Re: TNV-2 to Earth requirement

[Andre Boons]

Ed,

The requirement of 6.3.3 (ref 950/A4) is meant to prevent mains voltages on 
a telecom line in case there is a single fault in class I equipment between 
basic insulation and PE - and this PE terminal is not connected properly or 
plugged into a socket outlet without PE).

From your additional information, my opinion is a follows:

1. CO batteries are always connected to PE at the pos. pole (BATRET)
Thus, your TNV-2 circuit is reliably earthed at the CO and it is of no 
importance whether the metal chassis is connected to earth or not (in 
service access area).

2. The TNV-2 circuit is not connected to a telecom network, but provides 
power for a telecom equipment. SC 6.3.3 talks only about requirements for 
circuitry connected to a "telecom network".

3. If your way of reading the standard is correct, all CO equipment would 
need SI between battery, battery related, SELV circuits and earth.
I assume this is not the case anywhere.

Hope this might help.

Andre

Hi everyone and thanks for all of the info thus far.

Here is some more info on the filter: The input to the filter derives it's 
power from batteries at a C.O. The output is meant to power telecom 
equipment. The input and output are considered TNV-2. Now even though the 
filter input is considered a secondary circuit, has anyone also considered 
that there will be a battery charger in that circuit charging the batteries? 
The battery charger  is mains connected and is required to have reinforced 
insulation from the mains input to the output. Therefore I believe if 
everyone agrees the DC filter does require supplemental insulation to earth, 
the battery charger should also meet this requirement.

I have read clause 6 over and over, and in my opinion supplemental 
insulation is required (for Norway and Sweden) from this TNV-2 circuit to 
earth regardless of the filter being connected to the mains or not. It's 
just funny how these clauses are worded because they mainly seem to refer to 
mains connected products (permanently connected, pluggable type B, etc.).

Ed





From: "Ron Pickard" To: davehe...@mediaone.net CC: bosesaf...@hotmail.com, 
treg@world.std.com, emc-p...@ieee.org Subject: Re: TNV-2 to Earth 
requirement Date: Thu, 17 Jan 2002 16:20:14 -0700


Hi Dave,

According to Annex B of ETSI document EG 201212 "Electrical safety; 
Classification of interfaces for equipment to be connected to 
telecommunication networks": "48 Volt" Station Battery is to be considered 
as SELV where Vmax =< 57Vdc. "60 Volt" Station Battery is to be considered 
as TNV-2 where Vmax =< 75Vdc.

As Ed described the input as going up to 72Vdc, then, IMHO, this circuit 
should be classified as TNV-2 with the above reference and with the TNV-2 
circuit definition found in IEC/EN/UL60950. Also see clause 5.3 of EG 
201212 for user information recommendations.

The above assumes that Ed's product connects to a telecommunication 
network.

Please note that as the EG of EG 201212 refers to "ETSI Guide" (see the 
foreward), its hardly a regulatory requirement, however, it is a useful 
document that provides guidance for the classification of most TNV type 
circuits. And, it can be downloaded for free from the ETSI site.

I hope this helps clarify this issue. Comments?

Best regards,

Ron Pickard rpick...@hypercom.com





davehe...@mediaone.net Sent by: To: bosesaf...@hotmail.com 
owner-emc-pstc@majordom cc: treg@world.std.com, emc-p...@ieee.org 
o.ieee.org Subject: Re: TNV-2 to Earth requirement


01/17/02 02:33 PM Please respond to daveheald







Does your equipment plug into a primary (AC) circuit? Any TNV circuit is 
considered a secondary circuit and if any and all power is derived from the 
TNV network, the notes you referenced would not apply as a primary circuit 
is not present.

Best Regards, Dave Heald

Ed Eszlari wrote: > > All, > > I have a DC to DC "filter" which is rated 32 
- 72 VDC input and output > which I am considering to be TNV-2 according to 
EN60950/IEC60950 2nd > edition. > > This filter has a metal chassis which 
is earthed, and it will be > installed in a service access area only by 
qualified service > personnel. It is not permanently connected or pluggable 
type B, and > does not have a provision for a permanently connected 
earthing > conductor. With all this considered, it seems that Norway and 
Sweden > are the only Countries that require Supplemental insulation for a 
> primary circuit between this TNV-2 circuit and earth. > Is there any way 
around this requirement due to this filter operating > at 72VDC and not 
being directly connected to mains? > > Any help would be appreciated. > > 
Ed


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Hi everyone and thanks for all of the info thus far.
Here is some more info on the filter: The input to the filter derives it's power from batteries at a C.O. The output is meant to power telecom equipment. The input and output are considered TNV-2. Now even though the filter input is considered a secondary circuit, has anyone also considered that there will be a battery charger in that circuit charging the batteries? The battery charger  is mains connected and is required to have reinforced insulation from the mains input to the output. Therefore I believe if everyone agrees the DC filter does require supplemental insulation to earth, the battery charger should also meet this requirement.
I have read clause 6 over and over, and in my opinion supplemental insulation is required (for Norway and Sweden) from this TNV-2 circuit to earth regardless of the filter being connected to the mains or not. It's just funny how these clauses are worded because they mainly seem to refer to mains connected products (permanently connected, pluggable type B, etc.).
Ed
 

>From: "Ron Pickard" 
>To: davehe...@mediaone.net
>CC: bosesaf...@hotmail.com, treg@world.std.com, emc-p...@ieee.org
>Subject: Re: TNV-2 to Earth requirement
>Date: Thu, 17 Jan 2002 16:20:14 -0700
>
>
>Hi Dave,
>
>According to Annex B of ETSI document EG 201212 "Electrical safety; Classification of interfaces for
>equipment to be connected to telecommunication networks":
>"48 Volt" Station Battery is to be considered as SELV where Vmax =< 57Vdc.
>"60 Volt" Station Battery is to be considered as TNV-2 where Vmax =< 75Vdc.
>
>As Ed described the input as going up to 72Vdc, then, IMHO, this circuit should be classified as
>TNV-2 with the above reference and with the TNV-2 circuit definition found in IEC/EN/UL60950. Also
>see clause 5.3 of EG 201212 for user information recommendations.
>
>The above assumes that Ed's product connects to a telecommunication network.
>
>Please note that as the EG of EG 201212 refers to "ETSI Guide" (see the foreward), its hardly a
>regulatory requirement, however, it is a useful document that provides guidance for the
>classification of most TNV type circuits. And, it can be downloaded for free from the ETSI site.
>
>I hope this helps clarify this issue. Comments?
>
>Best regards,
>
>Ron Pickard
>rpick...@hypercom.com
>
>
>
>
>
> davehe...@mediaone.net
> Sent by: To: bosesaf...@hotmail.com
> owner-emc-pstc@majordom cc: treg@world.std.com, emc-p...@ieee.org
> o.ieee.org Subject: Re: TNV-2 to Earth requirement
>
>
> 01/17/02 02:33 PM
> Please respond to
> daveheald
>
>
>
>
>
>
>
>Does your equipment plug into a primary (AC) circuit? Any TNV circuit
>is considered a secondary circuit and if any and all power is derived
>from the TNV network, the notes you referenced would not apply as a
>primary circuit is not present.
>
>Best Regards,
>Dave Heald
>
>Ed Eszlari wrote:
> >
> > All,
> >
> > I have a DC to DC "filter" which is rated 32 - 72 VDC input and output
> > which I am considering to be TNV-2 according to EN60950/IEC60950 2nd
> > edition.
> >
> > This filter has a metal chassis which is earthed, and it will be
> > installed in a service access area only by qualified service
> > personnel. It is not permanently connected or pluggable type B, and
> > does not have a provision for a permanently connected earthing
> > conductor. With all this considered, it seems that Norway and Sweden
> > are the only Countries that require Supplemental insulation for a
> > primary circuit between this TNV-2 circuit and earth.
> > Is there any way around this requirement due to this filter operating
> > at 72VDC and not being directly connected to mains?
> >
> > Any help would be appreciated.
> >
> > Ed
> >
> > ----------------------------------------------------------------------
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