After considering all 950 compliance requirements the bottom line is: The TE, at user end, must provide protection for the general public.
NEC still exempts public utitlity facilities. But, if the utitlity has products it sells, leases or are used by general public compliance is required. I'm not a corporate lawyer, but a friend that is says, "In his opinion the present legal climate in N. A. is forcing public utility companies into the direction of 950 self compliance." Duane >From: "Patterson, Gordon" <[email protected]> >Subject: RE: UL 1950 3rd, and IEC 950 > >Jim, > >Network equipment is installed and operated by trained craftspeople who >are well aware of the associated hazards. > >950, ITE, type equipment is installed and operated by common folk who >may or may not have any idea of the possible hazards. > >950 attempts to reduce these hazards by placing barriers between SELV >circuits and sources of shock hazards, > >dielectric withstand between TNV-1 and SELV >basic insulation and dielectric withstand between TNV-3 and SELV. > >Then it follows that if you have TNV-3, TNV-1, and SELV you need basic >insulation between TNV-3 and TNV-1. > >As to your second question, no RBOC will guarantee the safety of the >network connection to your home or anywhere else. That's what started >UL1459. > >Regards, > >Gordon Patterson >Racal-Datacom > -----Original Message----- > From: JIM WIESE [SMTP:[email protected]] > Sent: Wednesday, April 29, 1998 6:02 AM > To: 'emc-pstc'; 'TREG'; 'NEBS FORUM' > Subject: UL 1950 3rd, and IEC 950 > > 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]
