrode requirements) that have no scientific or factual background. We both know that a GEC over 25' in most cases is worthless at HF for lightning protection, but we will still run them 100' to hit the water main, or other electrode.
My thought on this is:
A code or law should have the backup of fact! before it can be published as a code.
I know I'm dreaming :D
 
Re: BICSI Forum.

Wayne, I know and you are correct. I would not have said a word if it had not been for two incidents.

1. The person who made the comment " Make sure that responses apply to our industry not the power industry. And yes they are very effective if properly installed with good bonding practices " Has a BICSI RCDD certification which is the highest level of certification BICSI offers.

2 The same person emailed me and asked me not to post erroneous incorrect information and to do more background research before making any more post. :mad:

[ December 29, 2005, 11:01 AM: Message edited by: dereckbc ]
 
Re: BICSI Forum.

Usually way to busy to place a post....BUT this one needs help! The CBC (as described by BICSI) is recognized and supported in IEEE Std. 1100 (Emerald Book EB). The new EB update soon to be published has more info. The CBC was ORIGINALLY developed to enhance noise mitigation capability on small OSP cables incoming to PBX (commercial customer telephone systems). By adding this conductor, the size of the small metal shield around the OSP cable was effectively increased so as to conduct higher amouints of current due to impinging fields in the OSP environment. With a higher current on the shield, the interaction with similar currents on the pairs inside the cable served to cancel a larger portion of the total noise influence and thus reduce the noise influence on the cable pair circuit. Ergo - quieter (less noisy) cable pair circuits to the PBX. THEN, AT&T Bell Labs came along and noted that local impinging (has to be changing) fields within the PBX environment (the building) were also reduced in a similar fashion. Accordingly, they arranged for this info to go into the BICSI TDMM (I think edition 4). IN A NUTSHELL, the CBC is primarily useful where small cables serve the PBX. It serves to allow for more current to occur on the shielded circuit for noise control purposes. Typically, on the tel voice circuit we are looking for low 20's dbrnc circuit differential noise and over 60 db separation from longitudinal noise values. This is why the typical telephone circuit pair is closely twisted and held to close tolerances on length and capacitance - to maintain balance and arrive at low 20's dbrnc noise values - so we can talk and be heard in comfort.

Also note that the EB refers to the use of a CBC at a DC power plant (as descibed in these posts) as a dc equipment grounding conductor (DCEG)(from the ground reference source to the power plant framework).

William Bush
Chair: Chapter 9: Telecom, ITE and Internet
IEEE Std. 1100 Powering and grounding electronic equipment

Extensive experience including international stds development on grounding, bonding, protection, EMC, PQ, etc. Corporate standards, etc. at SPGS, TRS, Nortel, Verizon, etc.
 
Status
Not open for further replies.
Top