On Wed, 18 Sep 1996, Mark Murphy wrote:
> Dear Treg, After reviewing immunity and telecom documents
> concerning surge requirements and compatibilty of telecommunications
> terminal equipment, several questions have arisen:
> 1. IEC 1000-4-5, EN 61000-4-5, and prEN 55024 define requirements
> for surge to voltage levels of 4.0 kV. As I understand these test
> procedures, telecommunications terminal equipment is tested to 1.5
> kV without external protection. For levels which exceed 1.5 kV, a
> primary protection circuit is installed between the surge generator
> and the terminal equipment. Is this understanding correct?
In countries where primary surge protection is installed as a matter
of course, this may be sufficient. I guess the 4KV and 1.5KV limits
come from ITU-T sources, however there is some debate about the
adequacy of these recommendations (K.20, K.21). In countries where
external primary protection is not fitted as a part of the
installation, it is a bit of a lottery.
> 1a. If this understanding is correct, can anyone provide a
> reference for this primary protection?
There are many references, some relating to devices themselves and some
relating to installations. A short list of sources. ITU-T, IEC,
Bellcore, BSI.
> 3. Are there any international or country specific surge
> requirements (longitudinal or metallic) which exceed a voltage
> amplitude of 2 kV (without primary or other external protection)?
The Australian version of IEC950 (AS3260) has a 7kV impulse and 3kV AC
test requirement for case (a) type equipment (hand held telephones and
headsets). In Australia, primary protection is only installed as part
of the installation where the carrier considers it a high lightning
risk area.
> Any assistance with these questions will be greatly appreciated.
>
> Thanx, in advance, for any assistance.
>
>
>
> Mark Murphy
> Motorola ISG
>
Chris Healy
Liaison Manager, Standards and Approvals
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