Right!
But can the UL1950 (or its IEC derivatives) standards take into
account NEBS requirements unless they formally reference those
standards, which they have not done?
Thus, Jim's premise still has validity. So, is the TNV1/TNV3
separation requirement nothing more than "cover my...."
on the part of the IEC/EN/UL...950 standards? I don't know.
But I still consider Jim's question a very good one that needs
an answer.
Tania Grant, Lucent Technologies, Octel Messaging Division
[email protected]
______________________________ Reply Separator
_________________________________
Subject: Re: UL 1950 3rd, and IEC 950
Author: "Jan Purwin" [SMTP:[email protected]] at CORP
List-Post: [email protected]
Date: 4/29/98 8:13 AM
Jim you are not quite right.
There is a lot of protection and separation that are defined in NEBs
and
NEDS standards.
Those are incorporated into the equipment that is installed in a central
office.
If you have a chance to go to typical central office and look how RBOC
installes equipment you would
had better idea about protection separation and equipment construction
that
goes into CO equipment.
Jan Purwin
JIM WIESE wrote:
> I am looking for some guidance in understanding the separation
> (creepage/clearance) requirements with regard to TNV circuits in UL
1950
> 3rd and IEC 950 and its derivatives.
>
> Why is there a requirement that TNV circuits have basic insulation
> between TNV1 and TNV3 circuits?
>
> I am asking the question for the following reasons:
>
> The telco network provider is generally exempt from listing
requirements
> altogether. They have no restrictions on separation of circuits and
> have TNV 1, TNV 3 and span powered circuits (200 VDC HDSL, T1 etc.)
> intermingled at the central office in channel banks, cross connects
etc.
> They provide these services via cables that are spliced, cross
> connected and intermingled in the Outside Plant. They are also
> intermingled without regard to spacings at the distribution and
> demarcation points. Since it is a fact that these services are not
> separated by "basic" insulation, why would it be important to separate
> TNV1 and TNV 3 in the terminating equipment. To me it seems like a
> chain made of paper, and at the end of the chain the standards are
> requiring a steel link.
>
> Secondly, do the standards assume that faults of TNV 1, TNV 3, and
other
> high voltage telco services could be faulted by the telco provider
> inadvertently and therefore this type of fault is accounted for by the
> dielectric test (and other restrictions) between SELV/chassis and TNV
1,
> and TNV 3.
>
> Any input would be appreciated and helpful.
>
> Thanks,
>
> Jim
>
> Jim Wiese
> ADTRAN, INC.
> 901 Explorer Blvd.
> P.O. Box 140000
> Huntsville, AL 35814-4000
> 256-963-8431
> 256-963-8250 fax
> [email protected]
